武汉城区秋季大气挥发性有机物污染特征及部分物种来源的初步分析

摘要

于2014年10月采用GC-MS挥发性有机物(VOCs)在线监测系统在武汉城区开展大气VOCs连续监测,并分析VOCs体积分数的时间变化特征、光化学活性差异及来源解析.结果表明,武汉城区总VOCs体积分数为45.14×10-9,从高到低依次为烷烃>烯烃>芳香烃;VOCs日变化呈双峰型特征,峰值分别出现在 6:00-8:00和19:00-23:00;T/B和E/E的平均比值分别为0.94和0.61,表明气团受机动车影响显著,且存在老化现象;烯烃对OH消耗速率(LOH)和臭氧生成潜势(OFP)的贡献率最大,芳香烃次之,烷烃最低;以3-甲基戊烷为机动车排放示踪物,计算得出非机动车源对乙烯、甲苯和间/对-二甲苯的贡献率分别为85%、55%和70%.%A continuous observation was carried out with the GC-MC volatile organics online monitoring system for one month in October 2014 in the urban area of Wuhan, the temporal variation characteristics of VOCs were analyzed,as well as their photochemical reactivity and source apportionment.The results showed that the total VOCs was 45.14×10-9(volume fraction), and alkanes were found to be the largest part of VOCs, followed by alkenes,and aromatics were the least.The diurnal variation showed a bimodal characteristic, the maximum value of VOCs occurred at 6:00-8:00 and 19:00-23:00.The ratios of T/B and E/E were 0.94 and 0.61, indicating the significant impact of motor vehicle emission, and possibly due to the aging of the air mass at this site. Alkenes contributed the largest parts of the OH consumption rate(LOH) and the ozone formation potential(OFP), followed by aromatics, and alkanes were the lowest.3-methylpentane, a tracer for vehicle emission, was used to estimate the contributions of traffic versus non-traffic sources.The non-traffic source contribution was significant for ethene(85%) , toluene(55%) and m,p-xylene(70%).