ABSTRACT Phosphorus (P) stores in gravel-bed rivers are released for uptake by periphyton when pH levels exceed 8.5. The Tukituki River has low alkalinity water and frequently experiences periphyton blooms, and daytime pH > 9 during summer low-flows. We measured dissolved reactive P (DRP) and EPC0, the water concentration of DRP at which no net release or sorption from the river bed occurs, in sediment samples from the Tukituki River subject to controlled pH levels before (2014) and after (2017) changes to two wastewater discharges that reduced P release to the river by 95%. DRP released from 2014 sediments at pH 8.5–10 were 30 ± 10 mg/m3 above background (pH 8) whereas those released from 2017 sediments were 5 ± 3 mg/m3 above background. EPC0 levels in 2014 and 2017 were 11 ± 6 and 7 ± 2 mg/m3, respectively. Field estimates of released DRP calculated from continuous pH and the Redfield equation suggested that most of the readily available DRP released from sediments at elevated pH is derived from material attached to recently deposited sediment. Subsequently, a reduction in wastewater inputs or agricultural runoff should reduce sediment DRP stores, and hence sediment fluxes, within a few years and mitigate periphyton blooms in addition to directly lowering water column concentrations.

中文翻译：

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砾石层河流泥沙与水体磷交换动力学

摘要 当 pH 值超过 8.5 时，砾石床河流中的磷 (P) 储存被释放以供附生生物吸收。Tukituki 河的水碱度较低，经常出现附生生物大量繁殖，夏季低流量期间白天 pH 值 > 9。我们测量了在（2014 年）之前（2014 年）和之后（2017 年）受控制 pH 值的 Tukituki 河沉积物样本中溶解活性磷 (DRP) 和 EPC0，即没有发生河床净释放或吸附时 DRP 的水浓度两次废水排放的变化使向河流中的磷释放减少了 95%。2014 年 pH 值 8.5-10 沉积物释放的 DRP 比背景 (pH 8) 高 30 ± 10 mg/m3，而 2017 年沉积物释放的 DRP 比背景高 5 ± 3 mg/m3。2014 年和 2017 年的 EPC0 水平分别为 11 ± 6 和 7 ± 2 mg/m3。从连续 pH 值和 Redfield 方程计算的释放 DRP 的现场估计表明，大多数容易获得的 DRP 从高 pH 值的沉积物中释放出来，来自附着在最近沉积的沉积物中的物质。随后，废水输入或农业径流的减少应该会在几年内减少沉积物 DRP 储存量，从而减少沉积物通量，除了直接降低水柱浓度外，还可以减轻附生生物的大量繁殖。