Modeling Air Emissions from Contaminated Sediment Dredged Materials

Volatilization rates for hydrophobic organic compounds from a confined disposal facility (CDF) containing contaminated dredged material are presently unknown. The primary purpose of this study is to indicate the availability of theoretical models for the evaluation of volatile emissions from a CDF. Four emission locales are identified and modeled: the sediment relocation (dredging) locale, the exposed sediment locale, the ponded sediment locale, and the vegetation-covered sediment locale. Rate expressions are derived to estimate the volatile organic chemical (VOC) emission from each locale. Emission rates (in mass of total VOCs per unit time) are primarily dependent on the chemical concentration at the source, the surface area of the source, and the degree to which the dredged material is in direct contact with air. The relative magnitude of these three parameters provides a basis upon which a tentative ranking of emission rates from the different locales can be given. Exposed sediment results in the greatest estimated emissions of volatiles followed by water with high levels of suspended sediments, such as might occur during dredging or during placement in a CDF. Expected to be lower in volatile emissions are dredged materials covered by a quiescent water column or vegetation.