Study On Regional Multimedium Environmental Behaviors Of Mercury

Mercury is one of the most toxic heavy metals in the environment.It is regarded as a global pollutant due to persistence,long-range transport and bioaccumulation.There are many species of mercury in environmental medium(e.g.Hg⁰,Hg²⁺and MeHg,etc.).It can transport and transform in multimedium because of its special physical and chemical properties.In order to study the multimedium environmental behaviors of mercury,the patition coefficients of Hg²⁺between soil and water were tested in 131 agricultural soil samples collected from all over the country,and a III level multimedium environmental model of Hg transport and species interconversion in six medium was developed and applied in Dalian.Our findings can provide a scientific basis for the environmental risk assessment and reducing anthropogenic mercury emission.Soil plays a key role in the biogeochemical cycle of mercury as the source and sink meanwhile.The physical and chemical properties of the soil samples have significant effects on patition of mercury.The results showed that the K_d values of mercury in paddy soil samples were higher than those of dryland soil samples about one order of magnitude.It was found that the main factors of dryland soil samples on K_d were DOM and granularity,while the main factor of paddy soil samples was total sulfur.The effects of redox on mercury distribution were further investigated by incubation experiment of flooding.It was found that most of dryland soil samples showed an obvious increase of K_d after 30 days,while most of the paddy soil samples kept a steady trend.The environmental behaviors of mercury in Dalian were simulated by III level multi-medium environmental model.In order to give a better simulation of real environment,besides atmosphere,water,sediment which have been mentioned in precious study,soil,vegetable and organic film on impervious surfaces were also included in this model.The results of the model showed that the atmospheric advection and the ocean advection were the main input path and the main output path in Dalian,respectively.The sensitivity and uncertainty of the model were analyzed by Monte Carlo.The results showed that the atmospheric advection concentration,oceanic advection concentration and atmospheric direct emission rate of mercury were the sensitivity parameter values of the model.The predictive ability of the model was evaluated by experimental measurements or literature investigations.The model had a fairly good prediction.