Environmental Geochemical Characteristics Of The Lengfengdong Valley Tailings Area In Wanshan, Guizhou

After the Guizhou Wanshan Mercury Mine responded to the national policy and implemented the mine policy-based shutdown,the remaining problems in the local area still affected the environment.One of them was the slag and waste rock accumulation reservoir area represented by the cold wind and shovel area.The waste generated from smelting in the area is not stored in the natural environment without any permanent treatment,which poses a risk of pollution and poses a great threat to local ecological security.The paper relies on the research project of Environmental Protection Public Welfare Industry of the Ministry of Environmental Protection of China,“Research on Identification and Pollution Risk of Groundwater Heavy Metal Pollution in Southwest Mining Area”（Project No.201509024）.Based on the regional geological and hydrogeological background research obtained by the project,the tail is ascertained.The content and spatial distribution of heavy metals in the soil and water bodies of the mining area.The main research results of the thesis are as follows:The study on the geochemical content of surface soil showed that the surface soil in the area was total alkaline,and the pH in the tailings area was higher,followed with the high content of Hg,Cd and As in the surface soil.The soil value specified in GB15615-2018 was adopted,As a standard value comparison,it is found that the over-standard rate of Hg element exceeds 80%and the coefficient of variation reaches 0.99;the over-standard rate of Cd element is 40%,the coefficient of variation is 0.39;the over-standard rate of As element is less than 10%.The spatial analysis shows that the high content area of Hg element coincides with the position of the main tailings pile in the middle part of the tailings area,and coincides with the high alkalinity area;the high content area of Cd element is concentrated in the middle and lower part of the tailing area,indicating Hg Cd elements and pH is closely related to the tailings pile.The relationship between the tailings zone and other lower elements is weaker.The lateral migration ability of Hg and Cd is weaker,and the migration to the distant may be based on water.The main transportation mode is mechanical transportation.The main factors affecting the migration may be time and pH.Source analysis shows that Hg and pH are greatly affected by mine source;Cr,Ni,Zn and Cu are mainly natural backgrounds;Cd The influence of elements is dominated by other people,such as agricultural activities;Pb has dual sources of tailings and other human activities,and As is mainly affected by natural activities,followed by tailings.The influence degree of tailings area on soil heavy metals is roughly Hg>Pb>Cd>As>other elements.Totally,The soil profile has a higher pH value,and the pH is much higher in other boreholes near the tailings pile.At the same time,the pH suddenly appears to decrease.The closer to the tailings heap,the higher the position of the interface of the abrupt interface.The vertical direction of the Hg element in the tailings area is very obvious,and it does not have the ability to migrate downward in the study area.The distribution of Cd elements is not obvious,Cd elements have the ability to migrate to deep soils,and are less affected by tailings heaps;the ability of As elements to migrate deeper is weaker;overall,the soil profile of the study area Heavy metals are mainly from the surface soil.The research of water shows that the water in the study area is mainly HCO₃-Ca type and Cl·SO₄-Ca type,the TDS content is small and the surface water is neutral alkaline,the heavy metal elements in the surface water are lower than the detection limit,and the heavy metal elements are The enrichment of surface water is small;the main anion content of groundwater is SO₄^2->HCO₃^->Cl^-,the main cation content is Ca²⁺>Na⁺>Mg²⁺>K⁺,and the TDS is low.The heavy metal elements in groundwater in the study area are lower than the detection limit.The potential impact of heavy metals on groundwater shows that the dominant form of Pb in the study area is Pb（OH）₂.Lead hydroxide has strong influence on Pb²⁺ions,and its impact on groundwater is small.The ability of the medium is weak;the dominant form of Zn in the study area is Zn（OH）₂;the zinc hydroxide has stronger constraints on Zn²⁺,and its influence on groundwater is less,and the ability to migrate to other media with groundwater is better.Weak;the dominant form of Cd element in the study area is CdSO₄;OH^-has weaker inhibition ability to Cd²⁺,which has a greater impact on groundwater,and has stronger ability to migrate to other media with groundwater;Hg element in the study area The form of storage is mainly elemental mercury,which is less in groundwater,has less impact on groundwater,and has a weaker ability to migrate to other media..