Effects Of Different Chemical Fertilizers On The Availability Of Cadmium In Soil And The Uptake Of Cadmium By Plants

In the face of a large number of Cd polluted farmland.The phytoremediation technology has less influence on the surrounding environment,lower pollution treatment cost,lasting pollution control effect and ecological value of purifying and beautifying the environment because of its in situ remediation.Fertilization is the most important link in agricultural production,which can promote the growth of plants and increase the biomass,and through fertilization can adjust the soil environment and the available state of heavy metals in soil,thus affecting the efficiency of phytoremediation.In this paper,three kinds of soils polluted by Cd in different degrees were used as research materials.The effects of 5 kinds of fertilizers（NH₄Cl、（NH₄）₂SO₄、CO（NH₂）₂、KH₂PO₄ and KCl）on Cd dissolution and different forms of Cd in polluted soil were studied,and the rape（Brassica napus）and sedum（Sedum alfredii）were selected as the research objects,and pot experiments were carried out.The effects of NH₄Cl、（NH₄）₂SO₄ on the availability of Cd in soil were investigated,and the differences of Cd uptake and transport between rape and sedum were compared,and the optimum fertilization techniques for remediation of Cd contaminated soil were put forward.The main results were as follows:（1）there is no significant difference between the contrast blank of three kinds of soils under five kinds of fertiliser leaching and contrasting blanks,which are not conducive to Cd dissolving KH₂PO₄ and KCl treatment.The contrast blank of NH₄Cl、（NH₄）₂SO₄ is beneficial to the dissolution of heavy metal Cd in soil,and the difference of fertilization concentration is significant（300 mg/kg）.Cd dissolved in the three soils reached 12.87μg/L and 16.52μg/L,and NH₄Cl、（NH₄）₂SO₄ fertilization could reduce the contents of organic matter,sulfide-bound and residual Cd in soil.The content of exchangeable,carbonate bound and iron-manganese oxide bound Cd was increased,and the availability of Cd was increased.（2）the pH of soil treated with ammonium sulfate was lower than that of soil treated with ammonium chloride,and the pH of non-rhizosphere soil was lower than that of rhizosphere soil under fertilization treatment.The pH of non-rhizosphere soil at maturity was higher than that of rhizosphere soil.Ammonium sulfate and ammonium chloride increased the content of available Cd in soil.The concentration of available Cd in ammonium sulfate treatment was higher than that in ammonium chloride treatment,and the concentration of available Cd in three soils at maturity stage was higher than that in ammonium chloride treatment.The total Cd content in the rhizosphere soil was higher than that in the non-rhizosphere soil.（3）The order of Cd accumulation in different parts of rapeseed at maturity stage was leaf>root>stem>pod>grain.The order of transport coefficient was:TFl/r>TFs/r>TFp/s>TFs/s.The Cd transport coefficient of rape was the highest from root to leaf.The application of ammonium sulfate and ammonium chloride increased the Cd content in different parts of rape and the Cd content in the aboveground part of sedum,increased the enrichment coefficient and transport coefficient of rape and sedum,and effectively improved the phytoremediation efficiency of three different cadmium contaminated soils.（4）Rapeseed in three kinds of soils had high remediation efficiency under low concentration NH₄Cl treatment and high concentration（NH₄）₂SO₄ treatment.Rapeseed had the potential of phytoremediation to Cd contaminated soil.Under low concentration of NH₄Cl and（NH₄）₂SO₄,sedum in the three kinds of soils had higher remediation efficiency.