Influence of Bioclogging on Nitrogen Cycling in a Hyporheic Zone with an Undulate River-Bed
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摘要: 生物作用造成河床於堵普遍存在,并受到多种环境因素的影响.以往研究较少考虑生物堵塞对潜流带氮循环的影响. 采用数值模拟方法建立水流-溶质运移-生物生长耦合模型,模拟河床驱动下的潜流交换过程,探讨生物堵塞作用对氮素迁移转化的影响.研究表明:生物作用导致沙丘表面形成堵塞层和生物聚集区,并限制了NO3-的运移深度,潜流带中以NH4+为主;河水中充足的有机碳会增大堵塞程度,促进反硝化作用去除NO3-;强烈的河床起伏和较大的河流流速均会增大沙丘表面的压力差,增大堵塞范围和细菌生物量,从而加快硝化和反硝化作用速率,有利于NO3-、NH4+的去除.生物堵塞作用有利于氮污染物的去除,且主要受到河床表面的压力梯度和异养细菌生物量的影响.Abstract: River-bed clogging caused by biological agent is a common phenomenon and affected by many environment factors. But bioclogging was rarely considered when studying the nitrogen cycle in hyporheic zone. It establishes a numerical model by simultaneously coupling water flow, reactive transport of solutes and microbial growth, to simulate the hyporheic exchange driven by an undulate river bed and explore the effect of bioclogging. The~present study showed that bioclogging promotes the development of a low permeability layer and high biomass in superficial zone of dunes. Bioclogging limits the spatial distribution of NO3- and results in NH4+ contamination in hyporheic zone. The abundance of organic carbon in river enhances bioclogging extent, which improves the rates of denitrification to remove NO3-. The more fluctuated river bed surface and the larger surface water flow would increase pressure gradient along bed-dunes, bioclogging range and bacterial biomass, then the reaction rates of nitrification and denitrification. It is helpful for the removal of NO3- and NH4+. The bioclogging is beneficial to remove nitrogen pollutants in hyporheic zone and is affected at pressure gradient along bed-dunes, as well as biomass of heterotrophic~bacteria.
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Key words:
- hyporheic zone /
- bed-form /
- bioclogging /
- nitrogen cycle /
- heterotrophic~bacteria /
- biological geology
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