Solute dispersion in wetland flows with bed absorption

Bed absorption and vegetation in natural wetlands exert considerable influence on contaminant transport. A three-scale perturbation method is extended in this work to present an exact analytical solution for the spatial concentration distributions affected by vegetation distribution and bed absorption. Compared with concentration moments-based analytical methods that were adopted previously to solve vertical concentration distribution in wetland flows, the multi-scale method used in this study is more concise without complicate integrated operations. The analytical solution is explicit and applicable without complicated integral form. Moreover, by comparing with the analytical solution obtained by the moments method, the analytical solution given in this work is accurate particularly after the initial stage. This study focuses on a large time scale in investigating spatial concentration distribution. Results show that concentration distribution is not uniform in the vertical direction. Hence, this study recommends the accurate two-dimensional spatial distribution rather than the crosssection averaged concentration distribution to achieve accurate concentration predictions.