Air emissions from exposed contaminated sediments and dredged material

The sediment-to-air fluxes of two polycyclic aromatic hydrocarbons (phenant hrene and pyrene) and a heterocyclic aromatic hydrocarbon (dibenzofuran) fr om a laboratory-contaminated sediment and those of three polycyclic aromati c hydrocarbons (naphthalene, phenanthrene, and pyrene) from three field sed iments were investigated in experimental microcosms. The flux was dependent on the sediment moisture content, air-filled porosity, and the relative hu midity of the air flowing over the sediment surface. The mathematical model predictions of flux from the laboratory-spiked sediment agreed with observ ed values. The fluxes of compounds with higher hydrophobicity were more air -side resistance controlled. Conspicuous differences were observed between the fluxes from the laboratory-spiked and two of the three field sediments. Two field sediments showed dramatic increases in mass-transfer resistances with increasing exposure time and had significant fractions of oil and gre ase. The proposed mathematical model was inadequate for predicting the flux from the latter field sediments. Sediment reworking enhanced the fluxes fr om the field sediments due to exposure of fresh solids to the air. Variatio ns in flux from the lab-spiked sediment as a result of change in air relati ve humidity were due to differences in retardation of chemicals on a dry or wet surface sediment. High moisture in the air over the dry sediment in cr eased the competition for sorption sites between water and contaminant and increased the contaminant flux.