中原城市群国家干线公路SOA生成潜势估算

Estimation of the SOA Formation Potential of the National Trunk Highway in Central Plains Urban Agglomeration

二次有机气溶胶(SOA)是大气污染的主要成分之一,估算汽车尾气所生成的SOA对交通大气污染治理具有重要意义.本文基于国家干线公路交通量调查数据,根据监测站点和代表路段长度建立了中原城市群干线路网线性参考系统,并以车流量为基础数据,采用排放系数法测算出中原城市群干线道路VOCs排放量,再根据气溶胶生成系数对SOA的生成潜势进行估算,并经核密度计算后转换为线性连续分布,进行交通SOA的空间定量分布研究.结果表明:(1)甲苯的SOA生成潜势最高,但1,4-二乙基苯的SOA生成能力最强,芳香烃的SOA生成能力总体高于烷烃;(2)中小型汽油客车是最大的SOA生成源,占SOA生成量的1/3左右,但SOA生成能力最强的是小型汽油货车;(3)汽油车的SOA生成能力高于柴油车,客车的SOA生成能力略微高于货车;(4)中原城市群的SOA排放强度具有明显的以郑州为中心的高强度聚集现象,汽油车的分布与总体相似,但柴油车的强度和聚集性明显下降,以郑州为中心,南北干线上的排放强度高于东西方向.

Secondary organic aerosols(SOAs)are among the main components of air pollution.Accurately estimating SOAs formed from automobile exhaust is crucial for controlling and mitigating traffic air pollution.Sufficient monitoring data is difficult for regional analysis owing to limited monitoring data over a small area or few observation stations.Indirect methods may be used to estimate SOA using data on the number and types of vehicles.A linear reference system of Central Plains urban agglomeration was built from the national trunk line network system and the traffic survey data of transportation.The numbers of different types of vehicles were assigned to road segments as the traffic flow according to the represented length between monitoring stations.Then,VOCs emissions were calculated through the emission coefficient method based on the previous traffic flow data.Moreover,further estimations of the SOA formation potential were made by the fractional aerosol coefficient approach.Through kernel density analysis,discrete point data of the observer station were transformed into line segments and expanded to a continuous spatial distribution for quantitative and spatial variation analysis of the SOA in the study area.The results show that(1)toluene has the highest SOA generation potential,1,4-diethylbenzene has the strongest ability to form SOA,and aromatic hydrocarbons exhibit higher SOA formation capacity than alkanes;(2)small and medium gasoline passenger cars generate the most SOA and account for about 1/3 of the total SOA,but small gasoline trucks exhibit the strongest capacity for SOA formation;(3)regarding the capacity of SOA formation for vehicles using different fuel types,gasoline vehicles have a higher capacity than diesel vehicles,and passenger cars have a slightly higher capacity than trucks;(4)in Central Plains urban agglomeration,the spatial distribution of SOA intensity data shows a trend of convergence to the center of Zhengzhou city.Gasoline vehicles exhibit a similar pattern overall,but diesel vehicles exhibit a weaker trend that decreases distinctly.SOA intensity along the north-south direction is much higher than that of the east-west direction around the center of Zhengzhou crossing.