Indonesian Oil Palm Research Institute, Medan, North Sumatra, Indonesia.
National Laboratory for Agriculture and the Environment, USDA-Agricultural Research Service, Ames, IA, United States of America.
PLoS One. 2018 Dec 14;13(12):e0209208. doi: 10.1371/journal.pone.0209208. eCollection 2018.
Sediments in streams that drain agricultural watersheds may be sinks that can adsorb P from the stream or sources that can release P to the stream. Sediment characteristics and environmental factors, including the oxidation-reduction (redox) potential of the water associated with the sediment, determine whether P will be adsorbed or released by the sediment. We investigated P adsorption and release by four sediments [three Holocene-age sediments (Camp Creek, Roberts Creek and Gunder) as well as Pre-Illinoian-age Till] that occur in Walnut Creek, a second-order stream in Jasper County, Iowa, that is representative of many small streams in the glaciated upper Midwest of the US. The effects of two redox potentials on phosphorus buffering capacity (PBC) and equilibrium phosphorus concentration (EPC) were evaluated in batch adsorption experiments. We also simulated aerobic and anerobic conditions over a 24-day period and measured solution-phase P concentrations in stirred systems where the sediments were isolated from the water by dialysis tubing. The batch experiment indicated that the EPCs of the three Holocene-age sediments were similar to one another and increased with decreasing redox potential. In the stirred flow reactors, more dissolved P was released from the Camp Creek and Roberts Creek sediments under anaerobic conditions than from the other sediments. This observation suggests that these two sediments, which are younger and higher in the stratigraphic sequence, are more likely to be P sources in suboxic settings. The P buffering capacity was greatest in the till. Where it is in contact with the stream water, the till is likely to serve as an adsorbing sink for P in the water column.
从农业流域流出的溪流沉积物可能是吸附 P 的汇，也可能是释放 P 的源，这取决于沉积物的特性和环境因素，包括与沉积物相关的氧化还原（redox）电位。我们研究了发生在爱荷华州贾斯珀县瓦尔纳特溪（一条二级溪流）中的四种沉积物[三个全新世沉积物（坎普溪、罗伯茨溪和冈德）以及前伊利诺伊纪的底土]对 P 的吸附和释放作用，瓦尔纳特溪是美国冰碛地貌上中西部地区许多小溪流的代表。我们在批量吸附实验中评估了两种氧化还原电位对磷缓冲容量（PBC）和平衡磷浓度（EPC）的影响。我们还模拟了 24 天的好氧和厌氧条件，并在搅拌系统中测量了溶液相 P 浓度，其中沉积物通过透析管与水隔离。批量实验表明，三种全新世沉积物的 EPC 彼此相似，并且随着氧化还原电位的降低而增加。在搅拌流动反应器中，在厌氧条件下，坎普溪和罗伯茨溪沉积物释放的溶解 P 多于其他沉积物。这一观察结果表明，这两个在地层序列中更新且更高的沉积物在缺氧环境中更有可能成为 P 的源。在底土中，P 缓冲容量最大。在与溪流水接触的地方，底土可能会在水柱中充当 P 的吸附汇。
