基于隧道PM_(2.5)取样研究南京市机动车尾气颗粒物排放特征

Emission characteristics of particulate emitted by motor vehicles in Nanjing based on PM_(2.5)sampling in tunnel

为研究南京地区机动车尾气颗粒物排放特征,于2020年8月对南京富贵山隧道内和隧道外进行PM_(2.5)采集,对样品中的水溶性离子、碳质组分的分布特征进行分析,综合总碳同位素(δ^(13)C)与主成分分析(PCA)探究隧道内PM_(2.5)来源,并使用质量平衡模型计算了污染物的平均排放因子.结果显示,隧道入口、出口及隧道外早晚高峰期内PM_(2.5)平均值分别为(69.25±24.19)、(116.67±28.70)和(60.87±16.08)μg·m-3,隧道内污染程度明显高于隧道外.隧道内外二次无机气溶胶(SNA)分布略有不同,隧道外NH_(4)^(+)主要以(NH_(4))_(2)SO_(4)的形式存在,其次为NH_(4)NO_(3);隧道内则主要以(NH_(4))_(2)SO_(4)和NH_(4)NO_(3)的形式存在.隧道内δ^(13)C存在着较小的分馏,平均值为-26.0‰±0.72‰,综合δ^(13)C与主成分分析,隧道内PM_(2.5)主要来源于机动车的一次排放、尾气颗粒物的二次转化和扬尘.富贵山隧道中PM_(2.5)、EC、OC的平均排放因子分别为82.86、24.22、7.07 mg·km^(-1)·veh^(-1),与国内外其他隧道实验排放因子的对比结果显示,通过柴油车比例为6%的富贵山隧道远低于柴油车比例较高的地区.

To explore chemical characteristics of particulate emitted by motor vehicles,PM_(2.5)was collected and analyzed from inside and outside of Fugui Mountain Tunnel in Nanjing during August 2020.This study explored and investigated the water-soluble ions and carbon components in the samples.In addition,a combination of stable carbon isotope(δ^(13)C)and principal component analysis(PCA)revealed the source of PM_(2.5).Finally,the average emission factors(EF)of pollutants were calculated by using mass balance model.The results showed that the average concentrations of PM_(2.5)at the entrance,exit and outside of the tunnel were(69.25±24.19),(116.67±28.70)and(60.87±16.08)μg·m-3,respectively.The average pollutant concentration inside of the tunnel was significantly higher than that outside of the tunnel.The distribution of secondary inorganic aerosol inside and outside of the tunnel was slightly different.Outside of the tunnel NH_(4)^(+)mainly existed in the form of(NH_(4))_(2)SO_(4),followed by NH_(4)NO_(3).While inside of the tunnel,NH_(4)^(+)mainly existed in the form of(NH_(4))_(2)SO_(4)and NH_(4)NO_(3).There was a small fractionation ofδ^(13)C in the tunnel,with an average value of-26.0‰±0.72‰.Combined withδ^(13)C and PCA,PM_(2.5)in the tunnel mainly comes from primary vehicle emissions,secondary conversion of exhaust particulate matter and dust.The EF of PM_(2.5),EC,and OC in tunnel were 82.86,24.22 and 7.07 mg·km^(-1)·veh^(-1),respectively.Compared with other tunnel,the results showed that the EF in the Fugui Mountain Tunnel(the proportion of diesel cars passing was 6%)was lower than that of tunnels with a high proportion of diesel vehicle passing.