为研究昆明市大气细颗粒物(PM2.5)中碳组分特征,于2014年7月21-27日、2014年10月27-11月2日、2014年1月9-15日、2015年4月14-20日采集了昆明中心城区3个采样点的大气PM2.5四季样品,采用IMPROVE热光分析法准确地测量了样品的有机碳(OC),元素碳(EC)及其中的8个碳组分含量,分析了OC和EC的时空变化特征、相关性关系及其比值特征,并采用因子分析方法研究了主要排放来源对总碳的贡献.结果显示,昆明城区的OC和EC年平均浓度分别为17.83±9.57.μg·m-3、5.11±4.29 μg· m-3,OC浓度显示冬季≈春季＞秋季＞夏季的变化趋势,EC浓度显示冬季＞春季≈秋季＞夏季的变化趋势,OC与EC浓度季节分布的不一致反映了两种不同性质碳组分排放源之间可能存在差异.从空间分布上来说,OC和EC均呈现金鼎山(工业区)＞东风东路(交通密集区)＞西山森林公园(清洁对照区)的特点,与PM25的空间分布规律保持一致.OC和EC的相关性在冬、春季较显著,而夏、秋季的相关性较弱.二次有机碳(soC)对OC的贡献率在金鼎山、东风东路和西山森林公园的3个采样点分别为25.8％、23.7％和47.7％,SOC是总有机碳的重要组成部分.因子分析表明,4个季节燃煤、汽油车、柴油机排放及生物质燃烧对碳气溶胶贡献显著,都是碳组分的重要来源之一.其中,在常年尺度上,机动车排放和燃煤的混合贡献了碳组分的51.3％,是昆明城区碳气溶胶的最主要来源.
The purpose of this study was to investigate the characteristics of carbonaceous components in PM2.5 at three sites of Kunming.PM2.5 samples were collected during July 21 to 27,2014 (Summer),October 27 to November 31,2014 (Autumn),January 9 to 15,2014 (Winter)and April 14 to 20,2015 (Spring).Organic carbon (OC),elemental carbon (EC) and the eight carbon components were measured using thermal-optical method.And seasonal variation of OC and EC were investigated,the relationship between OC and EC and characteristics of OC/EC ratio were analyzed and compared.Factor analysis on the eight carbon fractions was performed to assess the main contribution to the total carbon emissions sources.Results show that the annual OC and EC concentrations in Kunming were 17.83±9.57 μg· m-3 and 5.11 ±4.29 μg· m-3,respectively.OC concentrations displayed seasonal variation as winter ≈ spring＞ autumn ＞ summer.EC concentrations decreased in the order of winter＞spring≈ autumn＞summer.The seasonal distribution of OC and EC suggests that there may be different soures of carbonous cōmponent.From the spatial distribution,the concentrations of OC and EC decreased as Jinding mountain (JDM)＞East Dongfeng road (DR)＞West mountain (WM),consistent with the spatial distribution of PM2.5.The OC/EC correlation coefficient is higher in winter and spring,while the correlation between summer and autumn is lower.The average concentrations of (secondary organic carbon) SOC accounted for 25.8％,23.7％ and 47.7％ of OC at DR,JDM and WM,respectively.Results suggested that SOC was an important component of OC in PM2.5 in Kunming.In general,vehicle exhaust,coal combustion and biomass burning were the important sources for carbonaceous aerosol in each season.Among them,a combination of vehicle exhaust and coal combustion contributed 51.28％ of carbonaceous aerosol on the scale of the year,which were the major sources for carbonaceous aerosol in Kunming.
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