粒子和光介导过程控制 Meromictic 池塘中的季节性氧化锰循环,ACS Earth and Space Chemistry

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粒子和光介导过程控制 Meromictic 池塘中的季节性氧化锰循环
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2023-05-16 , DOI: 10.1021/acsearthspacechem.2c00368
Hayley J. Gadol ₁ , Chadlin M. Ostrander ₂ , Luciana Villarroel _{2,

3} , Lina Taenzer _{2,

3} , Scott D. Wankel ₂ , Véronique E. Carignan ₄ , Colleen M. Hansel ₂

Affiliation

锰 (Mn) 氧化物是强氧化剂和营养物和污染物的吸附剂，因此它们的形成机制影响多个生物地球化学循环。含氧地表水中的锰通常以溶解的 Mn 形态存在，例如 Mn(II) 和 Mn(III)-配体络合物，而不是 Mn 氧化物。这被认为是氧化锰被过氧化氢还原的结果，与有机物的光解和阳光照射水域中直接有机物介导的还原有关。然而，Mn 氧化物可以在某些表面环境中持续存在，这表明对 Mn 氧化物分布控制的理解不完整。在这里，我们将基于现场和实验室的分析结合起来，以探索 Siders Pond 内的 Mn 氧化物分布、Mn 氧化速率和对 Mn 氧化物形成的潜在控制，Siders Pond 是 Cod 角（马萨诸塞州，马萨诸塞州）的一个半咸水和分流池美国）在 2020 年夏季和秋季期间。在阳光照射的地表水中始终观察到锰氧化物，其浓度在趋化层底部下降到检测不到。表面氧化锰浓度在夏末最高，达到~1 μM，在晚秋最低，仅达到~50 nM。使用基于同步加速器的吸光度测量确定的矿物质在结构上类似于 δ-MnO₂和 feitknechtite。大量光介导的 Mn 氧化仅发生在 Siders Pond 水的活孵化中，而净 Mn 还原在杀死的孵化中进行。因此，由微生物和矿物质引起的总颗粒介导的氧化结合超过了光还原，导致 Siders Pond 内 Mn 氧化物的净积累。我们的结果确定了微生物和矿物介导的氧化在确定自然环境地表水中氧化锰分布方面的重要作用，这一发现可能有助于解释其他地点的可比分布。

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Particle- and Light-Mediated Processes Control Seasonal Manganese Oxide Cycling in a Meromictic Pond

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-MnO₂ and 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.

更新日期：2023-05-16

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