Solute Transfer from the Soil Surface to Overland Flow: A Review

Transfer of agrochemicals from the soil surface to overland flow is a key process governing pollutant transport from soil to surface waters. Simulation models are effective tools for predicting pollutant loads from overland flow to surface water. In this study, we reviewed and summarized experimental observations to assess the factors that affect this transfer process, including: rainfall, topography, soil hydraulic properties, initial water and solute conditions, and management practices. Theoretical frameworks and models for describing the transfer process were also reviewed. The existing models were classified into four categories based on their principles: mixing‐layer models, interfacial diffusion‐controlled models, interfacial‐diffusion and rainfall‐dispersion models, and empirical models. The assumptions, parameters, applications, limitations or potential issues, and further improvements for each category of the models were discussed. It is recommended that new experimental methods be developed and current theoretical frameworks be further refined by considering the effects of other environmental factors and transport mechanisms on solute transfer from the soil surface to overland flow so that the models can be applied to a wider range of practical field conditions.