AIR EMISSIONS FROM EXPOSED, CONTAMINATED SEDIMENT AND DREDGED MATERIALS - 2 - DIFFUSION FROM LABORATORY-SPIKED AND AGED FIELD SEDIMENTS

The mass transfer of three polycyclic aromatic hydrocarbons (naphthale ne, phenanthrene and pyrene) and a heterocyclic aromatic hydrocarbon ( dibenzofuran) from sediment to air was studied in a large-area flux ch amber. A laboratory-spiked local (University Lake, UL) sediment and an aged contaminated field (Indiana Harbor Canal, IHC) sediment was used . The effects of initial sediment moisture content, and changing air r elative humidity were investigated. For high moisture conditions in th e UL sediment, the flux remained large whereas for low moisture condit ions, there was a sharp decrease in flux as a result of surface drying of the sediment. Under similar air velocities and moisture conditions , the flux from the aged MC sediment was considerably smaller than fro m the laboratory-spiked UL sediment. Whereas, the flux from laboratory -spiked UL sediment was predicted satisfactorily by a conceptual mathe matical model, that from the aged IHC sediment did not agree with the model predictions. It was concluded that only a portion of the contami nant was available for desorption from the aged sediment due to the di fferences in the sorption characteristics of relatively fresh and aged contaminated sediments. (C) 1998 Elsevier Science B.V.