Abstract
Abstract. Recent field and laboratory evidence indicates that the oxidation of isoprene, (2-methyl-1,3-butadiene, C5H8) forms secondary organic aerosol (SOA). Global biogenic emissions of isoprene (600 Tg yr−1) are sufficiently large that the formation of SOA in even small yields results in substantial production of atmospheric particulate matter, likely having implications for air quality and climate. Here we present a review of field measurements, experimental work, and modeling studies aimed at understanding the mechanisms, yield, and atmospheric importance of isoprene-derived SOA. SOA yields depend on a number of factors, including organic aerosol loading (Mo), NOx level (RO2 chemistry), and, because of the importance of multigenerational chemistry, the degree of oxidation. These dependences are not always included in SOA modules used in atmospheric transport models, and instead most yield parameterizations rely on a single set of chamber experiments (carried out over a limited range of conditions); this may lead to very different estimates of the atmospheric importance of isoprene SOA. New yield parameterizations, based on all available laboratory data (Mo=0–50 μg m−3), are presented here, so that SOA formation may be computed as a function of Mo, NOx level, and temperature. Current research needs and future research directions are identified.
Highlights
Atmospheric fine particles are linked to adverse health effects, visibility reduction and climate change
HO O glycolaldehyde methylglyoxal hydroxyacetone aqueous-phase pyruvic acid glyoxylic acid oxalic acid including: 1) inaccurate representation of Particulate organic matter (POM) emissions and treatment, (Robinson et al, 2007), 2) large uncertainty in emission inventories of precursor volatile organic compound (VOC) emissions (Goldstein and Galbally, 2007), 3) missing Secondary organic aerosol (SOA) precursors, 4) missing physical and chemical processes that contribute to SOA but are not accounted for in atmospheric models, (e.g. cloud processing or other aerosol phase reactions (Volkamer et al, 2009)), 5) errors associated with the extrapolation of laboratory data to the atmosphere, 6) uncertain meteorological inputs that distort concentration calculations (e.g. PBL height (Yu et al, 2007b)), and 7) uncertainties in the measurement of ambient
Czoschke, and coworkers showed that SOA yields from the ozonolysis of isoprene are greatly enhanced in the presence of acidic aerosol seed (Jang et al, 2002; Czoschke et al, 2003)
Summary
Atmospheric fine particles are linked to adverse health effects, visibility reduction and climate change. Including: 1) inaccurate representation of POM emissions and treatment, (i.e. not accounting for the full volatility distribution and reaction potential) (Robinson et al, 2007), 2) large uncertainty in emission inventories of precursor volatile organic compound (VOC) emissions (Goldstein and Galbally, 2007), 3) missing SOA precursors, 4) missing physical and chemical processes that contribute to SOA but are not accounted for in atmospheric models, (e.g. cloud processing or other aerosol phase reactions (Volkamer et al, 2009)), 5) errors associated with the extrapolation of laboratory data to the atmosphere, 6) uncertain meteorological inputs that distort concentration calculations (e.g. PBL height (Yu et al, 2007b)), and 7) uncertainties in the measurement of ambient. This paper presents a comprehensive summary of the recent literature on the topic, including field, laboratory, and modeling studies that tie isoprene and its oxidation products to POM. Remaining uncertainties in SOA yields from isoprene oxidation are explored, and the needs for future research in the area are discussed
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