基于PMF模式的南京市大气细颗粒物源解析

为研究南京市大气细颗粒物(PM2.5)污染来源,分别在3个点位、4个季节开展了PM2.5环境样品的采集,共获得170个有效样本.对样本进行了化学成分分析,包括Al、Fe、Na、Mg、K、Ba、Li、Tl、Mn、Co、Ni、Cu、Zn、Sb、Pb、Cr、Ce、Na+、NH4+、Mg2+、Ca2+、SO42-、NO3-、Cl-、以及OC、EC,共计26种.首先采用OC/EC最小比值法估算出二次有机气溶胶(SOA)的含量;然后利用正矩阵因子分解法(PMF)对PM2.5的非SOA部分进行来源解析,共解析出6类因子:二次无机气溶胶(SIA)、燃煤、机动车排放、地面扬尘、冶金和其它源,贡献率分别25.0%、23.5%、20.4%、17.1%、3.0%和11.0%;最后基于南京市SO2、NOx、VOCs三种主要前体污染物的排放量,分别对SIA和SOA在一次来源中进行再分配.最终结果表明,南京市PM2.5主要来源为燃煤、机动车、扬尘、工业和其它源,其贡献率分别为29.6%、22.4%、14.6%、18.7%和14.7%.

Source Apportionment of PM2.5 in Nanjing by PMF

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.