| Dadu River is the largest tributary of the Minjiang River which running throughHanyuan.With multiple medium-sized non-ferrous metals deposits output in Hanyuan,the environmental impact comes from mining on basin food safety related to localeconomic development and social stability.So it has important significance to find outthe influence scope and degree and ways in mine area and downstream watershedfrom mine development.This paper has make a detailed environment geochemistryresearch on the water, soil and rock around Wusihe zink-lead mine,Tangjia zink-leadmine and Fuquan zink-lead mine in Hanyuan Sichuan.Rock leaching test has revealedthe migration rules of heavy metals in sulfide minerals while oxidation in surfaceenvironment.The research results are as follows.The water pH of Dadu River from Hanyuan to Wusihe is between7.3-8.4, whichshowed weak alkaline.With the effects of acid mine drainage water on downstream,river water’s pH is slightly higher in the upstream areas than downstream.Ca2+andMg2+are the main cations and Na+,K+have low concentrations which conform themain features of water in Carbonate area. SO42-and HCO3-are the main anions.SO42-concentration range from10mg/L to215.2mg/L, the coefficient of variation is1.17.The areas of high SO42-concentration are anastomosed to the mine region.Except ofAS, metal elements such as Cu, Pb, Zn, Mn, Hg, Cd and Cr haven’t detected.As ismainly enriched in mine water, the source of the tailings. Single factor index andNemerow index method showed the study area has not been polluted water bodies.The surface soil pH of Wusihe lead-zinc is between8.42-8.55.Concentrations ofAs, Cu, Pb, Zn, Cr, Hg, Ni in all samples are lower than the heavy metals limits in theChina Soil Environmental Quality Standard(level2), Cd from one sample is higherthan the Cd limits in the China Soil Environmental Quality Standard(level3). Thevertical soil profile pH of Wusihe lead-zinc is between8.43-8.6. The concentrations of Cd, Cu, Pb, Zn in0-30cm depth are significantly higher than30-80cm which showedshallow accumulation. Nemerow index method and potential ecological hazard indexevaluation shows that the surface soil As, Cd, Cr, Cu, Hg, Ni, Pb, Zn have mildcontamination.The Ore Pb, Zn contents are1592.5mg/kg,136625mg/kg, which are obviouslydifferent from waste rock (41.4mg/kg,315.25mg/kg). The waste rock Pb, Zn contentsare higher than the element background at the eastern margin of Kangdian axis for Pb(39mg/kg)1.05times, Zn (110mg/kg)2.86times.Rock leaching test reveals that withthe Carbonate base rock, the pH of Leachates would be greater than7.Heavy metalconcentrations in the leachates inversed with leaching time and pH.Compared withthe pH of6and7, leachate with pH=5is easier to generate hydroxide and carbonate,hydroxide and carbonate could wrap sulfide minerals and adsorb heavy metals,making pH=5leachate concentrations of heavy metals lower than pH=6,7leachates.The leaching intensity of Cu in waste rock are75.2, higher than the ore for38times.Ore Co, Ni leaching intensity (respectively34.4,26.3) are higher than those of otherheavy metals in ores (all less than20).Because of the carbonate precipitation,theleaching intensity of Cd, Pb, Zn in ore are less than1,revealed difficult leachingfeature and migration behavior.As in Lead-Zinc mine at carbonate base rock area is easily dissoluted from therock and tailings and is easily to migrate into water.Precipitation formed of carbonaterock when the water-rock reaction could hinder the migration of Cd,Pb and Zn intowater. Correlation analysis of heavy metals in soil and rock showing a significantpositive correlation, suggesting that the waste rock, ore is one of the sources of heavymetals in the soil. |
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