The Absorption Characterastic Of Total And Methyl Mercury Concentrations In Mosses From An Abandoned Mercury Mining Region And Its Biomonitoring For Atmosphere

Mercury(Hg)is a global pollutant that can accumulate in an elemental form(Hg0)in atmosphere for a long term.Mosses have been widely employed as an indicator to characterize atmospheric Hg pollution.In this study,total 281 moss samples belonging to seven species of five families were collected from an abandoned Hg mining region in southwestern China for total Hg(THg)and methylmercury(MeHg)analysis.Results showed that THg concentration in mosses ranged from 0.21 to 126 ?g g-1 with an average of 4.9±11 ?g g-1.An elevated MeHg concentration reaching up to 262 ng g-1 with an average of 33±36 ng g-1 were observed.The highest levels of THg and MeHg were generally found in the samples collected from nearby atmospheric Hg polluted areas impacted by the activities of the chemical facilities related to metallic Hg productions.This suggested that the anthropogenic activities done on metallic Hg and producing its chemical compounds is currently the major contributor of atmospheric Hg since Hg mining and retorting activities ceased decades ago in the study region.No significant differences in accumulating ability of the element among all investigated moss species were observed,which justifies their combining utilization as bio-monitor of airborne Hg.At industry region and Wanshan town,six families of mosses,consisting of seven species were choosen for Hg concentration analysis.Simultaneously,the total gaseous mercury(TGM)concentrations were in sit measured at amounts of moss sampling sites.Results showed that the mean concentration of Hg in mosses was 80±46 ?gg-1 with a range of 0.96—126 ?gg-1,which was heavily impacted by chemical plants pertaining to Hg productions like mercuric chloride catalyst producing and abandoned catalyst recycling.A positive correlation between Hg in mosses and its corresponding ambient air TGM were observed,with a coefficient r=0.93(n=12,P=0.01030)in linear fitting,r=0.96(n=12,P=0.01169)in polynomial fitting,and r=0.96(n=12,P=0.00469)in logarithmic fitting.The estimated concentrations of TGM by using the logarithmic fitting equation exhibited that the pattern of TGM spatial distribution was consistent with that of Hg in mosses.Moss can be considered as a biological indicator of atmospheric Hg pollution and was proved by a quantitative/semi-quantitative method in the research.This proposes a new methodology for the evaluation of atmospheric Hg pollution in contaminated sites.Adopting Hypnum plumaeforme to monitor the Hg deposition at Industry area,Fourth adit,Fifth adit,Meizi creek,Aozhai township and Shenchongkou village by active biomonitoring method.During May to November in 2016,THg and MeHg in the moss placed in the seven sites were determined monthly.Results showed that the concentrations of THg in those mosses were mainly increasing month by month which indicated that traffic,residents activities and mercury migration might causing mercury pollution in regional atmosphere.Concentrations of THg were increasing by exposure time before saturation of absorption for Hg.Rate of absorption was influenced by concentration of Hg in air and the form of environmental media.MeHg in moss could be related to atmosphere.Analysis using XANES showed that the majority of mercury in moss was in a form ?-HgS,?-Hg S and Hg-cysteine,indicating that element Hg and ligands once inside the moss may be transformed to more stable and less toxicity complexes by a series of biochemical reactions.That may be the reason why moss couldaccumulation and bear the toxicity of heavy metal like Hg.