Study On Stablizing And Utilizing Of Farmland Heavily Polluted By Lead And Cadmium

With the development of social economy,soil heavy metal pollution in China is becoming increasingly serious,and threaten the ecological security and human health.In this study,the Cd and Pb combined polluted agricultural soil in Yunnan Lanping County was investigated,the stabilization of soil metal by the application of lime,sepiolite,biochar,calcium magnesium phosphate fertilizer,and the metal accumulating in corn were studied through soil culture experiment,greenhouse pot experiment and field experiments.The main results are as follows:(1)The results of soil culture test and greenhouse pot experiment showed that there were the significant differences effect for the material types and the dosages on soil available lead and cadmium.Lime,sepiolite,and high-dose biochar had significant decreasing effects on soil available Pb and Cd,and lime was the most effective stabilizer,but the effect increased less when the amount of lime exceeded0.2%.For the heavily metal contaminated soil(Cd 33.9 mg/kg,Pb 1277 mg/kg)used in this study,the combined application of lime and sepiolite gave the largest reduction at soil available Pb and Cd by 97.5% and 81.4%,respectively,while the concentration of Pb and Cd in the corresponding corns only decreased by 29.6% and 34.0%,and the absolute concentrations were still high,41.0 and 30.0 mg/kg,respectively.(2)The results of field experiment showed that similar to the pot experiment,the stabilizers also significantly reduced the soil available Pb and Cd concentrations in field condition.Compared with the soil without stabilizer,the available Pb and Cd in the soil with lime and biochar co-application significantly decreased by 81.1% and93.3%,respectively.The concentrations of Pb and Cd in corn grain in all treatments were lower than the permission levels of the national food safety production standards.However,the metals enrichment factors of Pb and Cd and the yields of corn grains were different among treatments.The enrichment factors of Pb and Cd in corn grain in soil treated with biochar was relatively low,0.0001 and 0.014 respectively.The yield of corn in soil with biochar + sepiolite and biochar + calcium magnesium phosphate increased by 44.3% and 41.7% respectively.The above results suggested that maize with low metal accumulating ability can be used for safely production at the pollution level of this field condition,and stabilizer can further decrease metal accumulation in corn grain.(3)For screening the low metal accumulating crops from 50 potential varieties of maize,a field experiment was conducted.The results showed that there were significant differences in metal enrichment coefficient of corn grains and yields among different varieties.The concentrations of Cd and Pb in grain of the 16 maize varieties were below the permission levels of the national food safety standards.There were 15 maize cultivars with high yield of grain,such as Chengxin No.1;the lowest Cd enrichment coefficient was Xianyu 987(blue),only 0.004;for Pb the low enrichment coefficient is 0.0001,the cultivars were Denghai 605,Chengxin No.5,Chengxin No.1 and Jinnong 109.Take consideration of grain yield and Cd and Pb accumulation,nine corn varieties such as Chengxin No.1,Jinnong 109,Good faith 6,Integrity 5,Longsheng 16,Strong 103,Powerful 101,Jade 987(blue),Runmin 8could be used for the safe production at highly Cd and Pb contaminated soil with the combining application with metal stabilizer.