Pedosphere 34(6): 1076--1085, 2024
ISSN 1002-0160/CN 32-1315/P
©2024 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Fe(II) oxidation after microbial Fe(III) reduction does not cause Cd release |
Zhaoyang SUN1,2, Wenjun ZHANG2, Lei WANG2, Hongwen SUN2, Yuxuan WAN2, Qi LI2, Chaolei YUAN1,2 |
1 School of Agriculture and Biotechnology, Sun Yat-sen University, Shenzhen 518107 (China);
2 College of Environmental Science and Engineering, Nankai University, Tianjin 300350 (China) |
| ABSTRACT |
| Soil flooding and drainage can cause the reduction and oxidation of iron (Fe), as well as the immobilization and mobilization of cadmium (Cd). However, the impact of Fe(II) oxidation following microbial Fe(III) reduction on Cd mobility remains unclear. In this study, we examined the behavior of Cd during microbial reduction of Fe(III) oxides and subsequent chemical re-oxidation of Fe(II) using batch reactor systems. The bacterium Shewanella oneidensis MR-1 was incubated with ferrihydrite, lepidocrocite, goethite, or hematite anaerobically and then aerobically in media containing 212 μg L-1 Cd, with or without pH buffering (initial pH = 7.0). Compared to the control systems without MR-1, microbial Fe(III) reduction significantly promoted the immobilization of dissolved Cd, as well as the conversion of dissolved and adsorbed Cd to strongly bound Cd that could not be extracted by 0.4 mol L-1 HCl. The mechanisms of Cd immobilization were different during the microbial reduction of different Fe(III) oxides. The buffering of system pH affected the phase of Fe oxides formed at the reduction and oxidation stages in the systems containing MR-1 and ferrihydrite or lepidocrocite. Nevertheless, in all the systems containing MR-1 and Fe oxides, irrespective of pH buffering, the concentration of dissolved Cd dropped to < 1 μg L-1 after 35 d of anaerobic incubation and remained < 4 μg L-1 after subsequent 72 h of aerobic incubation. This suggests that Fe(II) oxidation after microbial Fe(III) reduction (generating 0.025-0.22 g L-1 Fe(II)) does not result in Cd release. |
| Key Words: adsorbed cadmium,cadmium immobilization,cadmium mobility,dissolved cadmium,iron oxide,pH buffering |
| Citation: Sun Z Y, Zhang W J, Wang L, Sun H W, Wan Y X, Li Q, Yuan C L. 2024. Fe(II) oxidation after microbial Fe(III) reduction does not cause Cd release. Pedosphere. 34(6): 1076-1085. |
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