Effect of Sepiolite Application on the Migration and Redistribution of Pb and Cd in Soil Rice System in Soil with Pb and Cd Combined Contamination

Abstract

In order to research the coordination relation between sepiolite application and the contents of available lead(Pb) and cadmium(Cd) in soil or rice absorption and redistribution of Pb and Cd, a pot experiment was conducted by selecting the soil sampled from a area polluted by Pb and Cd combination in Shaoxing City of Zhejiang Province and atypical late Japonica Rice Varieties in Zhejiang Province(Jia 33) with lower accumulation for Pb, Cd. The results showed that:the contents of available Pb and Cd in soil were significantly negatively correlated with the concentration of sepiolite added, the correlation coefficients of contents of available Pb and Cd with the concentration of sepiolite added were -0.940 respectively and -0.952, which reached the significant level(P<0.01).The contents of Pb and Cd in rice roots, stems, leaves and polished rice had different reducing rates with the increase of the concentration of sepiolite. In addition, with the increase of the concentration of sepiolite added, the enrichment coefficients of Pb and Cd in rice roots, stems, leaves and polished rice decreased dramatically. At the same time, Pb and Cd absorbed by roots transferred to the stems decreasingly, Pb and Cd absorbed by stems transferred to the polished rice decreasingly. When the addition of Sepiolite was 9.00 g·kg-1 soil, the contents of Pb and Cd in polished rice of Jia 33 were(0.14±0.02) mg·kg-1 and(0.03±0.01) mg·kg-1 respectively, which were all lower than the national limit index(GB 2762-2012). Compared with the control group, the enrichment coefficients of Pb in roots, stems and leaves and polished rice decreased by 8.83%, 29.96%, 49.20%, 79.41% respectively, and the enrichment coefficients of Cd decreased by 23.08%, 63.22%, 44.00%, 82.35% respectively. In addition, the transportation coefficients of Pb and Cd absorbed by roots transfer to the stems were decreased by 23.18% and 52.19% respectively and the transportation coefficients of stem rice translocation of Pb and Cd absorbed by stems transfer to the polished rice were decreased by 70.83%, 52.00%, respectively. This result means the sepiolite had a good resistance control in the migration and redistribution of Pb and Cd in soil rice system on the soil polluted by lead and cadmium, indicating the combination of rational application of sepiolite and rice varieties with lower accumulation for heavy metals can achieve safe agricultural utilization of the soil with combined contamination by a relatively higher concentration of Pb and Cd.