AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Organosulfates from Pinene and Isoprene over the Pearl River Delta, South China
XIANG DING, Quanfu He, Xinming Wang, Jian Zhen Yu, Neil Donahue, Guangzhou Institute of Geochemistry, CAS
Abstract Number: 194 Working Group: Aerosol Chemistry
Abstract Biogenic organosulfates (OSs) are important markers of secondary organic aerosol (SOA) formation involving cross reactions of biogenic precursors (terpenoids) with anthropogenic pollutants. Till now, there is rare information about biogenic OSs in the air of highly polluted areas. In this study, fine particle samples were separately collected in daytime and nighttime from summer to winter 2010 at a site in the central of Pearl River Delta (PRD), South China. Pinene-derived nitrooxy-organosulfates (pNOSs) and isoprene-derived OSs (iOSs) were quantified using a liquid chromatograph (LC) tandem mass (MS/MS) coupled with negative electrospray ionization (ESI). The pNOSs with MW=295 exhibited higher levels in fall-winter than summer, probably owing to the elevated levels of NOx and sulfate in fall-winter. In contrast to observations elsewhere where higher levels occurred at nighttime, pNOSs levels in the PRD were higher during daytime in both seasons, indicating that the pNOS formation was driven by photochemistry over the PRD. This conclusion is supported by several lines of evidence: the specific pNOS which could be formed through both daytime photochemistry and nighttime NO$_3 chemistry exhibited no day-night variation in abundance relative to other pNOS isomers; the production of the hydroxynitrate that is the key precursor for this specific pNOS was found to be significant through photochemistry but negligible through NO$_3 chemistry based on the mechanisms in the Master Chemical Mechanism (MCM). For iOSs, 2-methyltetrol sulfate ester which could be formed from isoprene-derived epoxydiols (IEPOX) under low-NOx conditions showed low concentrations, largely due to the depression of IEPOX formation by the high NOx levels over the PRD.