The future underlying differential response of surface ozone to biogenic emissions in China (2019–2060)

Abstract

China's major megacity clusters experience severe summer ozone pollution, posing significant public health risks. In the context of declining anthropogenic emissions and increasing biogenic emissions driven by climate warming, understanding future surface ozone trends and their response to biogenic emissions is critical. This study integrates advanced biogenic emission and geochemical models to assess the impact of vegetation changes on ozone pollution in key regions—Beijing-Tianjin-Hebei (JJJ), Shandong (SDC), Chengdu-Chongqing (CCC), Fenwei Plain (FWP), Mid-Yangtze (MYC), Guangdong-Hong Kong-Macao Greater Bay Area (GHM), and Yangtze River Delta (YRD)—under 2030 and 2060 climate scenarios. Results demonstrate intensified ozone pollution by 2030 in GHM, MYC, FWP, and SDC, and by 2060 in JJJ, FWP, and GHM. The Random Forest model attributes ∼76.0 % of future ozone changes to biogenic emissions. Ozone source apportionment (OSAT) and brute force (BF) methods reveal increasing biogenic contributions to ozone formation in most scenarios. Mechanistic analysis shows biological nitrogen oxides (BNO_x) play a larger role than biogenic volatile organic compounds (BVOCs), especially in northern China with high nitrogen fertilizer use. While rising BVOCs increase RO₂ radicals, their ozone impact depends on NO_x levels: in NO_x-rich regions, BVOCs promote ozone via RO₂+NO reactions; in NO_x-scarce regions, RO₂+HO₂ reactions dominate, reducing ozone through competitive effects. This effect is observed in megacity clusters when P(H₂O₂)/P(HNO₃) exceeds 9. Overall, this study highlights the pivotal role of biogenic emissions in shaping China's future ozone pollution under climate and vegetation changes.