Characteristics Of Atmospheric Mercury And Its Wet Deposition In Chongming Island,Shanghai

Mercury(Hg)is a global pollutant,which can be transported for a long distance.China is one of the biggest emitters in the world,and mercury pollution has become a serious problem.However,monitoring of atmospheric mercury in China is lack of development,and there is short of monitoring of atmospheric mercury and its wet deposition in background area.This study mainly focuses on the monitoring of speciated atmospheric mercury and its wet deposition in Chongming Island,Shanghai,to replenish the data for background area of coastal eastern China,which is also significant to the study of mercury's transport and fate in China.Continuous monitoring of gaseous elemental mercury(GEM),reactive gaseous mercury(RGM)and particulate mercury(PBM)is conducted in the Dongtan wetland park in Chongming Island,Shanghai from March 2014 to February 2015.The average concentrations of GEM,RGM,and PBM are(2.75±1.13)ng·m-3,(13.39±15.95)pg·m-3,and(21.89±40.42)pg·m-3,respectively,higher than the background concentration of Northern Hemisphere.The atmospheric mercury shows obvious seasonal variations,with the higher seasonal average GEM concentration in summer and spring,mainly influenced by natural sources,and lower in autumn and winter,mainly influenced by anthropogenic sources.The concentration of RGM is highest in spring and lowest in winter,mainly influenced by the wind direction,while PBM shows higher concentrations in autumn and winter.The concentrations of GEM and PBM are the largest during 05:00-09:00 in the daytime,mainly influenced by the meteorological condition,while most of the high RGM concentration values occurred during 14:00-16:00 of all seasons due to the higher atmospheric oxidation.The correlations of mercury with air pollutants(such as CO?PM2.5)are analyzed and PSCF model is used to evaluate the potential sources of mercury pollution.The results show that the concentrations of atmospheric mercury in Chongming are mainly influenced by the industrial boilers in autumn and winter,and natural sources in summer.The PSCF results show that the atmospheric mercury mainly comes from the eastern area of China,including Anhui,Henan,Jiangsu,Shangdong,Zhejiang and Fujian province,and Shanghai City,as well as some areas of Japan and Korea.To better understand the characteristics of atmospheric mercury in Chongming,the typical pollution processes are analyzed for different seasons.The dust weather in spring has little impact on the speciated atmospheric mercury in Chongming,while straw burning in summer can promote the concentrations of GEM.In addition,there are some peaks on the concentrations of GEM while RGM,PBM and other air pollutants keep steady,which indicates emissions of natural sources.In autumn and winter,there shows a number of peaks on the concentrations of PBM due to air mass transport in the northern direction which contains high concentrations of PBM,as well as steady weather and low temperature.Mercury in wet deposition is also measured in Chongming Island from July 2014 to June 2015.The wet deposition flux and volume-weighted mean(VWM)concentrations of total mercury(THg)are 8.66?g·m-2·yr-1 and 8.13ng·L-1,respectively,which is lower than most of the urban and rural areas,and higher than some remote areas.The wet deposition fluxes are highest in summer,with a strong positive correlation with the rain depth,which indicates the wet deposition fluxes of mercury mainly decide on the rain depth instead of the concentrations of total mercury.