Study On Distribution Characteristics And Influencing Factors Of Heavy Metals In Typical Metal Mine Tailings Ponds In Lesser Khingan Mountains

Mining production process has a great impact on the surrounding soil environment,and heavy metal pollution is one of the main pollution methods.Therefore,it is of great significance to study the distribution of heavy metals in soil for the prevention and control of soil pollution.Taking the soil around the tailings pond of Lesser Khingan Mountains as the research object,the vertical and horizontal distribution characteristics and influencing factors of heavy metals were revealed by field sampling and indoor soil column leaching experiment,and the migration mechanism of heavy metals was explored.The results of field sampling experiments show that the horizontal distribution characteristics of heavy metals in the soil around the tailings of lead-zinc mine,molybdenum mine,iron ore and iron polymetallic ore tailings are:the enrichment coefficient of heavy metals As,Cd,Cu,Pb,Zn all show a linear relationship with the distance from the tailings pond(0?700 m)is much farther,the less the enrichment is,while the Cr,Hg,Ni and other elements are not enriched in the soil.The vertical distribution characteristics are as follows:the enrichment characteristics of heavy metals in different metal ores have a similar regularity.The enrichment coefficients of As and Hg decrease with the increase of soil depth,and tend to be stable when the soil depth is more than or equal to 80 cm.The enrichment coefficients of Cd,Cu,Pb and Zn accumulated at 20?40 cm,then decreased rapidly at 60 cm,and then tended to be stable.According to the cumulative index,Nemero pollution index and comprehensive potential ecological risk index,the pollution of iron polymetallic ore is the least,As,Cd,Cu,Hg,Pb,Zn have different degrees of pollution,and Cd is the most serious.According to the analysis,the source of As,Cd,Cu,Hg,Pb,Zn is mixed source,while that of Cr and Ni is natural source.By analyzing the distribution characteristics of heavy metal elements in different research areas,it is concluded that pH value,organic matter,humic acid,trace elements,elevation difference and wind force are the main factors affecting the distribution characteristics of heavy metal elements.In different research areas,there is a significant correlation between pH value,organic matter,humic acid,trace elements and heavy metal elements.The heavy metals As,Cd,Cu,Hg,Pb,Zn are obviously enriched in the A?F area of elevation difference,and the enrichment coefficients of these elements all increase firstly,and then decrease with the decrease of elevation difference.The distribution range of Cd,Cu and Zn is 0?20 m elevation difference,the safety area is defined as the scope of tailings dam surface>20 m,and the boundary of safety area below the dam surface is not obvious.The heavy metals As,Cd,Pb and Zn are most affected by wind direction,and the influence range is 0-600 m.The vertical distribution characteristics of heavy metal elements in the soil column and the influence of these three treatments on the distribution characteristics of heavy metal elements in the soil column after the tailings of metal mine tailings pond are studied.The results show that the enrichment coefficient of As element decreases with the increase of soil depth,and the soil depth is greater than or equal to 80 cm.The enrichment coefficient tends to be stable.The distribution of Cd,Cu,Pb,Zn elements first accumulated in 20?40 cm layer,then decreased,but the enrichment coefficient tended to be stable in 60?100 cm soil layer,which was basically consistent with the change trend of heavy metal elements enrichment coefficient with depth in soil profile under natural state.The cumulative contents of As,Cd,Cu,Pb and Zn in soil columns with different pH values are increasing,but the increasing ranges are obviously different.As,Cd,Cu,Pb,Zn contents of soil columns with different concentrations of humic acid increased as time.The order of heavy metal enrichment coefficient was 0.4%>0.3%>0.2%?0.1%.The enrichment degree was from slight enrichment to moderate enrichment,and only Cd element was significantly enriched.According to the average mobility of heavy metal elements under different treatment methods,pH value and humic acid can promote the migration of heavy metal elements and change the distribution characteristics of heavy metal elements.There are 56 figures,34 tables,and 156 references in this thesis.