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首页> 美国政府科技报告 >Effect of Residence Time on Net Nitrate Retention in Flow-Regulated Backwaters of the Upper Mississippi River
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Effect of Residence Time on Net Nitrate Retention in Flow-Regulated Backwaters of the Upper Mississippi River

机译：停留时间对密西西比河上游流量调节回水中硝态氮保留的影响

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摘要

This research investigated relationships between water residence time and net nitrate retention (i.e., loading minus discharge) in flow- controlled backwater systems of the Upper Mississippi River (UMR). Goals were to gain a better understanding of the management potential for removing nitrogen in large river systems by increasing connectivity between nitrogen- rich main channel areas and backwater habitats. Nitrogen (N) runoff to receiving streams and rivers, particularly in the form of nitrate-nitrite (NO3NO2-N), has increased several-fold in recent decades (Justic et al. 1995, Vitousek et al. 1997, Goolsby and Battaglin 2001). A consequence of accelerated N mobilization and transport has been water quality degradation of coastal areas and estuaries which are sensitive to N inputs (Nixon 1995). For instance, increased N loading from the Mississippi River basin has been associated with the development of extensive areas of anoxia and hypoxia (Rabalais et al. 1994) and declines in fish and invertebrate abundance (Pavela et al. 1983) in the Gulf of Mexico. Continued unchecked N loading to coastal systems could lead to significant declines in the diversity and abundance of higher trophic levels and increased bloom frequency of noxious and toxic algae (Vitousek et al. 1997). In addition to managing NO3NO2-N runoff input to large river systems (i.e., watershed N source and transport control, wetland detention, riparian buffers, restored bottomland hardwood floodplains), there is a need to promote in-stream removal of NO3NO2-N by biological uptake, bacterial denitrification, and burial in order to reduce N transport to coastal systems (Mitsch et al. 2001). In-stream N transformation and removal do occur in large rivers, but are typically low and represent a small percentage of the overall load (5 to 20 percent, Seitzinger 1988).

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