Awareness of groundwater‐borne dissolved inorganic phosphorus (DIP) loadings into lakes and its role in lake eutrophication is increasing, albeit DIP of natural origin is often ignored. Release of geogenic DIP from an adjacent aquifer and its transport with groundwater into a eutrophic lake is described by combining hydrogeochemical data collected in this study (sampling of piezometers, hydrogeochemical profiles, and seepage meters) with groundwater flow and discharge rates from earlier studies. The major part of the DIP that entered the lake with discharging groundwater was mobilized from iron hydroxides reduced by organic matter buried in the sediments of the old lake bottom. This is indicated by the correlation between DIP and ferrous iron (Fe²⁺) concentrations, with a DIP/Fe²⁺ molar ratio of 0.06, and an increase in pH. One‐dimensional reactive transport modeling indicated that high discharge rates (> 0.1 m d⁻¹) of anoxic groundwater upwelling in areas adjacent to the lakeshore prevent downward diffusion of oxygen into the aquifer and do not leave enough time for DIP to become rebounding to the mineral phases at the sediment‐water interface. The groundwater‐controlled DIP input into the lake calculated along a two‐dimensional cross‐section averaged 0.01 mol DIP m⁻² yr⁻¹. A 2 m wide offshore high discharge zone delivered approximately 13% of the DIP into the lake. The continuous, external loading of geogenic DIP sustains lake eutrophication and explains the failure of two previous lake restoration attempts.

中文翻译：

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地下水控制的磷从含沙含水层的释放和运输到湖泊

尽管人们常常忽略了天然来源的DIP，但人们对地下水中溶解的无机磷（DIP）装载到湖泊中的意识及其在湖泊富营养化中的作用正在提高。通过将本研究中收集的水文地球化学数据（压力计的采样，水文地球化学剖面和渗漏计）与早期研究的地下水流量和排放速率相结合，描述了从邻近含水层中释放出的地源DIP以及其与地下水一起向富营养化湖泊的迁移。DIP的主要部分是通过排放地下水进入湖泊的，而该氢氧化物是由氢氧化铁所调集的，而氢氧化铁又被掩埋在旧湖底沉积物中的有机物所还原。这通过DIP / Fe ²⁺与DIP和亚铁^离子（Fe ²⁺）浓度之间的相关性来表示。摩尔比为0.06，pH值增加。一维反应性输运模型表明，在湖岸附近的区域中，高流速的缺氧地下水（> 0.1 m d ^-1）向上涌流会阻止氧气向下扩散到含水层中，并且没有留出足够的时间使DIP反弹到矿物上沉积物-水界面的相。沿二维截面计算的地下水控制的DIP输入到湖泊中的平均DIP m ^-2 yr ^-1为0.01 mol DIP 。一个2 m宽的海上高排放区将大约13％的DIP输送到了湖泊中。不断发生的外源性地质成因DIP维持了湖泊富营养化，并解释了先前两次湖泊修复尝试的失败。