Characterization and source analysis of VOCs and PM2.5 species in Lanzhou, northwestern China in 2017-2021: Implications for pollution control strategies.

Volatile organic compounds (VOCs) are common precursors of ozone (O3) and PM2.5 pollution. This study analyzed the characteristics, sources, and chemical effects of VOCs and PM2.5 from 2017 to 2021 in Lanzhou, China-a complex environment affected by petrochemicals and dust. The study used the photochemical-age-based parametric method, the positive matrix factorization model, and formation potential estimation. The mean concentrations of VOCs and PM2.5 in Lanzhou were 42.5 ppbv and 64.1 μg/m3, respectively. The main constituents of VOCs and PM2.5 were oxygenated VOCs (OVOCs) and mineral dust, respectively. The concentrations of VOCs and PM2.5 were lower during the COVID-19 pandemic. Source apportionment considering photochemical losses showed that the main source of VOCs was solvent use (32.7 %), with the greatest contribution from anthropogenic sources of acetaldehyde. Dust (25.1 %) and industry (24.9 %) were the main sources of PM2.5. Formation potential estimations revealed that acetaldehyde and methanol were the main contributors to O3 generation on O3-polluted days. Toluene, benzene, and α-pinene were the main contributors to secondary organic aerosol generation on PM2.5-polluted days. VOC oxidation explained 37.8 % of secondary organic aerosol formation, with its contribution being 6 % higher on dust-polluted days, when Fe and Ti elements were more likely to contribute to VOC-related secondary organic aerosol generation. Accordingly, control of solvent use, dust, and industrial emissions (OVOCs, aromatic hydrocarbons, and Fe and Ti elements) should be prioritized to mitigate O3 and PM2.5 pollution.