Sediment-air equilibrium partitioning of semi-volatile hydrophobic organiccompounds 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 sediment/air partiti on coefficient (K-SA) for phenanthrene and dibenzofuran on a local sediment from the Campus Lake, Baton Rouge. The effects of sediment moisture conten t, air relative humidity and temperature on K-SA for phenanthrene were asce rtained. The saturated vapor pressures of the compounds were also measured. The sediment moisture content had a striking effect on K-SA; increasing se diment moisture content decreased K-SA. Temperature also had a dramatic eff ect on K-SA. 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 ma ss of water) sediments. The heat of adsorption for phenanthrene normalized to unit molecular surface area indicated for the physically adsorbed organi c compound was seven times smaller than that for a water molecule. The expe rimental Value of K-SA was used to test a proposed theoretical model. A goo d 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. (C) 2000 Elsevier S cience B.V. All rights reserved.