Diversion input lakes usually have a low catchment area/lake area ratio and pulsing pollution input. Various pollutants might accumulate in the lake continuously owing to the concentration effect under high evaporation but low precipitation over the entire area, typically for sedimentary cyclic elements such as phosphorus (P). However, the detailed transportation, sedimentation, and internal release mechanisms of P in the diversion input lakes remain unclear. This study conducted a year-long investigation of the littoral wetlands and open water areas of the shallow Lake Hengshui in the semi-humid region of North China. Results revealed that the average total P concentrations in the water and surficial sediment reached as high as 0.202 mg L and 878.21 mg kg in summer. The high water P levels in the lake were mainly regulated by the high internal P loading during summer and autumn, with the internal P loading being approximately nine times the external P loading. The littoral wetland area serves as a higher sedimentation sink and release source of P than the open water area. The concentrated P was continuously transported to the littoral wetland area through detritus burial, coprecipitation, and deposition of suspended particles. The release of P was mainly controlled by the dissolution of redox-sensitive Fe-P and Org-P at high temperatures and organic matter mineralization in the sediment, accompanied by the potential release capacity of apatite P (Ca-P). Future management of eutrophication and P levels in similar diversion input lakes should pay more attention to the high internal P loading in the sediment and the differentiated sedimentation and release processes in the littoral wetland and open water areas.

中文翻译：

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华北半湿润地区引水浅湖磷浓度的内部负荷调节：滨海湿地和开阔水域的差异过程

引水湖泊通常具有较低的集水面积/湖泊面积比和脉冲污染输入。由于全区蒸发量大、降水量少的浓缩效应，各种污染物可能会在湖中不断积累，特别是磷（P）等沉积循环元素。然而，磷在引水湖泊中的详细输送、沉积和内部释放机制仍不清楚。本研究对华北半湿润地区衡水浅湖沿岸湿地和开阔水域进行了长达一年的调查。结果表明，夏季水体和表层沉积物中总磷平均浓度高达0.202 mg·L和878.21 mg·kg。湖水高磷水平主要受夏秋季高内磷负荷的调节，内磷负荷约为外磷负荷的9倍。滨海湿地是比开阔水域更高的沉降汇和磷释放源。浓缩的磷通过碎屑埋藏、共沉淀和悬浮颗粒沉积不断输送到滨海湿地区域。 P的释放主要受氧化还原敏感的Fe-P和Org-P在高温下的溶解以及沉积物中有机质矿化的控制，同时伴有磷灰石P（Ca-P）的潜在释放能力。未来类似引水湖泊的富营养化和磷水平管理应更多地关注沉积物中的高内部磷负荷以及滨海湿地和开阔水域的差异性沉积和释放过程。