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Coastal sites provide evidence of both the intensive anthropogenic sources from inland areas and the behavior of mercury in the marine boundary layer including mercury evasion from sea surface,oxidation of elemental mercury and capture of reactive mercury.The ambient concentrations of the total gaseous mercury(TGM),the reactive gaseous mercury(RGM)and the particulate-bound mercury(PHg)were observed at a rural site on Chongming Island in the East China Sea,which is located at the estuary of Yangtze River.The Tekran 2537B mercury analyzer and the URG 2000 speciated mercury sampling system were adopted in this study.TGM was measured in three periods during 2009-2012,and RGM and PHg were observed in one month each season during summer,autumn and winter of 2010,and spring of 2012.The overall average concentrations of TGM,RGM and PHg were 2.65±1.73 ng/m3,8.0±8.8 pg/m3 and 21.5±25.4 pg/m3,respectively during the monitoring periods.The average TGM concentration was higher than the Northern Hemispheric background,with the highest value in winter and the lowest in spring,indicating significant impacts from the inland mercury emission sources.High RGM concentration in summer was caused by the intensive solar radiation,while high PHg concentration in autumn resulted from the poor diffusion condition.The significant correlation between TGM and CO concentrations indicates the great influence of anthropogenic sources.High correlation between RGM and O3 indicates the photo-oxidation of the gaseous elemental mercury(GEM)is an important source of RGM.The partition of RGM and PHg is relative to the PM2.5 concentrations and temperature,and in summer the partition is much more sensitive to temperature.HYSPLIT back-trajectory analysis identified the local and regional emission sources in heavy pollution episodes at Chongming site.The results from the potential source contribution function(PSCF)model based on the HYSPLIT results indicated that the total mercury concentration at Chongming site was mainly contributed by Yangtze River Delta(YRD)Region in summer while by both North China Plain(NCP)Region and YRD Region in autumn and winter.