邯郸市PM_(2.5)和PM_(10)中有机碳与元素碳的污染特征

Pollution characteristics of organic carbon and elemental carbon in PM_(2.5)and PM_(10) of Handan City

为了研究邯郸市PM_(2.5)和PM_(10)中有机碳(OC)与元素碳(EC)的污染特征,于2016年1月—10月对邯郸市大气PM_(2.5)和PM_(10)样品进行采集,运用热光反射法(TOR)分析了样品中的OC、EC的质量浓度,同时对OC和EC浓度水平与季节变化、OC/EC的比值特征及其相关性、二次有机碳(SOC)的估算、碳组分与气态污染物及气象因素的相关性和碳质气溶胶来源进行分析.结果表明,邯郸市PM_(2.5)和PM_(10)的质量浓度均呈现冬季>春季>秋季>夏季的规律,PM_(2.5)和PM_(10)中OC质量浓度均值为20.8μg·m^(-3)和34.9μg·m^(-3),EC质量浓度均值为6.6μg·m^(-3)和10.9μg·m^(-3);OC、EC对邯郸市PM_(2.5)质量浓度的年均贡献率分别为24.0%和7.0%,对PM_(10)质量浓度的年均贡献率分别为18.7%和5.9%;总碳气溶胶(TCA)占PM_(2.5)的比重为45.4%,TCA/PM_(10)为35.8%,碳质气溶胶是邯郸市PM_(2.5)的重要组成部分;PM_(2.5)和PM_(10)中OC/EC年均值分别为3.6和3.4,各季OC/EC比值均大于2,表明邯郸全年均存在SOC污染;PM_(2.5)和PM_(10)中SOC浓度在秋季和冬季相对较高,春季和夏季较低;SOC对PM_(2.5)和PM_(10)的贡献率分别为11.7%和7.3%.OC、EC和SOC与SO_(2)和NO_(2)呈显著正相关,表明邯郸市大气环境常年受燃煤和机动车尾气排放影响.后向轨迹分析得出,研究期间到达邯郸市的气团主要来自我国东北、西北和东南地区;颗粒物浓度雷达图分析,颗粒物、OC和EC可能与西北风向的关联性更强,表明当地西部工业区和高度城市化对当地碳质气溶胶的污染有一定的贡献.

To study the pollution characteristics of carbonaceous aerosols, PM_(2.5)and PM_(10)samples were collected in Handan from January to October, 2016. Thermal optical reflection(TOR) was used to analyze the mass concentrations of organic carbon(OC) and elemental carbon(EC) in the PM_(2.5)and PM_(10)samples. The characteristics including pollution level and seasonal variation of OC, EC,OC/EC ratio, correlation between OC and EC, estimation of secondary organic carbon(SOC),relationship between carbon components and gaseous pollutants with meteorological factors, and possible sources of OC and EC, were investigated. Results showed that the mass concentrations of PM_(2.5)and PM_(10)displayed seasonal variation as winter > spring > autumn > summer. The mean of OC concentrations in PM_(2.5)and PM_(10)were 20.8 μg·m^(-3) and 34.9 μg·m^(-3), respectively, while EC were 6.6 μg·m^(-3) and 10.9 μg·m^(-3), respectively. The average annual contribution rate of OC to PM_(2.5) was 24.0%, and it is 7.0% for EC. The contribution values to PM_(10) were 18.7% and 5.9%,respectively. Total carbonaceous aerosol(TCA) accounted for 45.4% and 35.8% in PM_(2.5)and PM_(10),respectively, suggested that the pollution of carbonaceous aerosol was serious in fine particles. The average annual OC/EC ratios of PM_(2.5)and PM_(10)were 3.6 and 3.4, respectively. The ratios of OC/EC in four seasons were all larger than 2, which indicated that SOC were formed. The seasonal characteristics of SOC in PM_(2.5)and PM_(10)were ranked by the order of winter > autumn > spring >summer. The average mass fractions of SOC in PM_(2.5)and PM_(10)were estimated to be 11.7% and7.3%, respectively. OC, EC and SOC were positively correlated with SO_(2) and NO_(2), which implicated that the air environment in Handan was affected by the emission of coal combustion and vehicle exhaust all the year round possibly. The air parcel back trajectory and concentration radar chart approaches were applied to investigate the source of carbonaceous aerosols. Back trajectory analysis suggested that the air masses reached to Handan during the study periods mainly came from the northeast, northwest and southeast China. The research of concentration radar chart showed that particulate material, OC and EC may have stronger correlation with the northwest wind direction,which indicated that the industrial area and high urbanization in the west region had a certain contribution to the pollution of local carbon aerosol.