Silveira Fabio C, Cochrane Thomas A, Bello-Mendoza Ricardo, Charters Frances
Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, 8140, Christchurch, New Zealand.
Environ Monit Assess. 2024 Dec 11;197(1):51. doi: 10.1007/s10661-024-13459-4.
In-channel water treatment systems remove excess nutrients through biological, chemical, and physical processes associated with the hyporheic zone. However, the impact of surface and groundwater interactions on these treatment processes is poorly understood. This research aims to assess the influence of varying groundwater conditions (neutral, drainage water, and groundwater seepage) and different bed sediment hydraulic conductivities on nitrogen and phosphorus dynamics in in-channel treatment systems. A flume containing bed sediment was used to study changes in surface water quality under different groundwater and bed sediment conditions. Compared to inlet and outlet concentrations, dissolved reactive phosphorus (DRP) and ammoniacal nitrogen (NH-N) levels in the surface water increased by 11-65% and 10-51%, respectively, while nitrate (NO-N) concentrations decreased by 11% under groundwater seepage conditions. The increase in NH-N was due to ammonification, while the decrease in NO-N was due to denitrification and mixing and dilution with the groundwater. The upward groundwater flux through the bed sediment transported both DRP and NH-N into the surface water. Low hydraulic (LH) conductivity sediment led to greater changes in nutrient concentration than high hydraulic (HH) conductivity sediment (DRP increased by 65% and NH-N by 51% for LH, compared to 11% and 10% for HH, respectively). However, HH conductivity sediment led to greater variations in pH and Eh values. The findings could assist the design and monitoring of in-channel treatment systems where groundwater and surface water interact.
渠道内水处理系统通过与渗流带相关的生物、化学和物理过程去除过量养分。然而，地表水与地下水相互作用对这些处理过程的影响却知之甚少。本研究旨在评估不同地下水条件（中性、排水和地下水渗流）以及不同河床沉积物水力传导率对渠道内处理系统中氮和磷动态的影响。使用一个装有河床沉积物的水槽来研究不同地下水和河床沉积物条件下地表水水质的变化。与进水和出水浓度相比，在地下水渗流条件下，地表水中溶解态活性磷（DRP）和氨氮（NH-N）水平分别增加了11%-65%和10%-51%，而硝酸盐（NO-N）浓度下降了11%。NH-N的增加是由于氨化作用，而NO-N的减少是由于反硝化作用以及与地下水的混合和稀释。通过河床沉积物向上的地下水通量将DRP和NH-N都输送到了地表水中。低水力传导率（LH）沉积物导致的养分浓度变化比高水力传导率（HH）沉积物更大（LH条件下DRP增加65%，NH-N增加51%，而HH条件下分别为11%和10%）。然而，HH传导率沉积物导致pH值和氧化还原电位（Eh）的变化更大。这些研究结果有助于设计和监测地表水与地下水相互作用的渠道内处理系统。
