Mechanisms of active-particle transport in a wetland flow under wind are significant for understanding various biological and ecological processes associated with wetlands. A transport model has been formulated to characterize the transient dispersion of active particles in a typical free-surface wetland flow exposed to wind. The transient evolution of total quantity, centred moving velocity, longitudinal dispersivity, skewness, and kurtosis of the active-particle cloud are analysed, using concentration moment method. It is found that the migration of active-particle cloud can eventually reach a stable status under the combined action of wind, hydrodynamics, and cell motility. The strong reverse wind can result in the negative centred moving velocity and longitudinal dispersivity along each streamline. The strong wind can considerably change the skewness and kurtosis of cell concentration distribution. The analytical solution of depth-averaged and two-dimensional concentration of active particles are derived based on Chatwin’s long-time expansion method, showing a distinct deviation from Gaussian distribution during the initial stage, which is in good agreement with the concentration moment analysis.

风下湿地流中的活性粒子传输机制对于理解与湿地相关的各种生物和生态过程具有重要意义。已经制定了一个传输模型来表征活性粒子在暴露于风的典型自由表面湿地流中的瞬态分散。采用集中矩法分析了活性粒子云的总量、中心运动速度、纵向弥散性、偏度和峰度的瞬态演化。研究发现，在风、流体动力学和细胞运动的共同作用下，活性粒子云的迁移最终可以达到稳定状态。强逆风会导致沿每条流线的负中心移动速度和纵向弥散性。强风可以显着改变细胞浓度分布的偏度和峰度。基于Chatwin长时间展开法推导出活性粒子深度平均和二维浓度的解析解，初始阶段与高斯分布有明显偏差，与浓度矩分析吻合较好。