Atmospheric Dry And Wet Deposition Of Water-soluble Organic Carbon On Typical Urban And Forest Ecosystems

Organic carbon is an important component in the atmosphere,and its concentration is higher than that of nitric acid and sulfuric acid.The water-soluble organic carbon trapped in the atmosphere has a strong radiative forcing effect,which is a hot topic of climate change.Organic carbon can enter the surface environment from the atmosphere through dry and wet deposition,which has a profound impact on the ecosystem.Previous studies estimated that the global wet deposition flux of water-soluble organic carbon is about 0.5Gt,which is equivalent to 1/3 of carbon loss.Due to the lack of first-hand observation data,the study of water-soluble organic carbon deposition in China was extremely scarce.Based on the long-term sampling and laboratory chemical analysis of China ecosystem research network field stations,Beijing and Qianyanzhou were selected as typical urban and forest underlying surfaces,and the precipitation passive sampler and Anderson classification sampler were used to study the concentration change,size distribution and evolution rule of atmospheric water-soluble organic carbon in precipitation and particulate matter in 2013 and 2018,and to quantitatively study the deposition of atmospheric water-soluble organic carbon into the surface ecosystem through precipitation and aerosol The purpose of flux is to provide a scientific basis for assessing the ecological and environmental effects of atmospheric water-soluble organic carbon deposition in China.The main conclusions are as follows:(1)In Beijing,the concentrations of water-soluble organic carbon in aerosols were higher in winter than that in summer.In winter,water-soluble organic carbon were mainly distributed in fine mode.In summer,it were mainly distributed in two peaks,with one peak in coarse mode and one peak in fine mode.In winter,coarse and fine mode water-soluble organic carbon were related to secondary processes.In summer,fine mode water-soluble organic carbon were related to secondary processes and coarse mode was mainly related to dust and sea salt coarse particles.In Qianyanzhou,the concentrations of water-soluble organic carbon in summer were higher than that in winter,and the particle size distributions showed bimodal distribution.The fine mode in winter were related to the secondary processes,the fine particle size in summer were related to biomass burning.The coarse mode in winter and summer were mainly related to the sea salt particles.(2)The volume-weighted mean concentrations of water-soluble organic carbon in Beijing and Qianyanzhou were winter > spring > autumn > summer.The results of backward trajectories analysis showed that both Beijing and Qianyanzhou were affected by Northwest air masses.The precipitation source of water-soluble organic carbon in Beijing was mainly related to secondary processes.The main sources of precipitation in Qianyanzhou were biomass burning and agricultural sources.(3)The wet deposition fluxes of water-soluble organic carbon in Beijing and Qianyanzhou showed different seasonal characteristics.In Beijing,the summer wet deposition flux was the largest,which was mainly affected by precipitation amount.In Qianyanzhou,the winter wet deposition flux was the largest,and the emission intensity might be the main factor controlling the wet deposition flux of Qianyanzhou.(4)The dry deposition fluxes of Beijing and Qianyanzhou were mainly affected by coarse mode in winter and summer.The ratio of fine mode in dry deposition flux in Qianyanzhou was larger than that in Beijing,which was mainly due to the different underlying surface,and the difference between the coarse and fine mode deposition velocity.(5)In Beijing,the contributions of dry deposition were larger than wet deoposition in winter and summer.In winter,this was mainly because of the little precipitation amount.In summer,this was mainly because of the high concentrations of aerosol WSOC and the large proportion of coarse mode WSOC.In Qianyanzhou,the contributions of dry and wet deposition were alomost same,and the wet deposition contributions were larger than dry deposition in summer.This was mainly because of the different precipitation amount in winter and summer.In addition,the dry deposition velocity in winter and summer was different.Both of them affected the contributions of dry and wet deposition.The innovation of this paper is that:(1)the size distribution,formation mechanism and source of water-soluble organic carbon in aerosols were systematically studied,and its dry deposition fluxes on different ecosystems of cities and forests were estimated;(2)combining the observation data of dry deposition and wet deposition,and studing the total amount and change rule of atmospheric water-soluble organic carbon entering different ecosystems through dry and wet deposition,which provided scientific parameters for the subsequent study of the ecological environment effect of atmospheric water-soluble organic carbon deposition.