运城市区夏季大气挥发性有机物污染特征及来源解析

Pollution Characteristics and Source Apportionment of Atmospheric Volatile Organic Compounds in Summer in Yuncheng City

基于2020年6~8月运城市区VOCs、O_(3)和NO_(2)的在线监测数据,分析了运城市区夏季VOCs的污染特征,同时使用正交矩阵因子分解法(PMF)确定了其主要排放源,并通过最大增量反应活性法(MIR)和气溶胶生成系数法(FAC)对VOCs的化学反应活性进行了评估.结果表明,运城市区夏季凌晨和傍晚时段受VOCs和NO_(2)污染较为严重,VOCs日变化峰值分别出现在08:00和20:00,峰值的出现主要受交通早晚高峰的影响;6~8月的ρ(VOCs)为50.52μg·m^(-3),质量分数最高的物种为烷烃(39.39%)和含氧挥发性有机物(OVOCs,34.63%).利用PMF模型共确定了5个VOCs排放源,其中贡献率最大的为机动车尾气排放源(33.10%),其次为工业排放源(29.46%)、天然气及煤燃烧源(17.31%)、溶剂使用源(11.94%)和植物排放源(8.19%),控制机动车尾气排放源是缓解运城市夏季VOCs污染的关键.VOCs的臭氧生成潜势(OFP)均值为162.88μg·m^(-3),其中OVOCs的贡献率(45.37%)最高,乙醛、丙醛、乙烯、异戊二烯和甲苯等是关键的活性组分,工业排放源是贡献率最高的排放源;VOCs的二次有机气溶胶生成潜势(SOA_(p))均值为0.40μg·m^(-3),其中芳香烃的贡献率最高(88.00%),溶剂使用源是贡献率最高的排放源.

Based on the online monitoring data of VOCs,O_(3),and NO2 in Yuncheng City from June to August 2020,the pollution characteristics of VOCs in Yuncheng City in summer were analyzed.At the same time,the main emission sources were determined using a PMF model,and the chemical reactivity of VOCs was evaluated using the maximum incremental reactivity(MIR)method and fractional aerosol coefficients(FAC).The results showed that the urban area of Yuncheng was seriously polluted by VOCs and NO2 in the early morning and evening during summer,the peak value of VOCs daily variation occurred at 08:00 and 20:00,respectively,and was mainly affected by the morning and evening peaks in traffic.Theρ(VOCs)from June to August was 50.52μg·m^(-3),and the species with the highest proportion were alkanes(39.39%)and oxygenated volatile organic compounds(OVOCs,34.63%).Five VOCs emission sources were determined by the PMF model,of which the largest contribution was from motor vehicle exhaust emission sources(33.10%),followed by industrial emission sources(29.46%),natural gas and coal combustion sources(17.31%),solvent use sources(11.94%),and plant emission sources(8.19%).Controlling motor vehicle exhaust emission sources is the key to alleviate VOCs pollution in summer in Yuncheng City.The average ozone formation potential(OFP)of VOCs was 162.88μg·m^(-3),in which OVOCs had the highest contribution rate(45.37%);acetaldehyde,propionaldehyde,ethylene,isoprene,and toluene were the key active components;and industrial emission sources were the emission sources with the highest contribution rate.The average value of secondary organic aerosol formation potential(SOAp)of VOCs was 0.40μg·m^(-3),in which the contribution rate of aromatic hydrocarbons was the highest(88.00%),and the solvent use source was the emission source with the highest contribution rate.