A physicochemical model for colloid exchange between a stream and a sand streambed with bed forms
A physicochemical model for colloid exchange between a stream and a sand streambed with bed forms
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DOI：
10.1029/2000wr900059
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发表时间：
2000-08-01
影响因子：
5.4
通讯作者：
Morgan, JJ
中科院分区：
文献类型：
--
作者：
Packman, AI;Brooks, NH;Morgan, JJ
细泥沙交换之间的流和周围的地下影响下游污染物的传输和河流生态。这种交换的基本模型是根据（1）床形驱动的平流孔隙水流的水力学和（2）地下胶体输运过程开发的。首先，发展了一个模型来预测水流在床面上引起的沙床平流。由此产生的“泵送”交换率计算的基础上的水流条件，床的形状几何形状，和床的深度。然后，通过叠加平流输运和颗粒在床层中的沉降，并考虑床层泥沙的物理化学过滤作用，计算悬浮泥沙的泵送交换。过滤系数的方法被用来预测减少的浓度输送颗粒。沉降和过滤都导致胶体被困在河床中，相对于保守的溶质产生更高的净交换率。当输送的颗粒在一次通过床中被完全捕获时，交换计算被简化，因为仅必须考虑到床的颗粒通量。在这种情况下，净交换率可以由有效活塞速度（通量/浓度）或流的对流-弥散方程中的床的损失率充分表示。溶质和胶体交换预测模型不使用拟合系数，只有可测量的水力和颗粒参数作为模型输入。模拟结果表明，净颗粒交换的流参数，沉降和过滤的效果。这种模拟河流-地下交换的基本方法对于理解和预测河流中活性物质的运输和归宿可能具有很大的实用性。
Fine sediment exchange between a stream and the surrounding subsurface influences downstream contaminant transport and stream ecology. Fundamental models for this exchange were developed on the basis of (1) the hydraulics of bed form-driven advective pore water flow and (2) subsurface colloid transport processes. First, a model was developed to predict the advective flow induced in a sand bed by stream flow over bedforms. The resulting "pumping" exchange rate was calculated based on the streamflow conditions, bed form geometry, and bed depth. The pumping exchange of suspended sediment was then calculated by superimposing advective transport and particle setting in the bed and including the effect of physicochemical filtration by bed sediment. The filtration coefficient approach was used to predict the reduction in the concentration of transported particles. Both settling and filtration cause colloids to be trapped in stream beds, producing a higher net exchange rate relative to conservative solutes. When transported particles are completely trapped in a single pass through the bed, the exchange calculation is simplified because only the particle flux to the bed must be considered. In this case, the net exchange rate may be adequately represented by an effective piston velocity (flux/concentration) or loss rate to the bed in the advection-dispersion equation for the stream. Solute and colloid exchanges are predicted by the models without the use of fitting coefficients; only measurable hydraulic and particle parameters were used as model inputs. Simulations are presented which show the effect of stream parameters, settling, and filtration on net particle exchange. This fundamental approach to modeling stream-subsurface exchange potentially has great utility for understanding and predicting the transport and fate of reactive substances in streams.