天津市PM_(2.5)碳组分空间差异性及来源解析

Spatial Variability and Source Apportionment of PM_(2.5) Carbon Components in Tianjin

2021年在天津市不同功能区共设置4个点位同步采集细颗粒物(PM_(2.5))样品,测定了其中8种碳质亚组分的含量.结果表明,采样期间各点位ρ[有机碳(OC)]为3.7~4.4μg·m^(-3),ρ[元素碳(EC)]为1.6~1.7μg·m^(-3),OC浓度在中心城区最高,EC浓度差别较小.采用最小比值法对二次有机碳(SOC)进行估算,结果表明环城区二次污染较为突出,SOC占OC的比例达48.8%.各功能区碳质亚组分间的相关性强弱呈现出外围区>中心城区>环城区的特征,均表现出EC1与OC2和EC1与OC4相关性最强.正定矩阵因子(PMF)来源解析结果显示,道路扬尘源(9.7%~23.5%)、燃煤源(10.2%~13.3%)、柴油车尾气(12.6%~20.2%)和汽油车尾气(18.9%~38.8%)是天津市PM_(2.5)中碳组分的主要来源.不同功能区碳组分污染源存在差异,中心城区和外围区主要受汽油车尾气影响;环城区受二次污染和柴油车尾气的影响更为突出.

The contents of eight carbonaceous subfractions were determined by simultaneously collecting PM_(2.5) samples from four sites in different functional areas of Tianjin in 2021.The results showed that the organic carbon(OC)concentration was 3.7μg·m^(−3) to 4.4μg·m^(−3),and the elemental carbon(EC)concentration was 1.6μg·m^(−3) to 1.7μg·m^(−3),with the highest OC concentration in the central urban area.There was no significant difference in EC concentration.The concentration of PM_(2.5) showed the distribution characteristics of the surrounding city>central city>peripheral area.The OC/EC minimum ratio method was used to estimate the concentrations of secondary organic carbon(SOC)in PM_(2.5),and the results showed that the secondary pollution was more prominent in the surrounding city,with SOC accounting for 48.8%.The correlation between carbon subcomponents in each functional area showed the characteristics of the peripheral area>central area>surrounding area,all showing the strongest correlation between EC1 and OC2 and EC1 and OC4.By including the carbon component concentration into the positive definite matrix factorization(PMF)model for source apportionment,the results showed that road dust sources(9.7%-23.5%),coal-combustion sources(10.2%-13.3%),diesel vehicle exhaust(12.6%-20.2%)and gasoline vehicle exhaust(18.9%-38.8%)were the main sources of carbon components in PM_(2.5) in Tianjin.The pollution sources of carbon components were different in different functional areas,with the central city and peripheral areas mainly affected by gasoline vehicle exhaust;the surrounding city was more prominently affected by the secondary pollution and diesel vehicle exhaust.