The Regional Atmospheric Chemistry Mechanism, version 2 (RACM2) William R. Stockwell 1,2 and Wendy S. Goliff 2 1 Department of Chemistry, Howard University 2 Division of Atmospheric Sciences, Desert Research Institute
Mechanism Ancestry RADM2 Regional Acid Deposition Mechanism, version 2 (Stockwell et al., 1990): Developed to predict regional atmospheric chemistry and acid rain formation. RACM1 Regional Atmospheric Chemistry Mechanism, version 1 (Stockwell et al., 1997): The aromatic chemistry scheme was improved using available laboratory data. Included reaction schemes for biogenic compounds such as isoprene, limonene and α-pinene.
RACM2 RACM2 is being developed from RACM1. It contains a new schemes for: Acetone Aromatic compounds (based upon Calvert et al. (02)) Isoprene (based upon Geiger et al. (03) and improved by adding methyl vinyl ketone explicitly) α-pinene d-limonene About 1 Chemical Species in 300 Reactions
ISO + HO ISOP ISOP + NO 0.95 HO2 + HCHO + 0.42 MACR + 0.58 MVK + 0.05 ISON + 0.95 NO2 ISOP + HO2 ISHP MCAR ISOP + MO2 1.50 HCHO + 0.50 HO2 + 0.58 MVK + 0.42 MACR ISOP + ACO3 0.50 HO2 + 0.50 MO2 + 0.50 ORA2 + HCHO + 0.42 MACR + 0.58 MVK ISOP + NO3 GEIGER ET AL. 03 Isoprene HO2 + HCHO + 0.42 MACR 0.58 MVK + NO2
α-pinene API + HO APIP APIP + NO 0.82 HO2 + 0.23 HCHO + 0.43 ALD + 0.11 ACT + 0.44 KET + 0.07 ORA1 + 0.18 ONIT + 0.82 NO2 APIP + HO2 APIP + MO2 APIP + ACO3 APIP + NO3 OP2! --- ATKINSON 1994, 03 2 HO2 + HCHO + ALD + KET HO2 + MO2 + ALD + KET HO2 + ALD + KET + NO2
LIM + HO LIMP + NO LIMP + HO2 d-limonene LIMP 0.90 HO2 + 0.03 ACT + 0.25 KET 0.25 MACR + 0. ONIT + 0.90 NO2 OP2 LIMP + MO2 2 HO2 + 0.60 MACR + 0. OLI + 1. HCHO LIMP + ACO3 HO2 + 0.60 MACR + 0. OLI + 0. HCHO + MO2 LIMP + NO3 HO2 + 0. OLI + 0. HCHO + 0.60 MACR + NO2 GILL AND HITES 02; ATKINSON 03
Walker Branch Forest Oak Ridge National Laboratory, Oak Ridge, TN J.D. Fuentes
Thesis Forested ecosystems capable of high rates (> 50 nmoles m -2 s -1 ) of biogenic hydrocarbon emissions, and in the vicinity of modest rates of nitrogen oxide emissions from suburban automobile traffic, can support a unique and active photochemistry. Regional air quality models will likely need to include the in canopy processing of biogenic hydrocarbons, if they intend to accurately represent the photochemical production of pollutants.
Biosphere - Atmospheric Interactions Simulations of Biogenic Emission Measurements Climate Change Light Scattering Carbon Assimilation Air Quality Forecasting Ozone Aerosol Particles Emissions from Canopy Deposition Surface Emissions Emissions In Canopy Chemical Processing
Simulations Based on Oak Ridge Measurement Data for July, 1999 39.8 Sampling Heights (m) 31.5 25.6 17.7 9.4 0.2
Diurnal variations of photosynthetically active radiation (PAR) above and below the forest canopy. 1 s 2 moles mpar in PAR (µmoles m -2 s -1 ) 00 500 0 28 Above canopy Below canopy 4 8 12 16 24 Time (hours) C o
oles mpar in Measured at 36.6 m above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999. 0 Temperature ( C) C o Air temperature in 28 24 4 8 12 16 24 Time in hours
Diurnal variations of ozone mixing ratios measured within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999. Ozone (ppbv) ]i [O b 3 80 60 0.2 m 39.8 m 0 4 8 12 16 24 Time in hours
Diurnal variations of nitrogen oxide mixing ratios measured within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999. 8 39.8 m 0.2 m NO x (ppbv) X ]i [NO b 6 4 2 0 4 8 12 16 24 Time in hours
Averaged vertical variations of (a) ozone, (b) nitrogen oxide, and (c) isoprene mixing ratios within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). The horizontal bars denote one standard deviation from the mean mixing ratios. H i h i 30 0 0 4 8 12 16 [Isoprene] in ppbv 60 80 [O 3 ] in ppbv 0 2 4 6 [NO X ] in ppbv
α-pinene Methyl-vinyl-ketone Methacrolein Isoprene Relative VOC Speciation (by Carbon Number) d-limonene Below Canopy HCHO C3-Alkane C5-Alkane C8-Alkane Methyl-vinyl-ketone Methacrolein Isoprene HCHO HC3 Terminal Alkenes HC5 HC8 d-limonene α-pinene Internal Alkenes OLT Dienes OLI Toluene DIEN Xylene TOL XYL ISO MACR MVK API HCHO LIM Above Canopy C3-Alkane C5-Alkane C8-Alkane Terminal Alkenes Internal Alkenes Dienes Toluene Xylene HCHO Alkane C3 Alkane C5 Alkane C8 Termaina Alkene Internal Alkene Diene Toluene Xylene Isoprene MACR MVK API LIM
Initial Conditions Ozone and NOx Hour 16 35 30 25 15 5 Ozone 0.00 0.0.0.0 60.0 80.0 0.0 60 80 35 30 25 15 (ppb) (ppb) 5 NO x (ppb) 0.00 0.0 2.0 4.0 6.0 0.0 2.0 4.0 6.0 A
Initial Conditions VOC and VOC/NOx Hour 16 35 30 25 15 5 VOC 0.00 0.0 60 0.0.0.0 60.0 80.0 0.0 80 0 35 30 25 15 5 VOC/NO x 0.00 5.0.0 15.0.0 25.0 0.0 5 15 (ppbc) (ppbc/ppb) A
Simulated HO Radical Hour 16 35 30 25 15 Series1 RACM1 RACM2 Series1 5 0.00 0.0E+00 5.0E-05 1.0E-04 1.5E-04 2.0E-04 2.5E-04 0.0 3.0E-04 (ppb)
Simulated NO 3 Radical Hour 16 35 30 25 15 RACM1 Series1 RACM2 Series1 5 0.00 0.0E+00 1.0E-04 2.0E-04 3.0E-04 0.0 4.0E-04 (ppb)
Simulated NO 3 Radical 0% ([RACM2] - [RACM1])/[RACM1] 35 Hour 16 30 25 15 Series1 5 0.0 0-5% 0% 5% % 15% % 0.0 0 5 4.0E-04 (%)
HNO3 Hour 16 35 30 25 15 RACM1 Series1 RACM2 Series1 5 0.0 0 0.0 0.0E+00 1.0E-01 2.0E-01 3.0E-01 4.0E-01 5.0E-01 (ppb) 5.0E-01
HCHO Hour 16 35 30 25 15 RACM1 Series1 Series1 RACM2 5 0.0 0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 (ppb) 6.0
HNO 3 /HCHO Hour 16 35 30 25 15 Series RACM1 RACM2 Series 5 0.00 0.0 0.14 0.00 0.02 0.04 0.06 0.08 0. 0.12 0.14
PAN Hour 16 35 30 25 15 RACM1 Series1 RACM2 Series1 5 0.0 0 0.0E+00 1.0E-01 2.0E-01 3.0E-01 0.0 4.0E-01 (ppb)
H2O2 Hour 16 35 30 25 15 RACM1 Series1 RACM2 Series1 5 0.0 0 0.0 0.0E+00 5.0E-02 1.0E-01 1.5E-01 2.0E-01 (ppb) 2.0E-01
HNO3/H2O2 Hour 16 35 30 25 15 RACM1 Series RACM2 Series 5 0.00 0.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 6.0
Organic Peroxide Hour 16 35 30 25 15 RACM1 Series1 RACM2 Series1 5 0.00 0.0 0.0E+00 1.0E-02 1.0E-01 2.0E-01 2.0E-02 3.0E-01 3.0E-02 4.0E-01 4.0E-02 5.0E-01 5.0E-02 6.0E-01 6.0E-02 (ppb) 6.0E-02
Organic Acids Hour 16 35 30 25 15 RACM1 Series1 RACM2 Series1 5 0.0 0 0.0 0.0 0.1 0.2 0.3 0.4 (ppb) 0.4
Averaged HO X radical production rate modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). The dash line on the y-axis denotes the canopy height. H i ht i 30 Ozone Formaldehyde BVOCs 0 0 1 2 3 4 5 x 6 HO X radicals cm -3 s -1
Averaged vertical variations of nitrate and hydroxyl radicals modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). [NO 3 ] [HO]*0.1 H i ht i 30 0 0.0 0.5 1.0 NO 3 and HO mixing ratio in pptv
Averaged vertical variations of (a) isoprene, (b) a-pinene, and (c) d-limonene loss modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). A B C HO HO NO 3 NO 3 O 3 O 3 HO NO 3 O 3 H i ht i 30 H i ht i 30 H i ht i 30 0 0 1 2 3 Isoprene loss (molec s -1 ) * 7 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 α-pinene loss (molec s -1 ) * 5 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Limonene loss (molec s -1 ) * 5 Figure 9a Figure 9b Figure 9c
Averaged methacrolein and methyl vinyl ketone production rate modeled within and above a mixed deciduous forest canopy at Oak Ridge, TN on July 1999 during 14:00 to 19:00 hours (local time). MACR MVK H i ht i 30 0 0.0 0.5 1.0 1.5 2.0 Ppbv per hour
The Fifteen Worst American Regions for Ozone 1) Los Angeles/Riverside/Orange County, California 2) Fresno, California 3) Bakersfield, California 4) Visalia/Porterville, California 5) Houston/Baytown/Huntsville, Texas 6) Merced, California 7) Sacramento/Arden/Arcade/Truckee, California, Nevada 8) Hanford/Corcoran, California 9) Knoxville/Sevierville/La Follette, Tennessee ) Dallas/Fort Worth Texas 11) Washington/Baltimore/North Virginia, DC., MD., VA. 12) Philadelphia/Wilmington/Atlantic City, PA.,DE.,MD. 13) New York/Newark/Bridgeport, NY., NJ., CN., PA. 14) Charlotte/Gastonia/Salisbury, NC., SC. 15) Cleveland/Akron/Elyria, Ohio The Wall Street Journal, November 17, 04
Beltsville Location
Beltsville
0 90 80 70 60 50 30 0 Air Quality Forecast Evaluation Beltsville Series1 9:00 AM 11:00 AM 1:00 PM 3:00 PM 5:00 PM 7:00 PM 9:00 PM 11:00 PM 1:00 AM 3:00 AM 5:00 AM 7:00 AM Ozone July 18-19, 06 5:00 AM 7:00 AM ppbv
Beltsville Meteorological Tower
Collection Points for VOC Samples
Conclusions - I Simulations of measurements from a forest canopy were made with the RACM1 and RACM2 mechanisms. RACM1 and RACM2 forecast similar HO and NO 3. RACM1 and RACM2 forecast similar relative reaction rates of HO, O 3 and NO 3 with isoprene, α-pinene and d-limonene. The two mechanisms forecast different concentrations of HNO 3, PAN, HCHO, H 2 O 2, organic peroxides and organic acids. Ratios HNO 3 /HCHO and HNO 3 /H 2 O 2 similar.
Conclusions - II Substantial nitrate (NO 3 ) and hydroxyl (HO) radical formation occurred within the forest canopy, with maximum NO 3 and HO levels approaching 1 part per trillion on a volume basis (pptv) and 0.05 pptv, respectively. These NO 3 and HO levels, combined with within-canopy ozone (O 3 ) molar mixing ratios of 60 parts per billion (ppbv), reacted with biogenic hydrocarbons and produced substantial amounts (0.6 ppbv) of peroxy radicals.
Acknowledgements Dr. Jose D. Fuentes (University of Virginia) and Dr. Daniel Wang (Environment Canada) for sharing ozone, NOx, and VOC data. Support: NASA under the Experimental Program to Stimulate Competitive Research (EPSCoR), grant number NCC5-583 NOAA Center for Atmospheric Sciences Howard University
See our session: Advertisement Want more Beltsville? More suburban sites? Atmospheric Chemistry at the Interface between Rural and Urban Regions All Day Monday 11, 06 at the Fall American Geophysical Meeting