Carbon Isotope Composition Characteristics And Source Analysis In Aerosol Of The Inland Area In Nanchang And Remote Sea Area In The Western North Pacific

With the development of the times and economy,air pollution has become one of the most important pollution problems in China.Among them,atmospheric aerosol is an important component that causes increasingly serious environmental pollution.In recent years,with the increasing concentration of particulate matter,urban air pollution has become more and more serious,which not only leads to the frequent occurrence of haze events,but also affects the composition of the ocean atmosphere through long-distance atmospheric transmission,especially in winter.As an important component of atmospheric particulate matter,carbon is considered as an important factor for haze formation and transformation,and it is also an important component affecting global climate change and the carbon cycle of the oceans.Therefore,in order to understand the source differences between the remote marine atmospheric aerosol and urban aerosol,this study collected marine atmospheric aerosols over the western North Pacific,and collected aerosols samples in Nanchang to determine the total carbon concentration（TC）、black carbon（BC）concentration and its stable carbon isotope values(δ¹³C_TC andδ¹³C_BC).The results showed that:（1）Characteristics and sources of total carbon isotopes composition in aerosols over the western North Pacific in winterThe TSP concentration in winter was 44.8±28.1μg/m³ in the western North Pacific,with obvious fluctuation range.The results show that the average concentration of TC was 4.0±4.4μg/m³,and the average value ofδ¹³C_TC was-26.6±0.8‰over the western North Pacific.The average concentrations of TC were 6.0±6.8μg/m³ and 3.1±2.7μg/m³ in the nearshore and remote region,and theδ¹³C_TC were-26.0±1.2‰and-26.9±0.4‰,respectively.According to the backward trajectories at different sampling sites,the differences of TC concentration andδ¹³C_TC between nearshore and remote region may be caused by different contributing sources.The high TC concentration in the nearshore is mainly derived from biomass burning and motor vehicle exhaust.In contrast,the TC in the remote region may be associated with a relatively high proportion of SOA formation.（2）Characteristics and sources of total carbon isotopes composition in PM_2.5 of Nanchang CityThe annual average concentration of TC was 12.1±2.13μg/m³ during the sampling period.The concentrations of TC in PM_2.5 was significantly higher in winter than that in summer,and the seasonal variations of TC concentration may be influenced by meteorological factors and source changes in different seasons.The annual average ofδ¹³C_TC is-26.1±0.18‰,which generally shows a trend of high winter and low spring,and may be affected by different sources.Through the Bayesian model,we have calculated that TC in PM_2.5 in Nanchang area mainly came from C₃ plant combustion and motor vehicle exhaust,with the annual contribution of 49.3%and 28.7%,respectively.Besides,coal burning and C₄ plant burning contributed 17.7%and 4.2%,respectively.The results also showed that lowδ¹³C_TC value in spring is due to the relatively high contribution of C₃ plant combustion,while the higher δ¹³C_TC in winter is due to the increased contribution of coal combustion.The results of the backward trajectory of cluster show that the local air mass transport is dominant in winter and spring,and the influence of ocean air mass is great in summer,in Nanchang area.（3）The difference of total carbon sources between the western North Pacific and Nanchang area in winter aerosolsBy comparing the TC concentration,δ¹³C_TC and their sources in the aerosol in the remote western North Pacific and the inland Nanchang area,it is found that the large difference in the TC concentration in the two study areas is due to the different air mass sources.The large difference ofδ¹³C_TC value is that lowδ¹³C_TC value in the western North Pacific may be associated with a relatively high proportion of SOA formation,while the higherδ¹³C_TC in Nanchang area is related to the increased contribution of coal combustion.In addition,there are large differences in pollution sources.The western North Pacific is mainly affected by the air mass long-distance transportation of terrestrial anthropogenic pollution sources,while Nanchang area is mainly affected by local pollution sources.（4）Characteristics and sources of black carbon isotopes composition in PM_2.5 in Nanchang CityIn Nanchang area,the annual average concentration of BC in PM_2.5 is 1.3±0.9μg/m³.The concentration of BC in winter reached the highest in three seasons,and the concentration of BC in spring and summer was basically the same,which may be affected by the meteorological factors in different seasons.The annual average value ofδ¹³C_BC in PM_2.5 is-25.4±0.8‰,which generally shows a trend of high winter and low spring.The result also shows that lowδ¹³CBC value in spring is due to the relatively high contribution of C₃ plant combustion,while the higherδ¹³CBC in winter is due to the increased contribution of coal combustion.Through the Bayesian model,we have calculated that BC in Nanchang PM_2.5 mainly came from motor vehicle exhaust and C₃ plant combustion,with the annual contribution of 47.8%and 26.8%,respectively.Besides,coal burning and C₄ plant burning contributed 24.0% and 1.4%,respectively.