菏泽市冬季大气PM2.5和PM10中碳组分来源解析

Source Apportionment of Carbonaceous Species in Atmospheric PM_(2.5) and PM_(10) during Winter in Heze City,China

为研究菏泽市冬季大气颗粒物中碳组分的污染特征和来源,于2016年1月采集菏泽市冬季大气PM2.5和PM10样品,基于热光反射法分析样品中OC(有机碳)、EC(元素碳)及8个碳组分[OC1、OC2、OC3、OC4、EC1、EC2、EC3和OP(裂解碳)]的含量,并计算得到ρ(Char-EC)(Char-EC为燃料燃烧后固体残渣中的EC)和ρ(Soot-EC)(Soot-EC为燃烧后气相挥发物质再凝结形成的EC),以定性识别大气颗粒物中碳组分的来源.结果表明,菏泽市冬季大气颗粒物样品中碳组分浓度处于较高水平,PM2.5中的ρ(OC)、ρ(EC)分别为26.34、9.22μg/m3,PM10中ρ(OC)、ρ(EC)分别为31.82、10.71μg/m3.采样期间大气PM2.5中碳组分(OC、EC、OC1、OC2、OC3、OC4、EC1、EC2、EC3、Char-EC、Soot-EC)浓度与PM10中相应各组分浓度的比值均大于0.5(0.60~0.90),表明碳组分多集中于细粒子(PM2.5).大气颗粒物样品中各碳组分浓度具有明显空间差异,各点位大气PM2.5和PM10中ρ(OC)均显著高于ρ(EC)(T检验,P<0.05).菏泽市冬季大气PM2.5和PM10中Char-EC/Soot-EC(二者质量浓度之比)分别为10.04、8.00,并且存在显著的空间差异性(T检验,P<0.05).PMF(正定矩阵因子分解法)解析结果表明,菏泽市冬季大气PM2.5和PM10中碳组分来源主要有4类,包括两类柴油车(1类排放的碳组分中以EC2为主,定义为柴油车-1;1类排放的碳组分中以EC3为主,定义为柴油车-2)、汽油车、生物质燃烧和燃煤混合源,对大气PM2.5中碳组分的分担率分别为13.98%、5.13%、24.47%、41.97%,对大气PM10中碳组分的分担率分别为16.08%、8.21%、18.34%、47.35%.可见,菏泽市冬季大气PM2.5和PM10中碳的主要来源是柴油车、汽油车、生物质燃烧和燃煤.

To investigate the characteristics and sources of carbonaceous species in atmospheric PM2.5 and PM10 in Heze City,atmospheric PM2.5 and PM10 samples were collected in January 2016. The organic carbon（OC）,element carbon（EC） and eight carbon fractions（OC1,OC2,OC3,OC4,EC1,EC2,EC3 and pyrolytic carbon（OP）） were analyzed using thermal/optical reflectance. In addition,the concentrations formed from the solid residues of combustion（Char-EC） and formed from volatiles within and recondensed from the hightemperature gas phase（Soot-EC） were calculated. The results indicate that the concentrations of carbonaceous species in atmospheric particulate matter were higher in winter. The concentrations of OC and EC in atmospheric PM2.5 were 26. 34 and 9. 22 μg/m^3,respectively,and those in atmospheric PM10 were 31. 82 and10. 71 μg/m^3,respectively. During the sampling period,the concentration ratios of carbon fractions（OC,EC,OC1,OC2,OC3,OC4, EC1, EC2, EC3, Char-EC and Soot-EC） in atmospheric PM2.5 to those in PM10 were greater than 0. 5,indicating that these fractions were widely concentrated in fine particles（PM2.5）. The carbonaceous species in atmosphericPM2.5 and PM10 showed significant spatial differences,and the concentrations of OC in atmospheric PM2.5 and PM10 were significantly higher than those of EC in PM2.5 and PM10 at each site（T-test,P〈0. 05）. The Char-EC/Soot-EC（the ratios of the mass concentrations）in atmospheric PM2.5 and PM10 were 10. 04 and 8. 00,respectively,and there were obvious spatial differences in Char-EC/Soot-EC（Ttest,P〈0. 05）. Four emissions sources of carbonaceous species in atmospheric PM2.5 and PM10 were identified by using the PMF model during winter in Heze. These sources mainly included two types of diesel vehicles（diesel vehicles dominated by factor profile EC2 were defined as diesel vehicle-1,and diesel vehicles dominated by factor profile EC3 were defined as diesel vehicle-2）,gasoline vehicles,and the mixture of biomass combustion and coal combustion. The contributions of the four emissions sources to carbonaceous species in atmospheric PM2.5 were 13. 98%,5. 13%,24. 47% and 41. 97%,respectively,and to those in atmospheric PM10 were 16. 08%,8. 21%,18. 34% and 47. 35%,respectively. The main sources of carbonaceous species in atmospheric PM2.5 and PM10 were diesel vehicles,gasoline vehicles,biomass burning and coal combustion.