Impact Assessment And Source Apportionment Of Regional Transmission On PM_2.5 In Luohe,Henan Province

Luohe has been urbanising rapidly in recent years,and car ownership has soared,with fine particulate pollution in Luohe still high,despite stricter requirements from governments at all levels,there is also a mismatch between the concentration and emissions of particulate matter from regional transport,making it urgent to study the extent of the impact of regional transport on fine particulate matter in Luohe,quantitative assessment of the impact of regional pollution on Luohe and local source apportionment in Luohe is essential.In this study,meteorological data,air quality monitoring data,global data assimilation system GDAS data,PM_2.5chemical composition data from Luohe air pollution monitoring super station were used to analyze the heavy pollution process of fine particulate matter in Luohe from 2015 to2020,the four parameters proposed are used to describe the effect of regional transportation on Luohe,the backward trajectory,potential source contribution factor（PSCF）,concentration weighted trajectory（CWT）,chemical composition analysis of particulate matter and source apportionment of PM_2.5（PMF）were used.The results show that the stagnation period and delay period of pollutants in Luohe were 2-10 hours and 4-23 hours.The increment of PM_2.5in heavy pollution process was 8-311μg/m³and∑PM_2.5was 274-2334μg/m³.In contrast to Luohe,the regional transport of pollutants has worsened air quality in the provinces of Nanyang,Luoyang,Sanmenxia and Xinyang,with Luoyang’s PM_2.5reaching a maximum of more than 9000μg/m³.The backward trajectory simulation shows that the air mass from the South（track 2）and the Northeast（track 3）have a greater influence on the air quality in Luohe.The characteristics of these two types of trajectories are short trajectory,slow moving and passing through heavily polluted regions,the probability of two types of track pollution is high because of the easy-carrying pollutants.The results of potential source analysis show that the areas that contribute most to fine particulate matter in Luohe mainly come from the central,eastern and southern parts of Henan Province,southern part of Hebei Province and western part of Shandong Province.The contribution of short-distance transport to PM_2.5in Luohe is even more significant.From 2019 to 2020,the total water-soluble ions accounted for 79.3%of the sum of all components of PM_2.5.The contribution of SNA（Secondary Inorganic Aerosol）to PM_2.5was 64.13%on average,accounting for 80.87%of total water-soluble ions.The content of total water-soluble ions was higher in winter and spring,followed by autumn,lowest in summer.OC and EC accounted for 11.27%of the sum of PM_2.5,and heavy metal elements accounted for 2.74%of PM_2.5.K,Ca,Fe,Cu and Zn accounted for 90.95%of the total inorganic elements.Luohe has high ammonia content,SOR is higher in spring and summer,SOR is higher than 0.5,NOR is higher in autumn and winter,and NOR is higher in spring and winter,next in autumn and lowest in summer,the oxidation rate of nitrogen was above 0.4 in all seasons,which indicated that there was a certain secondary transformation process in Luohe.From 2019 to 2020,eight major sources have been identified in Luohe.They are secondary sources,coal-fired sources,industrial sources,biomass combustion,construction dust and sea salt,fugitive dust sources,motor vehicles and agricultural sources,the contribution to PM_2.5was 35.22%,24.33%,6%,6.52%,8.76%,7.31%,2.14%and 9.73%respectively.The major sources contributing to PM_2.5in each season are:secondary sources in spring,building dust and sea salt,industrial sources,secondary sources in summer,biomass combustion and agricultural sources,and secondary sources,coal combustion,building dust and sea salt in autumn,in winter,it is a secondary source,a coal-burning source and a dust-raising source.