Spatially resolved analysis of speciated VOC emissions and their contributions to secondary pollutant formation: a comparative assessment of anthropogenic and biogenic sources in China.

Volatile organic compounds (VOCs) significantly impact ozone (O) and particulate matter (PM) formation, requiring spatially resolved emission and reactivity assessments for air pollution control. Here, we developed a 27 km-grid speciated VOC emission inventory involving both anthropogenic and biogenic sources over mainland China in 2021, by combining the traditional emission factor method with refined spatial allocation method. Total VOC emissions reached 66.7 Tg, with biogenic sources contributing 65.0 % and anthropogenic sources 35.0 %, and their emission intensities varied from 0 to 684.9 t/km, peaking in South (24.7 t/km) and East China (23.8 t/km), while lowest in the Northwest (1.7 t/km). Then, the speciated VOC emissions were further combined with their OH reaction rates and secondary organic aerosol (SOA) yield, to respectively achieve their OH reactivity (OHR) and SOA formation potential (SOAP). The national average OHR, calculated across all grid cells in China, for VOCs was 3028.9 s, far exceeding the counterparts for inorganic components, while the national mean SOAP was 0.3 t/km, contributing 38.3 % to PM emission. Both OHR and SOAP displayed significant spatial heterogeneity, with OHR decreasing from south to north, peaking in South China (11016.0 s) and reaching its lowest in the Northwest (602.6 s). In contrast, SOAP showed less regional variation but was highest in urban agglomerations, including the Pearl River Delta (1.6 t/km), Yangtze River Delta (1.3 t/km), and Beijing-Tianjin-Hebei (0.6 t/km). This study is the first to quantify the spatial variability of OHR and SOAP using a gridded emission inventory, uncovering differences between anthropogenic and biogenic contributions and supporting targeted regional pollution control strategies.