δ34S and δ18O of dissolved sulfate as biotic tracer of biogeochemical influences on arsenic mobilization in groundwater in the Hetao Plain, Inner Mongolia, China

• Published in: Ecotoxicology (London) Vol. 23; no. 10; pp. 1958 - 1968
• Main Authors: Li, M. D, Wang, Y. X, Li, P, Deng, Y. M, Xie, X. J
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.12.2014; Springer US
• Subjects: arsenic; Arsenic - analysis; bacteria; China; dissolved oxygen; Earth and Environmental Science; Ecology; Ecotoxicology; Environment; Environmental Management; Environmental Monitoring - methods; fertilizer application; groundwater; Groundwater - chemistry; gypsum; isotopes; oxides; oxygen; Oxygen Isotopes - analysis; Sulfates - analysis; sulfur; Sulfur Isotopes - analysis; Water Pollutants, Chemical - analysis; wells; China; Biogeochemistry; Arsenic; Anthropogenic activities; Sulfur and oxygen isotope; Hetao Plain
• ISSN: 0963-9292; 1573-3017
• DOI: 10.1007/s10646-014-1310-y

Environmental isotopology of sulfur and oxygen of dissolved sulfate in groundwater was conducted in the Hetao Plain, northwestern China, aiming to better understand the processes controlling arsenic mobilization in arsenic-rich aqueous systems. A total of 22 groundwater samples were collected from domestic wells in the Hetao Plain. Arsenic concentrations ranged from 11.0 to 388 μg/L. The δ³⁴S-SO₄and δ¹⁸O-SO₄values of dissolved sulfate covered a range from +1.48 to +22.4 ‰ and +8.17 ‰ to +14.8 ‰ in groundwater, respectively. The wide range of δ³⁴S-SO₄values reflected either an input of different sources of sulfate, such as gypsum dissolution and fertilizer application, or a modification from biogeochemical process of bacterial sulfate reduction. The positive correlation between δ³⁴S-SO₄and arsenic concentrations suggested that bacteria mediated processes played an important role in the mobilization of arsenic. The δ¹⁸O-SO₄values correlated non-linearly with δ³⁴S-SO₄, but within a relatively narrow range (+8.17 to +14.8 ‰), implying that complexities inherent in the sulfate-oxygen (O-SO₄²⁻) origins, for instance, water-derived oxygen (O-H₂O), molecular oxygen (O-O₂) and isotope exchanging with dissolved oxides, are accounted for oxygen isotope composition of dissolved sulfate in groundwater in the Hetao Plain.