Abstract：In order to identify the main emission sources of fine particulate matter (PM2.5) in Nanjing, a total of 170 ambient samples were collected at three receptors and in four typical seasons. Chemical compositions were analyzed, including Al, Fe, Na, Mg, K, Ba, Li, Tl, Mn, Co, Ni, Cu, Zn, Sb, Pb, Cr, Ce, Na+, NH4+, Mg2+, Ca2+, SO42-, NO3-, Cl-, organic carbon (OC) and element carbon (EC). First, secondary organic aerosol (SOA) was estimated by using the OC/EC minimum ratio method. Then, the positive matrix factorization (PMF) model was applied for source apportionment basing on the non-SOA compositions. The PMF indicated six contribution factors of PM2.5, which are secondary inorganic aerosol (SIA, 25.0%), coal combustion (23.5%), motor vehicle (20.4%), airborne soil (17.1%), metal processing (3.0%) and undefined sources (11.0%). Furthermore, based on the total emissions of SO2, NOx and VOCs in Nanjing, which are major precursors of secondary aerosols, the SIA and SOA were further apportioned among the primary sources. Final results show that the main sources of PM2.5 in Nanjing are coal combustion, motor vehicle, airborne soil, industry and others, with contributions of 29.6%, 22.4%, 14.6%, 18.7% and 14.7%, respectively.
