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首页> 外文期刊>Freshwater science >River sediment nitrogen removal and recycling within an agricultural Midwestern USA watershed
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River sediment nitrogen removal and recycling within an agricultural Midwestern USA watershed

机译：农业中西部水域中的河流泥沙氮气去除和回收

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The Lower Great Miami River (LGMR) lies within the Mississippi River watershed and contributes to nutrient loads that promote seasonal hypoxia in the northern Gulf of Mexico. Moreover, the LGMR has recently experienced algal blooms caused by excess N and P. To investigate N cycling in the LGMR, we incubated intact sediment cores with stable ~(15)N isotope additions in a continuous-flow system. We measured sediment nutrient fluxes, N sinks and sources (denitrification/anammox and N fixation, respectively), and potential dissimilatory NO_(3)~(?) reduction to NH_(4)~(+) (DNRA) in spring and summer at 6 locations along a river reach (~50 km) influenced by urban and agricultural nutrient loads. LGMR sediments were a source of bioavailable NH_(4)~(+) and orthophosphate to river water. However, high denitrification rates resulted in LGMR sediments being a net sink for N in the river reach. NO_(3)~(?) amendments did not consistently stimulate denitrification, a result suggesting that denitrifiers were functioning at or near maximum rates. Anammox and DNRA were not consistently observed, and N fixation occurring simultaneously with denitrification was not observed. We estimate that denitrification in LGMR sediments removed 8 to 33% of external N loads to the river from the watershed, with the remainder exported downstream. This result indicates that denitrification can be an important N sink in the LGMR, but further decrease of external N inputs will be required to minimize eutrophication in the LGMR and N export to downstream systems.
机译：较低的迈阿密河（LGMR）位于密西西比河流域内，有助于促进墨西哥湾湾季节性缺氧的营养负荷。此外，LGMR最近经历过多余的N和P引起的藻类绽放。为了在LGMR中循环循环，我们在连续流动系统中孵育完整的沉积物核心。我们测量沉积物营养通量，N水槽和源（分别脱氮/厌氧毒素和氮），以及春季和夏季的潜在的聚散，〜（3）〜（？）〜（+）（DNRA）在沿河达到的6个地点（〜50公里）受城市和农业养分负荷的影响。 LGMR沉积物是生物可利用的NH_（4）〜（+）和河流水的正磷酸盐来源。然而，高脱氮率导致LGMR沉积物是河流范围内N的净水槽。 NO_（3）〜（？）修正案并未始终如一地刺激脱氮，结果表明脱氮剂在最大速率下运作或接近。不始终如一地观察厌氧和DNRA，未观察到与脱氮同时出现的N固定。我们估计LGMR沉积物中的反硝化除去8至33％的外部N负载到流域的河流，其余的下游出口。该结果表明，脱氮可以是LGMR中的重要N沉积，但是外部N个输入的进一步降低将需要最小化LGMR和N导出到下游系统中的富营养化。

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