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2004 Progress Report: Fundamental Experimental and Modeling Studies of Secondary Organic Aerosol
EPA Grant Number: R831075Title: Fundamental Experimental and Modeling Studies of Secondary Organic Aerosol
Investigators: Seinfeld, John , Clegg, Simon , Flagan, Richard
Current Investigators: Seinfeld, John
Institution: California Institute of Technology , University of East Anglia
Current Institution: California Institute of Technology
EPA Project Officer: Hunt, Sherri
Project Period: July 1, 2003 through June 30, 2006
Project Period Covered by this Report: July 1, 2003 through June 30, 2004
Project Amount: $449,991
RFA: Measurement, Modeling, and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5) (2003)
Research Category: Particulate Matter
Description:
Objective:The objective of this research project is to understand the sources, molecular composition, and chemistry of formation of atmospheric secondary organic aerosol (SOA), which represents a key problem in atmospheric chemistry.
Progress Summary:A significant fraction of atmospheric organic aerosols are formed through in situ oxidation of precursor hydrocarbons followed by partitioning of low-volatility products into the aerosol phase. This component of atmospheric organic aerosols is referred to as SOA. Understanding the mechanisms of formation of SOA represents an outstanding problem. Recent discoveries have indicated that a full understanding of the molecular mechanisms of SOA formation is lacking. A number of laboratory studies, including the present work, have identified polymeric species as potentially major components in SOA from the ozonolysis of α-pinene, isoprene, and a number of cycloalkenes. It has been proposed that these polymers are formed in the aerosol phase through heterogeneous reactions involving oxidation products with low MW (below 200 Da). In light of these results, it becomes crucial to understand heterogeneous reactions that occur and the effect of such reactions on the formation of SOA. We are carrying out a comprehensive study of SOA formation from key biogenic and anthropogenic precursor hydrocarbons, spanning a range of particle acidity, temperature, and relative humidity.
Future Activities:The presence of oligomers in SOA, as well as the observed increase in SOA yields with increased seed particle acidity, strongly suggests that chemical reactions play an important role in organic aerosol growth. The identities of such reactions, however, are not known, and we lack the quantitative understanding required to incorporate their effects into models of SOA formation and growth. Therefore, we have begun studying directly the contribution of heterogeneous chemistry (reactions between gas-phase and particle-phase species) to aerosol growth. By monitoring changes in aerosol size and composition when seed particles are exposed to a single gas-phase compound, we may isolate individual heterogeneous reactions, with no interference from the complex chemistry that occurs in hydrocarbon oxidation experiments. Focusing on relatively volatile species, as well as continually measuring aerosol composition, will ensure that observed aerosol growth is a result of chemical reaction and not merely physical absorption into the condensed phase. Early objectives include the identification of atmospherically relevant compounds that may take part in heterogeneous reactions and the characterization of the reactive pathways by which they are incorporated into the aerosol. Rates of growth and aerosol yields then will be quantified as functions of experimental conditions, so that we may better understand what factors control heterogeneous chemistry. Reaction conditions to be varied include gas-phase reactant concentration, relative humidity, and seed particle size, phase, and composition. The results from these studies may be incorporated into models of SOA formation and growth.
Journal Articles on this Report: 4 Displayed | Download in RIS Format
| Other project views: | All 16 publications | 16 publications in selected types | All 16 journal articles |
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Gao S, Keywood M, Ng NL, Surratt J, Varutbangkul V, Bahreini R, Flagan RC, Seinfeld JH. Low-molecular-weight and oligomeric components in secondary organic aerosol from the ozonolysis of cycloalkenes and α-pinene. Journal of Physical Chemistry A 2004;108(46):10147-10164. |
R831075 (2004) R831075 (2005) R831075 (Final) |
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Gao S, Ng NL, Keywood M, Varutbangkul V, Bahreini R, Nenes A, He J, Yoo KY, Beauchamp JL, Hodyss RP, Flagan RC, Seinfeld JH. Particle phase acidity and oligomer formation in secondary organic aerosol. Environmental Science & Technology 2004;38(24):6582-6589. |
R831075 (2004) R831075 (2005) R831075 (Final) |
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Keywood MD, Kroll JH, Varutbangkul V, Bahreini R, Flagan RC, Seinfeld JH. Secondary organic aerosol formation from cyclohexene ozonolysis: effect of OH scavenger and the role of radical chemistry. Environmental Science & Technology 2004;38(12):3343-3350. |
R831075 (2004) R831075 (Final) |
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Keywood MD, Varutbangkul V, Bahreini R, Flagan RC, Seinfeld JH. Secondary organic aerosol formation from the ozonolysis of cycloalkenes and related compounds. Environmental Science & Technology 2004;38(15):4157-4164. |
R831075 (2004) R831075 (Final) |
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troposphere, health effects, environmental chemistry, analytical, air, ecosystem protection/environmental exposure and risk, pollutants/toxics, air pollution effects, analytical chemistry, atmospheric sciences, chemicals, environmental engineering, environmental monitoring, monitoring/modeling, air toxics, particulate matter, volatile organic compounds, VOCs, aerosol analyzers, aerosol particles, air quality model, air quality models, air sampling, atmospheric dispersion models, atmospheric measurements, atmospheric particulate matter, carbon particles, emissions, human exposure, human health effects, measurement methods, modeling, modeling studies, monitoring stations, particle phase molecular markers, particulate matter mass, secondary organic aerosol, SOA, secondary organic aerosols,
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Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Air, Scientific Discipline, RFA, Air Pollution Effects, air toxics, Chemicals, Atmospheric Sciences, Environmental Engineering, particulate matter, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, aerosol analyzers, health effects, Volatile Organic Compounds (VOCs), carbon particles, particulate matter mass, secondary organic aerosols, particle phase molecular markers, measurement methods, aerosol particles, air sampling, atmospheric dispersion models, emissions, air quality models, human health effects, monitoring stations, monitoring of organic particulate matter, modeling studies, atmospheric particulate matter, atmospheric measurements, analysis of organic particulate matter, modeling, secondary organic aerosol, transport modeling
Progress and Final Reports:
Original Abstract
2005 Progress Report
Final Report