Evaporation from contaminated, exposed earthen cracks

Evaporation from exposed, contaminated earthen surfaces is important from an air pollution risk assessment perspective. Earthen cracks are formed in drying exposed earthen solids, such as soils, mudflats, exposed dredged sediment, or sludge. Evaporation of hazardous chemicals from exposed flat surface solids has been reported in literature. This study focuses on evaporation from within the cracks formed in these earthen materials. Evaporation of water vapor and phenanthrene from a simulated crack-like surface was measured using a flux chamber. Evaporation flux was measured as a function of the crack aspect ratio (depth/length) and air velocity. Postexperiment sectioning of the crack surface revealed the vertical profile of drying within the crack. It was generally observed that the flux (based on the actual crack surface area) was higher for wider cracks than that for narrower cracks. Computational fluid dynamics simulations were also carried out to visualize circulation of air within a crack. These studies provided estimates of the vertical extent of convection within a crack. Flux data from all experiments were used to obtain a correlation for the mass transfer coefficient with crack dimensions as a parameter. A simplified chemodynamic model was presented and the model predictions are compared with experimental data. © Mary Ann Liebert, Inc.