Evaluation Of Heavy Metal Health Risks In Major Rivers In Hunan Province

This paper investigates the four major rivers-Xiang River Zi River,Yuan River and Lishui River in Hunan province,the main non-ferrous metals producing area,and gathers statistics of the long term monitor results by the Environmental Protection Department of Hunan.It concludes the general rules and characteristics of three kinds of heavy metal-cadmium(Cd),arsenic(As),lead(Pb)-pollution in the four rivers.Using the "four steps" put forward by the U.S.National Academy of Sciences and the health risk assessment model recommended by US EPA,it calculates the health risks of adults and children in the study area caused by the three heavy metals through water exposure and skin contact exposure respectively.Develop a human health risk visual warning subsystem program based on the existing automatic monitoring system technology,optimize the existing water quality automatic monitoring system,and provide reference for the environmental management work of relevant departments.Research shows that:(1)in recent years,Level I-? water of Xiang River Zi River,Yuan River and Lishui River is on the rise.Three kinds of heavy metal concentration for the whole year of 2016 is up to Level II of the national surface water quality,with the average density of As > Pb > Cd.(2)health risks of the three kinds of heavy metal in the four rivers: As>Cd>Pb and the health risk mean is As 1.61E-03,Cd 6.30E-05,Pb 1.13E-07,with over 93% of influence contribution rate for the carcinogen As,under 0.03% of influence contribution rate for the non-carcinogenic Pb.The carcinogenic health risk value of As and Cd for adults is 2.47 ~ 2.83 times than for children.Non-carcinogenic heavy metal Pb imposes a higher health risk to children than adults,1.18 to 1.35 times higher.According to the exposure ways,health risk of exposure through drinking water is greater than the skin contact exposure with a mean of 1.74E-03 for water exposure and 1.22E-06 for skin contact.The influence contribution rate of water exposure reached 99%.(3)In terms of river,the mean of the health risks of three kinds of heavy metals: Lishui River > Zi River > Xiang River > Yuan River,the health risk mean of Lishui River(adults 2.68E-03 children 1.08E-03)is about 16% higher than that of Yuan River(adults 2.25E-03 children 9.12E-04).The Dahetan station of Xiang River has the largest risk value in all the study sites of the four rivers,3.96E-03 for adults and 1.60E-03 for children,which is lower than 7.47E-03(meaning: about 7.47 of the population of the region's population in their life-time were affected by As,Cd and Pb,which caused health problems or deaths.),the lifetime acceptable health risk level of those in the study area.(4)the visualization risk early-warning subsystem for the health risks of heavy metals is divided into five levels: normal,?,?,? and ?,and the visual color corresponding risk is green,blue,yellow,orange and red.In yellow,the residents should notice.In red,the relevant departments should take measures to investigate the pollution sources and strictly strengthen the monitoring and management of water quality.Generally speaking,the maximum heavy metal risk value in the study area is Level II.It's almost normal,but there is a risk of cancer in a few areas.It's necessary to focus on strengthening the supervision and management of risk source for the relevant waters in critical areas.