Particle- and Light-Mediated Processes Control Seasonal Manganese Oxide Cycling in a Meromictic Pond
Particle- and Light-Mediated Processes Control Seasonal Manganese Oxide Cycling in a Meromictic Pond
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DOI：
10.1021/acsearthspacechem.2c00368
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发表时间：
2023-05
影响因子：
3.4
通讯作者：
H. Gadol;C. Ostrander;Luciana Villarroel;L. Taenzer;S. Wankel;Véronique E. Carignan;C. Hansel
中科院分区：
文献类型：
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作者：
H. Gadol;C. Ostrander;Luciana Villarroel;L. Taenzer;S. Wankel;Véronique E. Carignan;C. Hansel
锰氧化物是强氧化剂以及营养物质和污染物的吸附剂，因此其形成机制影响多个生物地球化学循环。锰在好氧表层沃茨中通常以溶解的锰物种形式存在，如Mn（II）和Mn（III）-配体络合物，而不是Mn氧化物。这被认为是与有机物的光解和阳光照射的沃茨内直接有机物介导的还原相关的过氧化氢还原氧化锰的结果。然而，锰氧化物可以持续在一些表面环境，这表明锰氧化物分布的控制不完全的理解。在这里，我们结合了基于现场和实验室的分析，以探索2020年夏季和秋季在科德角（马萨诸塞州，美国）的半咸水和部分混合池塘Siders Pond内锰氧化物的分布，锰氧化速率和对锰氧化物形成的潜在控制。在有阳光照射的表层沃茨中始终观察到锰氧化物，其浓度在化学跃层的底部下降至无法检测。表面锰氧化物浓度在夏末最高，达到0.1 μM，在晚秋最低，仅达到0.50 nM。利用同步加速器吸收测量确定的矿物在结构上类似于δ-MnO 2和Feitknechtite。大量的光介导的锰氧化只发生在活孵化的赛德斯池塘水，而净锰减少进行杀死孵化。因此，总颗粒介导的氧化微生物和矿物质相结合的速度超过光还原，导致锰氧化物的净积累内赛德斯池塘。我们的研究结果确定了微生物和矿物介导的氧化在确定锰氧化物的分布在自然环境的表面沃茨内的重要作用，这一发现可能有助于解释在其他地方的可比分布。
Manganese (Mn) oxides are strong oxidants and sorbents of nutrients and contaminants, thus their formation mechanisms impact multiple biogeochemical cycles. Manganese in oxic surface waters is often found as dissolved Mn species, such as Mn(II) and Mn(III)-ligand complexes, rather than Mn oxides. This is believed to be a result of Mn oxide reduction by hydrogen peroxide associated with photolysis of organic matter and direct organic matter-mediated reduction within sunlit waters. Nevertheless, Mn oxides can persist in some surface environments, which indicates an incomplete understanding of controls on Mn oxide distributions. Here, we couple field- and lab-based analyses to explore Mn oxide distributions, Mn oxidation rates, and underlying controls on Mn oxide formation within Siders Pond, a brackish and meromictic pond on Cape Cod (Massachusetts, USA) during the summer and fall of 2020. Manganese oxides were observed consistently in sunlit surface waters with concentrations declining to undetectable at the base of the chemocline. Surface Mn oxide concentrations were highest in late summer, reaching concentrations of ∼1 μM, and lowest in late fall, reaching only ∼50 nM. Minerals identified using synchrotron-based absorbance measurements were structurally similar to δ-MnO2and feitknechtite. Substantial light-mediated Mn oxidation only took place in live incubations of Siders Pond water while net Mn reduction proceeded in killed incubations. Thus, total particle-mediated oxidation by microbes and minerals combined outpaced photoreduction, leading to net accumulation of Mn oxides within Siders Pond. Our results identify important roles for microbial- and mineral-mediated oxidation in determining Mn oxide distributions within surface waters of a natural setting, a finding that may help explain comparable distributions in other locations.