贵阳市大气臭氧前体挥发性有机物特征及来源解析

Characteristics and Source Analysis of Ozone Precursor Volatile Organic Compounds in the Atmosphere of Guiyang

选择在贵阳市三个典型地点进行观测和分析获取大气VOCs环境浓度数据的基础上,通过分析各组分的化学反应活性,识别当地臭氧生成潜势较大的关键大气光化学活性VOCs组分,并采用点苯/甲苯/乙苯比值分析,识别各类源在在贵阳市大气芳香烃的排放贡献情况,为后续对受体点进行VOCs来源解析提供研究基础。研究成果表明:(1)2021年贵阳市总臭氧前体VOCs的年平均浓度为27.11ppbv,总大气臭氧前体VOCs的观测浓度高于成都、南京、重庆、武汉和北京等地;(2)贵阳市大气臭氧前体VOCs的烷烃组成中乙烷、丙烷、正丁烷、异丁烷、正戊烷和异戊烷六种组分占比较高,芳香烃中甲苯占比非常突出,烯烃中乙烯为优势物种,炔烃中的乙炔贡献也较为显著。(3)贵阳市大气臭氧前体VOCs在冬季的浓度最高,乙烷、乙烯、乙炔和苯具有很强的季节变化规律,且每个季节上述组分的浓度波动幅度不大,均为冬季浓度最高,秋季浓度最低;(4)大气臭氧前体VOCs总平均臭氧生成潜势,都是冬季的臭氧生成潜势最大,甲苯、二甲苯、C_(4)-C_(5)烷烃是贵阳市臭氧生成潜势的主要贡献者,在以植物生长茂盛,植被覆盖率广的地区,春夏季节植物排放的异戊二烯是臭氧生成潜势的优势贡献组分;(5)苯/甲苯/乙苯比值分析可知机动车排放源在贵阳市大气芳香烃的排放贡献中占重要部分。

On the basis of the atmospheric VOCs environmental concentration data obtained by observation and analysis at three typical locations in Guiyang City,through analysis of the chemical reactivity of each component,to identify the key atmospheric photochemical active VOCs with high potential for ozone generation,and the point benzene/toluene/ethylbenzene ratio analysis to identify the contribution of various sources to the emission of aromatic hydrocarbons in the Guiyang Atmosphere,which provided a basis for further study on source apportionment of VOCs at receptor sites.The results showed that:(1)In 2021,the average annual concentration of total atmospheric ozone precursor VOCs in Guiyang was 27.11 ppvb,and the observed concentration of total atmospheric ozone precursor VOCs was higher than that in Chengdu,Nanjing,Chongqing,Wuhan and Beijing.(2)The alkanecomposition of atmospheric ozone precursor VOCs in Guiyang City is relatively high in ethane,propane,n-butane,iso-butane,n-pentane and iso-pentane,the proportion of toluene in aromatic hydrocarbons is very prominent,ethylene in olefin is the dominant species,and the contribution of acetylene in alkyne is also relatively significant.(3)In Guiyang City,the concentration of atmospheric ozone precursor VOCs is the highest in winter.Ethane,ethylene,acetylene and benzene have a strong seasonal change rule,and the concentration fluctuation of the above components in each season is not large,with the highest concentration in winter and the lowest concentration in autumn.(4)The total average ozone formation potential of atmospheric ozone precursor VOCs is the highest in winter,and toluene,xylene and C_(4)-C_(5) alkane are the main contributors to the ozone formation potential of Guiyang City.In areas with lush plant growth and wide vegetation coverage,isoprene emitted by plants in spring and summer is the dominant contribution component to the ozone formation potential.(5)The ratio analysis of benzene/toluene/ethylbenzene showed that vehicle emission sources play an important role in the emission of atmospheric aromatic hydrocarbons in Guiyang City.