南通市大气VOCs四季变化特征和臭氧生成潜势分析

Analysis on Seasonal Variation Characteristics of Atmospheric VOCs and Ozone Formation Potential in Nantong City

于2019年在南通市采用TH-300B大气挥发性有机物(VOCs)在线分析仪对57种VOCs开展在线监测,对比分析了VOCs组分变化、季节变化、日变化特征,并用最大增量反应活性(MIR)估算了VOCs的臭氧生成潜势(OFP),找到了南通市VOCs的优控物种。结果表明,2019年南通市VOCs平均体积分数为15.57×10^(-9),不同组分体积分数排序为:烷烃(9.65×10^(-9))>芳香烃(2.85×10^(-9))>烯烃(1.84×10^(-9))>炔烃(1.23×10^(-9)),总体表现为冬季高、夏季低的特征。和国内其他城市比较,南通市VOCs和各组分体积分数处于较低水平。烯烃和炔烃的日变化特征均呈现较明显的双峰分布,峰值位于7:00-8:00和19:00-21:00;烷烃的日变化特征均呈现较明显的单峰分布,峰值位于6:00-8:00;芳香烃的日变化特征在4个季节变化趋势有所不同。烷烃和芳香烃夜间体积分数均高于白天。VOCs的OFP年均值为108.17μg/m3,季节排序为:冬季(122.70μg/m^(3))>春季(116.15μg/m^(3))>秋季(111.26μg/m^(3))>夏季(82.58μg/m^(3))。VOCs优控物种为丙烷、乙烯、异戊烷、甲苯、间/对二甲苯,因此控制市区臭氧浓度的首要任务是控制机动车排放、加油站油气挥发和溶剂使用。

TH-300B online VOCs analyzer was used to determine 57 kinds of atmospheric volatile organic compounds(VOCs)in 2019,the component variation characteristics,seasonal and daily variation characteristics were analyzed.By using the maximum increment reactivity(MIR),the ozone formation potential(OFP)was estimated and the priority controlled VOCs were found in Nantong.The results showed that the average volume fraction of VOCs in Nantong in 2019 was 15.57×10^(-9),and the volume fraction of different component ranked as follows:alkane(9.65×10^(-9))>aromatic hydrocarbons(2.85×10^(-9))>alkenes(1.84×10^(-9))>alkynes(1.23×10^(-9)).The values were higher in winter and lower in summer.Compared with other cities in China,the volume fraction of VOCs and its components in Nantong is at a low level.The daily variation characteristics of alkenes and alkynes showed obvious bimodal distribution in four seasons,with the peak at 7:00-8:00 and 19:00-21:00,and the daily variation characteristics of alkanes showed obvious unimodal distribution in four seasons,with the peak at 6:00-8:00.The daily variation characteristics of aromatic hydrocarbons were different in four seasons.The concentrations of alkanes and aromatics were higher at night than at day.The average OFP was 108.17μg/m^(3),and the seasonal OFP ranked as follows:in winter(122.70μg/m^(3))>in spring(116.15μg/m^(3))>in autumn(111.26μg/m^(3))>in summer(82.58μg/m^(3)).The priority controlled species are propane,ethylene,isopentane,toluene and m/p-xylene.The primary task of ozone concentration control in Nantong urban area is to control vehicle emission,gas volatilization and solvent use in gas stations.