Accessment And Remediation Technology Research On Farmland Soil Polluted By Cd,Cu And As

Soil is one of the important elements of the natural environment, and also the basis for agricultural production. Heavy metal pollution in soil is a major global environmental problems,and farmlands surrounded by Industrial and mining enterprises suffered most from heavy-metal contamination. For instance,enhance soil monitoring, evaluation and remediation technology research is helpful to comprehensive management of heavy metal pollution of farmland soil nowdays.Two farmland regions around a smelter in eastern Hubei was selected as our representative example.The heavy metals from farmland soil in this two areas were sampleed and investigated to evaluate the concentrations of Cd,Cu,As,Pb and Zn. Meanwhile,the research on the remendiation of paddy soil with heavy metals was carried out by adding the Modifier C,the Modifier P,the Modifier M and the Modifier H to the polluted soil pots planted with maize.The main results are given as follows:1. Cd,Cu and As concentrations of these two areas exceeded the secondary standers of the national soil environmental quality standard(GB15618-1995),and the content range of Cd:1.82～6.39mg/kg,Cu:53.2～231.9mg/kg,As:19.3～175.5mg/kg Pb: 51.2～290.5mg/kg and Zn:30.1～274.2mg/kg.Rates of the exceeded samples shows to be Cd:100%,Cu:92%,As:80%. Analyze with N.L.Nemerow index,these investigation farmland areas belongs to the specific serious pollution.2.Soil conductivity and pH value increased in varying degrees when the Modifier C,the Modifier P,the Modifier M and the Modifier H were added to the polluted soil pots planted with maize.When the dosage reach the level 20g/kg,the Modifier C increased 0.82unit, the Modifier P increased 1.25 unit,the Modifier M 1.12 unit and the Modifier H 0.25uni.The different processing soil pH value order as:Modifier P> Modidier M>Modifier C>CK>Modifier H.3.The application of the Modifier C and the Modifier P obviously reduced the concentrations of exchange condition Cd in the soil from both dryland and paddyfield,and the Modifier P,as well as the Modifier H, obviously reduced the concentrations of carbonate union condition Cu.And meanwhile, the Modifier H reduced the bioavailable condition As of the polluted soil to some extent.The application of all four kind of modifiers increases the ferro-maganese oxidation sate,the organic synthesis condtion and the residual condition proportion.The remediation of Cd and Cu in paddyland soil with the injection of the Modifier P and the M illustrated a better consequent than that of dryland soil.4.The average plant height and the biomass of maize were obviously increased after the application of these four kind of modifiers.At the meantime,The concentrations of the heavy metal in leaf and stem of maize were reduced apparently.For dryland maize samples,the sequences of the reduction effect are:M> Modifier P>Modifier C>Modifier H,Modifier C>Modifier M>Modifier P>Modifier H,Modifier H>Modifier C>Modifier P>Modifier M,but for the paddyfield maize samples,sequences as:Modifier P>Modifier H>Modifier M>Modifier C,Modifier P>Modifier C>Modifier H>Modifier M,Modifier P>Modifier M>Modifier C> Modifier H.Comprehensive the reduction of Cd,Cu,As concentrations in maize leaf and stem,the optimum dosage of these four kind of modifiers seems as:the Modifier C 10 g/kg,the Modifier P 20g/kg,the Modifier M 20 g/kg and the Modifier H 10 g/kg.5.Relevance analysis showed that the exchang condition Cd,Cu in both dryland soil and paddyfied soil were significantly positively correlative with the contents of Cd,Cu in leaf and stem of maize.The pH value was significantly positively correlative with exchang condition Cd in dryland soil and Cd in leaf and stem of maize.For paddy field samples, As in leaf and stem of maize was significantly positively correlative with that in root.As well as the dryland samples, As in root was significantly negatively correlative with pH value of the paddyfied soil.6.The research discovered that the Modifier C,the Modifier P,the Modifier M and the Modifier H are efficacious modifiers for remediating polluted soil by heavy metal.Meantime, the Modifier P and the Modifier H seem to effect most ideal in polluted paddyfield,however, the Modifier C and the M are more suitable to govern polluted dryland.