| As an important non-ferrous metal resource,Lead-zinc ore has made great contributions to China's industrial development.However,at the same time,Mining and smelting of lead-zinc ore produced abandoned wastes that have caused varied degrees pollution to surrounding environment.A typical lead-zinc mining area(Danzhai County,Guizhou Province)was selected as study area.Samples of tailing,surface water,sediment and soil were collected in study area,and total amounts and chemical forms of heavy metals were analyzed and tested in each sample.The single-factor index method,The Nemerow comprehensive pollution index method,The potential ecological hazard index method,The geoaccumulation index method,and The secondary phase and primary ratio method were used to evaluate pollution status of heavy metals in sediments and soils.At the same time,the cluster analysis method and the principal component analysis method were used to analyze the pollution sources of the seven heavy metals in sediments and soil in research area of the four seasons and the correlation between pollution sources.In laboratory,we further studied that migration characteristics and bioavailability of heavy metals in lead-zinc slag-soil system through laboratory simulation experiments.The main conclusions were as follows:(1)Comparing the water quality standard limits of Class III in the Environmental Quality Standards for Surface Water(GB3838-2002),only the contents of Hg in surface water in four seasons exceeded the standard.The contents of Mn in upstream of tailings accumulation area and farmland in tailings accumulation area in spring and farmland in tailings accumulation area in summer exceeded the standard.The contents of Hg in all sampling points in four seasons all exceeded the standard.In winter,The contents of Pb,Zn,Cd and Hg in sediments,In spring,Pb,Zn,Cu,Cd and Hg in sediments,In summer,Zn,Cu and Hg in sediments,and Zn and Cu in sediments all exceeded background value in autumn.The contents of As at each sampling point in sediments did not exceeded background value in four seasons.(2)The Nemerow comprehensive pollution index method evaluated that the four seasons of lead-zinc mines were most seriously polluted by Hg,and the four seasons of sediments were mainly in light and heavy pollution levels.According to the potential ecological hazard index method,only Hg in sediments of winter,spring and summer produced moderate ecological risks.Seven heavy metals in sediments in autumn all produced mild ecological risks.The sediments in four seasons were mainly light,medium and strong ecological risk levels.The geoaccumulation index method evaluates that surrounding sediments of the lead-zinc mine area were most polluted by Hg in four seasons.Thesediments were slightly polluted by heavy metals in four seasons,and the individual points were moderately polluted.The secondary phase and primary ratio method evaluated that the seven heavy metals mainly produced mild and severe ecological risks in sediments in four seasons,and the sediment in four seasons was mainly mainly at the level of heavy pollution.(3)In winter,the contents of Pb,Zn,Cd and Hg in soil(0?10 cm),The contents of Pb,Zn and Hg in soil(10?20 cm)exceeded background value,and the contents of Pb and Zn exceeded the risk screening values of heavy metals in Risk Control Standard for Soil Contamination of Agriculture Land in China(GB 15168-2018).The contents of Zn and Hg in soil(0?10 cm)exceeded background value in spring,and only the contents of Hg exceeded risk screening value.The contents of Zn,Cu and Hg in soil(10?20 cm)exceeded background value.The contents of seven heavy metals was less than risk screening value.In summer,The contents of Zn and Hg in soil(0?10 cm)exceeded background value,and only the contents of Hg exceeded risk screening value.The contents of Zn,Cu,and Hg in soil(10?20 cm)exceeded background value.The contents of seven heavy metals were all less than risk screening value.In autumn,the contents of Pb,Zn,Mn,Cu,and Cd exceeded background value in soil(0?10 cm),and only the contents of Zn exceeded risk screening value.The contents of Pb,Zn,Mn,Cu,Cd,and Hg exceeded background valuein soil(10?20 cm),and the contents of Pb,Zn,and Cd exceeded risk screening value.The contents of As in soil(0?10,10?20 cm)at sampling points did not exceed background value and risk screening value in four seasons.In winter,only the contents of As exceeded background value.(4)The distribution patterns of five chemical form of heavy metals in sediments and soils in four seasons at each sampling point were basically similar,and distributions of chemical forms of different heavy metals were different.The proportions of seven heavy metals in sediments and soils were as follows: Among the five chemical forms of Pb,the proportion of carbonate bound state was highest and proportion of exchangeable state of Pb was lowest.Among the five chemical forms of Mn,the proportion of iron-manganese oxides was highest and proportion of exchangeable states of Mn was lowest.Among the five chemical forms of Cd,the highest was exchangeable state and proportion of residue state of Cd was lowest.Among the five chemical forms of Hg,the proportion of residue state was highest and proportion of iron-manganese oxide bound state of Hg was lowest.Among the five chemical forms of Zn,Cu,and As,the proportion of residue state was highest and proportion of exchangeable state was lowest.(5)The evaluation of Nemerow comprehensive pollution index method showed that the soil around the lead-zinc mine area was most polluted by Hg during the four seasons,and the soil in four seasons wasmainly at a clean,light,and severe pollution level.According to the potential ecological hazard index method,only Hg in soil in winter,spring and summer produced strong ecological risks,and each heavy metal in autumn had a slight ecological risk.The soil in four seasons was mainly at a mild,moderate and strong ecological risk level.The geoaccumulation index method evaluated that the Hg pollution index in soil at all sampling points was highest in four seasons,and the soil in four seasons was mainly at the pollution-free,non-pollution-light pollution,light pollution,and moderate pollution levels.The evaluation of the secondary phase and primary ratio method showd that the seven heavy metals mainly produced mild and severe ecological risks in soil in four seasons,and the soil in four seasons was mainly at the level of pollution.(6)The main pollution sources of heavy metals in sediments and soils in research area of the four seasons were Lead-zinc mining pollution sources,gold and mercury mining pollution sources,industrial and agricultural activities and natural sources.(7)The contents of Pb,Zn,Mn,Cu,Cd,Hg and As in Lead-zinc slag exceeded background value,which was 48.18,9.17,3.16,10.72,3.71,69.27,6.35 times.Under the leaching of light rain,leaching rate of seven heavy metals in lead-zinc slag was Mn>Zn>Pb>Cu>Cd>Hg>As.Under the leaching of medium rain,big rain and heavy rain,the leaching rate ofseven heavy metals leaching rate in lead-zinc slag was Mn>Zn>Pb>Cd>Cu>Hg>As,and under the torrential rain leaching,the leaching rate of seven heavy metals in lead-zinc slag was Mn>Zn>Pb>Cd>Hg>Cu>As.The order of bioavailable state,bioavailable state,and unavailable state of 7 heavy metals in lead-zinc slag were Cd>Pb>Hg>Zn>As>Cu>Mn,Mn>Cu>Zn>Pb>Hg>As>Cd,As>Cu>Zn>Hg>Mn>Pb>Cd. |
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