Composition And Sources Of Organic Compounds In PM_2.5 In Southern China

Atmospheric organic aerosols have become a research hotspot at home and abroad,and have great impact on both environmental effects and human health.There were few studies on fine organic aerosols in the southern border provinces of China,while to explore the impact of cross-border transmission on the southern region,the background site in Guangxi and the urban site in Kunming were selected.128 and 105 atmospheric fine particulate matter samples were collected from December 2019 to November 2020.Laboratory organic compounds were determined using meteorological chromatography-mass spectrometry(GC-MS),mainly including 6 categories:n-alkanes,PAHs,sugars,lignin,biogenic SOA tracers and aromatic acids.The methods such as organic molecular signatures,principal component analysis(PCA),and backward trajectory model were integrated to discuss the composition,pollution sources,and source area distribution of organic aerosols in Guangxi and Kunming during the season,with the following main results:1)In Guangxi background site(Shiwandashan Mountain),the concentration levels of organic compounds were winter(232.4±122.6 ng·m^-3)>autumn(142.7±87.9ng·m^-3)>summer(81.1±95.1 ng·m^-3)>spring(72.3±42.1ng·m^-3),with sugar compounds dominating,followed by biogenic SOA tracers The concentration levels of organic compounds in Kunming(Yunnan University)were spring(256.5±88.3ng·m^-3)>winter(171.4±85.9 ng·m^-3)>autumn(169.4±137.4 ng·m^-3)>summer(85.4±56.0 ng·m^-3),with sugar compounds dominating,followed by n-alkanes.2)Biomass combustion is an important source of organic compounds in the study areas,and the pollution source are different.In Guangxi background site(Shiwandashan Mountain),the contribution of biomass combustion to aerosols was more than 35%,followed by the influence of secondary organic aerosols,with a contribution of 26%,which were more significantly influenced by biomass combustion and biological primary emissions in autumn and winter,mostly by terrestrial cross-regional transmission,and more significantly influenced by secondary oxidized aerosols transmitted from the ocean in spring and summer,mostly by oceanic transmission in the east and south.In Kunming(Yunnan University),the overall impact by biomass combustion was more significant,not only by land-based cross-regional transmission and cross-border transmission,but also by local source emissions,followed by the impact of fossil fuel emissions.3)In the climatic context of global warming,the frequent occurrence of extreme dry weather in spring and the effective control of local biomass burning in Yunnan,extensive forest fires in the India-Burma region occurred along its border.The transmission of air currents to areas such as Kunming under the influence of monsoon circulation,resulting in large differences in the concentration levels of organic compounds in spring between the background site in Guangxi(Shiwandashan Mountain)and the urban site in Kunming(Yunnan University),with different degrees of biomass burning impact as well.