The excessive exploitation and utilization of mineral resources inevitably bring many problems of environmental pollution, and heavy metal contamination has become one of the main problems of environmental pollution in mining areas. A large amount of waste water, gas and slag containing heavy metals are produced during the mining,
these wastes will quickly spread to the soil, water and atmosphere around the mining area, and will be ingested by the human body through food chain, respiration and skin contact , which will pose great harm to human health. Therefore, this is a n urgent need for the risk management and control on heavy metal contamination in mining areas.
In this study, the Tielong town of Wengyuan county, Shaoguan city was collected as the research object. This paper analyze d the characteristics and the source of heavy metal contamination, and explore d the exposure level of the local environment and creature, assess ed the health risk on the Tielong town. Finally, the risk management
measures were implemented by identifying the main contaminated environmental med ia, contaminated elements and the exposure pathway. The main results of the research were as follows:
(1) The pollution level of agricultural soils was the most severely by comparing the heavy metal concentrations among the agricultural soils, woodland soi ls and grass land soils in the study area. T he results showed that t he level of Cd pollution belong s to the super severe pollution, Pb and Zn also exis t certain degree pollution in the agricultural soils. The agricultural soils in the study area exist ed relative high Cd and Pb bioaccessible concentrations according to the in vitro method, which lead to the high potential health risk. Combined with the results of the characteristic of the spatial distribution and cluster analysis, we can infer that the Pb contamination is highly related with the cement plant, the Cd and Zn are mainly derived from mining activities. Mining activities has the greatest influence on the enrichment of the total heavy metals in agricultural soils with the proportion of 59.3% by PMF model.
(2) Six different species of crops were collected in the field. The heavy metal contents of crops were all under the national fo od safety limits, which suggest that all the crops can be consumed safely. The continuous deposits of suspended part i culates from surface water lead to the relative ly high contents of heavy metals in the sediment,
the average Cd concentration in the sediments has exceeded the risk control value of agricultural soils. The interaction of sampling locations and months had no significant effect deposition rates, suggesting that heavy metal deposition was mainly governed by local anthropogenic activities.
(3) Human hair and urine are suitable indicators for the long term and short term exposure of heavy metal,respectively. 7 6 hair samples and 53 urine samples were selected from the local residents at random and tested for the heavy metal concentrations By combining with the average exp osure level of heavy metal in residents of other un exposure countries or regions, t he leve ls of hair Pb and urinary Cd contents in local inhabitants were relatively high. The mean concentration of Pb in local children w as higher than the national safety threshold value, indicating that local residents (especially for children) exposure level is relatively high.
(4)According to the calculation of the average daily dose of heavy metals via various exposure pathways, the soil had the greatest influence on the accumulation of Pb in the human body, and food constituted the main component of Cd accumulation. In addition, t he model of human health risk asse ss ment model was cited in the study,the results showed P b presents the highest potential non carcinogenic health risk to local children, with a HI value greater than 1; and the cancer risk of C d in local inhabitants was higher than the maximum safe value 10 4 . Risk control sho uld be taken to red uce the food ingestion exposure level of local residents (especially for children )),which was the dom inated contribution to the non cancer and cancer eff ect.
(5)Based on the results of former investigation and analyses the mainly contaminated environmental media was agricultural soils, and Cd was identified as the most contamin at ed element. By calculating the input and output fluxes of heavy metals in agricultural soils in the study area, the sewage irrigation was the main contribution factor of soil Cd. Therefore, the source of pollution should be controlled by shutting down the mine area or cement plant, and clean ing the water channel before the resto ration work , to prevent the agricultural soil being re contaminated. Th e significant spatial variation means that different safe utilization techniques are needed in the study area, to ensure the sustainable utilization of agricultural soils and the ecolog ical safety of agricultural products. The heavy metal in soil can be effectively uptaken by planting mulberry and prevented from entering the human body by breeding silkworms in the severely polluted area , and heavy metal contents in crops are effectively reduced in moderate/mild polluted area by the selection of different remediation technology and low absorbing crop varieties. Now , the restoration of agricultural soil has achieved good environmental and econo mic benefits.