福州市PM2.5中碳组分的污染特征研究

于2015年3月-2016年1月在福州市八个点位采集春夏秋冬四个季节的大气细颗粒物PM_2.5样品,共861个,采用热光反射法测定了PM_2.5中的含碳物质OC、EC,探讨OC、EC的浓度水平、季节变化、相关性、OC/EC的比值以及二次有机碳(SOC)的分布特征。结果表明,福州市大气PM_2.5中OC的浓度范围为(6.2~10.8)μg/m3,EC的浓度范围为(2.0~4.1)μg/m3,总碳TC在PM_2.5中所占的比例范围为(28.7~34.6)%。各点位中OC、EC的季节变化特征为春>冬>秋>夏。OC/EC的比值均大于2.0左右,说明各点位PM_2.5中存在二次有机碳。运用OC/EC最小比值法对SOC的含量进行估算,SOC年平均浓度为3.8μg/m3,占OC含量的46.8%。SOC对PM_2.5的贡献率春、冬季比夏、秋季高,这可能与夏季温度高、光照强烈有利于光化学反应进行有关。夏、秋、冬三个季节OC与EC的相关性较好,春季OC与EC的相关性差,说明夏秋冬三季节OC与EC的来源相同,春季OC与EC来源相对复杂。OC和EC中不同温度段的碳组分构成和TC与K+的相关性分析表明汽油车尾气排放、燃煤排放、生物质燃烧是福州大气碳质组分的主要来源。

Characteristics of organic carbon and element carbon in PM_(2.5) of FuZhou City

A total of 861 PM_2.5 samples were collected from eight sites in Fuzhou during March 2015 to January 2016.OC and EC were analyzed by thermal optical reflection method,and the concentration level,seasonal distribution,OC/EC ra?tios,correlations,secondary organic carbon(SOC)were analyzed in detail.Results showed that the concentration range of OC was(6.2~10.8)μg/m3,while the EC was(2.0~4.1)μg/m3,and the TC in PM_2.5 was(28.7~34.6)%.The seasonal varia?tion characteristics of OC and EC in each site were spring>winter>autumn>summer,and the ratio of OC/EC was greater than 2.0,which indicated that the secondary organic carbon was formed.The minimum OC/EC ratio method was used to esti?mate the SOC formation.The annual average concentration of SOC was 3.8μg/m3,accounted for 46.8%of OC.The higher contribution of SOC to PM_2.5 in spring and winter than in summer and autumn might be related to time change effect of air diffusion condition.The concentrations of OC were significantly correlated with EC in summer,autumn and winter,suggest?ed that they might had similar primary sources,while OC and EC had poor correlation in spring indicated that the source of OC and EC was relatively complex.By calculated and analyzed the abundances of eight kinds of carbon components and the correlation between TC and K+in PM_2.5,the gasoline vehicle emission,coal emissions and biomass burning were indicated to be the major sources of atmospheric carbon aerosols in FuZhou.