天津市夏季PM2.5中碳组分时空变化特征及来源解析

为研究天津市夏季PM_2.5中碳组分的时空变化特征及来源,于2019年7—8月设立2个点位分昼夜采集天津市PM_2.5样品,并测定了其中有机碳(OC)和元素碳(EC)的含量。结果表明,城区PM_2.5、OC和EC浓度日均值分别为(53.4±20.8)μg·m^-3、(8.72±2.56)μg·m^-3和(1.67±0.90)μg·m^-3,郊区PM_2.5、OC和EC浓度日均值分别为(54.2±24.5)μg·m^-3、(7.54±2.50)μg·m^-3和(1.82±1.06)μg·m^-3;白天PM_2.5、OC、EC的平均浓度分别为(47.3±16.1)μg·m^-3、(8.7±2.1)μg·m^-3和(1.5±0.6)μg·m^-3,夜间PM_2.5、OC、EC的平均浓度分别为(60.2±26.2)μg·m^-3、(7.5±2.9)μg·m^-3和(2.0±1.2)μg·m^-3。OC浓度表现为城区高于郊区,白天高于夜间;EC及PM_2.5浓度表现为郊区高于城区,夜间高于白天。OC/EC比值分析得,城区(6.04)高于郊区(5.08);白天(6.58)高于夜间(4.54)。城区OC与EC相关性弱于郊区,白天OC与EC相关性弱于夜间。采用EC示踪法与MRS模型对SOC含量进行估算,得到白天与夜间SOC浓度分别为(5.71±1.35)μg·m^-3和(3.81±1.20)μg·m^-3,白天SOC污染比夜间严重。丰度分析与主成分分析的结果表明,天津市夏季城郊区PM_2.5中碳组分均主要来源于燃煤和机动车尾气排放。

Spatial and temporal variation characteristics and source apportionment of carbonaceous components in PM2.5 during summer of Tianjin

In order to study the characteristics and sources of carbonaceous components in PM_2.5 in summer in Tianjin,two sites were set up in Tianjin from July to August 2019 to collect PM_2.5 samples during day and night,and the contents of organic carbon(OC)and elemental carbon(EC)were measured.The results showed that the daily mean values of PM_2.5,OC and EC concentrations in urban areas were(53.4±20.8)μg·m^-3,(8.72±2.56)μg·m^-3,and(1.67±0.90)μg·m^-3,and those in the suburbs were(54.2±24.5)μg·m^-3,(7.54±2.50)μg·m^-3 and(1.82±1.06)μg·m^-3.The concentration of OC was higher in urban areas than in suburb,and higher in daytime than at night.The concentration of EC and PM_2.5was higher in suburb than in urban and higher in night than in day.OC/EC value was higher in urban area(6.04)than in suburb areas(5.08),and that was higher in day(6.58)than in night(4.54).The correlation between OC and EC in urban areas was weaker than that in suburbs,and that between OC and EC in daytime was weaker than that at night.The EC tracer method and MRS model were used to estimate the SOC content,and the SOC concentration were(5.71±1.35)μg·m^-3 during the day and(3.81±1.20)μg·m^-3 during the night,indicating that the SOC pollution was more serious during the day than at night.The results of abundance analysis and PCA(principal component analysis)showed that the carbonaceous components in PM_2.5 in summer in urban and suburban of Tianjin mainly came from coal combustion and vehicle exhaust.