Characteristics and Reactivity of Ambient VOCs in Urban Hangzhou, China

Abstract

The ambient concentration of 122 volatile organic compound (VOC) species were continuously measured in urban Hangzhou, China from May 2018 to April 2019. The average mixing ratio of VOCs was (59.4±23.6)×10-9 and the oxygenated VOCs (OVOC) were the largest component. There was no clear "weekend effect" in urban Hangzhou, while the concentration of VOCs had a sharp decrease during long holidays. The concentration of VOCs had a positive correlation with air quality index (AQI) and reached the highest level when the primary pollutant was PM2.5. The assessment results of atmospheric chemical reactivity with·OH radical loss rate (L·OH) and ozone formation potential (OFP) showed the average value of L·OH was 7.5 s-1 and that of OFP was 152.1×10-9, among which carbonyl compounds, aromatics, and alkenes were the most abundant components. The overall chemical reactivity level of VOCs in Hangzhou was equivalent to 2-methylpentane. The average value of toluene/benzene (T/B) was 1.95, which implied the ambient VOCs in Hangzhou were influenced by vehicle exhaust. Secondary formation (17.6%), combustion (11.8%), industrial processing (12.3%), solvent use (18.1%), biogenic source (4.5%), and vehicle exhaust (35.7%) were identified as six major sources of VOCs in Hangzhou through the positive matrix factorization (PMF) model.