Different Material Effect Of Composite Additives On Soil Heavy Metal Chromium And Lead Speciation And Availability

Soil was a valuable resource that nature gives to human beings,currently, soil pollution was worsening, especially among heavy metal pollution. Heavy metals in soil not only harm plant, but also indirectly harm human health through the food chain. So, how to repaire heavy metal contaminated soil has always been a hot and important area of research disciplines and key issues of environment, soil, etc. In this study, orthogonal design L9(34) design was used, the pH adjusting agent(zeolite), organic material(peat), biochar(manure) three different kinds of heavy metals contaminated soil improvers was selected, for carrying out repair test of regulating chromium contaminated soil. Through dynamic culture tests in laboratory, different composite groups had influences on forms of soil heavy metal chromium, pH, organic matter, to explore the best combination of materials to reduce soil chromium effectiveness; A pot experiment was used to verify the different composites group effected on cabbage, radish absorbing chromium. The results are as follows:(1) Peat soil was significant factor for reducing the content of exchangeable chromium, and when the amount of peat level was 5% to reduce soil exchangeable chromium having the best result. Composites group 3(zeolite 0g.kg-1,peat 5%,chicken manure 3g.kg-1) effecting on reducing the content of exchangeable chromium in soil was the best.(2) Zeolite, peat and chicken manure were reducible significant factor for effecting the content of reducible chromium in soil. Zeolite 2 g. kg-1, chicken 3 g. kg-1 added to improve reducible chromium content in soil was the best, adding 5% peat to reduce soil reducible chromium content was the best.(3) Zeolite and peat were significant factors to improve the content of oxidisable chromium in soil, and the 4g. kg-1or 2 gï¹'kg-1 addition amount of zeolite, 5% addition amount of peat had the best effect on improving content of oxidisable chromium. Composites group 7(zeolite 4g.kg-1, 5% peat, chicken manure 1.5g.kg-1) was the best combination to improve content of oxidisable chromium.(4) Composite added group had no significant effect on soil residual chromium content.(5) Zeolite and peat obviously improved soil organic matter, and when the zeolite organic matter dosage was 2g. kg-1 or 4g. kg-1, the peat reached 5% level, they would have the best result to improve content of soil organic matter. Composites group 7(zeolite 4g.kg-1, 5% peat, chicken manure 1.5g.kg-1) was the best combination to improve the content soil organic matter.(6) Zeolite and chicken manure to improve the soil pH were significant factors, and when the amount of zeolite added level reached 4g. kg-1, amount of chicken manure level was 3g. kg-1, they could effectively increase soil pH. The group 8(zeolite: 4 g.kg-1, peat: 0, chicken: 3 g.kg-1) was optimum combination of materials, which could improve the soil pH.(7) The reduction of exchangeable heavy metals chromium content in soil had the direct reaction of the reduction the effectiveness of chromium in soil, and the content of reducible, oxidisable chromium increasing indirectly showed the reduction of chromium effectiveness. The Addition of zeolite increased soil pH and organic matter, thereby increasing content of soil oxidisable, reducible chromium, and then reducing the effectiveness of the Soil Chrome; The Addition of chicken manure added the content of reducible chromium by increasing the content of pH, thereby reducing the effectiveness of soil chromium. The Addition of peat improved the content of organic matter, thereby reducing the content of soil exchangeable chromium, increasing soil oxidisable chromium content, thus reducing the effectiveness of soil chromium.(8) The main factors for reducing the chromium content of cabbage were zeolite, chicken manure, analysing with composite materials on chemical forms of cadmium, it can be inferred that :The addition of zeolite improved the content of the soil oxidizable, reducible chromium by increasing soil pH, thus reducing the effectiveness of soil chromium. The Addition of chicken manure added the content of reducible chromium by increasing the content of pH, thereby reducing the effectiveness of soil chromium. Reducing of the effectiveness of soil chromium content directly reflected the lowering of chromium cabbage content.(9) The addition of zeolite improved the content of the soil oxidizable, reducible chromium by increasing soil pH, organic matter, thus reducing the chromium content in radish; The Addition of peat improved the content of organic matter, thereby reducing the content of soil exchangeable chromium, increasing soil oxidisable chromium content, thus reducing the chromium content in radish.(10) Composites group 3(zeolite 0g.kg-1, peat 5%, chicken manure 3g.kg-1) and composites group 7(zeolite 4g.kg-1, 5% peat, chicken manure 1.5g.kg-1) were the best combination of materials to reduce soil chromium effectiveness.