| Mining results in a large number of tailings exposed to the surface,which is easy to acidify after weathering and leaching,and then heavy metals will be separated out.When heavy metals are leached or moved with water,they can merge with the water suspension or form sediment through adsorption and finally enter the water and soil of the mining area.It destroy ecological environment and threaten human health.Therefore,in this study,a tailing area and its surrounding area in northern Guangdong Province are taken as the research area to study the extremely risky soil groundwater environment of the mine and to evaluate the risk of heavy metals in this area.This study focuses on the geochemical study of tailings,soil,surface water and underground water system in the mining area and discusses a series of environmental problems caused by slag accumulation and leaching in the polymetallic mining area in northern Guangdong,especially in the Fengwu-Liangqiao reach and its surrounding areas.At the same time,some suggestions are put forward for the improvement and reclamation of the mining area.The research results will have important theoretical significance and guiding value for the prevention and control of heavy metal pollution of groundwater in other mining areas.The specific work is as follows:(1)According to the regional topographic conditions and environmental status,fresh tailing ore,old tailing ore and tailing ore near the river bed were collected from the middle and upper reaches of Fengwu-Liangqiao reach,and then the leaching experiment was carried out after treatment.With the increase of leaching time,the content of Cu,Zn,Pb and Mn showed significant difference(P < 0.05),while the difference between Cd and sulfate was very significant(P < 0.01).At the same time,the experimental data also show that the content of heavy metals in the damming dam ore is more abundant than that in the old and conventional tailings.The heavy metals in the damming dam ore are more likely to precipitate in the leachate.(2)Four monitoring points were taken from Fengwu-Liangqiao reach to detect the five heavy metals of Cu,Zn,Pb,CD and Cr seasonally.It is found that the heavy metal pollution of groundwater around the mining area is mainly affected by surface runoff and leaching.The surface runoff has a greater impact on the transport of heavy metal substances and the self purification effect of rivers has no significant effect on heavy metal substances.The correlation between heavy metal content in groundwater during dry and wet seasons shows that the distribution of heavy metal content in groundwater is controlled by the primary geochemical environment,as well as the mining and mineral processing behavior and the natural circulation of substances.(3)Sampling points are set up along the vertical direction of the river flow with a spacing of 50 m and the quartering method is used to study the physical properties of soil at different distances from the river.The results showed that with the increase of distance,the content of clay decreased slightly,the change trend of bulk density was not significant and the water holding rate also showed some regularity.(4)In terms of soil chemical properties,the closer the sewage irrigation river is to the soil sample.The more obvious the acidification is,the lower the organic matter content is.The total nitrogen and alkali hydrolyzed nitrogen,effective phosphorus and total phosphorus also show a significant trend of reduction.It can be seen that the influence of river water on the chemical properties of surrounding soil has obvious correlation.In addition,the heavy metal sources in the study area are not only the short-term infiltration or atmospheric transport of surface water such as rivers,but also highly correlated with the geological background of the area based on the trend of soil depth heavy metal content. |
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