| This study was embarked from the farmland production practice for the purpose of screening for low accumulation-type rice cultivars from 30 different varieties of rice and forming a set of controlling technology by adding in sepiolite or humic acid. Field trials and screenhouse pot experiment were conducted on the the basis of Pb> Cd contaminated soil to provide scientific theory and practical skills for food safety outputs in contaminated areas. The main results were as follows:(1) 30 different varieties of rice were planted in the Pb & Cd contaminated area, which located in Danshan Village, Dongguan Town, Shaoxing City, Zhejiang Province in 2012. The content of Pb and Cd of each rice variety was tested, and 5 low accumulation varieties as well as 3 high accumulation varieties were initially screened out on the basis of Pb, Cd limited index of rice (GB 2762-2012,0.2 mg/kg). The 5 low accumulation varieties were:Jia 33, Xiushui 134, Xiushui 128,Xiushui 05, Hualiangyou 164, T-you 227; the 3 high accumulation varieties were:Xiushui 134,Zhefuliangyou 12, T-you 272.(2) 5 low accumulation rice varieties and 3 high accumulation rice varieties that selected in 2012 were taken as materials in the 2013 field experiment.2 lower accumulation rice varieties(Jia 33 and Hualiangyou 164) were screened out through the analysis of the content of Pb & Cd in rice. Dynamic characteristics of heavy metal Pb & Cd in various plant organs were analyzed and the results showed that the absorption and distribution law of Pb was:root> stem> leaf> rice husk> milled rice; the absorption and distribution law of Cd was:root> stem> leaf>milled rice> rice husk. The dynamic characteristics of heavy metal Pb & Cd in different growth stages were as follows, Pb content in roots:tillering stage> heading stage> maturity stage; Pb content in stems:tillering stage< heading stage< maturity stage; Pb content in leaves:tillering stage< heading stage< maturity stage; Cd content in roots: tillering stage> heading stage> maturity stage; Cd content in leaves:tillering stage <heading stage< maturity stage.(3) In 2014, the potting soil culture experiment materials were Xiushui 134 and Jia 33. The effects of different treatment levels of sepiolite(0、0.8996、2.6988、4.4980、 6.2972、8.9960 g/kg) and humic acids(0、0.2999、0.8997、1.4995、2.0993、2.9990 g/kg) were explored and the results showed that sepiolite could change soil pH, and the more sepiolite there was, the higher the pH would be. Both sepiolite and humic acids could reduce the content of available Pb and Cd in soil. The effect of Pb adsorption of sepiolite was better than that of humic acids, while the effect of Cd adsorption of humic acids was better than that of sepiolite. The results also showed that the content of Pb and Cd in roots, stems, leaves and milled rice tended to be lower when the level of sepiolite or humic acids became higher. The content of Pb of milled rice in Jia 33 was turned out to be under 0.2 mg/kg at the biggest concentration of sepiolite and humic acids whereas the content of Pb of milled rice in Xiushui 134 still higher than 0.2 mg/kg. It was suggested that more sepiolite or humic acids could be added in soil. The content of Cd of milled rice in Jia 33 was less than 0.2 mg/kg without adding in any amendments, not to mention adding in sepiolite or humic acids. Naturally, the content of Fe of rice iron plaque in Jia 33 was higher than that in Xiushui 134. Sepiolite and humic acids were turned out to have positive effect on the content of Fe of rice iron plaque, so as to increase the adsorption on soil heavy metal Pb、Cd and reduce the content of Pb、Cd in rice plants. |
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