Studies On The Reduction Control Technology Of Cadmium In Heavy Metal Polluted Rice

Heavy metal pollution is a serious problem in China, which is a death blow to agriculture of southern provinces, especially in Hunan. The human health is now threatened by “cadmium-polluted rice” which frequently happened in recent years. Therefore, how to decrease the concentration of Cd in rice grown in soil where the concentration of heavy metal beyong national standards, which has attracted increasing attention. There is a great need to decrease the concentration of Cd in polluted rice to meet the national standards, which is of great significance for human health and food safety.The five soil samples obtained from Zhuzhou County and Liling city both located around the city of Zhuzhou, were analyzed by Nemerow’s single and comprehensive factor pollution index and Hakanson’s ecological risk index. Moreover, the source of heavy metal(Cd、Pb、Ni、Cr、Cu、Hg) polluted in the soil was discussed. The results showed that the soil was strongly polluted with Cd, and polluted with Hg and Pb to a lesser extent. However, the soil had not been polluted with Cr, Ni and Cu. The outcomes from the spatial distribution of heavy metals showed that the level of heavy metal polluted in the soil was as following: Baishu village(Pz=9.31) > Xiangshi village(Pz=7.70) > Hengjiang village(Pz=5.32) > Nanyang qiao country(Pz=5.18) > Youtian village(Pz=1.30). Xiangshi village and Baishu village were heavily polluted and had high ecological risk. This is because the two villages were close to living quarters and Xiangjiang River. The Baishu village was the most heavily polluted than other sections. Compared with other sections, the Youtian village was polluted to some extent by the use of poor quality fertilizer, which was located in mountainous areas and far away from the living area and industrial zones. Hengjiang village and Nanyang qiao country were close to Zhuzhou county, the heavy metal pollution mainly from local living garbage and atmospheric deposition. The above results indicated that heavy metals caused different degrees of contamination and ecological risk in soil layers. The upper soil layer of 0-20 cm was polluted heavier than others. The upper soil layer of 40-60 cm was polluted to a lesser extent. The upper soil layer of 80-100 cm was scarcely any polluted.We developed a new type composite soil modifier which was mainly supplemented with the medicinal stone “maifanshi” and lime. It is based on the mechanism of heavy metals blunting and adsorption. The aluminium in the medicinal stone “maifanshi” has the function of regulating the p H of soil. Therefore, the p H of acidic soil can be raised which would be helpful for reduction of the content of exchangeable Cd. In addition, the medicinal stone “maifanshi” could adsorb Cd due to its own cellular structure. The lime could improve the p H of soil and reduce Cd of exchangeable.Based on the results above analyzed, we established two fields where the concentration of Cd is far beyong national standards and the concentration of Cd is lesser beyong national standards which are located in Baishu village and Youtian village, respectively. The concentration of Cd in Baishu village and Youtian village is 10 and 1-2 times national standards, respectively. We developed a new technology to reduce the concentration of cadmium existed rice by cropping rice in our established two fields. In addition, we studied and analyzed the concentration of heavy metals in potted rice. The new type technology is soil modifier + low accumulation of cadmium rice seed + foliar s ilicon fertilizer. The soil modifier could reduce Cd of exchangeable, using low accumulation of cadmium rice seed could effectively reduce cadmium accumulation, and the foliar silicon fertilizer doused on rice, which could prevent the transport of Cd from leaf to grain of rice, reduce the cadmium concentration of rice. The result indicated that the type technology to reduce the cadmium content of rice has a good effect, in general, it can reduce the cadmium content of about 50%, with the highest value of up to 63.59%.