徐州市重污染期碳质组分、水溶性离子特征及来源解析

Characteristics and source analysis of carbonaceous composition,water-soluble ion concentration in heavy pollution period in Xuzhou city

基于美国沙漠所研制的Model 2001A热/光碳分析仪对徐州市区2016年冬季重污染时期PM2.5中的碳质组分[有机碳(OC)和元素碳(EC)]以及水溶性离子(NO3^-、SO42^-、F^-、Cl^-、NO2^-、NH4^+、K^+、Ca^2+、Mg^2+、Na^+)进行昼夜采样监测,并采用优化的MRS算法对二次有机碳(SOC)含量进行了估算。结果表明,在采样期间徐州市区PM2.5平均质量浓度达到了(129.7±37.0)μg/m3。通过OC/EC比值分析,采样期间徐州市区碳质气溶胶主要受到汽油车和柴油车尾气排放影响。SOC平均质量浓度为3.4μg/m3,对OC的贡献达了44.3%,且夜晚二次污染程度要大于白天。重污染时期水溶性离子平均质量浓度达到了(126.0±24.0)μg/m3,3种主要水溶性离子(NO3^-、SO42^-、NH4^+)以NH4NO3、(NH4)2SO4的形式存在。通过对NO3-、SO42-质量浓度比值的分析,表明以燃煤为主的固定源对水溶性离子贡献较大。利用PMF模型分析重污染期间大气PM2.5的质量浓度来源主要有6个,分别为交通源(48.7%)、二次无机气溶胶污染源(24.3%)、海盐及燃煤燃烧源(14.9%)、二次化工污染源(12.1%)、生物质燃烧源(0.9%)、道路扬尘源(0.1%)。总体来说,大气中PM2.5的来源较为多源化,其中交通源以及二次无机气溶胶污染源占据主导地位。

Based on the Model 2001 A thermal/photocarbon analyzer developed by the US Desert,the carbonaceous components(organic carbon(OC)and elemental carbon(EC))and water soluble ions(NO3^-,SO42^-,F-,Cl^-,NO2^-,NH4^+,K^+,Ca^2+,Mg^2+,Na^+) in PM2.5 during heavy pollution in 2016 winter in Xuzhou city were monitored by day and night sampling,and the secondary organic aerosol(SOC)content was optimized by the optimized MRS algorithm. The results showed that the average mass concentration of PM2.5 in Xuzhou city reached(129.7±37.0)μg/m3 during the sampling period. Through the OC/EC ratio analysis,the carbonaceous aerosol in Xuzhou city during the sampling period was mainly affected by the exhaust emissions of gasoline vehicles and diesel vehicles. The average mass concentration of SOC was 3.4 μg/m3,and the contribution to OC reached 44.3%,and the degree of secondary pollution at night was greater than that during the day. The average mass concentration of water-soluble ions in the heavy pollution period reached(126.0±24.0)μg/m3,and the three main water-soluble ions of NO3-,SO42-,and NH4+ existed in the form of NH4NO3 and(NH4)2SO4. Through the analysis of NO3-and SO42- ratios,the fixed source of coal-burning contributed a lot to water-soluble ions. Using PMF model to analyze the mass concentration of atmospheric PM2.5 in heavy pollution period in Xuzhou city,there were mainly six,including traffic source(48.7%),secondary inorganic aerosol pollution source(24.3%),sea salt and coal combustion source(14.9%),secondary chemical pollution sources(12.1%),biomass combustion sources(0.9%),and road dust sources(0.1%). In general,the source of atmospheric PM2.5 in Xuzhou city is more multi-sourced,and the traffic source and secondary inorganic aerosol pollution source occupy a dominant position.