Organic Molecular Composition And Sources Apportionment Of Marine Aerosols In The Coastal Waters Of Eastern China

The coastal waters are the transition zone where air pollutants migrate from inland to the ocean.Monitoring the air pollutants in the coastal waters of China is of great significance for analyzing the sources of air pollutants and evaluating their pollution levels.However,there are few systematic reports on the concentration and spatial distribution of organic compounds in marine aerosols in the Yellow Sea（YS）and Bohai Sea（BS）,and there is a lack of research on the seasonal changes of marine aerosols in the eastern seas of China.Therefore,Shengsi Island was selected as a fixed coastal site in this study,collecting marine aerosol samples in different seasons through fixed-point observations.And the spring samples were collected by cruise observation in the open waters of the YS and BS.Gas chromatography-mass spectrometry technology was used to detect organic compounds in marine aerosol samples.And by combining other chemical components（organic carbon and elemental carbon）and analysis methods（organic molecular markers,PMF and backward trajectory analysis）to explore the composition characteristics and source apportionments of marine organic aerosols in the eastern coastal waters China.The results of this study are as follows:（1）Emissions from continental sources strongly affect the organic components in marine aerosols in the eastern coastal waters of China.The organic components in marine organic aerosols of Shengsi Island were significantly influenced by the long-distance transportation of continental emissions.And the long-distance transmission of continental pollutants had a greater impact on the composition characteristics of marine organic aerosols in the open waters of the YS and BS.（2）The most serious impact on the organic components in marine aerosols in the eastern coastal waters of China was biomass combustion.Among the marine aerosol samples collected on Shengsi Island,levoglucosan had the highest abundance,accounting for more than 80%of the total concentration of anhydrosugars.The concentrations of OC derived from biomass combustion in the three seasons of spring,autumn and winter were much greater than that produced by plant debris and fungal spores,suggesting the severity influence of biomass combustion.PMF results shown that biomass combustion was the most important source of marine organic aerosols in Shengsi Island,contributing more than 15%.Moreover,the biomass combustion-derived OC in the YS and BS marine aerosols contributed the most,accounting for 4.91±6.79%and 8.82±8.03%of the total OC,respectively.（3）The composition characteristics and source apportionments of organic components in marine aerosols collected from Shengsi Island were different in different seasons.During the sampling period on Shengsi Island,the average concentration of OC and EC showed a seasonal variation trend of winter>autumn>spring>summer.The highest concentration of levoglucosan in autumn was 329.69±344.91 ng m^-3,and most of the detected organic compounds had strong correlations with levoglucosan in autumn,indicating that the primary or secondary emissions were affected by biomass burning.Anthropogenic fossil fuel combustion had a serious impact during the winter.The high trehalose concentration in spring proved that the impact of sand and dust were greater.The concentrations of organic compounds detected in summer were generally small,and the OC derived from plant debris was 1.5 times higher than the biomass combustion-derived OC.（4）The BS was easier to accept the input of terrestrial pollutants than the YS.The concentrations of OC and EC detected in the BS samples were higher than those in the YS samples.The nearshore samples that are more affected by terrestrial sources have low OC/EC values,which may be due to the input of organic matter released by marine microorganisms and the reduction of the emission of fossil fuels from the mainland.The concentrations of organic matter detected in marine aerosols in the BS samples were all higher than those in the YS samples.The total contribution of primary and secondary organic carbon from biological sources in the BS sample was 2.7 times higher than that in the Yellow Sea sample,and the biomass burning-derived OC was 2.1 times higher than that in the YS.