Abstract Sediment phosphorus (P) diagenesis and release in polymictic systems are poorly understood. Here, we determine the mechanistic controls on the processes that drive P release from the sediments in Lake of the Woods (LOW). The vertical distributions of the relevant diagenetic parameters—including oxygen, pH, redox potential, dissolved P, iron (Fe) and other metals in the porewater—were measured, and the fluxes of dissolved oxygen and P across the sediment-water interface (SWI) at the four locations in LOW were quantified. We characterized solid P speciation and analyzed the iron and corresponding metal contents in five sediment P binding forms. Short-term diffusive fluxes of P ranged between 0.3 and 7.8 mg m−2d−1, controlled by the mineralization of freshly deposited organic matter and the redox-sensitive iron cycle. Long-term net P release rates were between 0.21 and 9.96 mg m−2d−1, controlled by the diagenetic remineralization of P binding pools, which regulates long-term sediment P releases. Hypoxia may have led to the release of previously stored Fe P in the sediments, which has likely increased internal P loading for a timescale that is longer than seasonal. While Fe-sorbed phosphorus is the major barrier for P release in the surface sediments, P is immobilized in deep sediments via the formation of calcium (Ca)-P, aluminum (Al)-P, and possibly vivianite. Our study demonstrates the importance of sediments as sources of the productivity-limiting nutrient phosphorus; reveals the geochemical controls on sediment P release; and helps further the understanding of how sediments regulate water quality and affect eutrophication and the possibility of algal blooms.

中文翻译：

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森林湖内部磷负荷的地球化学控制

摘要 混杂系统中沉积物磷 (P) 的成岩作用和释放知之甚少。在这里，我们确定了驱动从伍兹湖 (LOW) 沉积物中释放磷的过程的机械控制。测量了相关成岩参数的垂直分布——包括孔隙水中的氧、pH、氧化还原电位、溶解的 P、铁 (Fe) 和其他金属——以及溶解氧和 P 在沉积物 - 水界面 (SWI) 的通量) 在 LOW 的四个位置被量化。我们表征了固体 P 形态并分析了五种沉积物 P 结合形式中的铁和相应的金属含量。P 的短期扩散通量介于 0.3 和 7.8 mg m-2d-1 之间，由新沉积的有机物的矿化和氧化还原敏感的铁循环控制。长期净磷释放率介于 0.21 和 9.96 mg m-2d-1 之间，受磷结合池的成岩再矿化控制，其调节长期沉积物磷释放。缺氧可能导致先前储存在沉积物中的 Fe P 释放，这可能会增加内部 P 负荷，时间尺度比季节性更长。虽然铁吸附的磷是表层沉积物中磷释放的主要障碍，但磷通过钙 (Ca)-P、铝 (Al)-P 和可能的紫铁矿的形成固定在深层沉积物中。我们的研究证明了沉积物作为限制生产力的营养磷来源的重要性；揭示沉积物磷释放的地球化学控制；