昆明市干季碳气溶胶污染特征及来源解析

Characteristics and Source Analysis of Carbon Aerosol Pollution in Dry Season

为研究西南高原城市昆明的碳气溶胶浓度特征及其来源,2018年11月20日—2019年3月23日,在昆明主城区采集PM_(2.5)样品共117个,测定有机碳(OC,organic carbon)和元素碳(EC,elemental carbon)的质量浓度,对其进行源解析。结果显示:昆明市PM_(2.5)平均浓度为72.31±26.19μg/m^(3),碳气溶胶浓度(TC,total carbon)为38.04±18.74μg/m^(3),约占PM_(2.5)的53%。碳气溶胶以有机碳排放为主,OC约占TC的75%,EC平均质量为9.15±4.02μg/m^(3)。OC/EC值为3.23,二次有机碳(SOC,secondary organic carbon)约占有机碳的40%左右,存在二次有机污染物。碳组分浓度排序为:OC3>OC4>OPC>EC1>OC2>OC1>EC2>EC3,以汽油车尾气排放、燃煤、扬尘、生物质燃烧源占主导。外源气团影响了昆明市碳质气溶胶浓度水平和组成,与局地排放相比,西南风时OC3、OP占比较高,EC1占比降低;偏南风时OP占比增加;东北风时OC4占比增加明显。昆明碳气溶胶的潜在外源输入主要来自西南方向,如红河、玉溪及缅北等地,部分来自东南(文山)、东北(曲靖)方向,生物质燃烧和工业排放是区域传输的主要来源。

To study the characteristics and sources of carbon aerosol concentration in Kunming,a southwest plateau city,117 PM_(2.5) samples were collected in the urban area of Kunming from November 20,2018 to March 23,2019.The mass concentration of organic carbon(OC)and elemental carbon(EC)was determined and their sources were analyzed.The results showed that the average concentration of PM_(2.5) in Kunming was 72.31±26.19μg/m^(3),and the total carbon aerosol concentration(TC)was 38.04±18.74μg/m^(3),accounting for about 53%of PM_(2.5).Carbon aerosols were mainly derived from organic carbon emissions,and OC accounted for approximately 75%of TC,and the average EC mass was 9.15±4.02μg/m^(3).The OC/EC value was 3.23.Secondary organic carbon(SOC)accounted for about 40%of organic carbon.So there were secondary organic pollutants to some extend.The ranking of carbon component concentration was:OC3>OC4>OPC>EC1>OC2>OC1>EC2>EC3,dominated by gasoline vehicle exhaust emissions,coal burning,dust and biomass combustion in Kunming.The exogenous gas mass has affected the concentration and composition of carbon aerosols in Kunming.Compared with local emission,OC3 and OP increased in southwest wind and EC1 decreased;OP increased in southerly wind and OC4 increased in northeast wind.The potential exogenous input of the carbon aerosols in Kunming mainly came from the southwest,such as Honghe,Yuxi and northern Myanmar.And some parts came from the southeast(Wenshan)and northeast(Qujing).Biomass combustion and industrial emissions were the main sources of regional transmission.