Simultaneous alleviation of cadmium and arsenic accumulation in rice by applying zero-valent iron and biochar to contaminated paddy soils

• Published in: Chemosphere (Oxford) Vol. 195; pp. 260 - 271
• Main Authors: Qiao, Jiang-tao, Liu, Tong-xu, Wang, Xiang-qin, Li, Fang-bai, Lv, Ya-hui, Cui, Jiang-hu, Zeng, Xiao-duo, Yuan, Yu-zhen, Liu, Chuan-ping
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2018
• Subjects: Bioavailable As and Cd; Biochar; Fe fractions; Paddy soil; Zero-valent iron; Biochar; Bioavailable As and Cd; Fe fractions; Paddy soil; Zero-valent iron
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2017.12.081

The fates of cadmium (Cd) and arsenic (As) in paddy fields are generally opposite; thus, the inconsistent transformation of Cd and As poses large challenges for their remediation. In this study, the impacts of zero valent iron (ZVI) and/or biochar amendments on Cd and As bioavailability were examined in pot trials with rice. Comparison with the untreated soil, both Cd and As accumulation in different rice tissues decreased significantly in the ZVI-biochar amendments and the Cd and As accumulation in rice decreased with increasing ZVI contents. In particular, the concentrations of Cd (0.15 ± 0.01 mg kg−1) and As (0.17 ± 0.01 mg kg−1) in rice grains were decreased by 93% and 61% relative to the untreated soil, respectively. A sequential extraction analysis indicated that with increasing Fe ratios in the ZVI-biochar mixtures, bioavailable Cd and As decreased, and the immobilized Cd and As increased. Furthermore, high levels of Fe, Cd, and As were detected in Fe plaque of the ZVI-biochar amendments in comparison with the single biochar or single ZVI amendments. The ZVI-biochar mixture may have a synergistic effect that simultaneously reduces Cd and As bioavailability by increasing the formation of amorphous Fe and Fe plaque for Cd and As immobilization. The single ZVI amendment significantly decreased As bioavailability, while the single biochar amendment significantly reduced the bioavailability of Cd compared with the combined amendments. Hence, using a ZVI-biochar mixture as a soil amendment could be a promising strategy for safely-utilizing Cd and As co-contaminated sites in the future. [Display omitted] •The single zero valent iron amendment decreased the bioavailability of As.•The single biochar amendment reduced the bioavailability of Cd.•The ZVI-biochar amendments simultaneously reduced Cd and As bioavailability.•The Fe, Cd, and As in plaque increased significantly in the ZVI-biochar amendments.•The ZVI-biochar amendments increased the amorphous Fe oxides in soils.