Enhanced summertime ozone and SOA from biogenic volatile organic compound (BVOC) emissions due to vegetation biomass variability during 1981-2018 in China

Abstract

Coordinated control of fine particulate matter (PM2.5) and ozone (O3) has become a new and urgent issue for China's air pollution control. Biogenic volatile organic compounds (BVOCs) are important precursors of O3 and secondary organic aerosol (SOA) formation. China experienced a rapid increase in BVOC emissions as a result of increased vegetation biomass. We applied WRF-Chem3.8 coupling with MEGAN2.1 to conduct long-term simulations for impacts of BVOC emissions on O3 and SOA during 1981-2018, using the emission factors extrapolated by localized emission rates and annual vegetation biomass. In summer 2018, BVOC emissions were 9.91ĝ€¯Tg (in June), which led to an average increase of 8.6ĝ€¯ppb (16.75ĝ€¯% of the total) in daily maximum 8ĝ€¯h (MDA8) O3 concentration and 0.84ĝ€¯μgm-3 (73.15ĝ€¯% of the total) in SOA over China. The highest contribution to O3 is concentrated in the Great Khingan Mountains, Qinling Mountains, and most southern regions while in southern areas for SOA. Isoprene has the greatest contribution to O3, while monoterpene has the largest SOA production. BVOC emissions have distinguished impacts in different regions. The Chengdu-Chongqing (CC) region has the highest O3 and SOA generated by BVOCs, while the Beijing-Tianjin-Hebei (BTH) region has the lowest. From 1981 to 2018, the interannual variation of BVOC emissions caused by increasing leaf biomass resulted in O3 concentration increasing by 7.38ĝ€¯% at an average rate of 0.11ĝ€¯ppbĝ€¯yr-1 and SOA increasing by 39.30ĝ€¯% at an average rate of 0.008ĝ€¯μgm-3 yr-1. Due to the different changing trends of leaf biomass by region and vegetation type, O3 and SOA show different interannual variations. The Fenwei Plain (FWP), Yangtze River Delta (YRD), and Pearl River Delta (PRD) regions have the most rapid O3 increment, while the increasing rate of SOA in CC is the highest. BTH has the smallest enhancement in O3 and SOA concentration. This study will help to recognize the impact of historical BVOC emissions on O3 and SOA and further provide a reliable scientific basis for the precise prevention and control of air pollution in China.