嘉兴市碳质气溶胶的特征分析

Characteristics of Carbonaceous Aerosol in Jiaxing of China

2013年10月到2014年2月在嘉兴城区对大气中细颗粒物的质量浓度和含碳气溶胶进行了在线连续观测,获得秋冬季节碳质气溶胶的变化特征。观测期间,有机碳(organic carbon,OC)的平均质量浓度为12.5μg/m^3,日均质量浓度变化范围为2.1~61.1μg/m^3;元素碳(elemental carbon,EC)的平均质量浓度为4.2μg/m^3,日均质量浓度变化范围为0.7~17.1μg/m3。OC和EC分别占PM2.5质量浓度的15.8%和5.3%。总碳气溶胶(total carbonaceous aerosols,TCA=1.6×OC+EC)的平均质量浓度为24.2μg/m3,日均变化范围为4.1~114.9μg/m3,约占PM2.5质量浓度的30.5%。较强的OC与EC相关性表明其具有相似的污染来源。OC/EC值为3.0,说明其受汽车尾气和煤炭燃烧的影响较大。二次有机碳(secondary origin carbon,SOC)的平均质量浓度为6.6μg/m^3,占PM2.5中总有机碳的53.0%。潜在源贡献(potential source contribution function,PSCF)分析表明,EC在长三角地区呈显著的区域性污染,而OC在输送过程中容易老化,区域性污染特征相对较弱。

Concentrations of PM2.5 and carbonaceous aerosol were measured in Jiaxing during October 2013 to February 2014.Daily concentrations of organic carbon(OC)in PM2.5 ranged from 2.1μg/m^3 to 61.1μg/m^3 with an average of 12.5μg/m^3,and elemental carbon(EC)ranged from 0.7μg/m^3 to 17.1μg/m^3 with an average of 4.2μg/m^3.OC and EC were evaluated to account for 15.8%and 5.3%of PM2.5.The concentration of total carbo?naceous aerosols(TCA=1.6×OC+EC)ranged from 4.1μg/m^3 to 114.9μg/m^3 with an average of 24.2μg/m^3 and constituted 30.5%of PM2.5 mass.The strong correlation between OC and EC demonstrated that their main sources were similar,and the characteristic OC/EC ratios(3.0)indicated their dominant sources from motor vehicle ex?hausts and coal combustion.The average level of secondary organic carbon(SOC)was 6.6μg/m^3,accounting for 53.0%of the total OC in PM2.5.Potential source contribution function(PSCF)analysis showed that EC concentration in Jiaxing was influenced significantly by long-range transportation process,and the OC concentrations were considered to be more affected by local sources and surrounding cities.