AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Observation of Biogenic Secondary Organic Aerosols in the Atmosphere of a Mountain Site in Central China: Temperature and Relative Humidity Effects
JIANJUN LI, Gehui Wang, Institute of Earth Environment, Chinese Academy of Sciences
Abstract Number: 153 Working Group: Effects of NOx and SO2 on BVOC Oxidation and Organic Aerosol Formation
Abstract Secondary organic aerosols (SOA) derived from isoprene, pinene and caryophyllene were determined for PM10 and size-segregated (9-stages) aerosols collected at the summit (2060 m, a.s.l.) of Mt. Hua, central China during the summer of 2009. Estimated concentrations of isoprene, α-/β-pinene and β-caryophyllene derived secondary organic carbon (SOC) are 81±53, 29±14 and 98±53 ng m-3, accounting for 2.7±1.0%, 0.8±0.2% and 2.1±1.0% of OC, respectively. Concentrations of biogenic (BSOA, the isoprene/pinene/caryophyllene oxidation products) and anthropogenic (ASOA, mainly aromatic acids) SOA positively correlated with temperature (R=0.57-0.90). No significant relationship was found between sulfate and BSOA tracers in the current study. However, a decreasing trend of BSOA concentration with an increase in relative humidity (RH) was observed during the sampling period, although a clear trend between ASOA and RH was not found. Based on the AIM Model calculation, we found that during the sampling period an increase in RH resulted in a decrease in the aerosol acidity, and thus may reduce the effect of acid-catalysis on BSOA formation. Size distribution measurements showed that most of the determined BSOA are formed in the aerosol phase and enriched in the fine mode (<2.1μm) except for cis-pinonic acid, which is formed in the gas phase and subsequently partitioned into aerosol phase and thus presents a bimodal pattern with a small peak in the fine mode and a large peak in the coarse mode (>2.1μm).