Effect of Organic Coatings, Humidity and Aerosol Acidity on Multiphase Chemistry of Isoprene Epoxydiols

TY - JOUR

T1 - Effect of Organic Coatings, Humidity and Aerosol Acidity on Multiphase Chemistry of Isoprene Epoxydiols

AU - Riva, Matthieu

AU - Bell, David M.

AU - Hansen, Anne-Maria Kaldal

AU - Drozd, Greg T.

AU - Zhang, Zhenfa

AU - Gold, Avram

AU - Imre, Dan

AU - Surratt, Jason D.

AU - Glasius, Marianne

AU - Zelenyuk, Alla

PY - 2016/6/7

Y1 - 2016/6/7

N2 - Multiphase chemistry of isomeric isoprene epoxydiols (IEPOX) has been shown to be the dominant source of isoprene-derived secondary organic aerosol (SOA). Recent studies have reported particles composed of ammonium bisulfate (ABS) mixed with model organics exhibit slower rates of IEPOX uptake. In the present study, we investigate the effect of atmospherically relevant organic coatings of α-pinene (AP) SOA on the reactive uptake of trans-β-IEPOX onto ABS particles under different conditions and coating thicknesses. Single particle mass spectrometry was used to characterize in real-time particle size, shape, density, and quantitative composition before and after reaction with IEPOX. We find that IEPOX uptake by pure sulfate particles is a volume-controlled process, which results in particles with uniform concentration of IEPOX-derived SOA across a wide range of sizes. Aerosol acidity was shown to enhance IEPOX-derived SOA formation, consistent with recent studies. The presence of water has a weaker impact on IEPOX-derived SOA yield, but significantly enhanced formation of 2-methyltetrols, consistent with offline filter analysis. In contrast, IEPOX uptake by ABS particles coated with AP-derived SOA is lower compared to that of pure ABS particles, strongly dependent on particle composition, and therefore on particle size.

AB - Multiphase chemistry of isomeric isoprene epoxydiols (IEPOX) has been shown to be the dominant source of isoprene-derived secondary organic aerosol (SOA). Recent studies have reported particles composed of ammonium bisulfate (ABS) mixed with model organics exhibit slower rates of IEPOX uptake. In the present study, we investigate the effect of atmospherically relevant organic coatings of α-pinene (AP) SOA on the reactive uptake of trans-β-IEPOX onto ABS particles under different conditions and coating thicknesses. Single particle mass spectrometry was used to characterize in real-time particle size, shape, density, and quantitative composition before and after reaction with IEPOX. We find that IEPOX uptake by pure sulfate particles is a volume-controlled process, which results in particles with uniform concentration of IEPOX-derived SOA across a wide range of sizes. Aerosol acidity was shown to enhance IEPOX-derived SOA formation, consistent with recent studies. The presence of water has a weaker impact on IEPOX-derived SOA yield, but significantly enhanced formation of 2-methyltetrols, consistent with offline filter analysis. In contrast, IEPOX uptake by ABS particles coated with AP-derived SOA is lower compared to that of pure ABS particles, strongly dependent on particle composition, and therefore on particle size.

KW - LIQUID PHASE-SEPARATION

KW - REACTIVE UPTAKE

KW - ALPHA-PINENE

KW - MASS-SPECTROMETRY

KW - ANTHROPOGENIC EMISSIONS

KW - AMMONIUM-SULFATE

KW - UNITED-STATES

KW - SOA FORMATION

KW - SPLAT II

KW - PARTICLE

U2 - 10.1021/acs.est.5b06050

DO - 10.1021/acs.est.5b06050

M3 - Journal article

C2 - 27176464

SN - 0013-936X

VL - 50

SP - 5580

EP - 5588

JO - Environmental Science & Technology

JF - Environmental Science & Technology

IS - 11

ER -