成都平原PM2.5中碳质组分时空分布特征与来源

Spatio-Temporal Variations and Source Apportionment of Carbonaceous Species in PM2.5 Across Multiple Sampling Locations in the Chengdu Plain

为了探究成都平原碳质气溶胶污染特征及来源,于德阳、成都和眉山三地采集了1 a的PM2.5样品,利用光热透射法测量其有机碳(OC)和元素碳(EC).3个点年均碳质气溶胶的质量浓度(μg·m^-3)分别为眉山(OC:15.8±9.6,EC:6.6±5.3)>成都(OC:13.0±7.5,EC:4.7±3.6)>德阳(OC:9.6±6.1,EC:3.4±2.6),对应的总碳质气溶胶(TCA)在PM2.5中的占比分别为36%、34%和30%.由EC示踪法估算获得二次有机碳(SOC)在OC中的占比分别为眉山38%、成都46%和德阳47%.OC和EC质量浓度季节变化显著,呈现出秋冬季高夏季低的特征,在2013年10月12~13日、12月2~7日和2014年1月中下旬出现峰值,同期气溶胶中K+质量浓度激增,说明这些污染过程中生物质燃烧有重要贡献.PMF模型对碳质气溶胶来源解析结果表明,该地区总碳(TC)的主要来源为生物质燃烧源(46%~56%)、二次有机气溶胶源(26%~38%)、机动车排放源(9%~12%)、扬尘源(3%~4%)、燃煤源(2%~3%)和工业源(1%~2%),生物质燃烧源全年范围内对TC有显著贡献,尤以秋冬两季贡献最高.

To understand the characteristics and sources of carbonaceous aerosols,one-year PM2.5 samples were analyzed for their organic carbon(OC)and elemental carbon(EC)content,following the thermal/optical transmission protocol in three cities[Deyang(DY),Chengdu(CD),and Meishan(MS)]in the Chengdu Plain.The observed annual average concentrations(μg·m^-3)were in the following order:MS(15.8±9.6 OC and 6.6±5.3 EC)>CD(13.0±7.5 OC and 4.7±3.6 EC)>DY(9.6±6.1 OC and 3.4±2.6 EC).Organic matter(1.6 OC)and EC was regarded as the total carbonaceous aerosols(TCA)amount,and the TCA/PM2.5 ratios at the three above-mentioned cities were 36%,34%,and 30%respectively.The EC-trace method was used to estimate secondary organic carbon(SOC),which accounted for 38%,46%,and 47%of total OC in MS,CD,and DY.Daily variations of OC and EC concentrations exhibited significant daily variations,with simultaneous peaks on Oct.12 th to 13 th,2013,Dec.2 ndto 7 th,2013,and mid-to-late Jan.,2014.The surging concentrations of K+during the pollution period implied the contribution of biomass burning to heavy pollution.Six sources were resolved by the positive matrix factorization(PMF)model,whose contributions to the total carbon(TC)were:biomass burning(46%-56%),secondary aerosols(26%-38%),vehicle emission(9%-12%),fugitive dust(3%-4%),coal combustion(2%-3%),and industry emission(1%-2%).Biomass burning activities presented a significant influence on TC throughout the year,especially in autumn and winter.