Effect Of Soil Amendments On Heavy Metal Bioavailability In Polluted Soil In Guangxi Karst Area

Soil amendments are widely used in contaminated soil for remediation of heavy metal polluted farlmands.A pot experiment of Maize(Zea mays L.)was conducted to study the effect of different amendments(Lime,Lime+Peat,Lime+Peat+Silicon fertilizer,Lime+Peat+Sepiolite,Lime+Soudium Humate,Lime+Soudium Humate+Silicon fertilizer,Lime+Soudium Humate+Sepiolite,Lime+Peat+Silicon fertilizer+Sepiolite,Lime+Soudium Humate+Silicon fertilizer+Sepiolite,which were labeled as S,SN,SNG,SNP,SH,SHG,SHP, SNGP,SHGP in short respectively)on the bioavailability and chemical form of heavy metals in soil, and the accumulation of heavy metals in maize in the contaminated soil by heavy metals.The differences in soil pH,bioavailability and chemical form of heavy metals in soil,the biomass and grain yield of maize,the accumulation of heavy metals in maize in different treatments were determined to reveal the effects and the mechanisms of soil amendments on the bioavailability of Zn,Cu,Pb in soil-corn system.The results would provide the reference for the research and practice of remediation of heavy metal polluted farlmands.The Main results were shown as follows:1. The amendments significantly increased the biomass and yield of maize followed the order:SHGP≥SNGP> SHG≥SHP≥SNG>SNP≥SH≥SN≥S。2. The amendments significantly increased soil pH at earlier stage but gradually reduced along with time and finally stabilized.Those amendments inordinately reduced the content of acid soluble and reducible of Zn,Cu,Pb in soil, increased the content of oxidable and residual of Zn,Cu,Pb in soil.Different forms of Zn in soil had a stable change at four growth periods,while different forms of Cu and Pb were obviously changed from seedling stage to jointing stage,and become slow and more stable at heading and maturity stage. Overall,the treatments SHGP and SNGP were most effective amendments,followed by treatments SHG,SNG,SHP,SNP,SH,SN, while the treatment S was the least.3. Whether using the amendments or not, the uptake and accumulation of Zn among different organs of maize followed the order:root≥stem>leaf>grain,Cu and Pb were root> leaf>stem>grain.The capacity of the uptake and accumulation of Zn,Cu,Pb among the same organ was Zn>Cu>Pb,but were utilization significantly reduced among different organs of maize.In the treatments SHGP and SNGP were most effective amendments, while it was the least with amendments S and SN.Correlation analysis results also showed that the content of Zn,Cu,Pb in maize had a significant negative correlation with soil pH and the ratio of oxidable and residual of Zn,Cu,Pb in soil,but had a significant positive correlation with the ratio of acid soluble and reducible of Zn,Cu,Pb in soil.4.The transportation of Zn,Cu,Pb from root to other organs followed the order:leaf> stem>grain.The uptake and transportation of Pb in grain was minimum and obviously lower than Zn and Cu.The amendments could increase the transportation of Zn and Cu among stem and grain,but reduce the transportation of Zn among leaves. All amendments could increase the transportation of Pb among grain,but different amendments had different effects on the transportation of Pb among stem and leaf that some could increase but others may reduce.Generally,there was a few difference between different amendments in the transportation of Zn,Cu,Pb among different organs of maize.The results showed that the amendments significantly reduced the bioavailability and mobility of Zn,Cu,Pb,reduced the uptake and the transportation of Zn,Cu,Pb among different organs of maize by increasing soil pH,reducing the content of acid soluble and reducible of Zn,Cu,Pb,increasing the content of oxidable and residual of Zn,Cu,Pb in soil. Among the ten treatments,SHGP and SNGP were most effective amendments on reducing the bioavailability of Zn,Cu,Pb in maize,followed by treatments SHG,SNG,SHP,SNP,SH and SN,while treatment S was the least.