Department of Chemistry, Tarleton State University, Stephenville, TX 76402, USA.
J Environ Qual. 2010 Feb 19;39(2):548-57. doi: 10.2134/jeq2009.0313. Print 2010 Mar-Apr.
Understanding internal stream P transfers is important in controlling eutrophication. To determine the direction of groundwater and surface water interactions and evaluate P retention within streambank sediments, groundwater well pairs, about 5-m deep, were installed at three locations along a second-order, eutrophic stream in north-central Texas. Well cores were analyzed for P, and groundwater levels were monitored for about 2 yr. Water levels in wells furthest upstream always indicated a losing stream, while wells further downstream showed a gaining stream except during flow reversals with storm events and periods with reservoir backwater. Total-P from well cores ranged from 54 to 254 mg kg(-1) and was typically high near surface, decreased downward until redoximorphic features were encountered and then increased notably with depth to near or above surface concentrations. Very little extractable P occurred in sediments from the two upstream well sets; however, the set furthest downstream showed extractable P throughout with a high of 21 mg kg(-1) near the bottom. Repeated wetting-drying at sites A and B as noted by redoximorphic features may have shifted P into more stable sediment-bound forms. The decrease in extractable P at sites A and B compared to site C may be explained by conditions at C that were wetter and potentially anaerobic. Because the overall stream reach was more often losing than gaining, there appears to be a mass flow of P into streambank sediments. Streambank erosion may then transport this P downstream if not controlled.
理解内部水流 P 迁移对于控制富营养化非常重要。为了确定地下水和地表水相互作用的方向，并评估河岸沉积物中的 P 滞留，在德克萨斯州中北部的一条二级富营养化河流的三个位置安装了约 5 米深的地下水井对。对井芯进行了 P 分析，并监测了地下水水位约 2 年。最上游的水井水位始终表明是一条耗水河流，而下游的水井则表明是一条补水河流，除非在与风暴事件和水库回水相关的水流逆转期间。总磷从井芯中的范围从 54 到 254 毫克/千克，并且通常在靠近表面处较高，向下减少，直到遇到氧化还原形态特征，然后深度明显增加到接近或高于表面浓度。来自两个上游井组的沉积物中几乎没有可提取的 P；然而，最下游的一组则显示出整个沉积物都具有可提取的 P，最底部的含量高达 21 毫克/千克。在 A 和 B 点出现的氧化还原形态特征表明，反复的干湿交替可能会将 P 转移到更稳定的结合态沉积物中。与 C 点相比，A 和 B 点的可提取 P 减少可能是由于 C 点的条件更潮湿且可能是缺氧的。由于整个河道段耗水的时间比补水的时间多，因此似乎有大量的 P 流入河岸沉积物中。如果不加以控制，河岸侵蚀可能会将这些 P 输送到下游。
