Role of Heat Wave‐Induced Biogenic VOC Enhancements in Persistent Ozone Episodes Formation in Pearl River Delta.

Regional ozone (O3) pollution is influenced by a combination of anthropogenic sources and biogenic volatile organic compounds (BVOC) emitted from vegetation. Under the influence of warming climate and projected expansion of urban green space, O3 pollution may get worse, especially during heat waves (HWs). However, HW‐induced changes in BVOC and subsequent effects on regional O3 pollution have not been adequately assessed. In this study, we used the Weather Research and Forecasting‐Community Multi‐scale Air Quality models to investigate the formation of a typical O3 episode and quantify the O3 response to BVOC in the Pearl River Delta during a HW in 2017. The results showed that the rate of increase of O3 during the HW was 27.1 µg m−3 °C−1, reflecting the rapid O3 formation under high temperature. Compared with the non‐HW (NHW), gas‐phase chemistry and vertical transport were dominant contributors to O3 formation. Sensitivity experiments indicate that the contribution of BVOC to ground‐level O3 formation in Pearl River Delta was up to 42.1 μg m−3 because BVOC emissions in HW were 430 mol d−1 higher than the NHW. Under northerly winds and strong sea‐land breezes, BVOC and oxidation products from rural areas were transported to downwind VOC‐limited regimes and result in severe O3 pollution owing to intense photochemical reactions and accumulated O3 precursors. These findings point to the essential role of BVOC enhancements induced by HWs to O3 formation and suggest the consideration of BVOC emission potential of planted trees in urban greening strategies for avoiding the offset effects from BVOC. Key Points: A persistent regional ground‐level O3 pollution was observed during the heat wave (HW) period over the Pearl River Delta regionsGas‐phase chemistry and vertical transport processes affected by meteorological conditions are dominant contributors to O3 formationIntensive biogenic volatile organic compounds emissions enhance O3 pollution over VOC‐limited regimes under the northerly wind and sea‐land breezes during the HW period [ABSTRACT FROM AUTHOR]