| Heavy metal pollution in farmland soil poses a serious threat to soil environmental quality,agricultural product safety and human health,it is necessary for remediation of soil polluted by heavy metals.In this thesis typical cadmium(Cd)contaminated paddy soil from Hunan and Jiangsu Provinces was selected and field and pot experiments were conducted to exam the stabilization efficiency of Cd by different types and dosages of amendments,Cd accumulation among various rice varieties,and to explore the regulation of Cd availability by application of phosphorus and zinc in rice and Sedum plumbizincicola rotation system.Aims to provide a theoretical basis and technical support for efficient soil remediation and safe production in Cd contaminated farmland.The main consequences are as follow.Field experiments were carried out in Taicang City and Kunshan City,Jiangsu Province and the effects of different amendment materials and dosages on the availability of heavy metals and accumulation in rice were compared.The results of Taicang city shows that in soils with pH 6.9 and total Cd 3.59 mg kg-1,adding amendments can increase pH value of soil and decrease concentration of CaCl2 extractable Cd.Especially,the effects of adding calcium chloroaluminate and calcium magnesium phosphate is better than other amendments.And these reduction rates of CaCl2 extractable Cd are 82.7%and 79.7%,respectively.The concentration of Cd in rice grain is 0.39 mg kg-1 at control without amendments,while Cd concentrations are below 0.2 mg kg-1,the safety limit when adding complex amendments to soil in 300 kg mu-1 and 600 kg mu-1,chloride calcium aluminate in 300 kg mu-1 and 600 kg mu-1 and calcium magnesium phosphate in 200 kg mu-1.Similar to Taicang,results of Kunshan City showed that Cd concentrations in Xiushui 09 grain decreased from 0.26 mg kg-1(control)to 0.06 mg kg-1(calcium chloroaluminate at 400 kg mu-1)and 0.13 mg kg-1(complex amendments at 400 kg mu-1),respectively,and in Zhongxiang No.1 grain from 0.24 mg kg-1 to 0.19 mg kg-1 and 0.18 mg kg-1,respectively.The Cd accumulation were compared among different rice cultivars based on field plot experiments in a heavy metal polluted farmland soil in Taicang City,Suzhou City.The result showed that the productions of 9 rice varieties were range from 501 to 802 kg mu-1,and the order is Nanjing 5055>Xiushui 09>Jiahua>Wuyunjing 30>Suxiangjing 100>Xiushui134>Nanjing 46>Miyang 12085>Miyang12086.Moreover,Cd concentrations of grain ranged from 0.23 to 0.77 mg kg-1,and the grain Cd concentration in Miyang12086 was the lowest at 0.23 mg kg-1.Taking grain production into account,Suxiangjing 100,one of common varieties for local farmers,possessed low-accumulated character for Cd,and the concentration of Cd in grain is 0.38 mg kg-1.Collected typical cadmium-contaminated acidic soils in Hunan Province.The influence of phosphate(P)and zinc(Zn)amendments at rice growth season on Cd uptake in rice and succeeding Sedum plumbizincicolawas were studied in a pot experiment.The results showed that at the high P(P 400 mg·kg-1)treatment soil CaCl2 extractable Cd decreased compared with the control(P 100 mg·kg-1),and the Cd concentration in rice straw was not effected obviously,but the Cd transfer coefficient from straw to grain significantly decreased in the rice season.The soil CaCl2 extractable Cd concentration reduced under Zn treatment,and the Cd concentration in brown rice was reduced from 0.21 mg·kg-1(control)to 0.15 mg·kg-1.The P and Zn treatment at rice reason had no obvious influence on the shoot biomass and Cd concentration of S.plumbizincicola at next season.Zn treatment at rice reason increased Zn accumulation in rice and S.plumbizincicola.The P and Zn treatment at rice reason could reduce the risk of Cd accumulation in rice and had no obvious effect on Cd removal by succeeding S.plumbizincicola.So adding Zn and P can be regarded as an adjustable way to treat Cd polluted soil with 'production while remediation'. |
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