Single-Particle Characterizations of Ambient Aerosols during a Wintertime Pollution Episode in Nanning: Local Emissions vs. Regional Transport

Ambient aerosol during a heavily polluted episode in wintertime was characterized using real-time single particle aerosol mass spectrometry (SPAMS) in urban Nanning, a capital city in the Southwestern China. More than two million individual particles analyzed by SPAMS were classified into 8 major clusters based on the mass spectral patterns. A group of vanadium-rich particles were identified as the emissions from mining and smelting of vanadium mineral and were taken as markers of regional transported industrial emissions when air masses traversed northeast inland regions from Nanning. Number fractions of other industrially-emitted particles, including chromium-rich, elemental/organic carbon, organic carbon and fly ash, also increased during the regional transport events. During stagnant periods, local emissions sources, including vehicle exhaust (like Ca-EC particles) and local coal-fired power plants, contributed to the fine particles. During most of the sampling period, biomass burning particles produced by bagasse combustion were the most abundant, contributing similar to 25-80% of the total classified particles. Our observations suggest that biomass burning particles derived from industrial heat and electricity cogeneration processes could have a significant impact on the urban air quality without proper emission controls.