AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Characterization of Secondary Organic Aerosols from Isoprene, Monoterpenes, β-Caryophyllene, Toluene, and Naphthalene at Three Sites in the Pearl River Delta, China
JIAN ZHEN YU, Wing Yi Wong, X. H. Hilda Huang, Hong Kong University of Science and Technology
Abstract Number: 542 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Isoprene, monoterpenes, beta-caryophyllene, toluene, and naphthalenes are common volatile organic compound (VOC) precursors for secondary organic aerosol (SOA) in areas of significant biogenic and anthropogenic VOC emissions, such as the Pearl River Delta (PRD) in South China. Field measurements of their molecular tracers provide estimates of SOA specific to precursors that can not otherwise obtained through other SOA measurements. Tracers for SOA derived from isoprene, monoterpenes, beta-caryophyllene, toluene, and naphthalenes were quantified in PM$_(2.5) samples collected at two urban sites and one suburban site in the PRD in 2009. No clear urban-suburban gradient in SOC was observed in this data set consisting of two samples in each month of 2009 at each site. Average SOC levels from both biogenic and anthropogenic precursors at GZ (an urban location in Guangzhou) and NS (a suburban location of Guangzhou) were comparable while SOC at TW (an urban site in Hong Kong) was consistently lower (about 52-85% of those at GZ and NS). The average total SOC concentrations attributable to the target precursors were 1.54 µgC m$^(-3) accounting for 14% of OC at TW, 2.35 µgC m$^(-3) (16%) at GZ, and 2.08 µgC m$^(-3) (16%) at NS. On certain days, the percentage of SOC from these few precursors could explain as much as 39% of OC, highlighting the importance of these VOCs in contributing to SOA. Among the three biogenic VOC precursors, SOC by beta-caryophyllene contributes the most (average: 0.41-0.56 µgC m$^(-3)). The average SOC from naphthalenes is 0.33-0.53 µgC m$^(-3), comparable to the SOC attributable to toluene and xylenes (0.48-0.73 µgC m$^(-3)). This result suggests the need to characterize and quantify emissions of naphthalene and its methyl derivatives for the understanding of SOA formation in this region. It was found that the SOA tracers for beta-caryophyllene and naphthalene were strongly correlated (r$^2: 0.70) despite their apparently distinct sources, possibly suggesting oxidants rather than the VOC precursors are the limiting factors for the formation of SOA from these sources.