Field study on desorption rates of polynuclear aromatic hydrocarbons from contaminated marine sediment

The present study examines desorption kinetics of hydrophobic organic conta minants from sediment under conditions mimicking marine disposal. Trays of contaminated marine sediment were deployed in the subtidal zone of a pristi ne field site, and samples were taken at time intervals to study the desorp tion of acenaphthene, benzo[a]anthracene, benzo[b]fluoranthene. benzo[b]flu oranthene, benzo[a]pyrene, chrysene, fluoranthene, naphthalene, and phenant hrene over a period of 51 d. Results of the study indicated that 49.4 to 98 .0% df the polycyclic aromatic hydrocarbons (PAHs) in the contaminated sedi ment were desorbed upon disposal in the coastal environment. The field deso rption kinetics of these PAHs can be described by a two compartment model. The measured slow desorption rare constants, k(2), for acenaphthene, benzo[ a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, c hrysene, fluoranthene, naphthalene, and phenanthrene were found to be 0.018 , 0.061, 0.016, 0.028, 0.035, 0.021, 0.083,0.031, and 0.080/d, respectively . Some of these data were in accordance with literature-reported values fro m laboratory desorption studies in which desorbed PAHs were directly extrac ted from the aqueous phase. However, they were at least an order of magnitu de smaller than those obtained by conventional gas-stripping desorption tec hniques.