Denitrification in the Mississippi River network controlled by flow through river bedforms
Denitrification in the Mississippi River network controlled by flow through river bedforms
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DOI：
10.1038/ngeo2567
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发表时间：
2015-12-01
影响因子：
18.3
通讯作者：
Kiel, Brian
中科院分区：
文献类型：
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作者：
Gomez-Velez, Jesus D.;Harvey, JudsonW.;Kiel, Brian
世界主要河流中氮浓度的增加导致敏感的下游沃茨过度施肥（1-4）。流经河床和河岸沉积物的水流通过微生物介导的反硝化反应（5-10）去除河流中的氮。然而，很少有人知道在渠道网络中的生物物理过程是最有效的，为什么某些渠道更有效的氮反应器，以及如何管理的做法，可以提高氮的去除在水循环通过沉积物和地下水的地下水-hyporheic区（8，11，12）混合的地区。在这里，我们提出了数值模拟的潜流和反硝化作用在整个密西西比河网络使用水文地貌模型。我们发现，在潜流区与河床下的沉积物的垂直交换，由淹没的床型驱动，具有脱氮潜力，远远超过横向潜流交换与河道边的沉积物，由河坝和蜿蜒的银行。我们建议，地貌差异沿着河流走廊可以解释为什么反硝化效率不同的流域之间的密西西比河网络。我们的研究结果表明，促进河床的渗透性底形的发展，从而垂直潜流交换，将更有效地提高河流反硝化作用在大型河流流域比促进横向交换通过诱导通道弯曲。
Increasing nitrogen concentrations in the world's major rivers have led to over-fertilization of sensitive downstream waters(1-4). Flow through channel bed and bank sediments acts to remove riverine nitrogen through microbe-mediated denitrification reactions(5-10). However, little is understood about where in the channel network this biophysical process is most efficient, why certain channels are more effective nitrogen reactors, and how management practices can enhance the removal of nitrogen in regions where water circulates through sediment and mixes with groundwater-hyporheic zones(8,11,12). Here we present numerical simulations of hyporheic flow and denitrification throughout the Mississippi River network using a hydrogeomorphic model. We find that vertical exchange with sediments beneath the riverbed in hyporheic zones, driven by submerged bedforms, has denitrification potential that far exceeds lateral hyporheic exchange with sediments alongside river channels, driven by river bars and meandering banks. We propose that geomorphic differences along river corridors can explain why denitrification efficiency varies between basins in the Mississippi River network. Our findings suggest that promoting the development of permeable bedforms at the streambed-and thus vertical hyporheic exchange-would be more effective at enhancing river denitrification in large river basins than promoting lateral exchange through induced channel meandering.