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首页> 外文期刊>Journal of soil & sediments >Phosphorus transformations in stream bank sediments in Iowa, USA, at varying redox potentials
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Phosphorus transformations in stream bank sediments in Iowa, USA, at varying redox potentials

机译：在不同氧化还原电势下，美国爱荷华州河岸沉积物中的磷转化

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PurposeStream bank erosion is one of the main sources of suspended sediments in stream water, and it often carries phosphorus with it. With a controlled laboratory study, we investigated the changes in different forms of P in stream bank sediments at varying redox potentials. We hypothesized that there could be increases in labile forms of solid-phase P under low redox conditions.Materials and methodsSediment samples representing four major stratigraphic units were collected from alluvial banks of Walnut Creek in Jasper County, Iowa: Camp Creek, Roberts Creek, and Gunder members of the Holocene-age De Forest Formation and pre-Illinoian till, a glacial deposit that is older than 500,000years. We compared three treatments: no anaerobic incubation, anaerobic incubation, and anaerobic incubation with addition of glucose. After each treatment, soil P fractions were determined and classified as water-extractable P, labile P, slowly cycling P, stable P, and residual P. Labile P is extractable with 0.5M NaHCO3, slowly cycling P is extractable with 0.1M NaOH or 1M HCl, stable P is extractable with concentrated HCl, and residual P is associated with acid-insoluble compounds in the soil.Results and discussionRedox potential of the equilibrated systems was significantly less when sediments were incubated anaerobically than when they were not incubated, especially when glucose was added to the anaerobic incubation. Variations in redox potential did not significantly affect the total P, organic or inorganic stable P, or residual P in the sediments. In contrast, we found that the amount of inorganic labile P tended to increase at the same time that slowly cycling P associated with Fe decreased.ConclusionsThe younger sediments, higher in the stratigraphic profile and with more organic matter, had greater labile P and slowly cycling P that was associated with Fe, reflecting a greater potential to contribute to elevated levels of P in the stream water if subjected to low redox potential in the stream environment. The forms of P in the four bank sediments were redistributed among the fractions by reducing conditions. There was an increase in the concentration of inorganic labile P, which coincided with a decrease in slowly cycling P associated with Fe, especially in the Holocene-age sediments. These sediments appear to have a greater potential to contribute to elevated levels of P in the stream water when they are subjected to low redox potential in the stream environment.
机译：目的溪流侵蚀是溪流水中悬浮沉积物的主要来源之一，并且经常携带磷。通过一项受控的实验室研究，我们研究了在不同氧化还原电势下河岸沉积物中不同形式P的变化。我们假设在低氧化还原条件下不稳定的固相P形式可能会增加。材料和方法从爱荷华州贾斯珀县沃尔纳特克里克的冲积河岸收集了代表四个主要地层单位的沉积物样本：Camp Creek，Roberts Creek和全新世时期的德林地层和伊利诺伊时期之前的贡德成员，这是一种冰河沉积，年龄超过500,000年。我们比较了三种处理方法：无厌氧培养，厌氧培养和加葡萄糖的厌氧培养。每次处理后，确定土壤P组分并将其分类为水可萃取P，不稳定P，缓慢循环P，稳定P和残留P。不稳定P可用0.5M NaHCO3萃取，缓慢循环P可用0.1M NaOH或P 1M HCl，稳定的P可从浓HCl中提取，而残留的P与土壤中的酸不溶性化合物有关。结果与讨论厌氧条件下沉积物的氧化还原电位明显低于未孵育时的平衡氧化还原电位，特别是当将葡萄糖加入厌氧培养中。氧化还原电位的变化不会显着影响沉积物中的总磷，有机或无机稳定磷或残留磷。与此相反，我们发现，与铁相关的缓慢循环的P降低的同时，无机不稳定的P的数量也趋于增加。结论较年轻的沉积物，地层剖面较高且有机质更多，具有较大的不稳定的P和缓慢的循环与铁有关的磷，反映出如果在溪流环境中受到较低的氧化还原电位，则有更大的潜力有助于溪水中的磷含量升高。通过还原条件，将四个堤岸沉积物中的磷形态重新分配到各馏分之间。无机不稳定磷的浓度增加，这与与铁有关的缓慢循环的磷的减少相吻合，特别是在全新世时期的沉积物中。当这些沉积物在河流环境中遭受低氧化还原电位时，它们似乎具有更大的潜力来促进溪流水中的P含量升高。

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