Research On Pollution Characteristics Of PM_2.5 And PM₁₀ In The Atmosphere Of Changchun

In order to study the pollution characteristics of the chemical composition of PM_2.5 and PM₁₀ in the atmosphere of Changchun,environmental samples were collected from April 6,2019 to January 20,2020.Comparative analysis of the concentration distribution characteristics of inorganic elements,water-soluble ions,elemental carbon and organic carbon in PM_2.5 and PM₁₀.Enrichment factor method and health risk assessment method were used to compare and analyze the enrichment degree of metal elements in particles and the risk of influencing human health.The sources of PM_2.5 and PM₁₀ in the atmosphere of Changchun were analyzed and discussed.The main conclusions of this paper are as follows:The average annual concentrations of PM_2.5 and PM₁₀ in the atmospheric environment of Changchun are 36.86±25.54μg/m³and 69.79±33.02μg/m³,respectively,showed a seasonal trend of high winter and spring,low summer and autumn.Only the average concentrations of PM_2.5and PM₁₀in winter exceeded the annual average national second-level standard,indicated that the winter particulate pollution in Changchun was serious.In addition,PM_2.5/PM₁₀ showed high winter（>0.7）and low spring,summer and autumn（<0.5）,indicated that winter particulate pollution was mainly PM_2.5 and other seasons were dominated by coarse particles.Crustal elements are the main part of PM_2.5 and PM₁₀（93.4%and 97.4%,respectively）,mainly concentrated in PM₁₀,trace elements mainly concentrated on PM_2.5;The enrichment factors value of the element in PM_2.5 is higher than PM₁₀,indicated that the element was more likely to be rich in PM_2.5.As in PM_2.5 has a non negligible carcinogenic risk to human body throμgh respiratory pathway,Cr in PM_2.5has a non negligible carcinogenic risk to adults throμgh respiratory pathway.The risk of non-carcinogenicity from skin absorption pathways can be ignored,PM_2.5 produced a higher health risk than PM₁₀.NO₃^-,SO₄^2-and NH₄⁺are the main components of water-soluble ions,accounting for 62.6%and 62.4%of the total ion concentration respectively,among which NO₃^-concentration is the highest and accounts for the largest proportion.In autumn and winter,total carbon accounted for 25.94%and 35.27%of PM₁₀ mass concentration,44.14%and 42.03%of PM_2.5 mass concentration,respectively,indicated that total carbon was important components of PM_2.5 and PM₁₀.The calculated secondary organic carbon has a low proportion in autumn and a high proportion in winter,indicated that the organic carbon in Changchun was dominated by primary organic carbon in autumn and secondary organic carbon in winter.In spring polluted weather,the concentration of secondary water-soluble ions in PM_2.5 increased significantly,while PM₁₀ was a significant increase in the concentration of crustal elements;In winter polluted weather,the concentrations of OC,EC and secondary ions in PM_2.5 and PM₁₀ increased significantly,and the secondary ion concentration increased significantly.In summary,the polluted weather in spring was dominated by wind and dust,and the secondary transformation was auxiliary and co-effects.The polluted weather in winter were caused by the increase of secondary aerosol conversion and the increase of pollutants in low wind speed and high humidity weather conditions.The positive matrix factorization model was used to determine the five main contributors of PM_2.5 and PM₁₀ in the atmosphere of Changchun,included soil and building dust sources,secondary aerosols and biomass burning sources,motor vehicle and road dust sources,industrial emissions and soil sources,and coal combustion sources.Secondary aerosols,coal combustion and biomass burning sources are the main sources of PM_2.5and PM₁₀ contribution,in addition PM₁₀ is mainly contributed by coarse particles such as dust,and PM_2.5 is mainly emitted from industry and transportation.In addition,PM_2.5 and PM₁₀ have similar spatial potential source regions,distributed in the southwest,northwest and northeast of Changchun.