Evolution Of The Environmental Quality And The Early Warning Model Research On Heavy Metals In Dexing Copper Mine

Dexing copper mine in Dexing city, Shangrao in Jiangxi Provice, is the largestopen-air porphyry-type copper deposit in China. This paper divides Dexing area’senvironment problems into four areas according to river basin: Dawu river basin,4#tailings pond and its downstream, Leanjiang river basin and Daicun area in allusionto the heavy metal environment problems in ore concentration areas. In the firststage(2002-2006) and the second stage(2010-2012), they collected water, bottom mud,soil, and plant samples, made full use of these samples test data, and establishedmathematical model to research Dexing copper mine heavy metal environmentproblem from the following several aspects:(1)analyse data from different river basins and samples from different times, withnational standards and geochemical baseline values of Dexing area as standard, usingthe single pollution index method(Pi=Ci/Si), the geochemical baseline methodthe comprehensive pollution index methodniievaluate water, bottom mud, soil, and plant, study the heavy metals content, time andspace distribution law and environment quality’s evolution trend in Dexing area.Results show that the pollution of water, bottom mud, and soil in Dexing area mainlyconcentrated in the Dawu river basin, the main water pollution elements are Cu，Zn，Cd， the main bottom mud pollution elements are Cu, As, Cd, the main soil pollutionare Cu, As, Cd,Hg. Plant pollution distributes across Dexing area, and the mainpollution elements are Cu, Pb, Cd, As, Hg.(2)Predict the overweight age of soil’s heavy metal in Dexing area. Establishmathematical model, divide them into acceleration and uniform accumulate modelsaccording to area in different river basins, and finally deduce calculation formula ofoverweigh age, with national standard for the level III soil as soil benchmark. Theacceleration accumulate formula is, uniform accumulate formula is.The results show that the soil in Dexing areais mainly Cu, As, Cd, Hg overweight, and some samples will overweight in50years.We should still monitor these elements’ evolutionary trend.On the base of soil evaluation model and soil overweight age, we should makeearly-warning of soil heavy metal pollution in Dexing area. First, predict the soliheavy metal content after T years according to the acceleration and uniformaccumulate models, and then compare the soil quality score after T years and currentsoil quality score. Divide the early-warning models into three types: pollutiontyperapid deterioration typedeterioration typeThe results show that Dawu riverand4#tailing pond band both found pollution or rapid deterioration early-warning, andthere were rapid and slow deteriorations farther away from the band. Forecast for theearly-warning in soil heavy metal provide theoretical basis for soil environmentalgovernance in the future.(3)Use the edible parts of plant as standard, combine with the enrichmentcoefficient to determine the risk threshold of heavy metal in farming soil, namelyT=E/(W(A)/W(B)). The results show that Dexing area rice soil risk threshold of Cu is78.302μg/g，Pb is35.219μg/g，Cd is0.328μg/g, As is13.3μg/g, Hg is0.405μg/g, Cr is737.48μg/g; Cabbage soil risk threshold of Cu is61.902μg/g，Pb is6.465μg/g，Cd is0.029μg/g, As is1.804μg/g, Hg is0.063μg/g. This research solves two faults: there isobvious deviation using national standard in some areas; It’s too single for theconsideration species as to the plant effect, which provide a scientific basis forselecting locations of rice and cabbage in Dexing copper ore-concentrated area andgoverning pollution farmland soil.The cabbages’ heavy metal enrichment coefficient is higher, so use cabbage asrepairing additive to absorb heavy metal elements in soil, and the repairing age isThe results show that when using cabbageas repairing additive to absorb heavy metal elements in soil, it will take27years toabsorb the effective state of Cu,13years to absorb the effective state of Pb,61years toabsorb the effective state of Cd,2years to absorb the effective state of As,9years to absorb the effective state of Hg. Thus,it is feasible to use cabbage to absorb heavymetal in soil, to provide a useful way to govern soil.