The Status Of Mercury Pollution In Soil-crop System And Enviromental Risk Assessment In The Downstream Of One Mercury Mine In Guizhou Province

Mercury is one of the most toxic heavy metal pollutants,which has been listed as a prior controlled pollutant by United Nations,The world health organization and our country.The mining activities of mercury has a potential impact on the surrounding ecological environment.Mercury in different environmental media will eventually enter the human body and threat human health.This work has selected an area as the research region,which is located in the downstream of one mercury mine in Guizhou Province.The study was conducted under field research and further experimental analysis,in order to demonstrate the status of mercury pollution on the regional agriculture system and assess the environmental risk.It might contribute great effort on providing scientific basis for soil restoration work in this area.The main conclusions are as follows:(1)The soils in this area were acidic,and the mercury content were mainly distributed in the range of 0-20 mg/kg.The polluted degree of total mercury in the soil has a positive relationship with the distance from the Wawu River.At the side of closer to the bank of the Wawu River,mercury contamination was worsen,however at the side where far from the bank,the total mercury concentration in the soil was generally lower.(2)The crops in the area had also been contaminated to a certain extent.The referenced value is 20 ng/g in the National Standard for Food Safety(GB2762-2012).The excessive detection rate of rapeseed and white rice in this area is about 10%,and the excessive detection rate of brown rice is 33%.Different processing methods also affected the mercury contents in the crops,which follow the order: oil residue> rapeseed> oil,rice bran> polished rice.The results indicated that the extent of processing was increases accompany with removal rate of heavy metals.At the areas where the total mercury contents of the soil were not exceeded(0-1 mg/kg),however the planted rapeseed and rice exceeded the standard of 20 ng/g,and the locations were mainly distributed in the farmland beside the irrigation canal.The effects of water had led to the emergence of this phenomenon,which may due to the irrigation of water.(3)The results were based on the method of single factor index,geoaccumulation index,and potential ecological hazard,which showed the mercury pollution in the soil was heavier and might constituted strong ecological hazard.The health risks of residents in this region were assessed.The result showed that all exposure pathways had a risk factor < 1,although residents had the highest exposure to mercury by eating rice,but diet,skin contact and other routes did not pose a threat to human health.