Conceptual models of ultrafine particles from combustion sources Benefits from integrating studies of ultrafine particles with nanotoxicology

Transcription

1 Conceptual models of ultrafine particles from combustion sources Benefits from integrating studies of ultrafine particles with nanotoxicology JOAKIM PAGELS ERGONOMICS & AEROSOL TECHNOLOGY, LUND UNIVERSITY, SWEDEN CONTACT:

2 Ultrafine Particles (UFP) from Combustion Sources Exposure to ultrafine carbonaceous particles (soot/black carbon) from combustion linked to adverse health effects in the population. Two major sources of UFPs are traffic and small scale wood combustion Huge development in nanotoxicology and nanomaterial characterisation Few such studies on UFP emissions from combustion sources (Stone et al. EHP 2016) What phyisco-chemical properties of UFPs drive toxicological responses? Surface area (BET) predicts acute inflamatory repsonses for a range of materials including several carbonaceous (Schmid & Stoeger 2016) Less is known for longer term effects, genotoxicity etc Complexities specific for UFPs: solid vs liquid components, atmospheric processing etc

3 Aims Use time resolved analysis to investigate relationships between combustion conditions and UFP Particle Characteristics Residential Biomass Combustion, Traffic, Atmospheric Processing Describe what causes elevated emissions of genotoxic compounds (PAHs) Describe Simple Conceptual Models of Key Particle Types in Biomass Combustion Solid vs Liquid Particles, PAH-content, Ash/metals Effects of Atmospheric Processing Nanostructure of soot particles -> implications for surface reactivity Discuss the usefulness of Flame Soot Generators and Carbon Blacks as models for real-world UFPs

4 Time-Resolved Analysis with Aerosol Mass Spectrometry S ssssssssssssss Particle phase composition with high time- (~ s) and size resolution ( nm), DeCarlo et al. (2006), Onasch et al. (2012) Examples of components: Organic Aerosol (several classes), PAHs (by carbon number), Inorganic salts (nitrates, sulphates.), refractory Black Carbon (rbc), Transition metals adsorbed to BC etc. Eriksson et al Scientific Reports In Press

5 Soot Formation and Oxidation (removal) in a HD Diesel Engine Modern heavy duty diesel engine 2017

6 Time-Resolved Emissions Conventional Wood Stove Add Fuel Flaming Phase Eriksson et al. 2014, Env. Sci. & Techn., Martinsson et al. 2015, Env. Sci. & Techn. Nielsen et al. 2017, Atmos. Environment Flaming Phase

7 PAH Emission Factors Conventional Wood Stove PAH emissions varies by orders of magnitude dependent on combustion conditions Important finding as solid fuel biomass combustion is a major source of PAHs in European Air (EEA 2014) Organic Aerosol and Black Carbon emissions less variable (< factor of 3) To reduce PAH emissions Avoid large batches with small sticks and very dry fuel in conventional wood stoves! To reduce PM emissions Avoid humid fuels in poorly insulated stoves!

8 Conceptual Models of Particle Types in Biomass Combustion Sigsgaard et al. (online supplement)

9 Life Cycle of Traffic Soot in the Atmosphere UV Atmospheric Secondary Aerosol Formation Nordin et al Atmos. Chem. & Phys. Wittbom et al Atmos. Chem. & Phys. Eriksson et al Scientific Reports In Press SO 2 O 3 NH 3 Humidity Temperature H 2 SO 4 Partitioning & Heterogeneous Reactions VOCs Biogenics Aromatics Semivolatiles N 2 O 5 HNO 3 NO x Main Components of Semi-volatile Organic Coating on soot Traffic exhaust: Branched alkanes from Lube oil (hydrophobic) Biomass Combustion: Anhydrous Sugars, Methoxy-Phenols (hydrophilic) Secondary Organic Aerosol: Highly Oxidised Organic Compounds (hydrophilic)

10 Soot from Portable Flame Soot Generators as Models for UFP Portable well-controlled flame soot generators available (propane) Can simulate diesel-like mature soot cores well Can also generate more reactive immature soot (cooling by N 2 ) High PAH fraction can be removed by thermodenuder Shorter lamellas, more reactive edge sites Such soot: Stronger biological effects than P90 and P90 coated with BaP both ex vivo and in vivo Lindner et al (PF&T) Török et al. Submitted

11 Carbon Blacks vs UFPs - Surface Proerties Engineered Carbon Blacks d pp and Specific Surface Area (SSA) can be tailored Typically no semi-volatile organic coating, low PAH High degree of graphitization Tailored surface properties -> reactivity changes Oxygen content, Number of reactive edge-sites (XPS etc) Printex 90 Genotoxic at low doses.. (Pawlyta et al., 2013) (Smith et al., 1995) Petrol Diesel Relatively high degree of graphitization d pp nm Organic lube oil coating (20-50%) Metals from Lube oil, PAHs etc Renewable FAME Biodiesel (~10% Oxygen) BC emissions reduced by ~2 (Lapuerta et al. 2008) Less graphitized, smaller lammellae (Savic et al. 2016) d pp reduced (increased SSA) Often reduced PAH content

12 Conclusions and Outlook Ultrafine particles from combustion consist of mixtures of solid and liquid components of varying polarity Particle properties are dictated by the combustion conditions, fuel and after treatment system Genotoxic compounds such as PAHs commonly co-emitted with black carbon Strong emission episodes identified (combustion temperature reduced below 1000 C) Atmospheric processing changes UFP properties. Growth by SOA, NO 3 and SO 4 Rough simple conceptual models of the UFP Phys-chem properties presented. Should be complemented with data from nanomaterial charactersiation techniques Flame soot generators: Interesting alternative for toxicological studies Both diesel-like mature soot and less mature more reactive soot coated with potent PAH mixture Questions: What is the role of PAHs and black carbon surface properties in the genotoxicity of UFPs? Do PAHs stay adsorbed on particles in the Lung? What is the relevant surface are in the lung, shielding by organics?

13 Acknowledgements Ergonomics & Aerosol Technology, Lund University Axel Eriksson, Vilhelm Malmborg, Christina Andersen, Louise Gren Umeå University Christoffer Boman & Robert Lindgren Nuclear Physics, LU Birgitta Svenningsson & Erik Swietlicki Combustion Physics, LU Per-Erik Bengtsson & Sandra Török Combustion Engines, LU Martin Tuner & Öivind Andersson NRCWE, Copenhagen Ulla Vogel & Kirsten Kling