Study On The Remediation Of Heavy Mental Cu And Cd Contaminated Soil By Different Ameliorants

The amelioration effects of different ameliorants, including apatite, lime, charcoal, pigmanure and iron powder, were tested under the field experiment for the remediation of Cuand Cd contaminated soil. The effects of biomass and Cu, Cd content of ryegrass, the pHand Cu, Cd concentration in soil solution, and concentration of available Cu, Cd, anddistribution of Cu, Cd forms in soil, and soil enzymatic activity and amount of microbial,and the basic physical and chemical properties of soil were studied. At the same time, thebatch experiments were set up to test the effects of nano-scale hydroxyapatite, apatite andmicro-scale hydroxyapatite in doses of1%,3%and5%respectively, on the distribution ofCu, Cd forms, and enzymatic activities in soils. The findings will provide the theory forremediation of Cu and Cd contaminated soil. The main research contents and the resultsare as follows:1. Apatite, lime, charcoal, and pig manure could satisfy the growth condition ofryegrass in the first year, and the accumulated biomass for ryegrass followed the order:lime>apatite> charcoal> pig manure. However, pig manure and charcoal could notsatisfy the growth condition of ryegrass in the second year, only grew in treatments of limeand apatite, and the accumulated biomass for ryegrass followed the order: apatite>lime.The adsorption capacity of ryegrass for Cu, Cd followed the order: root> straw, but couldfind out a rule among different crop times. In the first year, the order of accumulated Cu,Cd in ryegrass was: lime> apatite> charcoal> pig manure. In the first year, the order ofaccumulated Cu, Cd in ryegrass was: apatite> lime. Compared with the first year, theaccumulated biomass and accumulated Cu, Cd of ryegrass in the second year were lessthan these in the first year.2. Lime, apatite and charcoal obviously increased the pH, and decreased concentrationof Cu, Cd of soil solution, which showed the capacity of the persistent. However, with timelapsed, iron powder and pig manure gradually decreased pH, increased Cu, Cdconcentration of soil solution. In the second year, the pH and Cu, Cd concentration in thetreatments of iron powder and pig manure nearly kept the same level with controltreatments.3.The soil pH was increased by1.3and1.2units, but not obviously effected on soilavailable Cu, Cd were decreased in five treatments, and iron powder and pig manuregradually decreased pH with time lapsed, increased available Cu, Cd, and nearly kept the same level with control treatments. The contents of exchange forms Cu with application oflime and apatite was decreased99.66mg/kg and84.51mg/kg in the first year, and84.96mg/kg and72.96mg/kg in the second year, Five amendments all increased the contents ofcarbonate form, Fe-Mn oxides bound form, organic form and residual Cu, Cd, whichpromoted the transformation of Cu, Cd from the active forms to the inactive ones.4. The amount of bacteria and fungi increased after amendments applied, and positivecorrelation existed between the amount of microbial and soil pH, especially for fungi, thecorrelation coefficient reached0.90. The activities of hydrogen peroxidase and acidphosphatase increased with apatite, lime, charcoal application, while urease activitychanged little.5.The soil organic matter were improved0.65g/kg,0.77g/kg and3.39g/kg, the soilCEC were improved0.17cmol/kg,0.14cmol/kg and0.31cmol/kg, soil exchange Ca2+wereincreased2.51cmol/kg,3.88cmol/kg and1.05cmol/kg with apatite, lime and charcoalapplication. lime, charcoal decreased soil bulk0.03g/cm3and0.04g/cm3, apatite and ironpowder increased soil bulk0.05g/cm3and0.07g/cm3, but not have obviously differentwith the control treatment.6. Results of indoor experiment showed: soil pH was increased with the application ofMicro-HAP, AP and Namo-HAP, and slightly increased with time lapsed, especially theMicro-HAP was stronger than the others. Soil pH for three amendments under the samedose followed the order Micro-HAP> AP> Namo-HAP. The activities of hydrogenperoxidase and urease increased, and decreased acid phosphatase with Micro-HAPapplication, however the activities of three enzyme also increased with AP and Namo-HAPapplication. The concentration of Cu, Cd were studied by Toxicity Characteristic LeachingProcedure, Cu, Cd bioavailability significantly decreased with the doses increased, and Cu,Cd bioavailability for three amendments under the same dose followed the order: AP>Micro-HAP> Namo-HAP. Micro-HAP and Namo-HAP significantly decreased thecontents of exchange forms Cu, Cd, and increased the contents of carbonate form, Fe-Mnoxides bound form, organic form and residual Cu, Cd.