Sediment]air equilibrium partitioning of semi-volatile hydrophobic organic compounds Part 2. Saturated vapor pressures, and the effects of sediment moisture content and temperature on the partitioning of polyaromatic hydrocarbons

A gas saturation methodology was used to determine the sedimentrair partition coefficient KSA. for phenanthrene and dibenzofuran on a local sediment from the Campus Lake, Baton Rouge. The effects of sediment moisture content, air relative humidity and temperature on KSA for phenanthrene were ascertained. The saturated vapor pressures of the compounds were also measured. The sediment moisture content had a striking effect on KSA; increasing sediment moisture content decreased KSA. Temperature also had a dramatic effect on KSA. The variation with temperature was used to evaluate the heats of adsorption on both ‘dry’ -0.8% by mass of water. and ‘wet’ )6% by mass of water. sediments. The heat of adsorption for phenanthrene normalized to unit molecular surface area indicated for the physically adsorbed organic compound was seven times smaller than that for a water molecule. The experimental value of KSA was used to test a proposed theoretical model. A good agreement was observed for both phenanthrene and dibenzofuran. The model can be extended to other compounds and sediment types for prediction of air emissions from exposed sediment and dredged materials.