成都市无车日期间PM_(2.5)污染特征研究

Characteristics of PM_(2.5) Pollution during the World Car Free Day in Chengdu

2013年9月20-24日,通过采集成都市无车日前后禁行区域内PM2.5样品,分析样品中主要的可溶性无机离子、碳组分和金属元素,研究无车日期间PM2.5污染特征变化并评估机动车尾气排放对成都市大气污染的影响。结果表明:在无车日期间,可溶性无机离子中二次离子NO3-、SO42-、NH4+的含量分别下降了29.2%、21.6%、20.5%;有车日期间,OC/EC的平均比值为2.64,而无车日OC/EC比值为1.95,表明减少机动车尾气排放有助于减少二次有机碳的转化;PM2.5中Pb、Cs、Ni、Cu、Zn、Cr、As富集因子大,主要来源于人为污染;Pb、Cu和Zn主要来源于机动车,无车日质量浓度分别下降3.7%、16.3%和19.4%。机动车对PM2.5中的二次离子(NO3-、SO42-、NH4+)、碳组分和重金属(Pb、Cu、Zn)均有较大贡献。因子分析表明,机动车排放源对成都市大气污染物细颗粒物PM2.5贡献量达25.8%。

The influence of vehicle emissions on air pollution in Chengdu is studied, through measuring the water solvent ions, carbonaceous species and metal elements in air samples of ambient PM2.5 at restricted areas on World Car Free Day from September 20 to 24,2013.The results showed that NO3-,SO43- and NH4＋ of secondary inorganic ions in PM2.5 decrease by 29.2%, 21.6% and 20.5% on World Car Free Day. The OC/EC was 2.64 in normal days when 1.95 on World Car Free Day, suggesting that motor vehicle exhaust contribute to conversion of secondary inorganic carbonaceous. Pb, Cs, Ni, Cu, Zn, Cr and As in PM2.5 is mainly derived from man-made pollution, in which Pb, Cu and Zn from vehicle emissions decrease by 3.7% ,16.3% and 19.4% on World Car Free Day.The pollution of vehicle emissions contribute to water solvent ions, carbonaceous species and metal elements and has accounted for 25.8% in PM2.5 in Chengdu.