Carbon‑sulfur coupling in a seasonally hypoxic, high-sulfate reservoir in SW China: Evidence from stable CS isotopes and sulfate-reducing bacteria

Mengdi Yang; Cong-Qiang Liu; Xiao-Dong Li; Shiyuan Ding; Gaoyang Cui; Hui Henry Teng; Hong Lv; Yiyao Wang; Xuecheng Zhang; Tianhao Guan

doi:10.1016/j.scitotenv.2022.154537

Carbon‑sulfur coupling in a seasonally hypoxic, high-sulfate reservoir in SW China: Evidence from stable CS isotopes and sulfate-reducing bacteria

Sci Total Environ. 2022 Jul 1:828:154537. doi: 10.1016/j.scitotenv.2022.154537. Epub 2022 Mar 12.

Authors

Affiliations

¹ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
² Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China; Tianjin Key Laboratory of Earth's Critical Zone Science and Sustainable Development in Bohai Rim, Tianjin University, Tianjin 300072, China.
³ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China; Tianjin Key Laboratory of Earth's Critical Zone Science and Sustainable Development in Bohai Rim, Tianjin University, Tianjin 300072, China. Electronic address: xiaodong.li@tju.edu.cn.
⁴ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China; State Key Laboratory of Environmental Geochemistry, Guiyang 550081, China.
⁵ Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, College of Environment and Planning, Henan University, Kaifeng 475004, China.

PMID: 35292324
DOI: 10.1016/j.scitotenv.2022.154537

Abstract

Anthropogenic input of sulfate (SO₄^2-) in reservoirs may enhance bacterial sulfate reduction (BSR) under seasonally hypoxic conditions in the water column. However, factors that control BSR and its coupling to organic carbon (OC) mineralization in seasonally hypoxic reservoirs remain unclear. The present study elucidates the coupling processes by analyzing the concentrations and isotopic composition of dissolved inorganic carbon (DIC) and sulfur (SO₄^2-, sulfide) species, and the microbial community in water of the Aha reservoir, SW China, which has high SO₄^2- concentration due to the inputs from acid mine drainage about twenty years ago. The water column at two sites in July and October revealed significant thermal stratification. In the hypoxic bottom water, the δ¹³C-DIC decreased while the δ³⁴S-SO₄^2- increased, implying organic carbon mineralization due to BSR. The magnitude of S isotope fractionation (Δ³⁴S, obtained from δ³⁴S_sulfate-δ³⁴S_sulfide) during the process of BSR fell in the range of 3.4‰ to 27.0‰ in July and 21.6‰ to 31.8‰ in October, suggesting a change in the community of sulfate-reducing bacteria (SRB). The relatively low water column stability in October compared to that in July weakened the difference of water chemistry and ultimately affected the SRB diversity. The production of DIC (ΔDIC) scaled a strong positive relationship with the Δ³⁴S in July (p < 0.01), indicating that high OC availability favored the survival of incomplete oxidizers of SRB. However, in October, Δ¹³C-DIC was correlated with the Δ³⁴S in the bottom hypoxic water (p < 0.01), implying that newly degraded OC depleted in ¹³C could favor the dominance of complete oxidizers of SRB which caused greater S isotope fractionation. Moreover, the sulfide supplied by BSR might stimulate the reductive dissolution of Fe and Mn oxides (Fe(O)OH and MnO₂). The present study helps to understand the coupling of C and S in seasonally hypoxic reservoirs characterized by high SO₄^2- concentration.

Keywords: OC mineralization; Seasonal hypoxic reservoir; Sulfate reduction; Sulfate-reducing bacteria; Sulfur isotope fractionation.

MeSH terms

Bacteria / metabolism
Carbon Isotopes / analysis
Carbon* / metabolism
China
Environmental Monitoring
Isotopes
Manganese Compounds
Oxides
Sulfates* / analysis
Sulfides / metabolism
Sulfur / metabolism
Sulfur Isotopes / analysis
Sulfur Oxides / metabolism
Water / metabolism

Substances

Carbon Isotopes
Isotopes
Manganese Compounds
Oxides
Sulfates
Sulfides
Sulfur Isotopes
Sulfur Oxides
Water
Sulfur
Carbon