International Workshop on Organic Speciation in Atmospheric Aerosol Research

Transcription

1 1 Reference of findings and recommendations presented by speakers participants of the International Workshop on Organic Speciation in Atmospheric Aerosol Research April 5-7, 2004 Desert Research Institute Las Vegas, Nevada USA Prepared by the Office of Community Services, Fort Lewis College, Durango, Colorado February 2005 Tim Richard, MA, Technical Editor The International Organic Speciation Workshop was made possible by the United States Environmental Protection Agency s Offices of Research and Development and Air Quality Planning and Standards, the National Science Foundation/ Atmospheric Chemistry Division, and the Western Regional Air Partnership/ Western Governors Association. This publication was made possible with funding from the US Environment Protection Agency s Office of Research and Development and Office of Air Quality Planning and Standards, and the Western Regional Air Partnership/Western Governors Association. This material is also based upon work supported by the National Science Foundation/Atmospheric Chemistry Division under Grant No Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

2 2 International Workshop on Organic Speciation Summary Report 2/2005 Contents Introduction...3 The Topics...5 1) Sampling Issues Related to Organic Speciation of PM and SVOC...7 2) Analytical Challenges ) Organic Speciation Related to Source Receptor Modeling ) Organic Speciation Needs for the Health Community ) Organic Speciation Effects on Regional and Global Scale Atmospheric Chemistry and Climate ) Unexplained and Unresolved Mass ) Exposure Assessment to Particulate Organic Compounds ) Organic Aerosol Analysis Using Thermal Desorption Aerosol Mass Spectrometry...70 Special Discussion: The Importance of Carbonaceous Aerosol in Air Quality Planning: Bridging the Gap between Researchand Application...80

3 3 Introduction The International State of the Science Workshop on Organic Speciation in Atmospheric Aerosol Research (April 5-7, 2004 in Las Vegas, Nevada at the Desert Research Institute/Frank H. Rogers Center) brought together diverse government, academic and industry researchers, graduates and post-docs, in order to identify information gaps in the characterization of organic aerosols, and to brainstorm ideas on how to fill them. The workshop gave air-pollution researchers in complementary disciplines such as air quality and source-receptor modeling, health hazard research, visibility, and climate opportunities to share ideas through networking and floor discussions. The workshop and this report have aimed to summarize the state of the science and articulate needs for further research; as much as possible from this brief two-and-a-halfday meeting. This booklet begins at least to list some of the limitations and where the greatest capacity for advancement exists. Information shared here is based on lectures by experimentalists and modelers. Open-forum discussions were held, as well. Each section is authored by topic leaders and contributors invited to the discussion of eight main questions posed. Some authors texts contained in this booklet were condensed in order to make their information more easily available. The International Organic Speciation Workshop was attended by 153 participants from 15 countries/regions. Presentations and discussions took place among researchers from diverse professional backgrounds, all of them possessing varied and distinctive exposure to, and perspectives on, the speciation of organic aerosol compounds. Organic speciation of atmospheric aerosols was the one thing they had in common. The information shared in this booklet is intended to assist on-going dialogue on these topics between the research community and sponsors in hopes of ultimately advancing the science itself and contributing to real world applications. More detailed information is available on the APACE website, including pre- and post-workshop synopses and summaries, powerpoint presentations, a participant directory and news about upcoming events. For More Information: Barbara Zielinska, Desert Research Institute (775) barbz@dri.edu Joellen Lewtas, EPA ORD (retired) (206) JLewtas@u.washington.edu Tim Richard, Fort Lewis College (970) ptrichard@starband.net Jake McDonald, Lovelace Respiratory Research Institute (505) jmcdonal@lrri.org

4 4 International Workshop on Organic Speciation Summary Report 2/2005 Acknowledgements The International Organic Speciations Workshop was the third in a series of meetings designed to stimulate dialogue on atmospheric aerosol research worldwide. The meetings, meant to be small and focused, are organized by members of APACE (Atmospheric Particulate Carbon Exchange), a network of private, academic and government researchers, sponsors, students, and supporting organizations. APACE emerged during 2003 out of efforts of the original ad hoc committee that raised funds and brainstormed topics for a workshop that would address needs in organic aerosol research. In the spirit of continuing that initial effort, APACE members continue reaching out to key experts and sponsoring organizations in hopes of identifying new capacities in organic aerosol research. Members of this rather informal network primarily lend in-kind support towards continuing the workshop series. Their interest is in building bridges among sponsors and researchers, science and policy, and air pollution researchers across complementary disciplines. Current and past participants in APACE include the following individuals and organizations, institutions, or agencies: John Watson, Judith Chow, Barbara Zielinska, Eric Fujita (Desert Research Center); Joellen Lewtas (retired), Charles Lewis (EPA Office of Research and Development); Douglas Johnson, Robert Edgar, and Douglas Latimer (EPA Region 8); John Reber, Mark Scruggs (National Park Service, Intermountain Region); Tim Richard (Fort Lewis College); Richard Countess (Countess Environmental Consultants); Marc Pitchford (NOAA); Sylvia Edgerton (Pacific Northwest Research Center); Tad Kleindienst, John Volckens (EPA National Exposure Research Lab); Scott Copeland (USDA Forest Service/CIRA); Jacob McDonald, Joseph Mauderly (Lovelace Respiratory Lab); William Malm (NPS/CIRA); Tom Moore, Lee Alter (Western Regional Air Partnership); Patrick Cummins (Western Governors Association); Paul Doskey (Argonne National Lab); Christopher Simpson (University of Washington), and numerous topic leaders and presenters from around the world. Past and current financial sponsors of the APACE workshop series include: EPA Region 8; National Science Foundation/Atmospheric Chemistry Division (Anne-Marie Schmoltner, Sylvia Edgerton, Bruce Doddridge); US EPA Office of Air Quality Planning and Standards (John Bachmann); EPA Office of Research and Development and National Exposure Research Lab (Charles Lewis); and the Western Regional Air Partnership/Western Governors Association (Patrick Cummins, Tom Moore).

5 5 The Topics Topic #1: Sampling Issues Related to Organic Speciation of PM and SVOC How are SVOC and PM associated OC defined: Theoretical Definitions; Operational Definitions; What are the potential bias or problems associated with different PM and SVOC sampling techniques?; Advances in sampling and analysis of SVOC; Advances in the identification of secondary organic aerosol formation events. Topic #2: Analytical Challenges How do extraction approach and sample handling impact the accuracy of PM and SVOC speciation? What have we learned and what emerging techniques for sample handling are being developed? How does analytical approach (instrument/standards) affect accuracy? What do we know about analysis of different classes of compounds? What emerging techniques are being used to improve analysis of challenging compounds? Topic #3: Organic Speciation Related to the Source Receptor Modeling What organic compounds (or compound classes) are useful for source apportionment? Do we need more compounds? Do we need less? What are the needs of the modeling community? What are primary versus secondary organics? How can additional measurements help apportion secondary material? Implications of using multi-variant receptor models (e.g., larger data needs)

6 6 International Workshop on Organic Speciation Summary Report 2/2005 Topic #4: Organic Speciation for the Needs of Health Studies Is there good evidence for the health importance of organic air contaminants? How is our current knowledge of the air quality-health relationship limited by the present lack of analytical data? How could health researchers utilize improved information? How can interactions between the analytical and health research communities be improved? Topic #5: Organic Speciation Effects on Regional and Global Scale Atmospheric Chemistry and Climate How does organic carbon, particularly its individual components, affect atmospheric chemistry, aerosol scattering and absorption, ultraviolet radiation, and climate? What organic species participate in heterogeneous chemical reactions and secondary organic aerosol formation? How do atmospheric models treat secondary organic aerosols formation, and what measurements are needed to improve the treatment? Topic #6: Unexplained & Unresolved Mass How can organic speciation help define the reconciliation of organic carbon mass measured by thermal techniques? How do we move towards mass closure of speciated organic PM? Will measurements of organic macromolecules in bulk be a good next step? Topic #7: What Types of Measurements are Needed for Exposure Assessment? What do We Know about Indoor Organic Speciation? What do we know about indoor and personal organic speciation? What role does OC play in contributing to personal and indoor PM 2.5 vs. outdoor PM? Current source apportionment findings on potential sources of personal and indoor exposures and the utilities of OC. What type of measurements are needed for exposure assessment to distinguish classes of OC by gaseous and particle-bound organics and sources? What are major indoor organic sources? Organic PM emissions from residential cooking. What is the extent of infiltrated outdoor sources to indoor and personal environments? These infiltrated sources may include traffic exhaust and wood smoke. Topic#8: Advances in Organic Characterization and Quantification Applicable to Organic Aerosols Advanced methods for polar compounds. Advances in analytical instruments & methods for aerosol speciation. Real-time aerosol methods.

7 7 1) Sampling Issues Related to Organic Speciation of PM and SVOC Topic Leader: Contributors: Lara A. Gundel, Lawrence Berkeley National Lab Douglas A. Lane, Environment Canada John Volckens, US EPA Oral Presentations: Lisa A. Graham, Environment Canada William K. Modey, Argonne National Laboratory 1a. How are SVOC and PM-associated OC defined? i. Theoretical Definitions SVOC. Borrowing from Van Vaeck et al (1984) and others (for example, Finlayson- Pitts and Pitts, 2000, p 412) we define semi-volatile organic compounds (SVOCs) as organic compounds that show significant gas and particulate concentrations in the atmosphere. Pankow (1993) generalized this by including other surfaces. He observed that SVOCs can have non-negligible fractions of their environmental masses in both the atmosphere and partitioned to surfaces such as soil, plants, building materials and sampling media. SVOCs have vapor pressures between about 10-4 or 10-5 and atm ( and 10-6 Pa; 10-1 and 10-8 Torr) over the ambient temperature range. Compounds with higher vapor pressures are present primarily in the gas phase, whereas low volatility compounds are found on or within particles. SVOCs are sticky or multi-phasic; they partition their mass between the gas phase and any surfaces that afford a degree of sorption, such as fine particles in air or sampling media. The degree of gas-particle partitioning affects the transport, deposition, and atmospheric fate of these compounds, since SVOCs, once airborne, can deposit onto vegetative surfaces, windows, carpets, soils, or even the human body. Nearly all classes of organic compounds contain semi-volatiles: alkanes, PAHs, PCBs, PCDDs, PBDEs, nitro-aromatics, terpenes, acids, carbonyls, and lipids, to name a few. SVOCs enter the atmosphere by direct emission, frequently as byproducts of incomplete combustion. Polar SVOCs are also produced by oxidation of precursor unsaturated compounds, and they can be incorporated into PM as secondary organic aerosols (SOA). Precursor organics are emitted from transportation, industrial and biogenic sources. Also, many of the potentially carcinogenic organic compounds found in the atmosphere are semi-volatile.

8 8 International Workshop on Organic Speciation Summary Report 2/2005 PM-associated OC. Roughly half the mass of urban fine particles in the US can be attributed to carbonaceous components. From 10 to 30% of this is elemental or black carbon, and carbonate-containing compounds have negligible contributions. Here we define PM-associated organic carbon as the complex mixture of organic compounds that are incorporated into airborne particles by direct emission, abrasion, condensation and surface reactions. The term PM-associated OC may be useful when considering the influence of the complex mixture of particle-associated organic compounds as a whole, for example, when investigating aerosol properties like organic film thickness, hydrophilicity, and optical absorption. Relationships between SVOCs and PM-associated OC: gas/particle partitioning. SVOCs and PM-associated OC are related through the partitioning of SVOCs onto PM. However, less than half of PM-associated OC is semi-volatile under temperate conditions. The partition coefficient K p is the most commonly used parameter for describing gas/particle partitioning, primarily because of its log-linear relationship to compound vapor pressure, p o. Although a compound s L vapor pressure at the temperature of interest has the greatest influence on partitioning, the interaction between compound structure and the sorptive medium plays an important role (e.g., compound size and polarity vs. adsorptive affinity or absorptive capacity). Plots of log K p vs. log p o can provide information on the nature of the partitioning and may indicate whether sampling L artifacts have impacted the measurement. Gas/filter partitioning coefficients can also be used to improve sampler and field study design (Mader et al., 2001b). The equilibrium partitioning of a semi-volatile compound to an environmental surface S can be represented most simply by where G i and P i represent the gas and particulate phases of the SVOC i. Since the gas and particulate phase concentrations are usually collected on an adsorbent and filter, respectively, their concentrations have been conveniently represented by A and F in the literature. If the sorbing surface is total suspended particulate matter, its concentration can be represented by TSP. (G/P theory takes the same form for size segregated particles, but TSP is used here to be consistent with Pankow s development as presented in Ch. 3 of Lane, ed. 1999). At equilibrium the gas/ particle partitioning constant K p for adsorption of the SVOC compound i onto the solid surface of a particle can be expressed as in (2): (1) (2) Pankow (1987) showed that Langmuir adsorption theory predicts that K p (at constant temperature) is inversely proportional to the vapor pressure of i. If i is a solid, the sub-cooled liquid vapor pressure p o is used. L

9 9 adsorption (3) N s and a tsp are terms for the number of adsorption sites per unit area and the surface area of the particles, respectively. For compounds of the same class, with similar enthalpies of desorption and vaporization Q among the members, plots of log K p versus log p o will be linear with slope L of 1, as shown in (4). adsorption (4) SVOCs can also absorb into liquid particles such as environmental tobacco smoke or liquid (organic and/or water) films on particles with solid cores. Gas/particle partitioning of SVOCs in urban areas is better explained as absorption than adsorption. The absorptive partitioning of SVOC i into a liquid organic layer on a particle is like a gas dissolving in a liquid (Finlayson- Pitts and Pitts, 2000, p 417), and the measured partitioning coefficient for absorption takes the same form as (2). absorption into a liquid film or droplet (5) F i,om represents the particle- associated concentration of i in air as measured from a filter, with explicit recognition that i has dissolved in liquid organic material, om, on the particle. For absorption into liquid films on particles, Pankow (1994) showed that K p is proportional to the weight fraction of om to TSP. absorption (6) K p is inversely proportional to the product of p o and the activity coefficient γ of i in the liquid L phase. Vapor pressure is the most important factor influencing K p, followed by activity coefficient and molecular weight. If the activity coefficient does not vary much across members of a class of SVOCs, plots of K p vs log p o will have a slope of -1 for both adsorption and absorption, L as in equations (4) and (7). Recent contributions to gas/surface partitioning theory address observed deviations from the predictions of equations (4) and (7). Jang et al. (1997) applied a comprehensive thermodynamic approach to calculate group contributions to activity coefficients for adsorption of SVOC into (7)

10 10 International Workshop on Organic Speciation Summary Report 2/2005 non-ideal organic films. This allows calculation of activity-normalized partitioning coefficients, K p,γ. Goss and Schwarzenbach (1998) argued that slope deviations from 1 in log K p vs log p o L plots do not necessarily indicate non-equilibrium conditions, and they indicated how these deviations can be used to identify types of sorbate/sorbent interactions and thus characterize sorption processes. For example, they showed how acid/base interactions can influence gas/surface partitioning polar SVOC. Harner and Bidleman (1998) demonstrated that using laboratory-derived octanol/air partitioning coefficients circumvents the need to estimate activity coefficients for compounds absorbed in the organic films that coat urban particles. Mader et al. (2000, 2001a, b) expanded partitioning theory to quartz and Teflon filter materials that are used to collect particles, thus tackling the sticky problem of SVOC adsorption artifacts in PM sampling on filters. ii. Operational Definitions Partitioning constants are calculated from measured concentrations of individual compounds in each phase. The terms A i and F i in equation (2) must be determined for individual compounds. For some classes of compounds, good estimates of vapor pressures can be calculated from observed molecular weight-vapor pressure relationships for members of the class. Whereas concentrations of PM-associated OC can be determined experimentally as the collective concentration of organic carbon by programmed evolved gas analysis, at present there is no way to determine total airborne concentrations of semi-volatile organic carbon in an analogous way. PM-associated OC includes temperature dependent PM-associated SVOC of largely uncertain composition. Thus, at present it is not possible to distinguish SVOC and PM-associated OC quantitatively and accurately without introducing technique-dependent bias. As Turpin et al. (2000) point out, the term SVOC is usually operationally defined, or undefined, as below: F i = particulate SVOC i = concentration of i measured from filter F, and Ai = gaseous SVOC i = concentration of i measured from adsorbent A (8a) (8b) Because the typical meaning of SVOC is rooted in sampling strategy, Turpin et al. (2000) prefer to use the term condensable for airborne compounds that are found in both the gas and particulate phases. The total carbon content of PM-associated OC can be determined by thermal analysis, as discussed at the OC/EC workshop in At present, measured concentrations of PM-associated OC depend on both the sampling and analytical methods. Assuming negligible particulate carbonate, Particulate C = PM-assoc. organic carbon (PM OC) + elemental carbon (EC). (9) However, even the widely used thermal-optical differentiation of PM-assoc. organic carbon from elemental carbon depends on operationally defined algorithms. If i and j represent individual semi-volatile and non-volatile organic species, respectively,

11 11 At present, the particulate SVOC term in equation (10) (P SVOC i ) can be estimated from thermal methods for particulate C (Fan et al., 2003) and possibly from source characterization (Schauer et al.,1999), but accurate determination of the organic carbon content of real-world SVOC (as a class) remains elusive. Fig. 1 has schematic representations of air sampler configurations that lead to different operational definitions of particulate-associated organic carbon. Component descriptors are given on the left, while the labels on the right indicate the function of each section. F denotes a particle-collecting section (usually a filter). A stands for the section that collects gas phase SVOC (sorbent-coated denuder, sorbent such as XAD resin, or backup filter for estimating the gas phase SVOC adsorption artifact that occurred on F). (10) Figure 1. Sampler designs with different operational definitions of particulate-associated organic carbon. The arrows show the direction of flow. The usual component descriptors are shown on the left, but the descriptors may not accurately describe the original phase of airborne SVOC that collect there. Origins are indicated using the notation of equation (8). The functions of the components are indicated on the right. F, F 1 and F 2 represent components that trap particulate OC; A, A 1 and A 2 represent components that trap the gas phase OC. Below are the operational definitions of the gas and particulate concentrations of SVOC i for the sampler designs in Fig 1. Gas phase (FA, DFA and EA) [SVOC i ] g = A i (11a) (FFA) [SVOC i ] g = A 1i + A 2i (11b)

12 12 International Workshop on Organic Speciation Summary Report 2/2005 Particulate phase (FA and EA) [SVOC i ] p = F i (12a) (FFA) [SVOC i ] p = F i - A 1i (12b) (DFA) [SVOC i ] p = F 1i + F 2i (12c) Partitioning coefficients derived from these designs differ, as discussed in Topic 1c. 1b. What are the potential bias or problems associated with different PM and SVOC sampling techniques? Filter-Adsorbent (FA) with configuration FA; equations (11a) and (12a). This is often referred to as the conventional sampler design, since it has been used for at least two decades for speciation of semi-volatile and particulate organics in airborne PM. The sorbent A is typically polyurethane foam, XAD resin or a foam/xad/foam sandwich. At equilibrium SVOC adsorb and desorb from particles. Particulate SVOC are trapped on the filter medium F, and gases pass through the filter F for adsorption on A. Positive sampling artifacts occur when gaseous SVOC adsorb to the filter medium. Negative artifacts result from particulate SVOC evaporating from the filter deposit during sampling. The volatilized SVOC become trapped on the adsorbent A. McDow and Huntzicker (1990) found that sampling artifacts for OC depend on face velocity and sampling duration. Turpin et al. (1994) showed that the quartz filter positive artifact decreased as a fraction of the total OC, with increasing sampling time, at constant face velocity and particle mass concentration. After reviewing studies available at the time, Turpin et al. (2000) concluded that positive artifacts for OC are usually larger than negative artifacts when sampling urban air. Several gas/particle partitioning measurements of individual semivolatile compounds found that negative artifacts dominated (alkanes, organic acids, polycyclic aromatic hydrocarbons: Van Vaeck et al., 1984; PAH: Miguel et al., 1986; and Fan et al., 1995). However, Schauer et al. (1999) found large positive artifacts for ketones, aldehydes and alkanoic acids in meat smoke. Filter-Filter Adsorbent (FFA) with configuration FA 1 A 2 ;equations (11b) and (12b) Two filters in series are often used in OC/EC measurements as a simple sampling approach to correct for positive artifacts in sampling particulate-associated OC on quartz filters (McDow et al., 1990; Kirchstetter et al., 2001). The double filter design has components FF with configuration FA 1. The FFA design with configuration FA 1 A 2 has not been used widely for measuring the gas/particle partitioning of individual species. Assuming that the upstream filter F has collected a negligible fraction of the total airborne SVOC, the downstream filter, used as the adsorbent A 1 for SVOC g, has the close to same amount of adsorbed SVOC as the upstream, particle-laden filter F. The remainder of the airborne SVOC will be trapped if an adsorbent component A 2 is used. The particulate-associated OC is then the difference between the OC on F and OC on A 1, equation (12b). An improvement on the double filter approach (FF/FA 1 ) is to use co-located filter pairs. The upstream filters are Teflon and quartz, but both downstream filters are quartz. This approach is sometimes called tandem sampling, and the pairs are referred to as TQ and QQ, respectively. The

13 13 OC on the quartz filter behind Teflon is subtracted from the OC on the upstream quartz filter. OC on the quartz behind Teflon should represent the positive artifact more accurately than OC on the quartz behind quartz, since Teflon filters do not have the adsorptive capacity of quartz. Turpin et al. (2000) concluded that artifact OC measured from A 1 could be up to 40% higher if determined from the quartz behind Teflon rather than from quartz behind quartz filter. Denuder-Filter-Adsorbent (DFA) with configuration AF 1 F 2 ; or A 1 FA 2 equations (11a) and (12c) When gas phase SVOC are collected upstream of filters, positive artifacts can be minimized. This process denudes the gas stream of its SVOC, and the adsorption occurs in a denuder, A (Possanzini et al., 1983). Because the gas/particle partitioning equilibrium is disturbed during sampling, particulate SVOC trapped on F 1 become more susceptible to volatilization, and a postfilter adsorbent, F 2 in Fig. 1, traps semivolatile species that have evaporated from particles. The PM OCis the sum of NV OC on F 1 and P SVOC on F 2, equation (12c). Figure 2 illustrates how a DFA sampler functions, using the Integrated Organic Gas and Particle Sampler (IOGAPS, Gundel and Lane, 1999) as an example. Gases and particles pass through a size selective inlet, then enter a diffusion denuder whose walls are coated with a sorbent or reagent. The IOGAPS uses an extractable fine coating of XAD-4 sorbent resin (Gundel et al., 1998). Gas phase molecules diffuse to the walls where they are trapped and retained until analysis. Because the particles have much smaller diffusion coefficients than gas molecules and small Reynolds numbers, they remain entrained in the laminar flow through the denuder and are collected on the filter F 1. Some of the particle-associated SVOC leave the particles, pass through the filter F 1 and are trapped on the sorbent component F 2 (here, XAD-4-impregnated quartz filters). Figure 2. Gas and particulate phase SVOC pass from left to right through the IOGAPS, a DFA sampler in AF 1 F 2 configuration. The small circles are SVOC that are shown as individual molecules in the gas phase and also associated with particles, the larger irregularly shaped objects. The arrows indicate the air flow direction. Lane et al. (1988), Coutant et al. (1988) and Eatough et al. (1993) pioneered application of denuder difference methods for sampling airborne semi-volatile and particulate organics. To remove SVOC upstream of filters, Lane et al. used Tenax-impregnated GC-stationary phase gum on multi-channel glass annular denuders, while Eatough et al used parallel strips of activated carbon-impregnated paper. Sorbents (F 2 ) were used downstream of the filters. These designs require co-located conventional samplers (FA) for gas/particle partitioning measurements because SVOC could not be determined directly from the denuders. Gundel et al. (1995) introduced extractable XAD-coated denuders for direct determination of gas and particle concentrations

14 14 International Workshop on Organic Speciation Summary Report 2/2005 without the need for co-located conventional samplers. XAD-coated denuders and filters have been incorporated into several sampler designs (Gundel and Lane, 1999; Lewtas et al., 2001; Mader et al., 2001a, b; Hammond et al., 2003). So far, the DFA (AF 1 F 2 ) sampling approach has worked better for gas/particle partitioning of individual species than for determination of aggregate particulate semi-volatile OC, the first term on the right side of equation (10). Lewtas et al. (2001) indicated that this is possible using carbon denuders as A, and XAD-impregnated filters as F 2. Fan et al. (2003) devised a thermal analysis method for determining ΣP SVOC in equation (10) from F 2 when XAD-impregnated quartz filters are used as the F 2 component in the IOGAPS. The trapping efficiency of a denuder is expressed as follows: which relates A i, the concentration of species SVOC i as it exits the denuder to the concentration that enters the denuder A o,i. A i is never zero but some finite quantity. The ratio A i /A o,i is predicted by the Possanzini equation (14): (13) (14) where equation (15) shows that Δ a,i depends on the diffusion coefficient SVOC i at the temperature of sampling (D), the length of the denuder coated surface (L), the flow rate of the air that passes through the denuder (F) and the inner and outer diameters (d 1 and d 2 respectively) of a particular annulus within the denuder (15) A number of assumptions are implicit in these equations, of which the most significant is that a gas molecule that collides with the denuder coating will stay at the surface and not exit the denuder. For organic gases reaching an XAD-sorbent coated wall, this is not the case because most organic molecules reversibly adsorb on, rather than react with, the coating. Consequently, at higher temperatures, the denuder will act like a chromatographic column. The organics gradually migrate along denuder axis, and, if the sampling is carried out over a sufficient length of time, exit the denuder. This behavior places a practical limit on the total air volume sampled per unit denuder surface area. Sampling at higher temperature favors initial trapping of gases because diffusion coefficients increase with temperature. The higher the flow rate through the denuder, the lower the collection efficiency will be. However, if other parameters are optimized, such as length and sampling time, a higher sampling rate can be quite advantageous because it decreases the transit time of particles through the denuder. Keeping the transit time below 1 sec is necessary to minimize evaporation of some P SVOC species from particles. Annulus width also plays a significant role: the narrower an annulus, the greater the pressure drop across the denuder, restricting the

15 15 flow rate, and increasing the Reynolds number. However, the denuder is more efficient because the molecules have less distance to migrate before they reach the walls. An annulus width of 1.0 mm is optimum, however, in practice, it is difficult to find glass tubing that will permit all annuli in a denuder to be exactly 1.0 mm. Consequently, the real efficiency of a denuder must be determined from the widest (least efficient) annulus. This then forces the question, how efficient must the denuder be? The efficiency requirement (99%, 99.9%, % or greater) constrains the choice of denuder parameters Another implicit assumption of denuder operation is that all particles, due to their larger momentum than gas molecules, will pass through the denuder. One might ask the question when does a particle not behave like a particle? to which the answer when it behaves like a gas could be given. Then particle diffusion becomes important. In a well aged aerosol, the particles are relatively large, well over 50 nm in aerodynamic mean diameter. However, close to sources such as diesel buses and generators, or in traffic, many particles have been found to be much smaller than 50 nm. We must, consequently, address the problem of particle diffusion in a denuder. Particle diffusion as described by (Hinds, 1999) in equation (15): Where the D p is the particle diameter, and D p, L, F a and d 1 and d 2 are defined above. Applying this to a 30 cm long, 8-channel denuder which has annuli widths of 1.0, 1.2 and 1.4 mm, the calculated particle loss for a large variety of particle diameters shows that the IOGAPS at 16.7 L min -1 suffers significant particle loss in the denuder for particles below 50 nm, whereas at 85 L min -1 its denuder suffers major particle loss only for particles smaller than 20 nm in diameter. Thus, it is important to have some idea of the particle size in the air being sampled. 1c. Lessons learned: K p for several sampling configurations and experimental conditions (Original title: Advances in sampling and analysis of SVOC) As mentioned in section 1a, the ratio K p is the most commonly used parameter for describing gas-particle partitioning, primarily because of its log-linear relationship to compound vapor pressure, p o. Gas-particle partitioning ratios (K ) are defined at equilibrium, when the rates of L p mass transfer between phases are equal and at steady state. However, the conditions governing SVOC equilibrium are easily disrupted, especially when trying to measure gas-particle phase distributions in air. Care must be taken with the use of K p because this ratio is easily corrupted by even minute artifacts. Such sampling artifacts are widely known but difficult to prevent, predict, or account for after the fact (Volckens and Leith, 2003a, b). Plots of log K p vs. log p o can provide information on the nature of the partitioning and may L indicate whether sampling artifacts have impacted the measurement. Furthermore, most timeintegrated sampling techniques (i.e. filter) cannot provide a true representation of average K p. A need exists to develop improved sampling techniques with less perturbation of semi-volatile (15)

16 16 International Workshop on Organic Speciation Summary Report 2/2005 equilibrium, shorter sampling periods, and lower limits of detection. The following discussion shows how measured K p varied with sampler type and experimental conditions in a chamber study of the gas/particle partitioning of alkanes. Lesson 1: The sampling method affects the measured partitioning coefficient. Measurements of K p are not necessarily equivalent when different sampling techniques are employed. As seen in Fig. 3, K p s measured for alkanes partitioning in a controlled laboratory experiment are widely divergent among methods, though each within-method data set appears log-linear, as predicted by equations 4 and 7. This result indicates that sampling artifacts may play a large role when reported slopes of log K p vs. log p 0 deviate from -1. For the data shown L here, alkane concentrations were kept constant throughout the sampling event, yet measured values of K p varied by a factor of 2 100, depending on the sampling method used. Lesson 2: FA-type samplers suffer from memory loss (most time-integrated samples are not averages). In Fig. 4 we see K p values as measured by a FA-type sampler for two different concentration profiles that vary in time. The upper profile, which favors an adsorption artifact, began with a TSP concentration of 25 µg m -3 and ended with a TSP of 75 µg m -3 ; the lower profile, favoring an evaporation artifact, used the same concentration ranges in reverse. Although the timeweighted average of log K p should be the same for these tests, the plots for the two FA samples are separated by approximately 0.5 log K p units, as seen in the figure. Additionally, the differ- Figure 3: Log K p vs. Log p 0 L for alkanes measured by FA, FFA, DFA, and EA samplers in the laboratory. EA refers to the electrostatic precipitator sampler used by Volckens and Leith (2002).

17 17 ence between log ([F/TSP]/A) for the adsorptive and evaporative portions of the concentration profiles (i.e. log 75 log 25) is approximately 0.47 log units. This observation indicates that aerosol collected during the latter half of the sampling duration affects the measured K p more than aerosol collected at the beginning. Such behavior is expected from time-integrated methods when the sample remains in contact with the flowing airstream, as collected particles will constantly attempt to re-establish equilibrium with aerosol that flows into the sampler (Pankow and Bidleman 1992). Hence, FA-type samplers suffer from memory loss; they do not report an average measure of K p, but rather a value that is weighted towards concentrations collected near the end of the sampling period. Samples collected in a DFA sampler are constantly in a state of non-equilibrium, because gas-phase compounds are quickly stripped from the airstream and collected particles are continually evaporating. Consequently, the DFA sampler is not affected by transient changes in concentration. Figure 4: Log K p vs. Log p 0 for alkanes measured by FA sampler for two concentration profiles with equivalent L average TSP. Lesson 3: The partitioning ratio, K p, is easily biased by artifacts near the tail ends in plots of log K p vs log p 0. L Equations 2 and 5 indicate that K p is the ratio of particle-phase to gas-phase SVOC concentrations. This ratio is useful because its log can be plotted in a linear free energy relationship to the log of compound vapor pressure, p 0. However, K is easily biased by even minute artifacts L p for compounds whose vapor pressures lie at either end of the SVOC spectrum. The following example with acenaphthene (p 0 L at 25 C) illustrates this point. Acenaphthene, under typical ambient conditions, may have 2 molecules present in the particle-phase for every 1000

18 18 International Workshop on Organic Speciation Summary Report 2/2005 present in the gas-phase. The theoretical K p for acenaphthene is then: If a DFA sampler were used to measure this compound and we assume that the denuder capture efficiency is 99%, then 1% of the gas-phase acenaphthene (i.e., 10 molecules) would penetrate to the backup adsorbent and be measured as being in the particle phase. This penetration error would propagate through K p as follows: (13) (14) In this example, the measured K p would exceed the actual K p by a factor of 6. A similar error would take place when low-volatility, particle-phase compounds deposit on the denuder walls during sampling. To avoid these types of errors, Harner and Biddleman (1998) suggest calculating the fractional particle concentration, φ = [F/(A+F)], instead of an absolute gas-particle ratio. Unfortunately, plots of log φ vs. log p 0 do not produce log-linear relationships. L Lesson 4: Know your limitations when sampling SVOC. Figure 5: Activity coefficient normalized values of log K p,γ vs. log p 0 for PAHs in diesel exhaust L measured by a DFA sampler.

19 19 No SVOC sampling method appears to outperform others in every sampling scenario. The DFA technique avoids the common adsorption and evaporation artifacts and shows promise as an SVOC sampler. However, DFA samplers are prone to biases from gas breakthrough and particle loss in the denuder, as seen in Fig. 5. If e p is taken as the fraction of particle mass is measured as gas-phase (i.e., particles that deposit in the denuder) and e g as the fraction of gas-phase mass that is measured as particle-phase (i.e., gas-phase SVOC that penetrates the denuder), then the measured K p will be in error according to the following expression: The predicted error for the measured K p (e p =0.1, e g =0.02) shows a reasonable fit to the experimental data, as seen in Figure 5. Equation 15 can be used to predict the errors associated with most types of sampling artifacts discussed above and may be used to set limits on the accuracy of K p measurements taken in the field. More importantly, however, the efficacy of sampling techniques must be characterized in situ. That is, in the case of DFA samplers, particle loss and gas breakthrough errors must be determined under actual sampling conditions. (15) References R.W. Coutant, L. Brown, J.C. Chuang, R.M. Riggin and R.G. Lewis (1988). Phase distributions and artifact formation in ambient air sampling for polynuclear aromatic hydrocarbons, Atmos. Environ., 22, D. J. Eatough, A. Wadsworth, D.A. Eatough, J.W. Crawford, L.D. Hansen and E.A. Lewis (1993). A multiple-system, multi-channel diffusion denuder sampler for the determination of fine-particulate organic material in the atmosphere, Atmos. Environ. 27A, Z.H. Fan, D.H. Chen, P. Birla and R.M. Kamens (1995). Modeling of nitro-polycyclic aromatic hydrocarbon formation and decay in the atmosphere. Atmos. Environ., 29, X.Fan, J.R. Brook and S. A. Mabury, (2003). Sampling atmospheric aerosols using an integrated organic gas and particle sampler, Environ. Sci. Technol., 37, B. Finlayson-Pitts and Pitts (2000). Chemistry of the Upper and Lower Atmosphere: Theory Experiments and Applications, Academic Press, San Diego, 969 pp; generally relevant: Chapter 9, Particles in the Troposphere, p ; especially relevant: Section 9.D, p K.-U. Goss and R.P. Schwarzenbach (1998). Gas/solid and gas/liquid partitioning of organic compounds: Critical evaluation of the interpretation of equilibrium constants, Environ. Sci. Technol., 32, L.A. Gundel, V.C. Lee, K.R.R. Mahanama, R.K. Stevens and J.M. Daisey (1995). Direct determination of phase distributions of semivolatile pollycyclic aromatic hydrocarbons using annular denuders, Atmos. Environ., 29, L.A. Gundel, J.M. Daisey and R.K. Stevens (2001). Method for fabricating a quantitative integrated diffusion vapor-particle sampler for sampling, detection and quantitation of semi-volatile organic gases,

20 20 International Workshop on Organic Speciation Summary Report 2/2005 vapors and particulate components, US Patent 6,226,852. L.A. Gundel and D.A. Lane, Sorbent-Coated Diffusion Denuders for Direct Measurement of Gas/Particle Partitioning by Semi-Volatile Organic Compounds, Chapter 11 in D.A. Lane, ed. (1999). Gas and Particle Phase Measurements of Atmospheric Organic Compounds, Vol. 2 of Advances in Environmental, Industrial and Process Control Technologies, Gordon and Breach, Amsterdam, 402 pp. S. K. Hammond, C. Perrino, I. B. Tager, F. Lurmann, P. Roberts, D. Vaughn, L Gundel, H. Margolis, Concentrations of Polycyclic Aromatic Hydrocarbons in the Fresno (CA) Asthmatic Children s Environment Study (FACES), presented at the International Society for Exposure Analysis, Stresa, Italy, September 21-25, T. Harner and T.F. Bidleman, (1998). Octanol-air partition coefficient for describing particle/gas partitioning of armatic compounds in urban air, Environ. Sci. Technol., 32, W.C. Hinds, 1999, Aerosol Technology, 2nd Edition, John Wiley & Sons, New York, pp M. Jang, R.M. Kamens, K.B. Leach and M.R. Strommen (1997). A thermodynamic approach to group contribution methods to model the partitioning of semi-volatile organic compounds on atmospheric particulate matter, Environ. Sci. Technol., 31, T.W. Kirchstetter, C.E. Corrigan and T. Novakov (2001). Laboratory and field investigation of the adsorption of gaseous organic compounds onto quartz filters, Atmos. Environ., 35, D.A. Lane, N.D. Johnson, S C. Barton, G.H.S. Thomas and W.H. Schroeder (1988) Development and evaluation of a novel gas and particle sampler for semivolatile chlorinated organic compounds in ambient air. Environ. Sci. Technol,. 22, D.A. Lane, ed. (1999). Gas and Particle Phase Measurements of Atmospheric Organic Compounds, Vol. 2 of Advances in Environmental, Industrial and Process Control Technologies, Gordon and Breach, Amsterdam, 402 pp Chapter 6, Mc Dow, Sampling Artifact Errors in Gas/Particle Partitioning Measurements, Chapter 11, Gundel and Lane, Sorbent-Coated Diffusion Denuders for Direct Measurement of Gas/Particle Partitioning by Semi-Volatile Organic Compounds. J. Lewtas, D. Booth, Y. Pang, S.Reimer, D.J. Eatough and L.A. Gundel, Comparison of sampling methods for semi-volatile organic carbon (SVOC), Aerosol Sci. Technol., 34, 9-22 (2001). B.T. Mader and J.F. Pankow (2000). Gas/solid partitioning of semivolatile organic compounds (SOCs) to air filters. 1. Partitioning of polychlorinated dibenzodioxins, polychlorinated dibenzofurans and polycyclic aromatic hydrocarbons to quartz fiber filters, Atmos. Environ., 34, B.T. Mader and J.F. Pankow (2001a). Gas/solid partitioning of semivolatile organic compounds (SOCs) to air filters. 2. Partitioning of polychlorinated dibenzodioxins, polychlorinated dibenzofurans and polycyclic aromatic hydrocarbons to teflon membrane filters, Atmos. Environ., 35, B.T. Mader and J.F. Pankow (2001b). Gas/solid partitioning of semivolatile organic compounds (SOCs) to air filters. 3. An analysis of gas adsorption artifacts in measurements of atmospheric SOCs and organic carbon (OC) when using teflon membrane filters and quartz fiber filters, Environ. Sci. Technol., 35, B.T. Mader, R.C. Flagan and J.H. Seinfeld (2001c). Sampling atmospheric carbonaceous aerosols using a particle trap impactor/denuder sampler, Environ. Sci. Technol., 35, S. R. McDow and J.J. Huntzicker (1990).Vapor adsorption artifact in the sampling of organic aerosol: face velocity effects, Atmos. Environ. 24A, A.H. Miguel, J.B. Andrade and S.V. Hering (1986). Desorptivity versus chemical reactivity of polycyclic aromatic hydrocarbons (PAHs) in atmospheric aerosols collected on quartz fiber filters, Intern. J. Environ. Anal. Chem., 26, J.F. Pankow (1987). Review and comparative analysis of the theories on partitioning between the gas and aerosol particulate phases in the atmosphere, Atmos. Environ., 21, J.F. Pankow, J.F. and T.F. Bidleman, (1992). Interdependence of the slopes and intercepts from log-log cor-

21 21 relations of measured gas-particle partitioning and vapor pressure - I. Theory and analysis of available data. Atmos. Environ., 26A, J.F. Pankow (1993). A simple box model for the annual cycle of partitioning of semi-volatile organic compounds between the atmosphere and the earth s surface, Atmos. Environ., 27A, J.F. Pankow (1994). An absorption model of gas/particle partitioning of organic compounds in the atmosphere, Atmos. Environ., 28, J.F. Pankow (1999). Pankow, Fundamentals and Mechanisms of Gas/Particle Partitioning in the Atmosphere, Chapter 3, D.A. Lane, ed. (1999). Gas and Particle Phase Measurements of Atmospheric Organic Compounds, Vol. 2 of Advances in Environmental, Industrial and Process Control Technologies, Gordon and Breach, Amsterdam, 402 pp. M. Possanzinini, V. DiPaalo, P. Gigliucci, M.C.T. Sciano and A. Cecinatoato (2004). Atmos. Environ., 38, J.J. Schauer, M.J. Kleeman, G.R. Cass and B.R.T. Simoneit (1999). Measurement of emissions from air pollution sources. 1. C1 through c29 organic compounds from meat charbroiling, Environ. Sci. Technol., 33, B.J. Turpin, J.J. Huntzicker and S.V. Hering, (1994). Investigation of organic aerool sampling artifacts in the Los Angeles Basin, Atmos. Environ. 28, B.J. Turpin, P. Saxena and E. Andrews (2000) Measuring and simulating particulate organics in the atmosphere: problems and prospects, Atmos. Environ., 34, L. Van Vaeck, K. Van Cauwenberghe and J. Janssens (1984). The gas-particle distribution of organic aerosol constituents: Measurement of the volatilization arteface in Hi-Vol cascade impactor sampling, Atmos. Environ., 18, J. Volckens and D. Leith (2002). Filter and electrostatic samplers for semivolatile aerosols: physical artifacts, Environ. Sci. Technol., 36, J. Volckens and D. Leith (2003a). Comparison of methods for measuring gas-particle partitioning of semivolatile compounds, Atmos. Environ., 37, J. Volckens, and D. Leith, (2003b). Effects of Sampling Bias on Gas-Particle Partitioning of Semivolatile Compounds, Atmos. Environ., 37:

22 22 International Workshop on Organic Speciation Summary Report 2/2005 2) Analytical Challenges Topic Leader: Contributors: Monica Mazurek, Rutgers University Bernd Simoneit, Oregon State Univ. Stephen Wise, National Insitute of Standards & Technology Michelle Schantz, National Institute of Standards and Technology Joellen Lewtas,EPA ORD (retired), Univ. of Washington I. Connection to Workshop General Topics Presentations and posters comprising Session 2: Analytical Challenges link primarily to the following workshop topics: Topic 2. What are the conventional and emerging methods for collecting and analyzing organic carbonaceous aerosols, and how do we assess those methods for their ability to fulfill the needs of public health, climate, and modeling? Topic 3. How do we assess accuracy and precision, and what criteria should be met for regulatory or other purposes? This workshop session addresses the current state-of-the-science for molecular marker analysis in aerosol complex mixtures. Invited presentations and posters focus on the detection and measurement of molecular markers in atmospheric fine particles. One common analysis method for organic mixtures employs Gas Chromatography/ Mass Spectrometry (GC/MS) to identify and measure molecular markers. Although GC/MS is a fairly routine application for organic compounds associated with ambient particles, little information about the precision of these measurements has been provided for the parts-per-billion determinations of single marker compounds in urban particular matter (PM) (Li et al., 2004). Such information is critical input to current source apportionment models since the uncertainty of analytical measurement itself is the primary quantifiable uncertainty in source receptor models. Regulatory groups must understand underlying measurement and precision factors relating to organic marker ambient mass concentrations before requiring and implementing any control strategies on specific urban sources of PM. Three critical elements underlying reliable identification and measurement of source specific

23 23 molecular markers are: 1) an analytical method having well-documented measurement precision and accuracy; 2) authentic standards for verification of the mass abundance of marker compounds, routine calibration of mass detector instruments, and for monitoring compound recovery throughout the analytical protocol; and 3) expanded and dedicated mass spectral libraries for molecular markers enabling improved interpretation of compound mass spectra and for verification of known and new molecular tracers. Invited presentations in Session 2. Analytical Challenges focus on: 1) components of the collection and analytical protocol necessary for identification and quantitation of molecular markers in fine particle samples; 2) standard reference materials, new standards for aerosol marker compounds, and results of intercomparison laboratory trials for molecular markers in urban dust standard reference material; and 3) advanced mass spectrometric interpretation methods for current and new target compounds in complex organic mixtures from airborne particles. Summaries for the invited presentations are presented in Section 2. II. Brief Overview of Current Knowledge Detection and measurement of organic compounds at the molecular level is now a routine practice for many air quality ambient monitoring studies. Molecular tracer analysis provides a powerful approach for linking major emissions with observed concentrations of fine particles. Quantitative estimates of major emissions to observed fine particle ambient mass concentrations are developed by using mass ratios of marker concentrations to the total organic aerosol ambient mass. Rogge et al., (1993) first described the molecular marker approach for fine particle apportionment work using ambient marker concentrations and emissions profiles measured for metropolitan Los Angeles. Further development of the mathematical model was published by Schauer et al., (1996) linking emissions inventories, emissions sources chemical compositions, and ambient concentrations of organic molecular tracers. Identification of molecular markers in ambient fine particles is incorporated into current research and monitoring activities on the sources and compositions of fine particles, including the current Supersites project funded by the U.S. Environmental Protection Agency. Typically, a single molecular marker compound comprises only a minute fraction of the organics fine particle mass fraction with ambient ratios of marker mass to total organics in units of ng m-3 and mg m-3, respectively. For example, ambient mass ratios of hopane fossil fuel biomarkers to organics can range from [ ]x10-3 for metropolitan New York City (Mazurek et al, 2004) to [ ]x10-3 for metropolitan Los Angeles (Schauer et al., 1996). Consequently, the analytical protocol for detecting and quantifying a molecular marker within ambient particulate matter must be sensitive and precise. Nearly two decades have passed since the gas chromatography/mass spectrometry based analytical protocol was developed by Mazurek and coworkers and applied to ambient fine particle samples (Mazurek et al., 1987; Mazurek and Simoneit, 1981; Rogge et al., 1993) and emission source samples (Mazurek et al, 1989, 1993; Hildemann et al., 1991) over the period 1982 to 1984 in metropolitan Los Angeles. Many innovations in molecular level analysis have occurred since this time involving advances in instrumentation, separation of complex organic mixtures,

24 24 International Workshop on Organic Speciation Summary Report 2/2005 improvements in measurement accuracy and precision, and in strategies for improved interpretation mass spectrometric data for target marker compounds. III. Subject Matter of the Presentations by Topic A.) A Critical Assessment of the Molecular-Level Analytical Protocol for Ambient Fine Particles Monica A. Mazurek, Department of Civil and Environmental Engineering, Rutgers University, 623 Bowser Road, Piscataway, NJ, Organic molecular tracers in fine particulate matter constitute only a minute fraction of aerosol mass. Given the sub parts-per-billion concentrations of organic marker compounds present in most urban atmospheres, the analytical protocol for detection and measurement is detailed and requires high precision and accuracy. An essential feature of the molecular analysis protocol involves a thorough quality assurance/quality control (QA/QC) plan. The QA/QC plan examines sampling, and filter handling and preparation steps evaluated also at the molecular level with identical instrumentation for compound detection and quantification. Typically, quadrupole electron-impact mass detection is used with pre-separation by high resolution gas chromatography (GC). Although the GC/MS molecular marker technology was developed in the early 1980 s, no general criteria have been developed for how accurately and precisely a marker compound must be measured, what are critical detection limits, or what surrogate analytes must be incorporated into a sample to monitor method, instrument, and analyst performance. Each of these factors is critical for producing molecular marker measurements of known quality (Budde, 2001). Finally, additional method validation steps, including laboratory duplicate sample aliquots, performance check standards, and field duplicate samples, generally are not conducted for molecular marker characterization work, but are essential to improving ambient mass concentration measurements. This presentation addresses these analytical protocol elements as key challenge areas for molecular marker measurement and identification in fine particle samples. B.) Reference Material and Quality Assurance Needs to Support Organic Speciation Measurements in Air Particulate Matter Stephen A. Wise and Michele M. Schantz, National Institute of Standards and Technology (NIST), Analytical Chemistry Division, 100 Bureau Drive Stop 8392, Gaithersburg, MD ; Joellen Lewtas, USEPA, NERL, Manchester Lab, 7411 Beach Dr. E., Port Orchard, WA One of the first environmental matrix Standard Reference Materials (SRMs) developed by the National Institute of Standards and Technology (NIST) for determination of organic species was SRM 1649 Urban Dust, an ambient total suspended particulate matter sample collected in Washington DC in the late 1970 s. Since SRM 1649 was issued in 1981, it has found widespread

25 25 use in the particulate matter (PM) measurement community, and NIST has assigned values for over 100 organic species in this material. However, there is a growing need for additional reference materials to support organic speciation of PM, particularly for the fine particulate matter fraction and representative of contemporary combustion sources. NIST is collaborating with the U.S. Environmental Protection Agency (EPA), with input from a group of investigators involved in EPA s PM research program and related studies, to develop additional SRMs and to provide interlaboratory comparison exercises to improve the accuracy and comparability of organic speciation measurements. SRM activities include development of both PM matrix and calibration solution SRMs for organic species of interest in PM characterization. For development of a future PM-matrix SRM, efforts are underway to obtain a suitable quantity of a fine PM either through collection of fine PM or size fractionation of existing total suspended particulate material to provide fine particulate fraction. We are assessing also the suitability of a fine PM on filter media SRM, which was developed for carbon measurements, for organic speciation measurements. Calibration solution SRMs containing a wide range of organic species are under development including: polycyclic aromatic hydrocarbons (PAHs) (two redesigned solutions with an expanded list of 53 PAHs and alkyl-substituted PAHs), aliphatic hydrocarbons, nitro-substituted PAHs (redesigned and expanded list of compounds), hopanes/steranes, and 13C-labeled levoglucosan for use as an internal standard. In addition to the SRMs developed in conjunction with EPA, several additional PM-matrix SRMs for organic speciation are currently in progress including: SRM 2585 Organic Contaminants in House Dust and SRM 1650b Diesel Particulate Matter. In addition to the SRM development activities, two NIST/EPA interlaboratory comparison studies have been conducted to assess and improve the comparability measurements of organic species in PM. This presentation will discuss these SRM and quality assurance activities and their potential impact on improving the accuracy of organic speciation measurements for PM characterization. This work has been funded in part by the U S Environmental Protection Agency. It has been subjected to Agency review and approved for publication. C.) Characterization of novel organic tracers in aerosols by mass spectrometry Bernd R. T. Simoneit, Oceanic and Atmospheric Sciences, Oregon State University, 104 Oceanography Administration Building, Corvallis, OR Organic compounds in aerosols are useful as tracers for assessment of sources, alteration and fate in indoor, urban and global air sheds. Indoor and urban pollution research has been reported mainly in the U.S. and European literature and both organic and inorganic tracers have been applied. Progress in defining new organic tracers in aerosols was mainly due to instrument development (GC-MS sensitivity) and the applications of the biomarker compounds elucidated in the geologic record by organic geochemists, the natural compounds characterized by natural product chemists, and the synthetic compounds from the chemical industry (Simoneit, 1999). Mass spectrometry (MS) is the analytical method of choice and compound identifications must be coupled initially with comparisons to authentic standards or structure proofs by MS, NMR and syntheses.

26 26 International Workshop on Organic Speciation Summary Report 2/2005 It is now routine to analyze total extracts (both organic or aqueous) directly by GC-MS after suitable derivatization of the polar compounds. Preparation of separated polarity fractions (by LC or TLC) remains an option for selected samples to gain additional functional group information. Derivatization is typically carried out by methylation and /or trimethylsilylation. This can involve MS interpretation because the derivatives (especially TMS) are not necessarily in the library or the free compound or acetate derivative MS may be archived. High temperature GC- MS can also be applied for high molecular weight compound identification ( e.g., wax esters to C40, alkanes to C100). The processes of MS interpretation and data evaluation (identification of the compounds in a mixture analyzed by GC-MS) will be illustrated here with some examples. Smoke from burning of contemporary (biomass, refuse, etc.) and fossil fuels are a global problem and the mass spectrometric identification of tracers for this process is discussed (Simoneit el al., 1999). Soil resuspension and erosion is another unquantified emission source and its contribution to the ACE-Asia aerosols is presented in another example (Simoneit et al., 2003). Also, a brief discussion of what not to do with organic tracer analyses is included (Simoneit, 2003). The total extract GC-MS analysis method with selected derivatization is a powerful tool for determining aliphatic homologous lipids, natural products, fossil fuel components, secondary oxidation products, PAH, UCM, phenols, saccharides, etc. and thus attaining an overview of the major and key organic tracers in aerosol PM. IV. Major Findings and Recommendations: Analytical Challenges Workshop presentations identified the following areas for further research where the greatest capacity for advancement exists for enhancing current science and technology for air pollution research and complementary disciplines: 1.) A chemical species mass balance provides a quantitative framework for assigning PM organic substances; from bulk carbon fractions (total carbon, elemental carbon, organic carbon) and chemical compound groups (alkanes, PAHs, alcohols, aldehydes, alkanoic acids, dicarboxylic acids) to individual marker compounds. The chemical species inventory is essential for relating PM source profiles to receptor site concentrations for OC, EC and molecular tracers emitted from primary emission sources. Although only a minor fraction of the total PM OC is identified at a molecular level, the chemical mass balance of PM carbonaceous species is a quantitative description that will accommodate new analytical technologies and new molecular tracers for comparison to existing bulk carbon and molecular level ambient PM data. 2.) Organic carbon (OC) and elemental carbon (EC) are critical bulk chemical measurements of ambient PM. Mass ratios are constructed routinely for molecular marker concentrations to sample OC and EC concentrations for source apportionment applications, ambient PM chemical compositions, and emission source chemical compositions. Currently 15 methods are used operationally to measure the OC and EC fractions of PM. Method intercomparisons using ambient PM samples and certified standards would link OC and EC results generated from the suite of measurement approaches.

27 27 3.) Incorporating more rigorous statistical design in PM collection and analysis protocols should improve current knowledge of method precision and bias for molecular marker concentrations in ambient PM samples and in emission source profiles. Co-location of duplicate PM samplers would increase confidence of PM organic chemical compositions. Simultaneous deployment of organic chemical species collectors and alternative bulk, chemical group, and molecular level analysis methods would improve current knowledge of overall bias and precision. 4.) New suites of certified reference materials for urban PM are becoming available to the measurement and analysis community through the National Institute of Standards and Technology. These reference materials are available from NIST for individual laboratory use. Additionally, NIST and US EPA are distributing the certified urban PM materials to PM research groups as part of laboratory trials. Results from the first two trials will be published soon, identifying factors which allow for greater precision and accuracy of molecular marker identification and quantitation in urban PM. NIST is soliciting recommendations from PM research groups for additional chemical standards that are either to expensive for individual groups to purchase and prepare, or are not available from commercial suppliers. The new NIST chemical standards will assist laboratories identify and measure key marker compounds in PM ambient and emission source studies. The NIST certified reference materials and the new chemical standards will improve current measurement and analysis methods and also assist with the development and validation of emerging technologies. 5.) Interpretation and validation of mass spectra for marker compounds in PM complex organic mixtures will benefit from the increased availability of authentic standards such as those produced from NIST. Novel marker compounds from major emission sources (anthropogenic, biogenic, synthetic, geogenic) and from secondary photochemical processes are important for improving the detail of PM organic chemical composition studies. Opportunities exist for merging dedicated mass spectral libraries, converting these to electronic formats, and increasing access by the PM research community. Because such an effort is not fundamental research, but more a synthesis and digital conversion process, funding mechanisms should be coordinated by federal and private sources to coordinate and support this necessary research tool for PM organic chemical molecular level research efforts and monitoring programs. References Budde, William L. Analytical Mass Spectrometry: Strategies for Environmental and Related Applications. American Chemical Society, Washington, DC. 386 pp., Hildemann, L. M., M. A. Mazurek, G. R. Cass, and B. R. T. Simoneit, Quantitative characterization of urban sources of organic aerosol by high-resolution gas chromatography, Environ.Sci.Technol., 25, , Li, M., S. McDow, D. Tolerud, M. A. Mazurek, Quantitation, detection, and measurement precision of organic molecular markers in urban particulate matter, Aerosol Science & Technology, submitted Mazurek, M. A., G. R. Cass, and B. R. T. Simoneit, Interpretation of high-resolution gas chromatography

28 28 International Workshop on Organic Speciation Summary Report 2/2005 and high-resolution gas chromatography/mass spectrometry data acquired from atmospheric organic aerosol samples, Aerosol Science & Technology, 10, , Mazurek, M. A., L. M. Hildemann, G. R. Cass, B. R. T. Simoneit, and W. F. Rogge, Methods of analysis for complex organic aerosol mixtures from urban emission sources of particulate carbon, in Measurement of Airborne Compounds: Sampling, Analysis, and Data Interpretation, edited by E. D. Winegar, pp , American Chemical Society Symposium Series, CRC Press, Inc., Boca Raton, FL, Mazurek, M. A., M. Li, S. McDow, J. Graham, D. Felton, C. Pietarinen, A. Leston, S. Bailey, Speciation of Organics for Apportionment of PM2.5 (SOAP) in the New York City Metropolitan Area, presented at the Mid-Atlantic Regional Air Management Association 2004 Science Meeting, January 27-29, 2004, Baltimore Maryland. Mazurek, M. A. and B. R. T. Simoneit, Characterization of biogenic and petroleum-derived organic matter in aerosols over remote, rural and urban areas, in Identification and Analysis of Organic Pollutants in Air, edited by L. H. Keith, pp , Ann Arbor Science/Butterworth, Boston, MA, Mazurek, M. A., B. R. T. Simoneit, G. R. Cass, and H. A. Gray, Quantitative high-resolution gas chromatography and high-resolution gas chromatography/mass spectrometry analyses of carbonaceous fine aerosol particles, Int.J.Environ.Anal.Chem., 29, , Rogge, W. F., M. A. Mazurek, L. M. Hildemann, G. R. Cass, and B. R. T. Simoneit, Quantification of urban organic aerosols at a molecular level: Identification, abundance and seasonal variation, Atmos. Environ., 27A, , Schauer, J. J., W. F. Rogge, L. M. Hildemann, M. A. Mazurek, and G. R. Cass, Source apportionment of airborne particulate matter using organic compounds as tracers, Atmospheric Environment, 30, , Simoneit, B.R.T. Organic matter in eolian dusts over the Atlantic Ocean. Marine Chemistry 5, Simoneit, B.R.T. A review of biomarker compounds as source indicators and tracers for air pollution. Environ. Sci. and Pollut. Res. Int. 6, , Simoneit, B.R.T. Polemic response to Mayol-Bracero et al. (2001) Atmos. Environ. 36, , Simoneit, B.R.T., J.J. Schauer, C.G. Nolte, D.R. Oros, V.O. Elias, M.P. Fraser, W.F. Rogge and G.R. Cass. Levoglucosan, a tracer for cellulose in biomass burning and atmospheric particles. Atmos. Environ. 33, , Simoneit, B.R.T., Kobayashi, M., Kawamura, K. et al., Saccharides, lipids and oxidation products in Asian dust and marine aerosols of the East Asia/Pacific region. Geochim. Cosmochim. Acta 67, A437, #2003.

29 29 3) Organic Speciation Related to Source Receptor Modeling Topic Leader: Contributors: Dr. Eric Fujita, Desert Research Institute Dr. Tad Kleindienst, U.S. Environmental Protection Agency Dr. Tim Larson, University of Washington What organic compounds (or compound classes) are useful for source apportionment? Source composition of combustion sources varies greatly with fuel type, emission controls, environmental conditions, operating mode, and the methods and procedures for sample collection and chemical analysis. These factors must be carefully considered before applying available profiles in receptor and source modeling. Most gasoline vehicles are relatively clean, especially in hot-stabilized mode. Virtually all of the PM emissions from normal emitters result from cold starts and hard accelerations with relatively higher amounts of elemental carbon. A relatively small fraction of high emitters are responsible for a disproportionate amount of the total PM emissions from gasoline vehicles. They have cumulative PM emissions that are more linear with time than normal emitters with higher relative amounts of OC. Elemental carbon is dominant in diesel exhaust, but is lower in newer technology diesel engines and during lower engine loads. Because of the variability of OC/EC splits,

30 30 International Workshop on Organic Speciation Summary Report 2/2005 gasoline and diesel vehicles cannot be apportioned by carbon analysis alone, and EC is not a unique tracer for diesel exhaust. Gasoline vehicle, whether low or high emitter, emit greater relative amounts of high molecular-weight particulate PAHs (e.g., benzo(b+j+k)fluoranthene, benzo(ghi)perylene, ideno(1,2,3-cd)pyrene, and coronene) that diesel vehicles. These PAHs are found in used gasoline motor oil but not in fresh oil nor in diesel engine oil. Diesel emissions contained higher proportions of dimethylnaphthalenes, methyl- and dimethylphenanthrenes, and methylfluorenes. Gasoline vehicles emit volatile PAH s (e.g., naphthalene and methylnaphthalenes) in amounts per unit of fuel that equals or exceeds that of diesel vehicles even normal emitters. These compounds require back-up traps to be quantitatively collected. The potential contributions of semi-volatile PAH and alkanes from motor vehicles to formation of SOA have not been determined. Hopanes and steranes are present in lubricating oil with similar composition for both gasoline and diesel vehicles and are not present in gasoline or diesel fuels. The relative abundances of hopanes and steranes to emissions of elemental carbon differ substantially for the diesel and gasoline vehicles. This difference in ratios of hopanes plus steranes to elemental carbon could be used to quantify the contribution of gasoline-powered and diesel-powered vehicles. A wide range of volatile, semi-volatile and particulate organic compounds is emitted from wood combustion from the release of resinous compounds (e.g., retene and 1,7-dimethylphenanthrene), and decomposition of cellulose (levoglucosan), hemicelluloses and lignin (e.g., guaiacols, syringols and their derivatives). Reactivity and phase distribution of methoxyphenols must be considered in receptor modeling applications. Levoglucosan is chemically stable but is emitted by different vegetation in widely varying proportion to total PM. Certain fatty acids (e.g. palmitic acid, stearic acid and oleic acid) as well as cholesterol have been used as possible marker for meat smoke. Long-chain ã-lactones are formed by lactonization of â-hydroxy fatty acids normally found in triacylglycerols. They also result from the oxidation of alkenals and oleic acid. These compounds are emitted in small amounts relative to PM2.5, but may be useful molecular markers for meat cooking. What are the primary versus secondary organics? How can additional measurements help apportion secondary materials? The apparent contributions of SOA to ambient PM2.5 concentrations have been associated in receptor modeling to the unidentified organic component. Both primary and secondary components of organic aerosols are complex and may partition between the gas and particulate phases with relative amounts that vary by region and season. Since

31 31 there are no direct measurements for these two categories, their relative fractions are uncertain. Aromatic and biogenic hydrocarbons are known to form SOA in laboratory smog chamber systems. Such data can be useful for prospective modeling of SOA in ambient fine particulate matter using emission inventories of biogenic and aromatic hydrocarbons as inputs to an air quality model. The origin of SOA in ambient samples can be determined by examining the organic fraction of ambient PM2.5 for marker compounds specific to various organic precursors or classes of precursors. Classes of compounds detected in ambient air include dicarboxylic acids, triols and tetrols, (di) hydroxy acids, methoxy dicarboxylic acids, ketodicarboxylic acids, acyl dicarboxylic acids, tricarboxylic acids, oxoacids, carbonyl compounds, hydroxy carbonyl compounds, polyketones, and hydroxy polyketones. Gas-phase PAH reactions produce nitro-pahs and nitro-pah lactones which may then condense onto particles. The specific nitro-isomers formed can be used as markers of OH radical or of NO3 radical chemistry in an airmass. Particle-associated markers of OH radical chemistry include 2-NF, 2-NP, 2-NBz and high 2-NF/2-NP ratios are markers of NO3 radical chemistry. The ambient concentrations of phthalic acid correlate with 3-nitrobiphenyl, a marker of OH radical reaction. Phthalic acid and methyphthalic acids may be ultimate particle-associated products of naphthalene and methylnaphthalene reactions. The complexity of SOA formation is such that it is unlikely the use of tracer compounds will produce the level of results obtained for primary PM2.5 emissions. What are implications of using multivariate receptor models? Multivariate receptor model algorithms (PMF, Unmix, COPREM, ME2) do not need source composition as inputs and simultaneously identifies factors and their contributions to a receptor sample. The ME2 algorithm can also include additional prior constraints (e.g. meteorology, particle size). Association between factors and source profiles can be ambiguous. More work is needed to merge these newer receptor models with explicit descriptions of meteorological transport and atmospheric chemistry and methods are needed to better describe the uncertainties in model predictions.

32 32 International Workshop on Organic Speciation Summary Report 2/2005 4) Organic Speciation Needs for the Health Community Topic Leader: Contributors: Dr. Joe Mauderly, Lovelace Respiratory Research Inst. Joellen Lewtas, EPA, ORD (retired), University of Washington Dr. Ronald Wyzga, Electric Power Research Institute The goal of this session was to assess current knowledge on the health importance of organic aerosols (and gases). Emphasis was placed on describing how studies have been conducted to determine the relationship between chemical composition and toxicity and how future studies can improve by advances in analytical technology and communication. 4a) Is there good evidence for the health importance of organic air contaminants? Introduction The NAAQS for PM2.5, the list of Hazardous Air Pollutants (HAPs), and the subgroup of Urban air Toxics would not exist if there were not substantive evidence that at some level of exposure, these air contaminants are harmful to health. There is substantive literature demonstrating that individual organic compounds and classes that are present as air contaminants are harmful to health. There is information from human and/or animal studies that the individual HAPs, and many organic species not included in the HAPs, can, at some dose, cause a wide spectrum of adverse health effects including irritation, inflammation, non-cancer diseases of multiple organs, cancer (or effects leading to cancer), birth defects, neurological abnormalities, and enhancement of allergic responses. A few recent examples were used to illustrate the spectrum of evidence (e.g., Lewtas et al., 1997; Rudell et al., 1999; Nel et al., 2001; Seagrave et al., 2002; Metzger et al., 2004; McDonald et al., 2004a).

33 33 Findings Ambient air regulations implicate dozens of specific organic pollutants (many in the gas phase) and mixtures of PM associated organic material as a component of PM2.5. Studies have shown that exposures of humans and/or animals to HAPs and other organic species (including mixtures) can induce health responses (dose dependent). Both epidemiology and laboratory studies have associated organic carbon, or specific components of organic carbon to health response. Recommendations See questions ahead for recommendations pertaining to the state of the science and needs for expanding both communication among researches and approaches to determine physical/chemical components of air that are associated with health effects. 4b) How is our current knowledge of the air quality-health relationship limited by the present lack of analytical data? Introduction Current analytical approaches can only resolve and account for a relatively small portion (typically < 50%) of the individual chemicals that make up particle associated organic carbon. With this limitation, determination of specific putative agents of ambient air or source emissions is difficult. Despite this, the principal problem of past research has been a failure to incorporate analyses into research programs and individual experimental designs (i.e., analytical availability). For toxicology studies involving exposures to humans, animals, or cells the exposures have typically been poorly defined and characterized. Only recently have animal toxicology studies incorporated exposure characterizations that are as comprehensive as the state-of-the-art allows (McDonald et al., 2004b). In addition to sparse information on detailed organic composition in ambient air, epidemiology studies have been limited by the lack of information on spatial homogeneity of classes of organic matter across a city and in areas where exposures are highest. Many classes of organic and inorganic pollutants co-vary because they are derived from the same sources and/or are affected similarly by meteorology. Knowledge of locations where, and the extent to which, different classes of organics might be unlinked would greatly facilitate the targeting of environmental studies to resolve exposure-effect relationships. Findings Current analytical technology has not resolved and conducted a complete mass-balance speciation of organic compounds in ambient air and source emissions. Past research, and many current studies, have failed to incorporate adequate detailed characterization of exposure in human and animal studies.

34 34 International Workshop on Organic Speciation Summary Report 2/2005 In addition to needs for thorough characterization, epidemiology studies need information on the homogeneity of organic aerosols in the environment. Recommendations We need technological advances that: 1) make a greater level of characterization of exposures to organic species practical for more widespread deployment in field and laboratory studies; and 2) provide a more thorough speciation of complex organic mixtures. At present, the former is more critical than the latter. We know enough to be confident that applying the current level of speciation capability more widely in health research could result in tremendous advances in our understanding of the health importance of airborne organic carbon (in all physical phases) even though we don t know what the answer might be. We need to make analytical techniques and equipment more practical for wide deployment, including use by non-specialists (simpler, faster, cheaper; that s right all three!). It is also possible to apply advanced analytical technologies at the prototype or research stage in limited health studies. For example, it would be useful to know whether or not the major fraction of complex organic matter that cannot now be readily resolved might have health importance (or conversely, whether we can relax and ignore it). Exploratory work using prototype technologies can be done with small samples and simple biological systems (e.g., cultured cells) or limited complex biological systems (i.e., instilled into lungs of small numbers of animals). 4c) How could health researchers utilize improved information? Introduction The problem is not a lack of plausible research strategies; it s primarily a lack of incorporation of organic speciation measurements into health research protocols. The full range of demonstrated and potential experimental designs were not discussed, but several examples that illustrate a spectrum of research strategies in which health researchers could make use of improved organic speciation were given and discussed. These are summarized in the findings below. Findings Epidemiology and population based studies that have linked chemical measurements of exposure to health response are sparse. Examples of successful interaction prove the potential for these studies to elucidate associations with chemical measurements (e.g. Lewtas et al., 1996; Talaska et al., 1996; Van Loy et al., 2000;Maykut et al., 2003; Metzger et al., 2004;). These studies are often limited by poor characterization of exposure, poor ability to control for confounding variables, and inability to disentangle effects of co-varying components (e.g., carbon monoxide and carbon). Administration of single components or mixtures to biological systems (e.g. cells,

35 35 animals) has been utilized. (e.g. Nel et al., 2001) to screen toxicity and plausibility of specific health responses. For complex mixture exposures, chemical composition of exposures have often been poorly characterized. In addition, cell and animal models are often not tested at enough doses to evaluate dose-response relationships and determine thresholds for effects. Chemical dissection, also termed biodirected fractionation, has been perhaps one of the most successful models of integration of biological and chemical sciences in air quality studies. Several variations of this approach have been tested (e.g. Scheutzle and Lewtas, 1986; Rudel et al., 1999; Nel et al., 2001). All have been limited to some extent by incomplete characterization of the composition of the samples (poor mass balance) and in some cases lack of validation of cell or animal models relative to human response. Statistical dissection has been utilized when composition and some health response are known and there are sufficient amount of samples to provide statistical power to define statistical associations (e.g., Eide et al., 2002; McDonald et al., 2004). This approach shares some of the same aforementioned limitations of the chemical dissection techniques. Recommendations Overall, there is ample opportunity for a greater incorporation of organic analyses into health research. In some cases, adequate analytical technology exists, and the issue is directing greater attention to health research on organic components of air pollution. In some cases, analytical instrumentation exist as research tools, but are not evolved into packages sufficiently standardized, simple, and inexpensive for widespread deployment. As indicated, several current approaches exist, but each has limitations that should be addressed. These limitations exist in both analytical technology and the health effects measurements. 4d) How can interactions between the analytical and health research communities be improved? Introduction There needs to be more dialogue between health researchers and the analytical community. A substantial portion of the health research community are insufficiently knowledgeable about the actual composition of air pollution (especially the organic components), how pollution works (source emissions, transport, and atmospheric chemistry), and analytical possibilities (what can be measured and how) to conceive innovative experimental designs. Many among the analytical community may not be sufficiently knowledgeable about the fundamentals (not the details) of the nature and range of health effects, the physical-chemical interface between airborne organic species and biological fluids and tissues, likely cellular-molecular biological mechanisms of

36 36 International Workshop on Organic Speciation Summary Report 2/2005 effects, and plausible biological experimental approaches (and their inherent limitations) to perceive the range of application of their technology to health research. Not only do we need more tutorial and brainstorming dialogue, there also needs to be a larger number of bridging scientists who consider themselves part of both research communities. Findings There is a need for better cross-fertilization within the health and analytical communities, as well as between those communities. Recommendations We need to take better advantage of several pathways for cross-fertilization between analysts and biologists. The publication by each community of its papers in its own journals is necessary and valuable, but is not an effective pathway for cross-disciplinary communication. There needs to be more development and dissemination of summary, tutorial, publications. The EPA Criteria Documents (e.g., EPA, 2003) contain the needed information for NAAQS pollutants, but few researchers read sections pertaining to other disciplines. The recent publication by NARSTO, Particulate Matter Science for Policy Makers (2003) is an excellent example of a tutorial synopsis that would be useful to biologists, although the title may not suggest its value to the health research community. Developing appropriate materials is only the first step; without distribution across disciplines, communication does not occur. Presenting both air quality and health sessions at scientific meetings in another pathway; however, the common practice of doing so in parallel sessions often hinders real cross-education. The conduct of cross-disciplinary tutorial sessions at scientific meetings (unopposed, when possible) is an excellent strategy, but not frequently implemented. Center programs containing both analytical and biological components (e.g., NIEHS Environmental Centers and EPA PM Centers) can be very productive, but typically struggle to truly integrate the disciplines into unified research strategies. There needs to be more emphasis on training researchers that span scientific disciplines, in order to expand the number and types of scientists conceiving and conducting truly integrative research. The NIEHS Mentored Quantitative Research Career Development program is an example of such an effort ( Federal agencies, states, and professional organizations could sponsor more training grants aimed specifically at cross-disciplinary training. Finally, there needs to be greater attention among funding organizations to incorporating organic analytical capabilities into health research. Simply getting the two communities to communicate is worthwhile, but does not necessarily result in joint research efforts. Scientists are most strongly motivated to action by the structure of funding opportunities. If research solicitations are framed to merge the two communities into joint research strategies, the scientists will conceive creative ways of doing so. Conversely, if research solicitations do not place a premium on such interactions, they are much less likely to occur.

37 37 References Eide, I., Neverdal, G., Thorvaldsen, B., Grung, B., Kvalheim, O. Toxicological evaluation of complex mixtures by pattern recognition: correlating chemical fingerprints to mutagenicity. Environ. Health Perspect. 110 (Suppl 6): , EPA, Environmental Protection Agency. Air Quality Criteria for Particulate Matter. Fourth External Review Draft, EPA/600/P-99/002, ad, bd, cfm?acttype=default, June Lewtas, J., Walsh, D., Williams, r. Dobias, L. Air pollution exposure-dna adduct dosimetry in humans and rodents: evidence for non-linearity at high doses. Mutat. Res. 378(1-2): 51-63, Maykut, N.N., Lewtas, J., Kim, E., Larson, T.V. Source apportionment of PM2.5 at an urban IMPROVE site in Seattle, Washington. Environ. Sci. Technol. 37(22): , Mauderly, J.L., Seagrave, JC. McDonald, J.D., Eide, E., Zielinska, B., Lawson, D. Relationship between composition and toxicity of engine emission samples. DEER 2003, Diesel Engine Emissions Reduction Workshop, FreedomCar and Vehicle Technologies Program, U.S. Department of Energy, Newport, RI, August 27, 2003 (view presentation at htm#session%209, full paper [McDonald, et al.] submitted to Environ. Health Perspect.). Metzger, K.B., Tolbert, P.E., Klein, M., Peel, J.L., Flanders, W.D., Todd, K., Mulholland, J.A., Ryan, P.B., Frumkin, H. Ambient air pollution and cardiovascular emergency department visits. Epidemiology 15: 46-56, NARSTO, North American Research Strategy for Tropospheric Ozone. Particulate Matter Science for Policy Makers: A NARSTO Assessment. EPRI , February, Access at cgenv.com/narsto/ and click on PM Science and Assessment. Summary available in English, French, and Spanish. Nel, A.E., Diaz-Sanchez, D., Li, N. The role of particulate pollutants in pulmonary inflammation and asthma: evidence for the involvement of organic chemicals and oxidative stress. Curr. Opin. Pulm. Med. 7(1: 20-26, NRC, National Research Council Committee on Research Priorities for Airborne Particulate Matter. Research Priorities for Airborne Particulate Matter III, Early Research Progress, National Academy Press, Washington, DC, Rudell B., Blomberg A., Helleday R., Ledin M.C., Lundbäck B., Stjernberg N., Hörstedt P., Sandström T. Bronchoalveolar inflammation after exposure to diesel exhaust: comparison between unfiltered and particle trap filtered exhaust. Occup. Environ. Med. 56: , Schuetzle D., and Lewtas J. Bioassay-directed chemical analysis in environmental research. Analyt. Chem. 58: 1060A-1075A, Seagrave JC., McDonald J.D., Gigliotti A.P., Nikula K.J., Seilkop S.K., Gurevich M., and Mauderly J.L. Mutagenicity and in vivo toxicity of combined particulate and semivolatile organic fractions of gasoline and diesel engine emissions. Toxicol. Sci. 70: , Talaska, G., Underwood, P., Maier, A., Lewtas, J., Rothman, N., Jaeger, M. Polycyclic aromatic hydrocarbons (PAHs), nitro-pahs and related environmental compounds: biological markers of exposure and effects. Environ. Health Perspect. 104 (Suppl 5): 901-6, Van Loy, M., Bahadori, T., Wyzga, R., Hartsell, B., Edgerton, E. The Aerosol Research and Inhalation Epidemiology Study (ARIES): PM2.5 mass and aerosol component concentrations and sampler intercomparisons. J. Air Waste Manag. Assoc. 50(8): , Watts, R.R., Wallingford, K.M., Williams, R.W., House, D.E., Lewtas, J. Airborne exposures to PAH and PM2.5 particles for road paving workers applying conventional asphalt and crumb rubber modified asphalt. J. Expo. Anal. Environ. Epidemiol. 8(2): , 1998.

38 38 International Workshop on Organic Speciation Summary Report 2/2005 5) Organic Speciation Effects on Regional and Global Scale Atmospheric Chemistry and Climate Topic Leader: Contributors: Mark Z. Jacobson, Stanford University Martin Schnaiter, Forschungszentrum Karlsruhe, Germany Song Gao, California Institute of Technology The main goal of this session was to address three sets of questions about organic speciation effects on regional and global chemistry and climate. Below, each question is given, followed by a discussion of the talks associated with the question. 5a. How does organic carbon, particularly its individual components, affect atmospheric chemistry, aerosol scattering and absorption, ultraviolet radiation, and climate? Introduction Organic compounds affect the absorption and scattering properties of atmospheric aerosol particles. In particular, when organic aerosol components are mixed internally with other aerosol components, such as black carbon (BC), the microphysical and optical properties of the aerosol are affected. Several zero-dimensional modeling studies have examined the effect of internal mixing on BC absorption (1-6). In three dimensions, a global modeling study of the evolution of the mixing state and radiative effects of BC, which treated BC as a core component within

39 39 aerosol particles, found that BC internally mixed as it aged, enhancing its direct radiative forcing by up to a factor of two over that of an external mixture (7). On the regional scale, one 3-D modeling study compared time-series model predictions of absorption coefficients and BC concentration with field data at several locations when BC was treated as internally-mixed as a core component in a core-shell model (8). However, few studies have compared theory with direct laboratory measurements (3,9). Results from the more recent of these studies (9) and subsequent work by the same group were reported here. Major findings are listed below. Findings The measured optical properties of BC are altered significantly due to the coating by OC. The increase in particle size due to the coating results in a decrease in the hemispheric backscattering ratio. The coating of BC by OC also causes a structural rearrangement of BC aggregates to form more compact particles. The measured absorption coefficient of BC may increase by a factor of two due to a coating. The amplification is wavelength dependent, with a factor of 1.8 at 450 nm and 2.1 at 700 nm. The BC absorption enhancement due to OC coating is represented well by a core-shell model. The model has greater problems reproducing the single scattering albedo, backscatter ratio, and Angstrom exponent, most likely due to the structural rearrangement of the soot aggregate, which affects scattering more than absorption. Recommendations Further laboratory experiments are needed to test the effect on absorption and scattering of black carbon coatings by additional organic compounds, by inorganic compounds, such as sulfate, nitrate, ammonium, and sea spray, and by mixtures of inorganic and organic compounds. Experiments are also needed to examine the effect of particle attachments (resulting from coagulation) in addition to coatings, on absorption and scattering coefficients. Finally, additional model comparisons with experimental data are needed to test different mixing rules and model types (e.g., core-shell, random inclusion). References Toon, O. B., and T.P. Ackerman, Algorithms for the calculation of scattering by stratified spheres. Appl. Opt. 20, , Chylek, P., V. Srivastava, R.G. Pinnick, and R.T. Wang, Scattering of Electromagnetic-Waves by Composite Spherical-Particles - Experiment and Effective Medium Approximations, Applied Optics, 27 (12), , 1988.

40 40 International Workshop on Organic Speciation Summary Report 2/2005 Videen, G., D. Ngo, and P. Chylek, Effective-Medium Predictions of Absorption by Graphitic Carbon in Water Droplets, Optics Letters, 19 (21), , Chylek, P., G. Videen, D. Ngo, R.G. Pinnick, and J.D. Klett, Effect of Black Carbon on the Optical-Properties and Climate Forcing of Sulfate Aerosols, J. Geophys. Res., 100 (D8), , Fuller, K.A., W.C. Malm, and S.M. Kreidenweis, Effects of mixing on extinction by carbonaceous particles, J. Geophys. Res., 104 (D13), , Lesins, G., P. Chylek, and U. Lohmann, A study of internal and external mixing scenarios and its effect on aerosol optical properties and direct radiative forcing, J. Geophys. Res., 107 (D10), doi: / 2001JD000536, Jacobson, M.Z., Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature, 409 (6821), , Jacobson, M.Z. Development and application of a new air pollution modeling system Part III. Aerosolphase simulations, Atmos. Environ. 31, , Schnaiter, M., H. Horvath, O. Mohler, K.H. Naumann, H. Saathoff, and O.W. Schock, UV-VIS-NIR spectral optical properties of soot and soot-containing aerosols, J. Aerosol Sci., 34 (10), , b. What organic species participate in heterogeneous chemical reactions and secondary organic aerosol formation? Introduction An accurate understanding of the molecular composition of secondary organic aerosols (SOA) is crucial for atmospheric chemistry, climate research, and human health studies. Although much work on the topic has been done (e.g., 1-6), obtaining a complete understanding has proven to be difficult due to the intrinsic complexity of SOA components and a lack of suitable analytical techniques, particularly for polar compounds as well as high-molecular-weight species. As a result of incomplete speciation and sampling or analysis artifacts, the current knowledge of SOA composition is incomplete. Three studies were presented that examined the issue of secondary organic aerosol formation. One of these talks examined reaction pathways resulting in the formation of oligomeric and low-molecular-weight components in secondary organic aerosols. Another talk examined water soluble organic carbon in Hong Kong, and a third talk discussed preliminary measurements of carboxylic and dicarboxylic acids with capillary electrophoresis. Findings High molecular weight ( Da) species were found in SOA from cycloalkene ozonolysis in abundance often comparable with and sometimes exceeding that of lowmolecular-weight species. High molecular weight ( Da) species were found in all SOA from alpha-pinene ozonolysis at a variety of initial seed phs. MS/MS analyses revealed that these components are very likely oligomers, and they are probably formed through acid-catalyzed heterogeneous reactions. Three such reactions are proposed.

41 41 Even though oligomers appear to be ubiquitous in SOA regardless of the initial seed ph or state (dry/wet), higher acidity leads to faster formation of larger oligomers, possibly as a result of faster catalysis. With the alpha-pinene ozonolysis system, oligomers in total have a much higher abundance than low-molecular-weight species in SOA. If the MS response factors are similar, oligomers are the predominant species in SOA from ozonolysis of alpha-pinene and some cycloalkenes. Water soluble organic carbon (WSOC) in Hong Kong exhibits a bimodal size distribution. The fine mode accounts for the major proportion of WSOC. Preliminary results of measurements of low molecular-weight carboxylic and dicarboxylic acids with a prototype analytical method were presented. Recommendations Further laboratory experiments are needed to verify the reaction pathways hypothesized and explore other reaction pathways involved. Reliable quantification of oligomers and accurate knowledge of aerosol density (with high-molecular-weight species accounted for) are needed to carry out a correct speciation closure of SOA. The presence of high-mw species in ambient aerosols needs to be explored. References Yu, J., D.R. Cocker III, R.J. Griffin, R.C. Flagan, and J.H. Seinfeld, Gas-phase ozone oxidation of monoterpenes: gaseous and particulate products, J. Atmos. Chem., 34, , Zoller, D.L., and M.V. Johnston, Microstructures of butadiene copolymers determined by ozonolysis/mal- DI mass spectrometry, Macromolecules, 33, , Jang, M., N. Czoschke, S. Lee, S., and R.M. Kamens, Heterogeneous atmospheric aerosol production by acid-catalyzed particle-phase reactions, Science, 298, , Limbeck, A., M. Kulmala, and H. Puxbaum, Secondary organic aerosol formation in the atmosphere via heterogeneous reaction of gaseous isoprene on acidic particles. Geophys. Res. Letters 30 (19), doi: /2003gl017738, Seinfeld, J. H., and J.F. Pankow, Organic atmospheric particulate material. Annual Rev. Phys. Chem., 54, , Kalberer, M. et al., Identification of polymers as major components of atmospheric organic aerosols, Science, 303, , 2004.

42 42 International Workshop on Organic Speciation Summary Report 2/2005 5c. How do atmospheric models treat secondary organic aerosols formation, and what measurement are needed to improve the treatment? Introduction Numerical models of the atmosphere are now treating aerosol processes in more detail than in the past. Major processes that affect aerosol evolution include emission, nucleation, condensation, dissolution, coagulation, transport, dry deposition, rainout, and washout. A major fraction of aerosol composition in many regions of the atmosphere is secondary organic matter (SOM). SOM enters aerosol particles primarily by condensation and dissolution. Soluble organic gases dissolve in existing particles containing liquid solutions; high-molecular-weight organics with low saturation vapor pressures condense onto existing particle surfaces. The size distribution of SOM evolves further by coagulation, chemistry, and removal. Relatively few three-dimensional models have simulated speciated SOM formation within aerosol particles to date (e.g., 1-4). A talk in this session examined the treatment of aerosol formation and evolution in numerical models. The talk discussed a sectional approach of examining the issue. It looked at numerical methods of treating aerosol particles in general and specific methods of treating condensation and dissolutional growth (5,6). Most such methods apply to formation of SOM. Findings discussed in the talk are discussed below. Findings A stable numerical solution to the problem of nonequilibrium growth/evaporation at long time step of multiple dissociating acids and a base was discussed. The solution eliminates nearly all oscillatory behavior observed otherwise observed at long time step. The solution is applicable across the entire relative humidity range, both in the presence and absence of solids. Analysis with the scheme suggests that, under some conditions of high relative humidity and concentration, some coarse-model particles <6 micrometers in diameter may reach equilibrium on a time scale of less than an hour. In a competition for vapor between homogeneous nucleation and condensation, the relative importance of condensation increases with an increasing number of background particles. In the absence of a continuous source of new particles, coagulation, condensation, dissolution, hydration, and chemical reaction may internally mix most particles within half a day under moderately polluted conditions. Condensation increases the fractional coating of small particles more than large particles.

43 43 Coagulation internally mixes particles of different original composition over the entire size distribution. Coagulation internally mixes a greater fraction of larger than smaller particles. Coagulation internally mixes larger particles with more other distributions than it does smaller particles. Recommendations Comprehensive field campaign data are needed to validate aerosol modules. Data necessary for useful model comparisons and inputs include highly-resolved (e.g., 5 kmx5 km) emission data, meteorological soundings throughout the measurement domain, surface and elevated gas and aerosol measurements, and radiative measurements. Aerosol measurements should include size and composition, where composition should include organic and inorganic species. Large-scale computational resources are also needed for global-scale aerosol simulations. Finally, additional measurements of organic aerosol composition (e.g., single-particle measurements) and the properties of organic gases and aerosol particles are needed. Some such properties include vapor pressures, imaginary refractive indices as a function of wavelength, and deliquescence properties. References Jacobson, M. Z., Isolating nitrated and aromatic aerosols and nitrated aromatic gases as sources of ultraviolet light absorption, J. Geophys. Res., 104, , Chung, S.H., and J.H. Seinfeld, Global distribution and climate forcing of carbonaceous aerosols. J. Geophys. Res., 107 (D19), 4407, doi: /2001jd001397, Griffin, R. J., D. Dabdub, M. J. Kleeman, M. P. Fraser, G. R. Cass, and G. H. Seinfeld, Secondary organic aerosol 3. Urban/regional scale model of size and composition-resolved aerosols, J. Geophys. Res., 107 (D17), 4334, doe: /2001jd000544, Zhang, Y., B. Pun, K. Vijayaraghavan, S.-Y. Wu, C. Seigneur, S.N. Pandis, M.Z. Jacobson, A. Nenes, and J.H. Seinfeld, Development and application of the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (MADRID), J. Geophys. Res., 109, D01202, doi: /2003jd Jacobson, M.Z., Analysis of aerosol interactions with numerical techniques for solving coagulation, nucleation, condensation, dissolution, and reversible chemistry among multiple size distributions, J. Geophys. Res. 107 (D19), 4366, doi: / 2001JD002044, Jacobson, M.Z., A solution to the problem of nonequilibrium acid/base gas-particle transfer at long time step. Aerosol Sci. Technol., in review, 2004.

44 44 International Workshop on Organic Speciation Summary Report 2/2005 6) Unexplained and Unresolved Mass How can organic speciation help define the reconciliation of organic mass measured by thermal techniques? How do we move towards mass closure of speciated organic PM? Will measurements of organic macromolecules in bulk be a good next step? Topic Leader: Contributor: Oral Presentations: Hans Puxbaum Andras Gelencser Murray Johnston Lisa Clarke 1. Introduction Hundreds of individual organic compounds have been identified in the organic atmospheric aerosol so far (e.g. Saxena and Hildemann, 1996), however, together they constitute less than 10% of the organic carbon (OC) of urban and rural aerosol (e.g. Rogge et al., 1993a; Puxbaum et al., 2000). The main analytical method used so far for separating and identifying organic individual species was Gas-Chromatography coupled to Mass Spectrometry (GC/MS). While aerosol extracts of non polar and weakly polar species were directly accessible to GC/MS analysis, for polar species such as organic acids, carbonyls, and multi functional compounds various derivatisation reactions had to be employed to increase the range of species to be identified. One of the recent results of the use of new derivatizing reagents was the observation of levoglucosan and related anhydrosugars in aerosol samples and their use as tracers for biomass combustion (Simoneit et al., 1999); as well as of novel di- and tricarboxylic acids in fine tropical aerosols (Zdrahal et al., 2001). Very recently Claeys et al. (2004) identified tetrols as major oxidation products of isoprene in aerosols from the Amazonian region. The analysis of extractable organic fractions so far concentrated on molecules accessible to gas chromatography, with carbon atoms generally less than 40. From considerations of the solubility, the behavior in the thermoanalytical methods as well as from observations with microscopical techniques we conclude that a large and until recently unaccounted fraction of the continental organic aerosol consists of polymeric or oligomeric substances.

45 45 Rogge et al. (1993a) and Zappoli et al. (1999) have shown, that a considerable part of the organic aerosol is not soluble in water and organic solvents, which points to larger molecular sizes of the insoluble compounds. Matthias-Maser and Jaenicke (1995) have demonstrated that up to 40% of the number of particles > 0.2 µm AD over a continental site were considered of biogenic origin. The high contribution of biogenic material to the particle number concentration points to biopolymers as a main source for the insoluble organic constituents in the atmospheric aerosol. Bauer et al. (2002a) introduced a quantification method for calculating the contribution of spores to OC in aerosols based on spore counts, and found considerable amounts of carbon from spores in background aerosol in Austria (Bauer et al. 2002b). But, according to current knowledge, the main constituents of the organic aerosol are the Humic Like Substances (HULIS), occurring in the aerosol as water soluble as well as water insoluble fractions (Havers et al., 1998). HULIS are present ubiquitously in continental aerosol samples at concentrations (HULIS-carbon) from 7-24 % of the OC (Havers et al., 1998; Zappoli et al., 1999; Facchini et al., 1999). HULIS are definitely macromolecular substances, possibly with manifold origin (e.g. from biomass burning Facchini et al., 1999; or from secondary reactions in the atmosphere Jang and Kamens, 2001; Gelencser et al., 2002 & 2003; Limbeck et al., 2003; Iinuma et al., 2004, Kalberer et al., 2004). Here we compile available data to investigate which species in the organic aerosol contribute significantly to the so far unaccounted organic carbon, and which part is still unaccounted Unexplained and Unresolved Organic Mass The high fraction of insoluble material in continental aerosols is indicative for the polymeric state of the compounds, potentially of natural as well as anthropogenic origin. According to Weissenbök et al. (2000) 70% of the insoluble filterable particulate carbon from snow collected in Austria at 3100 m elevation accounted of modern carbon, which is taken as evidence, that biogenic material dominates the insoluble aerosol fraction even in the mid troposphere. Bauer et al. (2002a) investigated the carbon content of different species of airborne spores and used these numbers for determining the contribution of bacteria and fungal spores to the organic carbon content of cloud water, precipitation and aerosols. Fungal spores were found in the size fraction of µm of organic background aerosol at a mountain site forming on the average 6 % of the organic carbon (OC) of the coarse size fraction (Bauer et al., 2002b). Pollen was considered of less importance for PM10 or PM2.5 aerosol size fractions. However, Schäppi et al. (1997) demonstrated, that some types of pollen grains expel upon influence of rain water much smaller particles, in the case of birch pollen of allergenic property. Thus, pollen may also be a source of fine particles. In a larger cooperative project taking place during the non-burning season in Amazonia a range of techniques was applied to quantify the contribution of natural sources to OC, based on microscopic and advanced chromatographic techniques (Blaszo et al., 2003; Graham et al., 2003). Analysts applying thermographic techniques for determining OC were for long aware, that

46 46 International Workshop on Organic Speciation Summary Report 2/2005 a refractory organic carbon fraction is omni present in atmospheric aerosols. Puxbaum (1979) described cracking of biopolymers as source of overlapping peaks with the black carbon peak. He investigated the thermal behavior of dried leaves, wood, pollen, natural rubber and lignin. All these substances formed double peaks during linear temperature programmed heating in oxygen, with partial overlap of the black carbon peak. The group of compounds showing the double peaks was referred to as organic debris. Also Ellis and Novakov, 1982 identified in thermograms of rural aerosol samples poorly resolved peaks (marked with α, β, γ, δ), corresponding to volatilization and/or oxidation of carbon species of increasing thermal/oxidation stability. After normalization to the source thermograms the excess peaks β and γ were hypothesized to be high molecular weight polymeric material, however, suggested to be a first-order measure of secondary organic carbon. Figure 1: Thermograms (linear heating in O 2 ) of two aerosol PM10 samples from an urban industrialized (Liesing) and a suburban (Schafberg) site. The highest peak at 440 C is BC, the last peak at 600 C is from carbonates. The refractory OC peak at 380 C is present in the background air and does not increase from urban activities. Chromatographic Techniques Recently, coupling of Liquid Chromatographic set ups with Mass Spectrometers applying Electrospray Ionisation ( ESI-MS ) allowed to determine the range of the molecular weights of organic compounds from aerosol extracts assigned to the HULIS-Fraction (e.g. Kiss et al., 2003). Similarly, formation of polymers from smog chamber experiments was demonstrated using capillary electrophoresis ESI-MS (Iinuma et al., 2004) or laser desorption ionization mass spectroscopy (Kalberer et al., 2004).

47 47 3. Classification of Atmospheric Bio-Aerosols Bio-Aerosols in the atmosphere may be viable or dead, detritus or debris of living matter, plants or animals. Such particles we will classify as primary biogenic particles. However, more recently, results from laboratory study indicate, that aerosol might also form on secondary pathways in the atmosphere from biogenic emissions. Table 1: Classification of Bio-Particles or related aerosol constituents PRIMARY VIABLE Bacteria Fungal Spores Algea Pollen Sattler et al Bauer et al. 2002a, b Schäppi et al DEBRIS/DETRITUS TRACER SECONDARY SMALLER MOLECULES (< 300 Da) Cellulose Lignin Amino Acids Hydrocarbons Fatty Alcohols Fatty Acids Etc. Terpene-Oxidation Prod. 1) Tetrols (Isoprene-Oxidation Products) Kunit and Puxbaum 1996 Blazso et al Zhang and Anastasio 2003 Simoneit 1980 Kavouras et al Claeys et al MACROMOLECULES (> 300 Da) HULIS 2) Havers et al ) Aerosol formation via absorption in pre-existing organic aerosol 2) HULIS are not exclusively of biogenic origin

48 48 International Workshop on Organic Speciation Summary Report 2/ Humic-Like Substances ( HULIS ) in the Atmosphere 4a. Observational studies of physical and chemical properties of HULIS In mass closure studies on organic aerosol humic-like substances (HULIS), or organic macromolecules, or polycarboxylic acids, are generally claimed to resolve a large fraction of unexplained mass of particulate organic carbon. Strictly speaking, however, HULIS are not speciated, their presence can only be inferred from various bulk aerosol measurements. Although by now there is conclusive evidence that such compounds are ubiquitous in the water-soluble organic aerosol, their quantitative determination is still subject to great conceptual and experimental uncertainties. Humic acids were first reported in aeolian dust by Simoneit (1977), and these findings were confirmed by Simoneit and Mazurek (1982) who found that humic acids constituted a major fraction of rural aerosol. Based on observed H/C ratio and δ 13 C values, a mixed origin from soil and lacustrine mud was inferred by the authors. Therefore the occurence of HULIS in soil-derived aerosol seemed to be well-understood. As mentioned above, thermographic techniques gave clues to the presence of polymeric material in ambient aerosol (Puxbaum, 1979; Ellis and Novakov, 1982). This idea was far too premature at that time to gain widespread recognition. It took another 15 years for the first field observations to rediscover atmospheric polymers (Havers et al., 1998; Zappoli et al., 1999). Combination of the thermal technique with water extraction revealed additional features of the bulk organic matter. For example, about half of the refractory aerosol component appeared to be soluble in water (Gelencsér et al., 2000a). The thermal properties of this refractory carbon differed markedly from those of the coarse aerosol, but seemed to resemble those of a reference humic acid on pre-baked quartz filters. The bulk characterization of organic carbon, in particular of its water-soluble fraction led to the surprising conclusion that almost all observed properties resembled closely those of natural humic substances. The first observations of this kind by UV-VIS spectrophotometry and proton nuclear magnetic resonance spectrometry (HNMR) were made on urban particulate matter (Havers et al., 1998). These authors were the first to introduce the term humic-like substances, HULIS, which has become widely accepted in the literature. At about the same time, a comprehensive study was published on the bulk properties of water-soluble organic matter in aerosol from a polluted, rural and marine environment (Zappoli et al., 1999). The major finding was that WSOC made up a significant fraction of fine aerosol carbon, and its detailed analytical characterization revealed a stunning resemblance to a reference humic acid. In spite of the high degree of similarity, the authors refrained from using the term humic-like for this major class of compounds. Instead, they termed this fraction macromolecular, though none of their analytical methods yielded direct evidence that these species were indeed of high molecular weight. They suggested biomass burning to be most likely source, and postulated direct condensation of high-molecular weight burning products as a possible formation mechanism. Their hypothesis assigned primary anthropogenic origin to this compound class, and was able to account for its observed abundance in the fine particle size range.

49 49 These pioneering works induced further studies on the occurrence and properties of HULIS in atmospheric aerosol. New analytical techniques were used to reveal the properties of the bulk WSOC, and to compare them to those of natural humic matter. It was shown that the electrochemical properties and metal-complexing ability of bulk organic matter in polluted fog water were nearly the same as those of a reference humic acid (Gelencsér et al., 2000b). Other studies applied various separation methods to characterize such compounds, most of which were based on their acid-base properties. The chromatograms or electropherograms showed a few poorly resolved broad peaks and/or an unresolved hump. Capillary zone electrophoresis of polluted fog water and aqueous extract of rural fine aerosol suggested a broad distribution of charge-to-size ratios of HULIS (Krivácsy et al., 2000). The observed ph-dependence implied that most acidic groups were found to be weaker acids than acetic acid. Decesari et al. separated the WSOC of the fine aerosol collected at a polluted site and the organic fraction was divided into there generic classes by preparative ion-exchange chromatography (2000). These were neutral/basic compounds, mono- and dicarboxylic acids, and polycarboxylic acids (with at least 3 negative charges per molecule). They determined the chemical structure of these broad compound classes by 1 HNMR spectrometry. The spectra of the neutral/ basic compounds revealed the presence of mainly hydroxylated/alkoxylated aliphatic species, with indications for the presence of polyols. Mono- and dicarboxylic acids were shown to be predominantly aliphatic carboxylic acids and hydroxy carboxylic acids, whereas polycarboxylic acids had a more pronounced unsaturated character, with an aromatic core having aliphatic chains with COOH, CH 2 OH, COCH 3 or CH 3 terminal groups. The observed features of the polyacidic compounds closely resembled those of terrestrial and aquatic humic matter. In general, the polycarboxylic acids were the most abundant class of WSOC throughout the year, except in summer, when mono- and diacids were predominant (Decesari et al., 2001). It should be noted that a large fration of the WSOC was UV-absorbing, and the specific UV-absorptivity was highest for the class of polycarboxylic acids. On the basis of group separation and HNMR measurements of the WSOC fraction, a representative mixture of individual compounds was suggested to simulate the physical and chemical properties of aerosol WSOC in model calculations (Fuzzi et al., 2001). The selection of the model compounds should be regarded as a conceptual approach which would serve as a basis for further research on organic aerosol. Varga et al. developed another preparative-scale separation method for the isolation of HULIS from the aqueous extracts of aerosol (2001). They optimized their method to isolate the fraction of WSOC that retained the key spectral properties also characteristic of reference humic and fulvic acids. Their separation was based on molecular interactions with the non-dissociated species, and is therefore conceptually different from the method based on the separation of ions, since polycarboxylic acids can be separated both in their ionic and molecular forms. Therefore both methods are believed to target broadly the same generic class of compounds, i.e. the terms polycarboxylic acids and HULIS possibly refer largely to the same fraction of organic aerosol. However, since there has been no intercomparison between these methods this statement is merely based on an assumption derived from the observed chemical properties of the isolated compounds, as well as on the fundamental principles of the separation. The method by Varga et al. (2001) allows the isolation of HULIS from inorganic compounds too, which is not possible in method by Decesari et al. (2000). This allows analytical determinations to be performed which

50 50 International Workshop on Organic Speciation Summary Report 2/2005 otherwise would not be feasible in the presence of interfering inorganic species. For example, the elemental composition of HULIS isolated from rural fine aerosol was found to be remarkably constant throughout the year, corresponding to an average molar ratio of C:H:N:O of 24:34:1:14 (Kiss et al., 2002). An important step towards the understanding of the origin of HULIS in rural aerosol collected in summer was the determination of their molecular weight distribution by ultrafiltration, liquid chromatography-atmospheric pressure ionization mass spectrometry, and vapor pressure osmometry (Kiss et al., 2003). The most interesting finding of this study was that virtually all WSOC passed through an ultrafiltration membrane having a 500 Da nominal molecular weight cut-off. The isolated HULIS which made up of more than half of WSOC by mass was further characterized to determine their ion mass distribution which was found to be continuous between about 100 and 500 Dalton, with maxima in the range of Da. These conclusions were confirmed by vapor pressure osmometry which provided direct estimates for the average MW of HULIS. The average molecular weight was found to be markedly lower than those of reference aquatic humic and fulvic acids under the same conditions. These observations are among the very few that pointed to important differences between HULIS and natural humic substances, and imply distinct mechanisms of their formation. Yu et al. have recently evaluated the mass size distributions of WSOC in marine and continental aerosol (Yu et al., 2004). Regardless of their origin, WSOC in aerosol exhibited a bimodal size distribution, with a dominant fine mode and a minor coarse mode having mass mean aerodynamic diameters of 0.7± 0.1 and 4.0 ± 0.3 µm, respectively. The mass in the fine mode ranged from two-thirds to four-fifths of that of the total WSOC. Both modes were further deconvoluted to low, medium, and high molecular weight polar compounds based on their thermal evolution features. While the low MW species had a bimodal distribution with a dominant coarse mode, the medium and high MW compounds exhibited a single peak in the droplet mode. This was interpreted as evidence that these latter species which might also be humic-like substances likely form during cloud-processing of aerosol. This finding would support the possible formation of HULIS in cloud processes (Gelencsér et al., 2003). In fact, very few analytical techniques are capable of providing chemical information directly on the carbonaceous component of the bulk aerosol collected on filter substrates or impactor plates. One of these methods is pyrolysis-gas chromatography-mass spectrometry which allows organic structure elucidation directly from aerosol filters. Taking into account the fact that HULIS contain functional groups (e.g. carboxylates) which yield non-specific thermal decomposition products (e.g. carbon dioxide) upon conventional analytical pyrolysis, in its very first application in aerosol chemistry a derivatization technique was introduced (Gelencsér et al., 2000c). The thermally assisted hydrolysis-methylation allowed labile functional groups to be converted into their respective esters, thus preventing decarboxylation upon pyrolysis and yielding more specific pyrolysis products. The analysis of rural fine aerosol by this method revealed overall structural similarities to those of natural humic substances. The predominant pyrolysis degradation products both in aerosol and terrestrial humic acids were n-alkanoic acids, α,ω-dicarboxylic acids (in the carbon number range of C 4 C 9 ), and benzenedicarboxylic acids. The apparent structural similarity to

51 51 terrestrial humic substances made the authors suggest the term atmospheric humic matter in place of HULIS. The rationale behind this suggestion was that HULIS in aerosol were thought to be chemically indistinguishable from the wide variety of natural humic substances present in other reservoirs. Using the same method Subbalakshmi et al. found similar compounds in urban aerosol, except that there higher substituted lignin pyrolysis products were also observed (2001). The pyrograms of biomass burning aerosol from Brazil, however, revealed some differences with respect to those of rural fine aerosol (Blazsó et al., 2003). Most importantly, in biomass burning aerosol there were several higher substituted aromatic compounds which were absent from rural aerosol. These species which are typical lignin degradation products were also shown to be present in the pyrogram of soil humic and fulvic acids (Martin et al., 1994). This finding made Gelencsér et al. reconsider their previous results on HULIS in rural fine aerosol (Gelencsér et al., 2002). Their conclusion was that in spite of all apparent similarities, these differences unambiguously prove the disparate origin of HULIS, namely their atmospheric formation in heterogeneous or multiphase processes. 4b. Laboratory evidence for the formation of HULIS in heterogeneous and multiphase processes Several hypothesis that heterogeneous or multiphase reactions can lead to the formation of humic-like substances (HULIS) as major SOA components were put forward by groups in Europe and the US. Gelencsér et al. (2002) observed HULIS formation in liquid phase from organic acids which are ubiquitous in the atmosphere. Jang et al. (2002) have presented laboratory evidence on acid-catalyzed heterogeneous carbonyl chemistry on aerosol particles, including various acid-catalyzed reactions, such as hydration, hemiacetal and acetal formation, aldol condensation, and polymerization in the aerosol phase. In terms of possible HULIS formation it

52 52 International Workshop on Organic Speciation Summary Report 2/2005 is important that equilibrium between an aldehyde and its hydrate favors the hydrate form and reacts further with carbonyls to yield dimers, trimers, and polymers. However, it is important to point out that these reactions, even polymerization are thought to be reversible. Limbeck et al. (2003) have then presented laboratory evidence for the irreversible formation of HULIS in heterogeneous reactions for the case of dienes like isoprene in the presence of sulfuric acid. The reactions yielded colored polymeric products whose humic-like character was evidenced by UV-spectrometry, thermal analysis, and FTIR diffuse reflectance spectroscopy. The authors hypothesized that isoprene whose SOA formation was thought to be negligible (Pandis et al., 1991, Griffin et al., 1999) is processed to humic-like polymers (HULIS) on highly acidic atmospheric sulfate clusters. It should be noted that these experiments were performed in bulk. Gelencsér et al. (2003) presented evidence about the irreversible formation of HULIS in atmospheric multiphase reactions in the laboratory. The precursors were aromatic hydroxy acids which are abundant lignin pyrolysis products in biomass burning aerosol. They showed that even a single representative compound can react with OH radicals yielding colored products under typical conditions prevalent in cloud water. The time-scale of the reactions was found to be hours, implying that the process does have atmospheric significance. The reactions proceed by radical dimerization and oligomerization to yield higher molecular weight products. A follow-up study on the molecular weights of the reaction products has revealed a continuous distribution well below 1000 Dalton, which confirms the high degree of similarity to atmospheric HULIS (Hoffer et al., 2004). In addition, this study has proven conclusively that the process is oligomerization rather than polymerization. In the same study, the results implied that HULIS consist of condensed and partially oxidized (e.g. quinone-like) phenolic structures crosslinked with shortchain aliphatic bridges which form by the oxidative cleavage of the phenolic ring. Two smog-chamber studies on the formation of HULIS or oligomers have been reported until now in Iinuma et al., (2004) investigated the ozonolysis of alpha-pinene in the presence of acidic particles. A thermographic method for the determination of TOC showed an increase of particle phase organics by 40% for the experiments with higher acidity. CE-ESI- MS analysis showed a large increase in the concentration of compounds with M w >300 from the experiments with sulfuric acid seed particles. Although in this paper the term HULIS is not used, the apparent similarity of the oligomers to HULIS (or vice versa) in their molecular weight distribution may entitle us to use these terms interchangeably. Kalberer et al. (2004) showed recently, that atmospheric polymers may form also from light initiated photochemistry of a trimethylbenzene NO x mixture. Experimental and/or observational evidences back up the hypothesis presented here, and so far there have been three studies in smog chambers which all support the oligomer formation. It is possible or even likely that to a certain extent all mechanisms could be operative this would explain the ubiquitous nature and abundance of HULIS in continental fine aerosol. What is known for certainty is that biomass burning is a source of HULIS however its secondary origin from biogenic as well as anthropogenic sources, and in particular the aerosol formation rates, is still to be determined.

53 53 Figure 1: Pathways of HULIS formation 5. Organic Carbon Mass Balance A remarkable set of new organic species of oxygenated organic compounds as well as of the group parameter humic like substances have been identified in the last years in the atmospheric aerosol. However, still there is a lack of quantitative data for different environments. Available data expressed as % of compound-carbon from OC are compiled in Table 2. The largest contribution of an individual group of compounds stems from humic like substances, which occur in the atmospheric aerosol in water soluble and water insoluble forms. The group of saccharides include levoglucosan, which is a tracer for wood or other biomass combustion. Based on test fires with different types of log wood a relation of 100+/-40 mg of Levoglucosan per gram of fine particle emitted OC was derived (Fine et al. 2001). Thus, from Levoglucosan levels in the aerosol the biomass-oc fraction can be estimated from Biomass-OC = 10* Levoglucosan (Eq. 1). Organic aerosol levels as derived from Levoglucosan data range from 5-50% at European as well as tropical sites. OC from biomass combustion, however contains humic like substances. Therefore it is not possible at present to sum up the group contributions from biomass burning as derived from equation 1 and the group of HULIS.

54 54 International Workshop on Organic Speciation Summary Report 2/2005 Table 2: Potential for contribution of different organic species or groups to % of OC observed at US or European Continental sites %C Reference of OC Alkanes - C 1 Unresolved Complex Mixture-C 5 Mono- and dicarboxylic acids-c 5-10 Tricarboxylic acids? Amazonia 6% Zdrahal et al Tetrols - C? Amazonia 10-20% Claeys et al Plant Debris (Cellulose)-C 1-5 Vienna Puxbaum & Tenze-Kunit 2003 Bacteria & Spores - C 1-5 Austria/Alpine Bauer et al. 2003b Saccharides - C 0,3-2 Ghent Up to 5% Rhondonia HULIS Water soluble-c 7-24 HULIS Water insoluble-c 5-20 Sum Recommendations Zdrahal et al The largest single group of organics in the atmospheric aerosol are Humic-Like-Substances HULIS. A standardized method for determining water soluble and water insoluble HULIS would be desirable. The group contribution of HULIS-Carbon to OC is estimated to amount 10-50%. Separation of HULIS from different sources such as primary or secondary should be achieved in the future. References Bauer H., Kasper-Giebl A., Zibuschka F., Kraus G.F., Hitzenberger R., Puxbaum H. (2002a) Determination of the carbon content of airborne fungal spores. Anal. Chem. 74, Bauer H., Kasper-Giebl A., Löflund M., Giebl H., Hitzenberger R., Zibuschka F., Puxbaum H. (2002b) The contribution of bacteria and fungal spores to the organic carbon content of cloud water, precipitation and aerosols. Atmos. Res. 64,

55 55 Bauer H., Giebl H., Hitzenberger R., Kasper-Giebl A., Reischl G., Zibuschka F., Puxbaum H. (2003) Airborne bacteria as cloud condensation nuclei. J. Geophys. Res. 108, D21, 4658, /2003JD Blazsó M., Janitsek S., Gelencsér A., Artaxo P., Graham B., Andreae M. (2003) Study of tropical organic aerosol by thermally assisted alkylation-gas chromatography mass spectrometry. J. Anal. Appl. Pyrolysis 68-69, Claeys M., Graham B., Vas G., Wang W., Vermeylen R., Pashynska V., Cafmeyer J., Guyon P., Andreae M.O., Artaxo P., Maenhaut W. (2004) Formation of secondary organic aerosol through photooxidation of isoprene. Science 303, Decesari S, Facchini MC, Fuzzi S, et al. Characterization of water-soluble organic compounds in atmospheric aerosol: A new approach. J. Geophys. Res. 105 (D1), , Decesari S, Facchini MC, Matta E, Lettini F, Mircea M, Fuzzi S, Tagliavini E, Putaud JP. Chemical features and seasonal variation of fine aerosol water-soluble organic compounds in the Po Valley, Italy, Atmos. Environ. 2001, 35, Ellis, E. C., and T. Novakov: Application of thermal-analysis to the characterization of organic aerosol particles. Sci. Tot. Environ. 23, , Facchini, M.C., Fuzzi, S., Zappoli, S., Andracchio, A., Gelencser, A., Kiss, G., Krivacsy, Z., Meszaros, E., Hansson, H.-C., Alsberg, T., Zebuhr, Y., Partitioning of the organic aerosol component between fog droplets and interstitial air. Journal of Geophysical Research, 104, Fuzzi S, Decesari S, Facchini MC, et al. A simplified model of the water-soluble organic component of atmospheric aerosols, Geophys. Res. Lett. 28 (21), , Gelencsér A, A. Hoffer, G. Kiss, E. Tombácz, R. Kurdi, L. Bencze, In-situ formation of light-absorbing organic matter in cloud water, J. Atmos. Chem. 45, 25-33, Gelencsér, A., A. Hoffer, Z. Krivácsy, G. Kiss, A. Molnár, and E. Mészáros, On the possible origin of humic matter in fine continental aerosol. J. Geophys. Res. 107, D21, doi: /2001JD001299, Gelencsér, A., Hoffer, A., Molnár, A., Krivácsy, Z., Kiss, G., Mészáros, E.: Thermal behaviour of carbonaceous aerosol from a continental background site. Atmos. Environ. 2000a, 34, Gelencsér, A., Sallai, M., Krivácsy, Z., Kiss, G., Mészáros, E.: Voltammetric evidence for the presence of humic-like substances in fog water. Atmos. Res. 2000b, 54, Gelencsér, A., T. Mészáros, M. Blazsó, G. Kiss, Z. Krivácsy, A. Molnár, E. Mészáros, Structural characterisation of organic matter in fine tropospheric aerosol by pyrolysis-gas chromatography-mass spectrometry, J. Atmos. Chem., 2000c, 37, Graham, B.; Guyon, P.; Taylor, P.E.; Artaxo, P.; Maenhaut, W.; Glovsky, M.M. ; Flagan, R.C.; Andreae, M.O. (2003) Organic compounds present in the natural Amazonian aerosol: characterization by gas chromatography-mass spectrometry. Journal of Geophysical Research, [Atmospheres] (2003), 108(D24), AAC 6/1-AAC 6/13. CODEN: JGRDE3 ISSN: AN 2004: Griffin, R. J., Cocker III, D. R., Flagan, R. C. & Seinfeld, J. H. Organic aerosol formation from the oxidation of biogenic hydrocarbons. J. Geophys. Res. 104, (1999). Havers, N., Burba P., Lambert, J., Klockow, D., Spectroscopic characterisation of humic-like substances in airborne particulate matter. Journal of Atmospheric Chemistry 29, Hoffer, A., G. Kiss, M. Blazsó, A. Gelencsér, Chemical characterization of humic-like substances (HULIS) formed from a lignin-type precursor in model cloud water, Geophys. Res. Lett., in press. Iinuma Y., Boge O., Gnauk T., Herrmann H. (2004) Aerosol-chamber study of the a-pinene/o 3 reaction: influence of particle acidity on aerosol yields and products Atmospheric Environment 38, Jang, M., Czoschke N., Lee S., Kamens, R. M. (2002) Heterogeneous atmospheric aerosol formation by acid catalyed particle-phase reactions. Science 298, Jang, M., Kamens, R. (2001) Atmospheric secondary aerosol formation by heterogeneous reaction of aldehydes in the presence of a sulfuric acid aerosol catalyst. Environ. Sci. Technol. 35, (2001).

56 56 International Workshop on Organic Speciation Summary Report 2/2005 M. Kalberer, D. Paulsen, M. Sax, M. Steinbacher, J. Dommen, A. S. H. Prevot, R. Fisseha, E. Weingartner, V. Frankevich, R. Zenobi, and U. Baltensperger (2004) Identification of Polymers as Major Components of Atmospheric Organic Aerosols. Science 303, Kavouras, I. G., Mihalopoulos, N. & Stephanou E. G. Formation of atmospheric particles from organic acids produced by forests. Nature 395, (1998). Kiss, G., B. Varga, I. Galambos, I. Ganszky, Characterization of water-soluble organic matter isolated from atmospheric fine aerosol, J. Geophys. Res, 107, D21, 8339, doi.: /2001JD000603, Kiss, G., E. Tombácz, B. Varga, T. Alsberg, L. Persson, Estimation of the average molecular weight of humic-like substances isolated from fine atmospheric aerosol, Atmos. Environ. 37, , Krivácsy, Z., Kiss, G., Varga, B., Galambos, I., Sárvári, Zs., Gelencsér, A., Molnár, A., Fuzzi, S., Facchini, M.C., Zappoli, S., Andracchio, A., Alsberg, T., Hansson, H.-C., Persson, L.: Study of humic-like substances in fog and interstitial aerosol by size-exclusion chromatography and capillary electrophoresis. Atmos. Environ. 2000, 34, Kunit, M., Puxbaum H., Enzymatic determination of the cellulose content of atmospheric aerosols. Atmospheric Environment 30, Limbeck A., Kulmala M., Puxbaum H. (2003) Secondary organic aerosol formation in the atmosphere via heterogeneous reaction of gaseous isoprene on acidic particles. Geophysical Research Letters 30(19), 1996, doi: /2003gl Martin, F., F. J. González-Vila, J. C. del Rio, and T. Verdejo, Pyrolysis derivatization of humic substances 1. Pyrolysis of fulvic acids in the presence of tetramethylammonium hydroxide, J. Anal. Appl. Pyrol., 28, 71-80, Matthias-Maser, S., Jaenicke, R., The size distribution of primary biological aerosol particles with radii > 0.2 µm in an urban/rural influenced region. Atmospheric Research 39, McCrone W.C., Delly J.G., The Particle Atlas (Ed. 2) Volumes I-IV, Ann Arbor Science Publishers, Ann Arbor, Michigan. Mukai, H. & Ambe, Y. Characterization of a humic acid-like brown substance in airborne particulate matter and tentative identification of its origin. Atmos. Environ. 20, (1986). Pandis S.N., S. E. Paulson, J. H. Seinfeld, and R. C. Flagan, Aerosol formation in the photooxidation of isoprene and β-pinene, Atmos. Environ. 25A, , Puxbaum H. (1979) Thermo-Gasanalysator zur Charakterisierung von Kohlenstoff- und Schwefelverbindungen in luftgetragenen Stäuben. Fresenius Zeitschrift für Analytische Chemie 298, Puxbaum H., Rendl J., Allabashi R., Otter L., and Scholes M. C. (2000) Mass balance of atmospheric aerosol in a South-African subtropical savanna (Nylsvley, May 1997). J. Geophys. Res. 105, Puxbaum, H., Tenze-Kunit, M. (2003) Size distribution and seasonal variation of atmospheric cellulose. Atmospheric Environment 37, Rogge, W. F., Mazurek, M. A., Hildemann, L. M., Cass, G. R., Simoneit, B. R. T. (1993a) Quantification of urban organic aerosols at a molecular level: identification, abundance and seasonal variation. Atmos. Environ. 27A, Rogge, W. F., Hildemann, L. M., Mazurek, M. A., Cass, G. R., Simoneit, B. R. T., 1993b. Sources of fine organic aerosol, 4. Particulate abrasion products from leaf surfaces of plants. Environmental Science and Technology 27, Sattler B., Puxbaum H., and Psenner R. (2001) Bacterial growth in supercooled cloud droplets. Geophys. Res. Lett. 28/2, Saxena, P. & Hildemann, L.M. Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds. J. Atmos. Chem. 24, (1996).

57 57 Schäppi, G.F., Taylor, P.E., Staff, I.A., Suphioglu, C., Knox, R.B. (1997) Source of Bet v 1 loaded inhalable particles from birch revealed. Sex Plant Reprod 10, Simoneit B. (1980) Eolian particulates from oceanic and rural areas their lipids, fulvic and humic acids and residual carbon. Physics and Chemistry of the Earth, 12 (Adv. Org. Geochem.) Simoneit, B. R. T., and M. A. Mazurek, Organic matter of the troposphere, II. Natural background of biogenic lipid matter in aerosols over the rural western United States, Atmos. Environ., 16, , Simoneit, B. R. T., Organic matter in eolian dusts over the Atlantic Ocean, Mar. Chem., 5, , Simoneit, B.R.T, Schauer, J.J., Nolte, C.G., Oros, D.R., Elias, V.O., Fraser, M.P., Rogge, W.F., Cass G.R. (1999) Levoglucosan, a tracer for cellulose in biomass burning and atmospheric particles. Atmospheric Environment 33, Subbalakshmi, Y., A. F. Patti, G. S. H. Lee, and M. A. Hooper, Structural characterisation of macromolecular organic material in air particulate matter using Py-GC-MS and solid state 13C-NMR, J. Environ. Monit. 2, , Varga, B., Kiss, G., Ganszky, I. Gelencsér, A., and Krivácsy, Z.: Isolation of water soluble organic matter from atmospheric aerosol. Talanta 2001, 55, Weissenbök R.H., Currie L.A., Gröllert C., Kutschera W., Marolf J., Priller A., Puxbaum H., Rom W., Steier P. (2000) Accelerator mass spectrometry analysis of non-soluble carbon in aerosol particles from high alpine snow (Mt. Sonnblick, Austria). Radiocarbon 42, Yu, J. Z., H. Yang, H. Y. Zhang, A. K. H. Lau, Size distributions of water-soluble organic carbon in ambient aerosols and its size-resolved thermal characteristics, Atmos. Environ. 38 (7), , Zhang Q., Anastasio C. (2003) Free and combined amino compounds in atmospheric fine particles (PM2.5) and fog waters from Northern California. Atmospheric Environment 36, Zappoli, S., Andracchio, A., Fuzzi, S., Facchini, M.C., Gelencser, A., Kiss, G., Krivacsy, Z., Molnar, A., Meszaros, E., Hansson, H.-C., Rosman, K., Zebühr, Y., Inorganic, organic and macromolecular components of fine aerosol in different areas of Europe in relation to their water solubility. Atmospheric Environment 33, Zdrahal Z., Vermeylen R., Claeys M., Maenhaut W., Guyon P., Artaxo P. (2001) Characterisation of novel di- and tricarboxylic acids in fine tropical aerosols. Journal of Mass Spectrometry 36, Zdrahal Z., Oliveira J., Vermeylen R., Claeys M., Maenhaut W. (2002) Improved method for quantifying Levoglucosan and related monosaccharides in atmospheric aerosols and application to samples from urban and tropical locations. Environmental Science and Technology 36,

58 58 International Workshop on Organic Speciation Summary Report 2/2005 7) Exposure Assessment to Particulate Organic Compounds L.-J. Sally Liu, Sc.D. Associate Professor Department of Environmental & Occupational Health Sciences, University of Washington Contribution of particulate organic compounds to indoor and personal exposures Organic carbon (OC) is a major constituent of indoor source emissions (Long et al. 2000) and a major component of PM2.5 mass. It may be responsible for some of the observed health effects previously associated with PM exposure. OC contributed an average of 24% of outdoor PM2.5 in U.S. cities, ranging from 17.8% in Detroit to 34.7% in Sacramento (U.S. EPA 2003). Recent receptor modeling for indoor measurements indicated that OC contributed 18% of the indoor PM2.5 in an unoccupied apartment in Baltimore (Hopke et al. 2003) and 65% of indoor PM2.5 in 9 occupied homes in Boston (Long et al. 2000). The OC contribution to indoor and personal PM2.5 has been difficult to quantify. Many particulate organic compounds (POC) are semi-volatile and exist in equilibrium between the gas and particulate phases. This characteristic provides a challenge of accurate measurement of POC in the presence of artifacts that can occur during sampling. A positive sampling artifact (Cui et al., 1997; Turpin et al., 1994; McDow and Huntzicker, 1990; Kim et al., 2001) results from the adsorption of vapor-phase, semi-volatile organic compounds (SVOC) onto the filter that collects particles, or even onto the particles themselves during sampling. A negative sampling artifact may result from desorption of vapor-phase SVOC during sampling or subsequent handling (Eatough et al., 1995; John et al., 1988). For indoor air samples, the net positive sampling artifact was found to be especially significant. Positive artifacts led to overestimation of indoor particulate OC measured with quartz filters in non-denuded Harvard Impactors for PM2.5 by 471% as compared with the average PM2.5 mass concentration measured with Teflon filters in identical samplers and outdoor particulate OC by 153% in the Seattle Exposure and Health Effects Panel Study (Claiborn & Liu, unpublished results). Adsorption saturation of quartz filters for gas phase OC was observed at indoor sites. The average quartz filter saturation level was estimated to be approximately 5.9 mg C/cm2 of quartz filter area. The highest volatility carbon fraction (OC1) is mostly from the adsorption of gaseous OC onto quartz filters during sampling, while the lowest volatility carbon fraction (OC4) fraction is mostly from the particulate phase.

59 59 Measurement methods The tandem-filter method was proposed to account for positive artifact (Fitz, 1990; Turpin et al., 1994). In this method, a single quartz filter is deployed in a sampler that is collocated with a second sampler that contains one upstream Teflon filter and one downstream quartz filter. Another method removes gaseous SVOC in an adsorbent-coated diffusion denuder upstream of the quartz filter. This method makes use of the fact that gases diffuse orders of magnitude faster than particles, allowing the particles to continue through the denuder to be collected on the quartz filter. To solve for the negative artifact, a sorbent or second quartz filter may be placed downstream of the filter. Denuder systems for the removal of gas phase organic compounds are the Brigham Young University Organic Sampling System (BOSS) (Eatough et al., 1993) and the sorbent-coated Integrated Organic Gas and Particle Sampler (IOGAPS) (Gundel and Lane, 1998; 1999). Both samplers are bulky and may not be suitable for deployment as personal samplers or in occupied residences. Pang et al. (2002) developed a promising personal particulate organic and mass sampler (PPOMS) that uses activated carbon-impregnated foam as a combined 2.5- m size-selective inlet and denuder for assessment of PM2.5 and OC free of the positive artifact. Alternatively, Fourier transformation infrared (FTIR) spectroscopy can be used to chemically characterize functional group information of outdoor, indoor, and personal PM2.5 samples, especially for those poorly understood organic fraction of PM2.5 (Turpin et al submitted). Turpin et al. showed the influence of indoor sources for aliphatic hydrocarbon and amide functional groups by demonstrating enhanced absorbances attributed to these groups in indoor and personal PM2.5 (Teflon) samples. Meat cooking was suggested as a possible source for particulate amides. Sources of indoor and personal PM2.5 Using a mass-balance model and 16 measured elements, Koutrakis et al. (1992) quantified the contribution of infiltrated outdoor PM and indoor sources including cigarette smoking, wood stoves, and kerosene heaters to indoor PM2.5 in 394 homes in two New York State counties. Yakovleva et al. (1999) used 18 elements analyzed from indoor, outdoor, and personal samples from 178 subjects in Riverside, CA, in a positive matrix factorization (PMF) analysis. They identified major indoor and personal PM2.5 sources to be soil, nonferrous metal operations and motor vehicle exhaust, secondary sulfate, and personal activities. Hopke et al. (2003) utilized both trace elements and OC measurements from indoor and outdoor samples in 3-way PMF and identified nitrate-sulfate, sulfate, OC, and motor vehicle exhaust as major indoor and outdoor sources. Their multilinear engine results indicated that sulfate (46%), personal activities (36%), unknown sources (14%), soil (3%), gypsum (0.7 %), and personal care products (0.4%) are major sources of personal PM2.5 exposure among elderly subjects. Using 3-way PMF, Larson et al. identified vegetative burning (41%), crustal materials (33%), secondary sulfate (19%), mobile vehicle exhaust (7%) as major personal PM2.5 sources. Recommendations for future work 1. Validate and cross-compare personal samplers that take into account the OC positive

60 60 International Workshop on Organic Speciation Summary Report 2/2005 and negative artifacts. 2. Develop methods to minimize the positive artifacts in existing OC measurements for exposure characterization. 3. Identify and characterize particulate organic compounds in indoor air and personal exposure and the utilization of these species in source apportionment analysis. Residential Cooking Wolfgang F. Rogge, Ph.D., P.E. Acting Department Chair and Associate Professor Department of Civil & Environmental Engineering Florida International University, Miami, FL In urbanized areas, restaurant and residential cooking often contributes 30% and more to the atmospheric fine particulate organic particle burden. Whenever no smoking occurs in homes, residential cooking has been suggested to be the major indoor source for respirable particulate matter. In order to fully understand the impact of cooking on indoor air quality and eventually on the overall urban air quality, we first have to have emission factors for all major pollutants. For that purpose, a specially designed airtight environmental chamber made of stainless steel was designed and built (3.7 m (L), 3.0 m (W), 2.5 m (H)). During the cooking studies, the chamber was operated under controlled airflow conditions, cleaning the incoming air first with an activated carbon filter bed, prefilter, and HEPA-filtering system. Altogether, more than 140 cooking experiments were conducted and the emission rates determined for: CO, NO, NO2, PM2.5, PM10, TSP. In addition, the PM2.5 samplers were followed by canisters loaded with polyurethane foam (PUF) plugs. The PM2.5 and PUF samples were furthermore subjected to detailed molecular analysis. Cooking was conducted using both electric and natural gas powered ranges and ovens. Many different food items were cooked using panfrying, stir-frying, sautéing, deep-frying, boiling, and oven cooking methods including baking, roasting, and broiling. TSP emissions were highest for pan-frying, with up to mg/kg of food cooked and varied drastically, depending on the food item pan-fried. Using natural gas, the TSP emissions were on average about 15% higher than observed for pan-frying with an cooking range powered by electricity. The next prominent cooking method was oven-broiling steaks, with TSP emissions up to 4300 mg/kg of food cooked. For this cooking method, oven broiling with natural gas as power source caused 10 times higher emissions than what was observed for oven broiling with electricity. In contrast, particulate emission factors for deep-frying did change very little for different food items. Boiling food with water revealed the lowest particulate emissions. Depending on the cooking method, about 20% to 100% of the TSP was made of PM10, and 30% to 70% of the PM10 consisted of PM2.5. In most cases, an increase in food fat content increased as well particulate emissions.

61 61 For most of the cooking experiments conducted, PM2.5 samples and PUF samples were analyzed for individual organic compounds using GC/MS and HPLC. Close to 150 individual organic compounds were quantified, including: n-alkanes, n-alkanoic acids, n-alkenoic acids, n-alkanols, n-alkanals, n-alkan-2-ones, dicarboxylic acids, furans, furanones, amides, steroids, polycyclic aromatic hydrocarbons (PAHs), heterocyclic aromatic amines (HAAs), and others. In general, oven roasting, broiling, and baking resulted in the highest PAH emission factors, ranging on average from about 10 µg/kg of food cooked to about 80 µg/kg of food cooked. In contrast, sautéing and stir-frying generated PAH emissions from about 2 µg/kg to 5 µg/kg. The PM2.5 and PUF samples were as well analyzed for 14 HAAs, of which 8 HAAs could be routinely identified and quantified, including: MeIQx, DiMeIQx, PhIP, AαC, Trp-P-1, Trp-P-2, harman, and norharman. The highest total HAAs emission factor was observed for pan-frying bacon, with about 3 µg/kg. Contributions from Outdoor PM Sources to Indoor and Personal PM Exposures Christopher D. Simpson, Assistant Professor Department of Environmental & Occupational Health Sciences University of Washington, Seattle, WA The US population typically spends a majority of its time indoors, and a major fraction of our PM exposures are encountered in indoor environments (Klepeis,2001; Klepeis,1996). Nevertheless, PM of outdoor origin (ambient PM) has been shown to infiltrate indoors efficiently and accounts for a significant fraction of the population s PM exposure. Furthermore, epidemiological evidence links ambient PM exposures with adverse health consequences (Samet,2000; USEPA,2001), and it is ambient PM that is regulated under the NAAQS. Therefore it is important from both a health and a regulatory standpoint to understand the contributions from outdoor PM sources to indoor and personal PM exposures. Recent studies have highlighted the value of source-specific organic chemical tracers molecular markers to identify and quantify the contributions of specific sources to ambient PM (Fraser,2003; Khalil,2003; Manchester-Neesvig,2003; Schauer,2000; Schauer,1996; Zheng,2002). Examples of molecular markers for biomass smoke include levoglucosan and methoxyphenols (Fine,2001; Fine, 2002; Hawthorne,1992). Examples of molecular markers for vehicle exhaust include polycyclic aromatic hydrocarbons, hopanes and steranes (Fraser,2003; Schauer,1999; Schauer,1996), and specific nitro-arenes (e.g. 1-nitropyrene) (Hayakawa,2000). This presentation aims to review the state of the science regarding the use of organic tracers to quantify indoor concentrations of and personal exposures to ambient PM. In particular, I shall focus on PM derived from diesel exhaust and biomass combustion. Woodsmoke tracers: A variety of metrics have been used to assess exposures to biomass smoke including measure-

62 62 International Workshop on Organic Speciation Summary Report 2/2005 ments of PM mass, CO, OC and potassium (Khalil,2003; Larson,1994; Maykut,2003). Several organic tracers have also been used, including methyl chloride, PAHs, levoglucosan and methoxyphenols (Khalil,2003; Larsen,2003; Schauer,2000). Levoglucosan is an anhydro sugar derived from the pyrolysis of the major wood polymer cellulose. Levoglucosan is one of the the most abundant particle bound - organic compounds in woodsmoke (Fine,2001; 2002). It is stable in the environment and has been used extensively to estimate woodsmoke levels in ambient PM samples (Katz, 04; Schauer, 00). Levoglucosan is present in other biomass smoke samples including smoke from tobacco, grasses and rice straw (Sakuma, 80; Simoneit, 98;). However, under conditions in which woodsmoke dominates the biomass smoke contribution to ambient aerosol, levoglucosan can be considered a unique tracer for woodsmoke. In a recent report measurements of levoglucosan in filter samples were used to validate the assignment of the woodsmoke feature in a PMF based source apportionment in indoor, outdoor and personal PM samples (Larson,2004).. However in our Seattle panel study we observed that for several residences, the 24hr average levoglucosan concentrations were higher indoors than outdoors in a number of samples. Levoglucosan is formed during the thermal alteration of starches and sugars (caramelisation), so residential cooking may produce levoglucosan-containing aerosols. Therefore, the possibility exists that indoor sources of levoglucosan exist that would confound its use as a tracer for ambient woodsmoke penetrating indoors. Methoxyphenols are a class of chemicals derived from the pyrolysis of the wood polymer lignin. This class of chemicals span a range of volatilities from relatively volatile (e.g. guaiacol) to exclusively particle-bound (e.g. sinapinaldehyde). These chemicals are relatively abundant in woodsmoke, albeit the most abundant compounds are predominantly in the vapor phase (Hawthorne,1989; Schauer,2001). Smoke from hardwood versus softwood burning can be distinguished by the relative proportions of substituted guaiacols compared to syringols. Diesel tracers: A variety of metrics have been used to measure diesel exhaust particles (DEP) in ambient samples, including measurements of ultrafine particles, elemental carbon (EC) PAHs, hopanes and steranes (Manchester-Neesvig,2003; Schauer,2003; Schauer,1999). Indeed the NIOSH method for assessing diesel exposures prescribes measurement of EC. However, these methods are not specific for DEP, and may be confounded by non-diesel sources. Some PAHs (e.g. BghiP) are enriched in DEP relative to other combustion sources, and ratios of BghiP to other PAHs (e.g. BghiP/iP, BghiP/BaA) have been proposed as markers for DE. Hopanes and steranes are present in engine lubricating oil, which comprises a significant component of the particle mass emitted from both gasoline and diesel vehicles (Manchester-Neesvig,2003; Schauer,1999). EC is enriched in diesel exhaust relative to gasoline exhaust, therefore the abundance of hopanes and steranes relative to EC can be used to differentiate gasoline from diesel emissions (Fine,2004; Manchester-Neesvig,2003). Several nitroarenes are enriched in DEP, and some nitroarene isomers appear to be highly specific markers for DEP. (Hayakawa,2000) 1-nitropyrene (1-NP) is one of the most abundant particle-phase PAHs in DEP, at a concentration of ~10-40 ppm (Bezabeh,2003). Photochemical nitration of pyrene in the atmosphere forms specifically 2 and 4-nitropyrene, and other combus-

63 63 tion sources produce minimal amounts of 1-nitropyrene. Therefore, 1-nitropyrene has been proposed as a unique marker for DEP in ambient PM. Levels of this compound are relatively low in ambient air (1-100 pg/m3) (Bamford,2003; Hayakawa,2000). However, analytical methods based on HPLC with fluorescence or chemiluminescence detection (Hayakawa,2000; Tang,2003), or GC-NICI-MS (Bamford,2003; Bezabeh,2003) have adequate sensitivity to detect 1-NP in low volume ambient samples. Issues with the use of organic sources tracers in indoor and personal samples: Given the success in using organic source tracers to apportion PM in outdoor (ambient samples), it is reasonable to apply the molecular marker approach to source apportionment of indoor and personal PM exposures also. However, the applicability of individual markers as suitable tracer compounds indoors should be carefully considered. Some potential concerns that should be addressed when using organic tracers to quantify indoor concentrations of and personal exposures to ambient PM are discussed below. Tracer fidelity: Compounds that are unique tracers for outdoor sources may be confounded by contributions from additional indoor sources. For example, incense burning may confound the use of woodsmoke tracers to assess penetration of ambient woodsmoke indoors. Gas-particle partitioning: For tracers that are semi-volatile, the particle vapor equilibrium will shift away from the particle phase as one moves indoors, due to elevated temperatures and the presence indoors of surfaces to adsorb vapor-phase chemicals. Particle characteristics: The physical characteristics of the individual particles may be important also. Infiltration efficiencies are highest for the size fraction m, and decline substantially for particles both smaller and larger than this range. Thus, where outdoor sources produce PM with different size distributions, we may expect to observe differential penetration efficiencies for the different sources of PM. We should also be aware that the concentrations of molecular markers which adsorb to particle surfaces will maximize in a different size fraction than PM mass. In a study conducted in Southern California (Fine,2004), Fine et al showed that while >80 % of PM2.5 mass was in the size range µm, ~40 % of hopanes and steranes were adsorbed to particles smaller than 0.18µm. Sensitivity: Typically indoor and personal samples are collected at low volumetric flowrates (2-10 L/minute). Thus, sampled volume and mass collected will be much lower for indoor/personal samples compared to ambient samples, and the analytical detection limits (expresses as ng/m3) will consequently be higher. These considerations may dictate the use of more sensitive analytical methods or more extensive sample extraction/pre-concentration procedures to optimize sensitivity (Simpson,2004). We may also have to accept a higher proportion of data close to the detection limits and missing data, and a concomitant increase in error in the analytical method. Continuous data: With measurements of PM mass it has recently been demonstrated that continuous data has great advantages for calculating ambient PM infiltration to indoor and

64 64 International Workshop on Organic Speciation Summary Report 2/2005 personal samples (Allen,2003). It is also recognized that indoor and personal PM exposures show greater short-term temporal variability that is characteristic of ambient PM. Instrumentation is available that provides continuous data for chemical classes of particle bounds organics (e.g. PAHs). Homeland security concerns are driving rapid technological development of continuous monitoring technology for bioaerosols. As a result, we can look forward to new generation analytical technologies capable of providing continuous data for specific particle bound organic tracers in the near future. Biomarkers: Obtaining accurate measures of personal exposure and, more importantly, absorbed dose, for particulate air pollution is inherently difficult. This is due to the substantial spatial and temporal variation in pollutant levels, coupled with the fact that people constantly move between different microenvironments. Thus, traditional fixed site monitors fail to capture the full variability in exposures experienced by individuals. While active personal monitors are effective in accurately monitoring personal exposures, it is impractical and cost prohibitive to implement active personal monitoring on a large scale. Furthermore, external personal monitors fail to account for substantial differences in ventilation volume, and hence inhaled dose, due to physical exertion. An alternative approach to exposure assessment, which addresses many of the limitations noted above is biomonitoring. Biomonitoring of exposure to particulate air pollution involves measurement of PM-derived chemicals in biological media such as human urine, blood, or hair, and the chemical so monitored is called a biomarker. A suitable biomarker for specific PM sources should possess the following characteristics: 1. It should be uniquely derived from the exposure of interest 2. It should be relatively abundant, such that ambient exposure levels generate sufficiently high biomarker levels to be measured reproducibly. 3. The parent marker should be chemically stable in the environment, and the compound (or its metabolites) should be chemically stable in biological samples. 4. The excretion kinetics in the media of interest (e.g. urine, blood etc) should be suited to the exposures and/or health endpoints of interest. Biomarker for woodsmoke exposures: Three classess of chemicals have been proposed as biomarkers for woodsmoke, PAH metabolites, levoglucosan and methoxyphenols (Dills,2001; Dorland,1986; Feunekes,1997; Rothman,1993). Feunekes et al. measured 1-hydroxypyrene in urine from firefighters (Feunekes,1997). They reported a positive association between urinary 1-hydroxypyrene and smoke exposure. In contrast, Rothman et al reported no association between PAH-DNA adducts in peripheral blood from wildland firefighters, and smoke exposures (Rothman,1993). PAHs are by no means specific to woodsmoke; they are a component of incomplete combustion and are present in a variety of PM sources including vehicle exhaust, gas and coal combustion and cooking fumes (Rogge, 91; 93;

65 65 Schauer, 99). Furthermore, for non-occupationally exposed non-smokers, the major portion of PAH exposure is through the diet (Chuang, 99; Vyskocil, 00). Therefore, PAH biomarkers in urine or blood are only likely to be associated with woodsmoke when woodsmoke exposures are very high, for example in occupationally exposed wildland firefighters. There is one report describing measurement of levoglucosan in human urine (Dorland,1986). Dorland et al used an approach combining TLC and GC/MS, and reported 0 to 0.8 mg levoglucosan per ml of urine. This finding should be replicated using modern techniques combining high resolution chromatography and mass spectrometry as the analytical methods used in the original study have limited specificity. The upper range of the urinary levoglucosan levels reported by Dorland et al are higher than would be achieved from inhalational exposure to woodsmoke at ambient levels, and the possibility exists of a substantial dietary contribution of levoglucosan from caramelized sugars (Ratsimba, 1999). Our group has described the use of methoxyphenols as potential biomarkers of woodsmoke exposure (Dills,2001). We have developed sensitive and specific methods based on GC/MS analysis for determination of approximately 12 methoxyphenols in human urine. A suite of isotopically labeled methoxyphenools are used to monitor analyte recovery in every sample. Multiple methoxyphenols are present in the urine of individuals with no known elevated exposure to woodsmoke, and a substantial increase in urinary methoxyphenol excretion was reported subsequent to inhalation of woodsmoke from a campfire (Dills,2001). It was also noted that ingestion of food items containing woodsmoke flavoring (e.g. smoked salmon) caused a substantial increase in urinary methoxyphenol excretion (Dills,2001). The utility of methoxyphenols as a biomarker for woodsmoke xposure at ambient levels was evaluated in a panel study in Seattle WA. Mutiple methoxyphenols were detected in all urine samples, and a dynamic range up to 1000-fold between lowest and highest reported concentrations was observed. Biomarkers for diesel exposures: Several biomarkers for diesel exhaust have been proposed, including various PAH and nitro- PAH metabolites in urine samples (short term exposure markers) or as adducts to DNA or blood proteins (longer term exposure biomarkers (Kuusimaki,2003; Scheepers,2002; Seidel,2002; van Bekkum,1997). PAH metabolite levels in urine samples have shown an association with DE exposure in some occupational settings, (Kuusimaki,2003) however, as noted above, PAHs are not source specific tracers. Thus, for exposure to ambient levels of DE, and where substantial not DE sources of PAHs are present, urinary PAH metabolites are not likely to be useful biomarkers for DE exposure. In contrast, several nitro-arenes are unique to (or at least greatly enriched in) DE, and their urinary metabolites hold promise as sensitive and specific biomarkers of DE exposure. Urinary metabolites of 1-nitropyrene and 3-nitrobenzanthrone have been reported in subjects with known occupational exposure to DE. (Seidel,2002) Unfortunately, in these studies concurrent personal PM samples were not collected so dose-response information for the nitro- PAH metabolites in human urine is not yet available. Future work with these biomarkers should involve establishing dose-response and timecourse of urinary excretion, adapting analytical methodology to permit the sensitive and specific determination of these markers in urine from non-occupationally exposed individuals, and established baseline urinary levels and variance in

66 66 International Workshop on Organic Speciation Summary Report 2/2005 individual exposed to ambient DE. Discussion items from workshop session 1. Are we measuring the right organic chemicals in air particulate? Many hundreds of organic chemicals are present in air particulate, only a small fraction of which are routinely measured. In the aerosol science field, the selection of which compounds to measure has been driven by ease of chemical analysis, regulations (criteria pollutants and hazardous air pollutants) and, more recently, compounds which aid source apportionment or provide insight into aerosol chemistry. In contrast, researchers outside the arena of aerosol science may focus on different chemicals. For example, a substantial body of environmental chemistry literature is devoted to measurements of organochlorine compounds and other pesticides in aerosol samples. Given the focus of the EPA aerosol research agenda on human health, an argument could be made that chemical analysis of aerosol samples should focus more explicitly on toxicologically important chemicals. In summary, workshop participants were encouraged to think broadly when selecting which organic chemicals to focus attention on when characterizing aerosol samples, and to be aware of the complimentary activities being conducted by reserachers outside the mainstream of aerosol science. 2. What novel analytical approaches might provide useful data for exposure assessment purposes? The vast majority of organic chemical measurements used in assessing exposures to ambient aerosol rely on chromatographic analysis of integrated samples collected on filter media. In contrast, less attention has been paid to development and utilization of portable real-time instrumentation that monitos specific chemicals or chemical properties. Given the importance of microenvironmental exposures and short-term variations in PM exposures, continuous and semi-continuous exposure metrics have great potential to improve our ability to provide accurate estimations of personal exposures. Advances in materials science nano-technology and biotechnology are facilitating the development of a range of portable analytical instrumentation based on a variety of spectroscopies (e.g. fluorescence, infrared, raman, etc) or immunological sensors. When coupled with GPS/GIS and telemetry, time, response and location information can be relayed to a central laboratory, reducing many of the logistical burdens in traditional field study. At present much of this technology is under development with military or homeland security applications in mind, however these devices offer tremendous possibilities in the arena of exposure assessment. References Allen, R., et al. Use of real-time light scattering data to estimate the contribution of infiltrated and indoorgenerated particles to indoor air; Environ Sci Technol (16), p Bamford, H.A. and J.E. Baker. Nitro-polycyclic aromatic hydrocarbon concentrations and sources in urban and suburban atmospheres of the Mid-Atlantic region; Atmospheric Environment (15), p

67 67 Bezabeh, D.Z., et al. Determination of nitrated polycyclic aromatic hydrocarbons in diesel particulate-related standard reference materials by using gas chromatography/mass spectrometry with negative ion chemical ionization; Analytical and Bioanalytical Chemistry (3), p Chuang, J.C., et al. Polycyclic aromatic hydrocarbon exposures of children in low-income families; J Expo Anal Environ Epidemiol (2), p Cui, W.; Machir, J.; Lewis, L.; Eatough, N.L.; Eatough, D.J. Fine particulate organic material at Meadview during the Project MOHAVE Summer Intensive Study, JAWMA 1997, 47, Dills, R.L., X. Zhu, and D.A. Kalman. Measurement of urinary methoxyphenols and their use for biological monitoring of wood smoke exposure; Environ Res (2), p Dorland, L., et al. 1,6-Anhydro-beta-D-glucopyranose (beta-glucosan), a constituent of human urine; Clin Chim Acta (1), p Eatough, D.J.; Tang, H.; Cui, W.; Machir, J., Determination of the size distribution and chemical composition of fine particulate semi-volatile organic material in urban environments using diffusion denuder technology, Inhal. Toxicol., 1995, 7, Eatough, D.J.; Wadsworth, A.; Eatough, D.A.; Crawford, J.W.; Hansen, L.D.; Lewis, E.A., A multiple-system, multichannel diffusion denuder sampler for the determination of fine-particulate organic material in the atmosphere, Atmos. Environ. 1993, 27A, Feunekes, F.D., et al. Uptake of polycyclic aromatic hydrocarbons among trainers in a fire-fighting training facility; Am Ind Hyg Assoc J (1), p Fine, P.M., G.R. Cass, and B.R. Simoneit. Chemical characterization of fine particle emissions from fireplace combustion of woods grown in the northeastern United States; Environ Sci Technol (13), p Fine, P.M., G.R. Cass, and B.R. Simoneit. Chemical characterzation of fine particle emissions from the fireplace combustion of woods grown in the Southern United States; Environ Sci Technol (7), p Fine, P.M., et al. Diurnal variations of individual organic compound constituents of ultrafine and accumulation mode particulate matter in the Los Angeles Basin; Environ Sci Technol (5), p Fitz, D.R, Reduction of the positive organic artifact on quartz filters, Aerosol. Sci. Technol. 1990, 12, Fraser, M.P., et al. Separation of fine particulate matter emitted from gasoline and diesel vehicles using chemical mass balancing techniques; Environ Sci Technol (17), p Gundel, L. A., and Lane, D. A., Direct Determination of Semi-Volatile Organic Compounds with Sorbent- Coated Diffusion Denuders, J. Aerosol Sci., 1998, 29: Suppl 1, s341 s342. Gundel, L.A. and Lane, D.A., Sorbent-coated diffusion denuders for direct measurement of gas/particle partitioning by semi-volatile organic compounds, 1999, in Advances in Environmental, Industrial and Process Control Technologies, Vol. 2, Gas and Particle Partition Measurements of Atmospheric Organic Compounds, D.A. Lane, ed. (Newark, Gordon and Breach) p Hawthorne, S.B., et al. Collection and quantiation of methoxylated phenol tracers for atmospheric pollution from residential wood stoves; Environ Sci Technol (4), p Hawthorne, S.B., et al. PM-10 high-volume collection and quantitation of semi- and nonvolatile phenols, methoxylated phenols, alkanes, and polycyclic aromatic hydrocarbons from winter urban air and their relationship to wood smoke emissions; Environ. Sci. Technol (11), p Hayakawa, K. Chromatographic methods for carcinogenic/mutagenic nitropolycyclic aromatic hydrocarbons; Biomed. Chromatogr (6), p Hopke P, Ramadan Z, Paatero P, Norris G, Landis MS, Williams R, Lewis C. Receptor modeling of ambient and personal exposure samples: 1998 Baltmore Particulate Matter Epidemiology-Exposure STudy.

68 68 International Workshop on Organic Speciation Summary Report 2/2005 Atmospheric Environment 37: (2003). John W.; Wall S. M.; and Ondo J. L. A new method for nitric acid and nitrate aerosol measurement using the dichotomous sampler, Atmos. Environ. 1988, 22, Katz, B., et al. Estimating the contribution of woodsmoke to PM2.5 at an urban IMPROVE site in Seattle, WA; in prep Khalil, M.A.K. and R.A. Rasmussen. Tracers of wood smoke; Atmospheric Environment (9-10), p Kim, B.; Cassmassi, J.; Hogo, H; and Zeldin, M. D. Positive Organic Carbon Artifacts on Filter Medium During PM2.5 Sampling in the South Coast Air Basin Aerosol Sci. & Tech. 2001, 34, Klepeis, N.E., et al. The National Human Activity Patter Survey (NHAPS): a resource for assessing exposure to environmental pollutants; J. Exposure Anal. Environ. Epidemiol , p Klepeis, N.E., A.M. Tsang, and J.V. Behar, Analysis of the National Human Activity Pattern Survey (NHAPS) respondents from a standpoint of exposure assessment. 1996, Report # EPA/600/R-96/074 to U.S. EPA. Koutrakis P, Briggs S, Leaderer B. Source apportionment of indoor aerosols in Suffolk and Onondaga Counties, New York. Environmental Science & Technology 26: (1992). Kuusimaki, L., et al. Urinary hydroxy-metabolites of naphthalene, phenanthrene and pyrene as markers of exposure to diesel exhaust; Int Arch Occup Environ Health (1), p Larsen, R.K., 3rd and J.E. Baker. Source apportionment of polycyclic aromatic hydrocarbons in the urban atmosphere: a comparison of three methods; Environ Sci Technol (9), p Larson T, Gould T, Simpson C, Claiborn C, Lewtas J, Liu L-J S. Source apportionment of indoor, outdoor and personal PM2.5 in Seattle, WA using positive matrix factorization. J Air Waste Manage Assoc: in press (2004). Larson, T.V. and J.Q. Koenig. Wood smoke: emissions and noncancer respiratory effects; Annu Rev Public Health , p Long CM, Suh H, Koutrakis P. Characterization of indoor particle sources using continuous mass and size monitors. J Air Waste Manage Assoc 50: (2000). McDow, S.R.; and Huntzicker, J.J. Vapor adsorption artifact in the sampling of organic aerosol: Face velocity effects, Atmos. Environ, 1990, 24(A), Manchester-Neesvig, J.B., J.J. Schauer, and G.R. Cass. The distribution of particle-phase organic compounds in the atmosphere and their use for source apportionment during the Southern California Children s Health Study; J. Air Waste Manage. Assoc (9), p Maykut, N.N., et al. Source apportionment of PM2.5 at an urban IMPROVE site in Seattle, Washington; Environ Sci Technol (22), p Pang, Y., L.A. Gundel, T. Larson, D. Finn, L.-J.S. Liu, and C.S. Claiborn, Development and evaluation of a novel personal particulate organic and mass sampler (PPOMS), Environmental Science and Technology 2002, 36 ( ). Ratsimba, V., et al. Qualitative and quantitative evaluation of mono- and disaccharides in D-fructose, D-glucose and surcose caramels by gas-liquid chromatography-mass spectrometry: Di-D-fructose dianhydrides as tracers of caramel authenticity; J. Chrom. A , p Rogge, W.F., et al. Sources of fine organic aerosol. 1. Charbroilers and meat cooking operations; Environ. Sci. Techno (6), p Rogge, W.F., et al. Sources of fine organic aerosol. 5. Natural gas home appliances; Environ. Sci. Technol (13), p Rothman, N., et al. Contribution of occupation and diet to white blood cell polycyclic aromatic hydrocarbon-dna adducts in wildland firefighters; Cancer Epidemiol. Biomarkers Prev (4), p

69 69 Sakuma, H. and T. Ohsumi. Studies on cigarette smoke. Part VIII. Particulate phase of cigarette smoke; Agric. Biol. Chem (3), p Samet, J.M., et al. The National Morbidity, Mortality, and Air Pollution Study. Part II: Morbidity and mortality from air pollution in the United States; Res Rep Health Eff Inst (Pt 2), p Schauer, J.J. Evaluation of elemental carbon as a marker for diesel particulate matter; J Expo. Anal. Environ. Epidemiol (6), p Schauer, J.J. and G.R. Cass. Source Appointment of Wintertime Gas-Phase and Particle-Phase Air Pollutants Using Organic Compounds as Tracers; Environ. Sci. Technol (9), p Schauer, J.J., et al. Measurement of emissions from air pollution sources. 3. C1-C29 organic compounds from fireplace combustion of wood; Environ. Sci. Technol (9), p Schauer, J.J., et al. Measurement of Emissions from Air Pollution Sources. 2. C1 through C30 Organic Compounds from Medium Duty Diesel Trucks; Environ. Sci. Technol (10), p Schauer, J.J., et al. Source apportionment of airborne particulate matter using organic compounds as tracers; Atmos. Environ (22), p Scheepers, P.T., et al. BIOMarkers for occupational diesel exhaust exposure monitoring (BIOMODEM)--a study in underground mining; Toxicol Lett (1-3), p Seidel, A., et al. Biomonitoring of polycyclic aromatic compounds in the urine of mining workers occupationally exposed to diesel exhaust; Int J Hyg Environ Health (5-6), p Simoneit, B.R.T., et al. Levoglucosan, a tracer for cellulose in biomass burning and atmospheric particles; Atmos. Environ (2), p Simpson, C.D., et al. Determination of levoglucosan in atmospheric fine particulate matter; J. Air Waste Manage. Assoc , p Tang, N., et al. Improvement of an automatic HPLC system for nitropolycyclic aromatic hydrocarbons: Removal of an interfering peak and increase in the number of analytes; Analytical Sciences (2), p Turpin, B.J.; Huntzicker, J.J.; Hering, S.V. Investigation of organic aerosol sampling artifacts in the Los Angeles Basin, Atmos. Environ. 1994, 28, Turpin BJ. et al. Functional group characterization of indoor, outdoor, adn personal PM2.5: results from RIOPA. Indoro Air, Submitted (2003). USEPA, Air Quality Criteria for Particulate Matter. 2001, Environmental Protection Agency: Washington, DC. US EPA. Air Quality Criteria for Particulate Matter. Washington, D.C.:United States Environmental Protection Agency Office of Research and Development, van Bekkum, Y.M., et al. Determination of hemoglobin adducts following oral administration of 1-nitropyrene to rats using gas chromatography-tandem mass spectrometry; J. Chrom. B (1), p Vyskocil, A., et al. Assessment of multipathway exposure of small children to PAH; Environ. Toxicol. Pharmacol (2), p Yakovleva E, Hopke P, Wallace L. Positive Matrix Factorization in Determining Sources of Particles Measured in EPA s Particle TEAM Study. Environmental Science & Technology 33: (1999). Zheng, M., et al. Source Apportionment of PM2.5 in the Southeastern United States Using Solvent-Extractable Organic Compounds as Tracers; Environ. Sci. Technol (11), p

70 70 International Workshop on Organic Speciation Summary Report 2/2005 8) Organic Aerosol Analysis Using Thermal Desorption Aerosol Mass Spectrometry Topic Leader: Contributors: Reinhard Niessner, Technical University of Munich Kimberly A. Prather, University of California, San Diego Paul J. Ziemann, University of California, Riverside Markus Kalberer, ETH Zurich Thorsten Hoffmann, University of Mainz New Advances in Organic Characterization and Quantification Applicable to Organic Aerosols Reinhard Niessner Organic aerosols are more and more in the focus of aerosol analysts. The simple reason for it is the inorganic part of the ambient aerosol can be measured easily with existing techniques (sampling & analysis). This is due to the thermo-dynamical stability of most inorganic compounds. Many measurement campaigns yielded a percentage between % for Total Organic Carbon (TOC) without knowing in detail the individual composition. Within the last 20 years, also, the problem of artefact formation became evident; e.g., interaction of organic trace compounds like PAH with reactive trace gases (ozone, nitrogen dioxide) during the enrichment step. Many attempts are reported to avoid this by means like denuder tubes or application of protective group reactions. There is general agreement within the community that in situ and on-line analysis would be the optimum strategy for observing labile compounds. A second obstacle with organic trace compounds is the enormous variety given. Not only do many isomers exist, even different modifications of the main element, carbon, causes enormous difficulties. Additionally, nature produces biogenic compounds of considerable complexity, like debris from living materials (organisms, plants etc.) or the microorganism itself. From the toxicological point of view it became also evident, that a non-negligible health risk is often connected with the presence of organic aerosols.

71 71 A good example is soot aerosol characterization in Europe. Not only the suspected health impact, but also the importance of light-absorbing particles within the surrounding light-scattering tropospheric and stratospheric aerosol (related to the radiation budget) stimulates the need for reliable means to analyse its mass fraction within the ambient aerosol. Selected was a thermal technique (combustion at 650 o C under oxygen flow, with a previous extraction/desorption of adsorbed organic substances). This technique (VDI Guideline 2465, Part 1) was adapted from the occupational hygiene people, since the Air Quality Criteria at that time were already officially published without knowing the appropriate measurement technique. The Institute of Hydrochemistry at Technical University of Munich (Prof. Niessner) got the task from the German EPA to evaluate this so-called coulometric technique (the evolved CO 2 is measured coulometrically) for its intended use as soot measurement technique. Beside the coulometric approach, the applicability of the British Black Smoke technique (determination of light reflection), the US light transmission technique, and the aerosol photoemission became thoroughly tested. Different locations in Germany, partly heavily impacted by traffic, as well as rural sampling sites, were characterized for three years in parallel using the different techniques. The outcome was critically assessed by the VDI panel, published 1995 (A. Petzold and R. Niessner; Mikrochimica Acta 117, ) Two competing methods, light reflection and light transmission, exhibited serious drawbacks: a) site dependency of calibration (transmission); and, b) large data scattering at low concentrations (< 5 µg elemental carbon (EC)/m 3 ), in case of the Black Smoke Method (reflection). Aerosol photoemission, originally developed for on-line PAH monitoring (e.g., R. Niessner; J. Aerosol Science 17 (1986) ), showed a tremendous sensitivity to changing humidity and source distance. Since a mass related signal was needed, the finding of water influencing the surface related aerosol photoemission was not surprising. Aerosol particles, either covered by non-photoemissive water molecules, or possessing a varying PAH profile on the particle surface, can t be expected to show a constant response. This was validated in independent studies (e.g. R. Niessner et al.; Analytical Chemistry 62 (1990) ). Within the following years the chosen thermal VDI technique came under heavy discussions. Many other groups, mainly from Austria, France and US, started Round Robin tests with aerosol samples from different locations. They compared the thermo-optical technique, a combination of transmission measurement and combustion, with combustion & CO 2 detection, reflectometry, and transmission measurement without combustion. Tested were several extraction procedures, too, before combustion. It became obvious, that non-elemental carbon (cell wall debris, pollen, proteins, cellulose, lignin etc.) contributes substantially to the EC determination, when samples from less polluted sites are analysed. An additional bottle-neck was the tedious extraction and combustion procedure limiting the daily throughput to about 20 filter samples per day. So the aerosol community started again searching for more reliable methods. From 1997 until now, various techniques show a renaissance : a) reflection under various observation angles and light wavelengths, b) photoacoustic spectroscopy; and c) Raman spectroscopy. It was Petzold et al. (Atmos. Environ. 31 (1997) ), who started the systematic search for using transmission and/or reflection measurement as a cheap and reliable technique for EC determination. It soon became clear, that the aerosol deposition within the filter matrix and

72 72 International Workshop on Organic Speciation Summary Report 2/2005 angle and wavelength depending particle/light interaction have a tremendous effect on the signal strength. The current status is best described by the recent German Patent DE B3 from the year 2004 (A. Petzold & M. Schoenlinner). They use an arrangement of photo-diodes operated at observation angles of 0 o, o, and o, cancelling out most of the size effects from particles and filter fibers. A commercialized system (Thermo Eberline ESM, Erlangen, Germany) is available in the meantime. Several comparison tests of the VDI method 2465 with the Eberline technique are reported as successful. The measurement uses a moving filter tape, recording and storing time-resolved aerosol deposits for further investigations. Photoacoustic spectroscopy (PAS) applied to soot samples has its origin in the US and dates back to the 70ties. Several attempts with laser irradiation (at a wavelength of about 480 nm) were published very early. The main advantage of PAS is the linear relationship between light intensity and the observed pressure signal as a consequence of modulated light absorption by black carbon. Secondly, by definition and experiment, no contribution of light scattering to the signal formation will be observed. After some years experience with Ar-ion lasers as light source, PAS analysis of soot aerosol became no longer prosecuted. The reason was the strong interference by NO 2 and H 2 O as trace gases in the soot aerosol. A lot of attempts were made by diffusion denuders or parallel arranged PAS cells with and without particles under illumination to avoid this interferences. A second difficulty was the shift of the resonance frequency observed with strong laser beams. Furthermore usage of chopper wheels inhibited any chance to correct this effect. With the advent of robust tuneable diode lasers in the mid of the 90ties the situation improved a lot. Petzold & Niessner (Applied Spectroscopy 66 (1995) ) were the first who used diode lasers at a wavelength of around 800 nm. The influence of NO 2 and water vapour became negligible. Presently, this technique is successfully used for fast monitoring of Diesel soot emission. Detection limits are in the lower µg-range for black carbon (H. Beck et al.; Analytical and Bioanalytical Chemistry 375 (2003) ) at a time resolution of 1 sec. A similar arrangement became successfully demonstrated for ambient air monitoring (L. Krämer et al.; Analytical Sciences S 175 (2001) s563 s566). Time resolution was set to 5 min, and a detection limit of 0.5 µg Black Carbon per m 3 was achieved. So far, determination of soot aerosol is of some arbitrariness. If only black properties are requested, the optothermal approach (e.g. PAS) seems to offer highest performance. On the other hand, it is quite clear, that any particulate material offering a measurable light absorption at the selected wavelengths, e.g. dark minerals or wood residues, will contribute to some extend to the detection signal. This limitation has led the community very early to the use of Raman spectroscopy for carbon species identification. The Raman effect gives access to the chemical and physical structure of carbon particles. T. Novakov et al. (1976) were the first reporting about the use of Raman spectroscopy for carbon identification. Unfortunately the Raman absorption cross section is rather low. Strong laser sources are therefore a must. Strong PAH fluorescence and light scattering in general avoided a breakthrough of the technique up to now. The new notch filter technology, paired with strong laser sources in the NIR opened within the last years first promising opportunities. By means of Raman spectroscopy a clear identification of graphitic or distorted carbon within the particle carbon lattice is possible. Twinned mineral phases within a particle conglom-

73 73 erate can be identified and quantified. First characterization experiments with NIST Diesel soot standard 1650 shows the direction where to go to (A. Sadezky et al. (2004) Raman Spectra of Soot : Spectral Analysis and Structural Information. Submitted to PCCP). Knowing the intrinsic structure of soot (degree of graphitization) gives also new possibilities for source apportionment. Latest results from Diesel engine developments in Europe indicate a change of the crystalline carbon structure along the course to initiate fast oxidation within exhaust after-treatment means. Distorted graphite structures show an oxidation under air at temperatures below 200 o C (A. Messerer et al. (2004) Topics in Catalysis 30/31, ; D. Su et al. (2004) Microstructure and Oxidation Behaviour of EURO IV Diesel Engine Soot : A Comparative Study with Synthetic Model Soot Substances. Catalysis Today, in press). This explains at least in part the observed failure of thermal and/or thermo-optical techniques for soot determination. Spectroscopical techniques, especially when laser light is used, possess an intrinsic high potential to serve as in situ and on-line analysis technique : they operate with (hopefully nonreactive) light, the light beam can be directed to the location of the problem, and the appropriate spectroscopical method has many degrees of freedom, which means a certain selectivity can be expected. Up to now, some laser-based techniques have been applied to organic aerosols : fluorescence for PAH detection, photoacoustic spectroscopy for soot, laser photofragmentation for N-, P- or S-species, and aerosol photoemission for PAH detection, too. In all cases, interferences by interaction of the analyte molecule with the particle core is seen. Only in rare cases, e.g. when desorption of the analytes is possible without destruction, the direct and undisturbed observation within the gaseous state is possible, e.g. PAHs (U. Panne et al. (2000) Fresenius Journal of Analytical Chemistry 366, 408). In general, the solid state yields less distinct, broad and often featureless spectra. Raman spectroscopy, so far applied on suspended single particles, is not sensitive enough. Fortification of the signal by the stimulated Raman effect is only possible after contacting an appropriate substrate. Photoacoustic spectroscopy offers a strong potential, but its sensitivity is limited by using favourable absorption bands in the optical spectrum. Similarly suited is Cavity Ring-down Spectroscopy (J. Thompson et al. (2003) Analytical Chemistry 74, ) offering detection limits (expressed as extinction coefficient) down to 10-9 cm -1. A different issue is the determination of analytes with a molecular weight > 1 kdalton. Presently only wet chemical group analyses are applicable. To determine biogenic organic compounds in the ng/m 3 range, large volume sampling to get some milligrams aerosol mass is needed. Classical digestion steps, followed by amino acid or sugar analysis are applied. Typical

74 74 International Workshop on Organic Speciation Summary Report 2/2005 separation tools, e.g. polyacrylamid gel electrophoresis, lack sensitivity and sometimes selectivity. Quantification is often impossible due to transfer problems of the separated proteins. Mass spectrometry needs the analyte in the gaseous state, and the change-of-state (solid to gas phase) makes enormous problems, even with ESI-TOF-MS or MALDI techniques. A different approach is the usage of high-affinity targets, like antibodies of molecular imprints. With the need to get rapid information on bioaerosol concentrations in air, the combination of quasi-continuous sampling (e.g. wetted wall cyclone) connected with rapid bioanalytical identification of the sampled material was developed. Not only detection of cell wall proteins by antibodies is common in the meantime, also the identification and quantification of difficult (in terms of stability and low concentrations) large organic molecules became feasible. Good examples are the determination of pollen proteins by immunoassays (T. Franze et al. (2003) Analyst 128, ). Within 30 min the complete analysis in the pg/m 3 range is done. Prerequisite is a clear strategy about what has to be analysed. Also the respective antibody must be available. Once this is fulfilled, very cost-efficient, fast and reliable analysis is possible. Upcoming chip technologies with multiple recognition targets in a high-parallel arrangement, combined with a fast read-out technique, allow rapid determination of many analytes within several minutes (e.g. A. Knecht et al. (2004) Analytical Chemistry 76, ). Very interesting applications are recently presented by D. Blake et al. (2003) Biochemistry 42, 497. They developed antibodies directed towards organometal species (e.g. Cd complexes). Currently the analytical community is developing artificial antibodies, so-called molecular imprints, for enhancing the performance of protein separation. The aerosol scientists will certainly make use of these developments within some years. Conclusions : From my point of view I see the following trend and needs : Analytes of molecular weight > 1 kdalton will become more important, to fill the gap within aerosol mass balance. Biogenic material is extremely complex. Detection and quantification is possible with typical bioanalytical techniques (immunoassay, polymerase chain reaction etc.). Combination with continuous sampling (wetted wall cyclone) is advantageous. Laser spectroscopy seem suited well, but compromises on selectivity have to be made as long as in situ observation is demanded. Also lack of strong photon-absorbing chromophor groups prevents successful use of spectroscopy. Polymorphism (e.g. elemental carbon in its different modifications) is a problem. Discrimination of internally mixed substances and the three-dimensional analysis of individual particles remains a strong challenge for future.

75 75 On-line analysis of organic species using single particle mass spectrometry Kim Prather Single particle mass spectrometry provides a rapid and unique picture of the particle mixing state of atmospheric particles, showing associations between sulfates, nitrates, and other secondary species with dust, sea salt, elemental carbon, and organic carbon particles. With many of these instruments, size-resolved composition can be obtained on individual particles(sipin, Guazzotti et al. 2003). Thousands of particles can be rapidly analyzed, providing temporal information on timescales as short as 10 minutes. The single particle mass spectral patterns show clear distinctions between elemental and organic carbon. The associations of chemical species within individual particles can be used in a number of ways including performing source apportionment, understanding health impacts of particles, and detailing the radiative properties of aerosols(bhave, Fergenson et al. 2001; Guazzotti, Suess et al. 2003). Using more efficient sample introduction methods, high efficiency single particle instruments have been developed which measure size-resolved composition of particles in the fine and ultrafine size modes(liu, Ziemann et al. 1995; Rhoads, Phares et al. 2003; Su, Sipin et al. 2004). Fragmentation which commonly occurs at the typical laser fluences used for the laser desorption/ionization step can often be used to identify the organic species(silva and Prather 2000; Angelino, Suess et al. 2001; Whiteaker and Prather 2003). Separating the desorption and ionization processes into two steps (L2DI) offers great promise as a potentially quantitative tool for organic speciation as the molecules undergo little to no fragmentation(morrical, Fergenson et al. 1998; Woods, Smith et al. 2001). The 2-step approach can even be used to gain insight into species in the core of the particle versus on the surface of the particle(woods, Smith et al. 2002). Recently, single photon ionization has been shown to be a sensitive tool and shows clear distinctions between particles from multiple sources based on organic tracers(oktem, Tolocka et al. 2004). Recent developments in unique ionization schemes such as PERCI by Pettruci et al. show on-line mass spectrometry of single particles can even be used to distinguish between isomeric organic compounds. References Angelino, S., D. T. Suess, et al. (2001). Formation of aerosol particles from reactions of secondary and tertiary alkylamines: Characterization by aerosol time-of-flight mass spectrometry. Environmental Science & Technology 35(15): Bhave, P. V., D. P. Fergenson, et al. (2001). Source apportionment of fine particulate matter by clustering single-particle data: Tests of receptor model accuracy. Environmental Science & Technology 35(10): Guazzotti, S. A., D. T. Suess, et al. (2003). Characterization of carbonaceous aerosols outflow from India

76 76 International Workshop on Organic Speciation Summary Report 2/2005 and Arabia: Biomass/biofuel burning and fossil fuel combustion. Journal of Geophysical Research- Atmospheres 108(D15). Liu, P., P. J. Ziemann, et al. (1995). Generating Particle Beams of Controlled Dimensions and Divergence.2. Experimental Evaluation of Particle Motion in Aerodynamic Lenses and Nozzle Expansions. Aerosol Science and Technology 22(3): Morrical, B. D., D. P. Fergenson, et al. (1998). Coupling two-step laser desorption/ionization with aerosol time-of-flight mass spectrometry for the analysis of individual organic particles. Journal of the American Society for Mass Spectrometry 9(10): Oktem, B., M. P. Tolocka, et al. (2004). On-line analysis of organic components in fine and ultrafine particles by photoionization aerosol mass spectrometry. Analytical Chemistry 76(2): Rhoads, K. P., D. J. Phares, et al. (2003). Size-resolved ultrafine particle composition analysis, 1. Atlanta. Journal of Geophysical Research-Atmospheres 108(D7). Silva, P. J. and K. A. Prather (2000). Interpretation of mass spectra from organic compounds in aerosol time-of-flight mass spectrometry. Analytical Chemistry 72(15): Sipin, M. F., S. A. Guazzotti, et al. (2003). Recent advances and some remaining challenges in analytical chemistry of the atmosphere. Analytical Chemistry 75(12): Su, Y. X., M. F. Sipin, et al. (2004). Development and characterization of an aerosol time-of-flight mass spectrometer with increased detection efficiency. Analytical Chemistry 76(3): Whiteaker, J. R. and K. A. Prather (2003). Hydroxymethanesulfonate as a tracer for fog processing of individual aerosol particles. Atmospheric Environment 37(8): Woods, E., G. D. Smith, et al. (2001). Quantitative detection of aromatic compounds in single aerosol particle mass spectrometry. Analytical Chemistry 73(10): Woods, E., G. D. Smith, et al. (2002). Depth profiling of heterogeneously mixed aerosol particles using single-particle mass spectrometry. Analytical Chemistry 74(7): Organic Aerosol Analysis Using Thermal Desorption Aerosol Mass Spectrometry Paul J. Ziemann A number of methods have been developed that employ various forms of thermal desorption-mass spectrometry for on-line analysis of organic aerosols. The most widely used instrument of this type is the Aerodyne Aerosol Mass Spectrometer (AMS), which is commercially available and can analyze organic particle size and composition in real time (Jayne et al. 2000). In the AMS, particles are focused by an aerodynamic lens into a narrow beam as they enter high vacuum. Particle aerodynamic diameter is determined from the particle velocity measured using a mechanical chopper. Particle chemical composition is determined via flash vaporization followed by electron ionization and quadrupole mass spectrometry. The separation of the particle vaporization and the vapor ionization steps enables quantitative analysis of

77 77 sulfates, nitrates and total organic mass. Although it is not possible to identify individual organic compounds with this method, information on specific source contributions can be obtained through the use of marker ions that are characteristic of particular sources, such as primary organics and secondary (or oxidized) organics. The identification of marker ions is based on time correlations with other measurements (e.g., CO and NOx for primary emissions and O3 and UV light for photochemical processes) and particle size-dependent mass spectra. One advantage of this method compared to the use of molecular tracers is that source apportionment is based on the analysis of the entire organic particle mass rather than a trace component whose relation to total organic mass may be difficult to determine. Future improvements to this method include the addition of an electron ionization time-of-flight mass spectrometer for quantitative analysis of single particles (this has already been demonstrated) and a thermal denuder to obtain information on the volatility of organics and some degree of component separation prior to analysis. An instrument called a thermal desorption particle beam mass spectrometer (TDPBMS) is similar to the AMS, but differs in that it does not use a chopper and, most importantly, the vaporizer can be cooled so that particles can be collected and subsequently analyzed as they desorb under slow heating (Tobias and Ziemann, 1999). This method separates components according to volatility and thus provides composition information as a function of component vapor pressure. When coupled to a particle concentrator (Kim et al. 2001), this instrument can be used for speciated analysis of sulfates, nitrates, and various organic components (primary and oxidized aerosol as well as some single compounds) in fine and ultrafine particles. A method for quantitative, semi-continuous, speciated analysis of organic aerosols has been developed by Hering (Aerosol Dynamics) and Goldstein (UC-Berkeley). This method employs an impactor to collect fine particles on a metal surface, which is subsequently heated to desorb the organic components. The vapor is collected on the front a gas chromatograph-mass spectrometer column for subsequent analysis. The time to collect and analyze one sample is about one hour. This technique provides much more speciated information than the AMS or TDPBMS, but is not a real-time analyzer and requires derivatization methods for the analysis of polar compounds. References Jayne, J.T., D.C. Leard, X. Zhang, P. Davidovits, K.A. Smith, C.E. Kolb, and D.R. Worsnop, Aerosol Sci. Technol. (2000) 33, Tobias, H.J., and P.J. Ziemann, Anal. Chem. (1999) 71, Kim, S., P. Jaques, M. C. Chang, J. R. Froines, and C. Sioutas, J. Aerosol Sci. (2001) 11,

78 78 International Workshop on Organic Speciation Summary Report 2/2005 Laser-Mass Spectrometry of Organic Aerosols Determining Specific Compounds and Bulk Properties Markus Kalberer Besides laser single particle techniques and thermal methods for organic aerosol analysis, new combinations of desorption and ionisation techniques are promising when the analytical focus is on the organic fraction of atmospheric aerosols. Especially when higher molecular weight compounds represent the analytes of interest, soft desorption and ionization techniques are required. Depending on the ionization method, these techniques can be either very compound selective or rather unselective measuring a broad variety of compounds. The following will give examples for these types of Laser-MS. A major problem for many analytical techniques when analysing solid samples is the varying and often unpredictable influence of the sample matrix. In Two-Step Laser Mass Spectrometry (L2MS) such effects are minimized by decoupling desorption and ionization of the analytes with two different lasers. The first laser, typically an IR-laser, is heating up the sample desorbing the analytes from the matrix and/or substrate and the second laser ionizes the compounds of interest in the gas phase where matrix effects are usually much smaller than in the liquid or solid phase. Since the analytes are directly desorbed from the solid aerosol sample no work-up or preparation of the sample is needed minimizing possible artefacts introduced by these processes. Choosing an adequate ionization wavelength especially aromatic compounds can be ionized very softly (e.g., with resonance enhanced multi-photon ionization, REMPI) preventing fragmentation, which greatly simplifies mass spectra interpretation. In addition REMPI is a very efficient ionization process making L2MS a very sensitive method. The technique has been applied for on-line single aerosol analysis (e.g., B. D. Morrical, D. P. Fergenson, and K. A. Prather, J. Am. Soc. Mass Spectrom., 1998, 9, ) and for offline analysis, i.e., aerosols collected on filters or impactor plates (O. P. Haefliger T. Bucheli, R. Zenobi, Environ. Sci. Technol., 2000, 34, ; C. Emmenegger, M. Kalberer, V. Samburova and R. Zenobi, The Analyst, 2004, DOI: /B401201A). One of the biggest disadvantages of L2MS is, that this method cannot distinguish compounds of the same mass. Tuneable ionization lasers offer in principle the opportunity for a highly compound selective analysis, because ionization spectra, similar to adsorption spectra, offer the possibility to distinguish compounds, even isomers. This requires to cool the desorption plume (generated by the desorption laser) in order to access the highly specific ionization spectra. See D. M. Lubman, R. Tembreull, and C. H. Sin (Anal. Chem. 1985, 57, ) for an example where this was achieved by means of a molecular beam and O. P. Haefliger and R. Zenobi (Anal. Chem., 1998, 70, ) showing that without cooling such compound specific ionization is almost impossible due to the broad bands of the ionization spectra in the hot desorption plume. Another disadvantage of laser-ms techniques is, that they are often not quantitative or only semi-quantitative. Recently M. Kalberer, B. D. Morrical, M. Sax and R. Zenobi (Anal. Chem., 2002, 74, ) presented for the first time a quantitative method for L2MS by adding an internal standard with an electrospray method on the aerosol sample

79 79 achieving limits of detection in the low picogram range, which is orders of magnitudes below conventional methods such as gas chromatography mass spectrometry. This high sensitivity can be used to perform ambient measurements with a high time resolution (C. Emmenegger, M. Kalberer, V. Samburova and R. Zenobi, The Analyst, 2004, DOI: /B401201A). Despite the somewhat complex experimental set-up of an L2MS instrument, this highly sensitive method has a large potential in aerosol analysis due to the minimal sample preparation necessary and due to the minimized matrix effects. Especially when taking advantage of the highly compound specific ionization spectra, L2MS could become a very powerful and much more widely used technique than nowadays. Other laser ionisation MS techniques, e.g., laser desorption/ionization (LDI) or matrix assisted laser desorption/ionization (MALDI), are less specific ionisation methods. This apparent disadvantage, however, allows analyzing the particle bulk, because a wide range of compound classes is ionized. LDI and MALDI-MS techniques require almost no sample preparation minimizing artefacts due to sample work-up, such as a transfer into a liquid solvent. Another advantage of MALDI-MS is the soft ionization process minimizing fragmentation of the analytes and thus the possibility to measure large molecules. This technique seems promising to investigate high molecular weight compounds as recently found in organic aerosols from laboratory and field experiments (Zappoli et al., Tolocka et al., Kalberer et al.). Future more detailed analysis of these recently detected polymeric aerosol components should include exact mass determination with methods such as Fourier Transform Ion Cyclotron Resonance (FTICR) - MS or elucidation of their chemical structure with MSn. Both methods can be coupled with MALDI ionization techniques. Another possibility to get information especially on the organic aerosol fraction is the combination of laser desorption techniques with other, non-laser based ionization techniques. A recently reported method comprises of an infrared (IR) laser pulse to desorb analyte species, followed by atmospheric pressure chemical ionization (APCI) with a corona discharge (LD-APCI) to effect ionization of the desorbed neutral analyte molecules (Coon et al.). Due to their MS/MS capabilities, especially ion traps appear to be appropriate mass analyzers for this purpose. The suitability of APCI as an ionization technique, in particular for the characterisation of secondary organic aerosol components, has already been demonstrated (Kueckelmann et al., Warscheid et al.). However, up to now the combination of IR-laser desorption and chemical ionisation techniques was only realized for off-line analysis of organic compounds, i.e. the analytes were deposited on target surfaces. In the future, it has to be shown that the concept also works for real-time analysis of organic aerosols.

80 80 International Workshop on Organic Speciation Summary Report 2/2005 Special Discussion: The Importance of Carbonaceous Aerosol in Air Quality Planning: Bridging the Gap between Researchand Application Topic Leaders: Dr. Tom Moore, Western Regional Air Partnership Dr. Brooke Hemming, National Center for Environmental Assessment, EPA Editor s Note: This is an updated version of the presentation of Tom Moore and Brooke Hemming on Wednesday April 7, Maps have been updated and text edited to reflect more precisely concerns and recommendations. Assistance was received from Tim Richard (writer/editor), John Watson, Judith Chow, Lee Alter, Douglas Fox, Ernie Wessman, and Eric Dieterle. Fine particles (PM 2.5 ) that contain carbonaceous aerosol material, a major component of air pollution, are implicated in visibility impairment and health effects, and may also significantly influence the earth s climate. Progress in particulate matter research has been extensively assessed (National Research Council [NRC] 2004; NARSTO 2003; Western Regional Air Partnership [WRAP] 2004), with special attention paid to monitoring and networks, emissions inventories, and atmospheric modeling capabilities. Lately, questions over how carbonaceous aerosol research can help to meet near-term needs for regulatory planning and policy development (e.g., NARSTO ) have stimulated a network of researchers, sponsors and supportive organizations, known as the Atmospheric Particulate Carbon Exchange (APACE), to identify how research processes and results can better inform policy. Three workshops have been held since 2001 during which participants discussed technical and scientific questions related to visibility, health, and climate. Little discussion took place over strengthening connections between scientific research and policy planning despite the intentions of organizers. In fact, it became apparent that little communication has ever developed about the relevance of science to policy and the implications policy has for research directions. Linking what is relevant to science with what is relevant to policy is not a commonly raised issue. This paper discusses the outcomes of the APACE workshops including relevant recent and ongoing technical analyses and then suggests how carbonaceous aerosol research activities might better inform regional haze planning and health standard nonattainment concerns.

81 81 What are the measured contributions of carbonaceous aerosols to haze and ambient PM? The following maps show the importance of carbonaceous aerosol as a major contributor to both PM 2.5 and regional haze. Contributions to regional haze air pollution in the western United States range from 7% to more than 50% of visibility impairment. The maps show effects of both organic and elemental carbon which make up total carbon mass. Organic carbon is formed from reactive organic gas emissions (certain complex chemical compounds) from industrial activity, cars, trucks, forest fires, and biogenic sources, such as trees. Elemental is often referred to as soot or black carbon produced by incomplete combustion of organic gases and particles and emitted from cars, trucks, forest fires and burning waste, and dust/soil from several sources. Measurements are from the IMPROVE network. MAPS 1, 2: average worst-case visibility conditions in the contiguous U.S. due to carbonaceous PM 2.5 aerosol (%) based on IMPROVE network observations (interpolated using the worst 20% average monitored values). Map 1: Organic Carbon Light Extinction Fraction Organic carbon is a very important contributor to visibility impairment in the West

82 82 International Workshop on Organic Speciation Summary Report 2/2005 Map 2: Elemental Carbon Light Extinction Fraction Elemental carbon is a less important contributor to visibility impairment across the nation. MAP 3: 2002 average ambient PM 2.5 composition at sites in rural, wilderness, and national park areas (contiguous U.S.). Total carbon is the sum of organic and elemental carbon as measured by IMPROVE. PM 2.5 Mass Composition at Non-Urban Sites Total carbon is an important contributor to non-urban PM 2.5 mass concentrations, particularly in the West.

83 83 MAP 4: 2002 average ambient PM 2.5 composition at sites in urban areas in the contiguous U.S. as measured by the EPA Speciation Trends Network (STN). Total carbon (no organic-elemental carbon split) is shown for better comparability to IMPROVE data in MAP 3. PM 2.5 Mass Composition at Urban Sites Total carbon is also an important contributor to urban PM 2.5 mass concentrations across the nation. MAPS 5, 6: IMPROVE and EPA STN data have been used to look at organic to elemental carbon ratios. Data suggest that OC/EC rations differ between urban and rural settings, and between eastern and western U.S. Maps 5 & 6 illustrate winter/summer ratio. Presumably this difference in ratios is due to a difference in source mixes. Data from IMPROVE analysis by W. Malm, personal communication. Organic & Elemental Carbon Ratio, Winter 2001