State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 430074, Wuhan, Hubei, PR China; Hubei Key Laboratory of Yangtze Catchment Environmental Aquatic Science, China University of Geosciences, 430074, Wuhan, Hubei, PR China.
Environmental Geochemistry Group, Bayreuth Center for Ecology and Environmental Research (BAYCEER), Bayreuth University, 95440, Bayreuth, Germany.
Environ Res. 2023 Feb 1;218:115033. doi: 10.1016/j.envres.2022.115033. Epub 2022 Dec 9.
Arsenic (As) is ubiquitous in geothermal fluids, which threatens both water supply safety and local ecology. The co-occurrence of sulfur (S) and As increases the complexity of As migration and transformation in hot springs. Microorganisms play important roles in As-S transformation processes. In the present study, two Tibetan alkaline hot springs (designated Gulu [GL] and Daba [DB]) with different total As concentrations (0.88 mg/L and 12.42 mg/L, respectively) and different sulfide/As ratios (3.97 and 0.008, respectively) were selected for investigating interactions between As-S geochemistry and microbial communities along the outflow channels. The results showed that As-S transformation processes were similar, although concentrations and percentages of As and S species differed between the two hot springs. Thioarsenates were detected at the vents of the hot springs (18% and 0.32%, respectively), and were desulfurized to arsenite along the drainage channel. Arsenite was finally oxidized to arsenate (532 μg/L and 12,700 μg/L, respectively). Monothioarsenate, total As, and sulfate were the key factors shaping the changes in microbial communities with geochemical gradients. The relative abundances of sulfur reduction genes (dsrAB) and arsenate reduction genes (arsC) were higher in upstream portions of GL explaining high thiolation. Arsenite oxidation genes (aoxAB) were relatively abundant in downstream parts of GL and at the vent of DB explaining low thiolation. Sulfur oxidation genes (soxABXYZ) were abundant in GL and DB. Putative sulfate-reducing bacteria (SRB), such as Desulfuromusa and Clostridium, might be involved in forming thioarsenates by producing reduced S for chemical reactions with arsenite. Sulfur-oxidizing bacteria (SOB), such as Elioraea, Pseudoxanthomonas and Pseudomonas, and arsenite-oxidizing bacteria (AsOB) such as Thermus, Sulfurihydrogenibium and Hydrogenophaga, may be responsible for the oxidation of As-bound S, thereby desulfurizing thioarsenates, forming arsenite and, by further abiotic or microbial oxidation, arsenate. This study improves our understanding of As and S biogeochemistry in hot springs.
砷（As）在温泉中普遍存在，这既威胁到供水安全，也威胁到当地生态。硫（S）和 As 的共存增加了温泉中 As 迁移和转化的复杂性。微生物在 As-S 转化过程中发挥着重要作用。在本研究中，选择了两个西藏碱性温泉（分别命名为咕噜[GL]和大八[DB]），它们的总 As 浓度（分别为 0.88mg/L 和 12.42mg/L）和不同的硫化物/As 比值（分别为 3.97 和 0.008）不同，用于研究沿流出通道的 As-S 地球化学与微生物群落之间的相互作用。结果表明，尽管两个温泉的 As 和 S 物种浓度和百分比不同，但 As-S 转化过程相似。在温泉的喷口处检测到硫代砷酸盐（分别为 18%和 0.32%），并沿排水道脱硫为亚砷酸盐。亚砷酸盐最终被氧化为砷酸盐（分别为 532μg/L 和 12700μg/L）。单硫代砷酸盐、总 As 和硫酸盐是影响微生物群落随地球化学梯度变化的关键因素。GL 上游部分的硫还原基因（dsrAB）和砷酸盐还原基因（arsC）的相对丰度较高，解释了高度硫代作用。GL 下游部分和 DB 喷口处的亚砷酸盐氧化基因（aoxAB）相对丰富，解释了低硫代作用。GL 和 DB 中丰富的硫氧化基因（soxABXYZ）。可能参与形成硫代砷酸盐的硫酸盐还原菌（SRB），如脱硫孤菌和梭菌，可能通过产生还原 S 与亚砷酸盐发生化学反应。硫氧化菌（SOB），如埃利奥拉氏菌、假单胞菌和假单胞菌，以及亚砷酸盐氧化菌（AsOB），如硫热菌、硫氢杆菌和噬氢菌，可能负责 As 结合 S 的氧化，从而脱硫硫代砷酸盐，形成亚砷酸盐，并通过进一步的非生物或微生物氧化形成砷酸盐。本研究提高了我们对温泉中 As 和 S 生物地球化学的认识。
