Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river
Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river
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DOI：
10.1029/2012jg002122
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发表时间：
2013-03-01
影响因子：
3.7
通讯作者：
Naden, Emma
中科院分区：
文献类型：
--
作者：
Krause, Stefan;Tecklenburg, Christina;Naden, Emma
已知在潜流带的生物地球化学周转有可能影响通过浅河床沉积物的地表水循环的化学特征。本研究探讨河床物理性质对低地河流河床上涌地下水中硝酸盐和溶解氧命运的影响。为了分析深度依赖的模式和分区的氮浓度，扩散凝胶探针在浅（顶部15厘米）河床沉积物已部署在嵌套设置与多层minipiezometers河床沉积物的15-150厘米。地下水上升流的空间异质性控制模式的低电导率泥炭和粘土层，造成局部封闭的条件下，这表明增加河床停留时间。上涌地下水中的硝酸盐浓度变化高达68.06毫克L-1的顶部15厘米的河床沉积物和高达107.47毫克L-1的深度为15-150厘米，表明显着的氮周转并不局限于浅河床沉积物。硝酸盐浓度的密集减少，特别是在附近的低电导率河床地层。在这些位置的封闭地下水上升和氧气浓度降低的巧合表明，增加的停留时间和相关的溶解氧的耗尽创造有利于硝酸盐还原的条件。我们的研究结果强调，在含水层-河流界面增加氮周转不一定局限于浅河床区，地表水与地下水混合，但可以影响地下水上升的反应热点，延伸到更大的河床深度和超越潜流混合区。引文：Krause，S.，C. Tecklenburg，M. Munz和E. Naden（2013），河床氮循环超出潜流区：流量控制水平模式和深度分布的硝酸盐和溶解氧在上升的地下水的低地河流，J.地球物理。生物地球科学研究，118，54-67，doi：10.1029/2012JG002122。
Biogeochemical turnover in hyporheic zones is known to have the potential to affect the chemical signature of surface water cycling through shallow streambed sediments. This study investigates the impact of streambed physical properties on the fate of nitrate and dissolved oxygen in groundwater upwelling through the streambed of a lowland river. For analyzing depth-dependent patterns and zonation of nitrogen concentrations, diffuse gel probes in shallow (top 15 cm) streambed sediments have been deployed in a nested setup together with multilevel minipiezometers for streambed sediments of 15-150 cm. Spatial heterogeneity of groundwater upwelling was controlled by patterns of low-conductivity peat and clay strata that caused locally confined conditions, suggesting increased streambed residence times. Nitrate concentrations in the upwelling groundwater changed by up to 68.06 mg L-1 within the top 15 cm of streambed sediments and by up to 107.47 mg L-1 at depths of 15-150 cm, indicating that significant nitrogen turnover was not restricted to shallow streambed sediments. Intensive reduction of nitrate concentrations was found, in particular, in vicinity of low-conductivity streambed strata. The coincidence of confined groundwater upwelling and reduced oxygen concentrations at these locations suggests that increased residence times and associated depletion of dissolved oxygen create conditions favorable for nitrate reduction. Our results highlight that increased nitrogen turnover at aquifer-river interfaces is not necessarily limited to shallow streambed zones, where surface water is mixing with groundwater, but can affect upwelling groundwater in reactive hot spots that extend to greater streambed depths and beyond hyporheic mixing zones. Citation: Krause, S., C. Tecklenburg, M. Munz, and E. Naden (2013), Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river, J. Geophys. Res. Biogeosci., 118, 54-67, doi:10.1029/2012JG002122.