Volatile emissions from variable moisture content sediments

The rate of volatile emission of organic compounds from contaminated soils is highly dependent on the soil's moisture content. The adsorption capacity of hydrophobic organic compounds is known to increase by several orders of magnitude in dry soils compared to moist soils. Dredged sediments, which often start with a high degree of saturation, are subject to surface drying with moisture being evaporated to the atmosphere. Exposed sediment and soils are also affected by cyclic wetting and drying due to the diurnal cycle. The aim of this paper is to develop analytical and semianalytical solutions to the diffusive transport equations to predict emission rates from contaminated soils and sediments that have their moisture content changing with time. The solution involves a series of integral transforms used to simplify the governing equation. The solution is found in transform space before inversions are applied to obtain contaminant concentrations in real space and time. To illustrate the application of these solutions, results from two cases studies are presented.