Ozone Formation at a Suburban Site in the Pearl River Delta Region, China: Role of Biogenic Volatile Organic Compounds

Abstract

Ozone (O3) is becoming an increasingly concerning air quality problem in China, and previous O3 control strategies focused primarily on reducing anthropogenic volatile organic compounds (AVOCs), while neglecting the role of biogenic VOCs (BVOCs) in O3 formation. In this study, a field campaign was conducted at a suburban site in the Pearl River Delta region of China with high BVOC emissions from 29 August to 3 September 2020. An empirical kinetic modelling approach (EKMA) showed that VOC-limited was the dominant feature for O3 formation at the site. The relative incremental reactivity (RIR) values calculated by the box model (AtChem2-MCM) revealed that isoprene, formaldehyde, methylglyoxal and acetaldehyde had the highest RIRs. Simulation results from the box model also showed that isoprene played a substantial role in the formation of secondary carbonyls, especially contributing 32–92% to the formaldehyde production rate. Box model simulations further showed that during the O3 pollution period with high BVOC emissions, only near zero AVOC emissions could prevent O3 if the levels of nitrogen oxides (NOx) remained unchanged. The results suggest that the presence of high BVOC emissions can greatly impact efforts to control O3 by reducing AVOCs, particularly in regions with relatively high NOx levels (up to 51 ppbv in this study). In the long term, it may be essential to control NOx and choose low BVOC-emitting tree species in urban planning to address this issue, particularly as BVOC emissions are projected to become a more significant source of reactive VOCs with enhanced control of AVOCs.