2014-2018年南京PM2.5中碳组分污染特征分析

利用在线高分辨率仪器对2014-2018年南京市PM2.5中有机碳(OC)、元素碳(EC)进行了连续监测,结果表明:离线分析法与在线分析法对OC、EC的测定结果具有很好的线性相关性,离线分析的EC、OC浓度高于在线自动监测值;2014-2018年南京OC与EC的平均质量浓度分别为(6. 38±3. 91)μg/m^3和(3. 12±1. 76)μg/m^3,整体呈下降趋势,冬季OC与EC均较高,夏季两者质量浓度较低。OC和EC均呈现夜间高、白天低的日变化规律,OC与EC第一个峰值均出现在08:00左右,OC第二个峰值出现在20:00前后;夏季OC与EC相关性最低,冬季最高,NO2、CO与OC、EC的相关性总体高于SO2,表明燃料燃烧对碳气溶胶有一定贡献,但没有交通源的贡献显著,夏季O3与OC呈现一定程度的正相关性。利用最小相关系数法(MRS)计算大气OC中一次有机碳(POC)和二次有机碳(SOC),结果显示OC中以POC为主,但SOC呈逐年上升趋势,2018年SOC质量浓度达1. 96μg/m3,在OC中占比达31. 9%,后续颗粒物污染治理的重点可能应关注VOCs。

Characteristics Analysis of Carbon Components in PM2.5 in Nanjing from 2014 to 2018

The continuous monitoring of OC and EC concentrations in PM2.5 in Nanjing from 2014 to 2018 was carried out by using online high-resolution instruments. The result shows that off-line and online analysis have a good linear correlation between EC and OC. The EC and OC values of offline manual analysis are generally higher than the online values. From 2014 to 2018,the average concentration of OC was (6. 38± 3. 91) μg/m^3 and EC was (3. 12± 1. 76) μg/m^3,EC and OC have shown a downward trend overall. Both OC and EC are higher in winter and lower in summer. OC and EC showed a daily variation with higher nighttime and lower daytime. The first peak of OC and EC appeared at around 8: 00 am,and the second peak of OC appeared around 8: 00 pm. The correlation between OC and EC was the lowest in summer and highest in winter. The correlation between NO2,CO and OC,EC was higher than SO2,indicating that carbon source aerosols from traffic sources are more significant than fuel combustion sources. Summer OC and O3 indicate a certain degree of positive correlation. The MRS method was used to calculate POC and SOC in OC,the results showed that POC was the main factor in OC,and the SOC was increasing year by year.The SOC concentration in 2018 was 1. 96 μg/m3,accounting for 31. 9% in OC. The focus of subsequent particulate pollution control may be concerned on VOCs.