Sulfur Cycling-Related Biogeochemical Processes of Arsenic Mobilization in the Western Hetao Basin, China: Evidence from Multiple Isotope Approaches

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• 作者：Huaming Guo ; Yinzhu Zhou ; Yongfeng Jia ; Xiaohui Tang ; Xiaofeng Li ; Mengmeng Shen ; Hai Lu ; Shuangbao Han ; Chao Wei ; Stefan Norra ; Fucun Zhang
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：December 6, 2016
• 年：2016
• 卷：50
• 期：23
• 页码：12650-12659
• 全文大小：577K
• ISSN：1520-5851

文摘

The role of sulfur cycling in arsenic behavior under reducing conditions is not well-understood in previous investigations. This study provides observations of sulfur and oxygen isotope fractionation in sulfate and evaluation of sulfur cycling-related biogeochemical processes controlling dissolved arsenic groundwater concentrations using multiple isotope approaches. As a typical basin hosting high arsenic groundwater, the western Hetao basin was selected as the study area. Results showed that, along the groundwater flow paths, groundwater δ³⁴S_SO4, δ¹⁸O_SO4, and δ¹³C_DOC increased with increases in arsenic, dissolved iron, hydrogen sulfide and ammonium concentrations, while δ¹³C_DIC decreased with decreasing Eh and sulfate/chloride. Bacterial sulfate reduction (BSR) was responsible for many of these observed changes. The δ³⁴S_SO4 indicated that dissolved sulfate was mainly sourced from oxidative weathering of sulfides in upgradient alluvial fans. The high oxygen–sulfur isotope fractionation ratio (0.60) may result from both slow sulfate reduction rates and bacterial disproportionation of sulfur intermediates (BDSI). Data indicate that both the sulfide produced by BSR and the overall BDSI reduce arsenic-bearing iron(III) oxyhydroxides, leading to the release of arsenic into groundwater. These results suggest that sulfur-related biogeochemical processes are important in mobilizing arsenic in aquifer systems.