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Valence-dependent dynamics: quantitatively understanding arsenic reallocations on iron oxyhydroxide mediated by microbial respiration.

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Title:	Valence-dependent dynamics: quantitatively understanding arsenic reallocations on iron oxyhydroxide mediated by microbial respiration.
Authors:	Hong, Zebin¹ (AUTHOR), Liu, Kai¹ (AUTHOR), Li, Fangbai¹ (AUTHOR), Borch, Thomas² (AUTHOR), Wu, Yundang¹ (AUTHOR), Liao, Congjian¹ (AUTHOR), Zhou, Xiaoxia¹ (AUTHOR), Liu, Tongxu¹ (AUTHOR) txliu@soil.gd.cn, Shi, Qiantao³ (AUTHOR), Fang, Liping¹ (AUTHOR) lpfang@soil.gd.cn
Source:	Chemical Geology. Dec2024, Vol. 670, pN.PAG-N.PAG. 1p.
Subjects:	Microbial respiration, Charge exchange, Environmental soil science, Biogeochemistry, Iron, Arsenic
Abstract:	Iron (Fe) oxyhydroxides are important reservoirs of arsenic (As) in soil and subsurface environments, and microbially-driven reductive transformation of Fe oxyhydroxides likely triggers arsenic release in soil under anoxic conditions. Due to a significant difference in the geochemical properties between As(III) and As(V), their interaction with Fe oxyhydroxides can be different. In addition, a quantitative understanding of the key processes that control the redistribution of As at the dynamically changing interface of water and Fe oxyhydroxides is of great importance, yet it remains elusive. Here this study quantitatively investigated the intricate arsenic redistribution at this dynamically changing interface of ferrihydrite (Fh) and water mediated by S. oneidensis under anoxic conditions. This work reveals that the dynamic changes in As reallocation at this interface is highly valance-dependent and distinctly contrasting. The microbial reduction of ferrihydrite led to a gradual release of As(III), while promoting fixation of As(V) on iron oxyhydroxides from water. Increasing As/Fe ratio inhibit the transformation of Fh, thereby reducing the release of As(III) and eenhancing As(V) fixation. Our kinetic model based on multi-process coupled reactions quantitatively unveiled that the transformation of Fh and Lp predominantly contributes 98.7 % - 99.2 % to the release of As(III) and As(V), while the formation of symplesite reversed the overall trend of As(V). These findings significantly expand our understanding of the coupled biogeochemistry of Fe and As, which may be useful for precise arsenic remediation and also for accurately predicting its geochemical behaviors in soil and subsurface environments. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

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Abstract:	Iron (Fe) oxyhydroxides are important reservoirs of arsenic (As) in soil and subsurface environments, and microbially-driven reductive transformation of Fe oxyhydroxides likely triggers arsenic release in soil under anoxic conditions. Due to a significant difference in the geochemical properties between As(III) and As(V), their interaction with Fe oxyhydroxides can be different. In addition, a quantitative understanding of the key processes that control the redistribution of As at the dynamically changing interface of water and Fe oxyhydroxides is of great importance, yet it remains elusive. Here this study quantitatively investigated the intricate arsenic redistribution at this dynamically changing interface of ferrihydrite (Fh) and water mediated by S. oneidensis under anoxic conditions. This work reveals that the dynamic changes in As reallocation at this interface is highly valance-dependent and distinctly contrasting. The microbial reduction of ferrihydrite led to a gradual release of As(III), while promoting fixation of As(V) on iron oxyhydroxides from water. Increasing As/Fe ratio inhibit the transformation of Fh, thereby reducing the release of As(III) and eenhancing As(V) fixation. Our kinetic model based on multi-process coupled reactions quantitatively unveiled that the transformation of Fh and Lp predominantly contributes 98.7 % - 99.2 % to the release of As(III) and As(V), while the formation of symplesite reversed the overall trend of As(V). These findings significantly expand our understanding of the coupled biogeochemistry of Fe and As, which may be useful for precise arsenic remediation and also for accurately predicting its geochemical behaviors in soil and subsurface environments. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:	00092541
DOI:	10.1016/j.chemgeo.2024.122426