Fuchs John W, Fox Garey A, Storm Daniel E, Penn Chad J, Brown Glenn O
Dep. of Biosystems and Agric. Engineering, Oklahoma State Univ., Stillwater, OK, USA.
J Environ Qual. 2009 Feb 6;38(2):473-84. doi: 10.2134/jeq2008.0201. Print 2009 Mar-Apr.
For phosphorus (P) transport from upland areas to surface water systems, the primary transport mechanism is typically considered to be surface runoff with subsurface transport assumed negligible. However, certain local conditions can lead to an environment where subsurface transport may be significant. The objective of this research was to determine the potential of subsurface transport of P along streams characterized by cherty or gravel subsoils, especially the impact of preferential flow paths on P transport. At a field site along the Barren Fork Creek in northeastern Oklahoma, a trench was installed with the bottom at the topsoil/alluvial gravel interface. Fifteen piezometers were installed surrounding the trench to monitor flow and transport. In three experiments, water was pumped into the trench from the Barren Fork Creek to maintain a constant head. At the same time, a conservative tracer (Rhodamine WT) and/or potassium phosphate solution were injected into the trench at concentrations at 3 and 100 mg/L for Rhodamine WT and at 100 mg/L for P. Laboratory flow-cell experiments were also conducted on soil material <2 mm in size to determine the effect that flow velocity had on P sorption. Rhodamine WT and P were detected in some piezometers at equivalent concentrations as measured in the trench, suggesting the presence of preferential flow pathways and heterogeneous interaction between streams and subsurface transport pathways, even in nonstructured, coarse gravel soils. Phosphorus transport was retarded in nonpreferential flow paths. Breakthrough times were approximately equivalent for Rhodamine WT and P suggesting no colloidal-facilitated P transport. Results from laboratory flow-cell experiments suggested that higher velocity resulted in less P sorption for the alluvial subsoil. Therefore, differences in flow rates between preferential and nonpreferential flow pathways in the field led to variable sorption. The potential for nutrient subsurface transport shown by this alluvial system has implications regarding management of similar riparian floodplain systems.
对于磷（P）从高地地区向地表水系统的输送，主要的输送机制通常被认为是地表径流，而地下输送被假定为可忽略不计。然而，某些局部条件可能导致一种地下输送可能很显著的环境。本研究的目的是确定沿以燧石或砾石底土为特征的溪流进行磷地下输送的可能性，特别是优先流路径对磷输送的影响。在俄克拉荷马州东北部的巴伦福克溪沿岸的一个实地站点，安装了一条底部位于表土/冲积砾石界面的沟渠。在沟渠周围安装了15个测压管以监测水流和输送情况。在三个实验中，从巴伦福克溪向沟渠抽水以维持恒定水头。同时，将一种保守示踪剂（罗丹明WT）和/或磷酸钾溶液分别以3和100mg/L的浓度（罗丹明WT）以及100mg/L的浓度（P）注入沟渠。还对尺寸小于2mm的土壤材料进行了实验室流动槽实验，以确定流速对磷吸附的影响。在一些测压管中检测到了与沟渠中测量浓度相当的罗丹明WT和P，这表明存在优先流路径以及溪流与地下输送路径之间的非均质相互作用，即使在非结构化的粗砾石土壤中也是如此。在非优先流路径中磷的输送受到阻滞。罗丹明WT和P的突破时间大致相等，表明不存在胶体促进的磷输送。实验室流动槽实验的结果表明，较高的流速导致冲积底土对磷的吸附减少。因此场地上优先流路径和非优先流路径之间的流速差异导致了不同的吸附情况。这个冲积系统所显示的养分地下输送潜力对类似河岸洪泛平原系统的管理具有启示意义。
