Effects of surface wind on bicomponent contaminant transport and dispersion in wetland flow

Wetlands act as natural water filters, removing pollutants and improving water quality. They provide critical habitat for diverse plants and animals, supporting biodiversity and helping to reduce flooding by absorbing excess rainwater and buffering storm surges. This paper develops an analytical framework to describe the concentration and dispersion process of a bicomponent contaminant in wetlands under the influence of surface winds. The vertical velocity distribution is derived from the momentum equation to characterise the flow field under surface-wind forcing, and the resulting velocity structure is illustrated using contour plots. Based on Mei's multiscale homogenisation technique, the common environmental dispersivity is derived, while the longitudinal mean concentrations and critical lengths are obtained separately for components A' and B'. This study reveals that, under co-flow conditions, as wind intensity increases, the peak longitudinal mean concentration for both contaminants decreases. Wind direction and intensity strongly modify both the hydrodynamic structure and the longitudinal spreading of the contaminants. Co-flow enhances environmental dispersion, while counter-flow can suppress the flow and produce localized recirculation under sufficiently strong wind forcing. The long-time concentration profiles of both contaminants remain smooth, symmetric, and bell-shaped, with increasing wind intensity reducing the peak concentration and broadening the contaminant plume. The skewness and excess kurtosis remain small and decay towards their Gaussian limits with time, indicating weak but finite transient non-Gaussian behaviour. The critical lengths for contaminants A' and B' under a specified water-quality threshold were determined, which may be useful in wetland restoration assessment and environmental risk management. The proposed model offers a quantitative framework for both natural and artificial water systems to optimise wetland restoration and improve sediment management.