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Effect of sulfur and sulfur-iron modified biochar on cadmium availability and transfer in the soil–rice system
- Rajendran, Manikandan, Shi, Lizheng, Wu, Chuan, Li, Waichin, An, Wenhui, Liu, Ziyu, Xue, Shengguo
- Chemosphere 2019 v.222 pp. 314-322
- biochar, cadmium, chlorophyll, developmental stages, food contamination, iron, iron oxides, manganese oxides, paddy soils, polluted soils, pollution, public health, remediation, rhizosphere, rice, roots, shoots, sulfur, tissues, China
- Cadmium (Cd) contamination in paddy soils has aroused global concern. Sulfur modified biochar (BC) could combine the benefits of BC and S for Cd remediation. However, no information is available on the impact of sulfur modified biochar on Cd phytoavailability in paddy soils. In this study, a pot experiment was conducted to investigate the effect of sulfur modified biochar (S-BC) and sulfur and iron (Fe) modified biochar (S-Fe BC) on Cd mobility and Cd transfer in the soil-rice system. The application of S-BC and S-Fe BC effectively reduced pore water Cd in the rhizosphere and non-rhizosphere pore water throughout the rice growth stages. S-BC and S-Fe BC addition increased the total chlorophyll content, as well as the root, shoot and grain biomasses of rice. Furthermore, S-BC and S-Fe BC amendments greatly increase the formation of Fe plaque on rice root surface, thus decreasing Cd accumulation in different rice tissues. In particular, S-Fe BC supplementation significantly reduced the Cd concentration in rice grains to 0.018 mg kg−1 in Cd-contaminated soil, which was lower than the China National standard for food contamination limit (0.2 mg kg−1 Cd). Sequential extraction results showed that S-BC and S-Fe BC can promote the transfer of exchangeable Cd to Fe-Mn oxide, organic and residual bound forms which reduce Cd in paddy soils. Thus, the amendment of S-Fe BC to Cd-contaminated paddy soil is an effective strategy to decrease Cd accumulation in rice grains and thereby protect public health.