The biogeochemical cycle of arsenic (As) inherently associates with its species. Bacterially mediated redox reactions, such as those accomplished by dissimilatory iron-reducing bacteria (DFeRB) and sulfate-reducing bacteria (SRB), are regarded as the most important mechanisms affecting As species transformation and mobilization. The novelty of this study is that partial least squares (PLS) path model was used to explore the possible pathways of As species transformation mediated by DFeRB and SRB in sediments during an ice-bound period based on continuous As species monitoring of a sediment–water system. Results showed that the effects of DFeRB and SRB on the reduction of As(V) were 1.5 and 2.5 times those of the sterilized group, respectively. Additionally, the TAs and As(III) concentrations in the aqueous mediated by SRB were 1.4 and 1.5 times those of the DFeRB group on average, respectively. The discerned trends reveal that DFeRB and SRB retained their reduction capacity and efficiency during the ice-bound period, which influenced the As species transformation. The amount reduced from As(V) to As(III) and the endogenous release of As mediated by SRB was higher than that of DFeRB. DFeRB mediated the reduction and indirectly influenced the As species transformation through the reductive dissolution and re-distribution of Fe(III) oxyhydroxides and As-containing Fe(III) minerals, while SRB mediated the reduction process, the As in sediment-overlying water system was gradually transformed into a more stable sulfide binding state. This study provides information for redirecting the environmental effects of DFeRB and SRB in the biogeochemical cycle of As in lakes and soils located in cold regions.

Graphical abstract

中文翻译：

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冰结期铁和硫酸盐还原菌介导砷物种的潜在转化途径

砷 (As) 的生物地球化学循环本质上与其物种相关联。细菌介导的氧化还原反应，例如由异化铁还原菌 (DFeRB) 和硫酸盐还原菌 (SRB) 完成的氧化还原反应，被认为是影响砷物种转化和动员的最重要机制。本研究的新颖之处在于，基于对沉积物-水体的连续 As 物种监测，使用偏最小二乘 (PLS) 路径模型探索了冰封期间由 DFeRB 和 SRB 介导的沉积物中 As 物种转化的可能途径系统。结果表明，DFeRB和SRB对As(V)还原的影响分别是灭菌组的1.5倍和2.5倍。此外，SRB 介导的水溶液中的 TA 和 As(III) 浓度分别为 1.4 和 1。分别是 DFeRB 组的 5 倍。观察到的趋势表明，DFeRB 和 SRB 在冰结期间保留了其还原能力和效率，这影响了 As 物种的转化。从 As(V) 减少到 As(III) 的量和由 SRB 介导的 As 内源性释放高于 DFeRB。DFeRB通过Fe(III)羟基氧化物和含As的Fe(III)矿物的还原溶解和重新分布介导还原并间接影响As物种转化，而SRB介导还原过程，沉积物上覆水系统中的As逐渐转变为更稳定的硫化物结合状态。

图形概要