A model to predict concentration enrichment of contaminants on soil adhering to plants and skin.

Transfer of soil contaminants into the food chain has long been a concern. However, certain aspects of the pathways involved have not been fully investigated. One is the enrichment of contaminant concentrations through physical processes such as size-sorting of soil particles. Fine particles selected from soil by processes such as adhesion onto plants will have much higher contaminant concentrations than the original soil. A saturation kinetics model of the process of soil adhesion to leaf surfaces was developed. The model helps identify the parameters that are least-well known and need experimental support. The ratio of clay and sand wash-off half times was especially important. With nominal values for the input parameters, estimated enrichments agreed well with observations to date, and ranged from slightly over unity for medium- and fine-textured soils to about tenfold for sandy soils. With a few reasonable assumptions, the model was generalised to apply to other soil adhesion scenarios such as adhesion to skin. The generalised model can be applied with minimal need for setting-specific information.