Study On The Characteristics Of Soil Heavy Metal Pollution And Amendment Steps On Mine Tailings

The soils are indispensable and resource of precious wealth to human being. But,with the fact that industry and agriculture and the course of urbanization fleetnessdeveloping, the dirt irrigates, metal smelting, the mining, pesticide and chemical fertilizerunreasonable employs, and so on, causes the soils heavy metal pollution. Heavy metalpollution of the farmland soil and the tailings has become the environmental question thatthe global solicitude for. The heavy metal pollution investigation of soil, the heavy metalbiology feasibility study and filtration of ameliorations is the important content ofphytostabilization to contaminate land. We sampled the smelter peripheral farmland ofZhejiang Fuyang, analyzed 0.43 mol/L HNO₃ extracted and 0.1mol/L NaNO₃ extractedsoil heavy metals. Taking Jiangxi Dexing copper tailings and Wuxi sludge compost asexample, we observed the toxic response that the tailings and sludge system (not adjust pHand adjust pH) to the barley root elongation. And by the leaching test, heavy metal and thesalinity change of filtrate and the pore water adding sludge to tailing had studied. Theresults from the present study will be valuable for phytostabilization to the farmland soilheavy metal pollution and filtration of ameliorations to mine tailings remediation. Themain results were summarized as follow:Farmland soils in research area in Fuyang Valley of Zhejiang had been polluted byheavy metals such as Cu, Zn, Pb and Cd due to smelting activities there. The averagecontents of Cu, Zn, Pb and Cd in research soils extracted by 0.43mol/L HNO₃ had alreadyexceeded secondary standard of national soil environmental quality standard. The spatialdistribution of heavy metal contents extracted by 0.43mol/L HNO₃ was influencedremarkably the smelters nearby. That is, the heavy metal content extracted by 0.43mol/LHNO₃ was higher in areas near the smelters and decreases while areas far from thesmelters. The spatial distributions of heavy metal contents extracted by 0.1mol/L NaNO₃were compared with that of soil pH. However, the spatial distribution of heavy metalcontent extracted by NaNO₃ had a poor relationship with that of content extracted byHNO₃.The Dexing tailings were strongly acidic. The EC of Wuxi sludge was 8.64ms/cmwith a high metal content at the same time. The sludge can increase the water holding capacity of tailings. Applying white lime into tailing-sludge system can increase its pH.The barley root elongation experiments for this system showed an increase and furtherdecrease with incremental sludge application. When sludge application＜10ï¼…, the mainfactors for barley root elongation in such system was the increasing pH and decreasing Cucontent extracted by 0.01mol/L CaCl₂. When sludge application fall in 10-20ï¼…, theremarkable increase of EC was the toxic factor for suppression of barley root elongation inthis system. By applying white lime to control the pH of this system to around 6～7, thebarley root elongation experiments showed decreasing root length while increasing sludgeapplication. At this time, the high saline in system was the toxic factor for barley rootelongation.The DOC in pore water and leachate of tailing and tailing-sludge system decreasedwhile precipitation increasing. The rainfall accelerates the DOC leaching, pH in two kindsof treatments leachate approached a plateau when precipitation reached 300mm, but pH intailing-sludge treatment was close to 7. Application of sludge increased EC of leaehate,but after 225mm precipitation, EC can be decreased remarkablely. Cu and Znconcentration in leachate of tailing-sludge system were higher than that in tailingtreatment. The Cu concentration in leachate of tailing-sludge treatment exceeded the thirdstandard of groundwater quality standards, but can be decreased by increasingprecipitation, or decreasing sludge application. Sludge can be applicable to remediation inmine tailing area as a matrix improvement agent.