Dissolved PCBs, PAHs, and HCB in pore waters and overlying waters of contaminated harbor sediments.

Abstract

Aqueous concentrations of polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pentachlorobenzene, and hexachlorobenzene (HCB) were determined by exposing low-density polyethylene (LDPE) strips to the pore waters and the overlying water in two contaminated harbors. LDPE strips were also exposed in the laboratory to sediment slurries and to stagnant sediments collected at the same locations. Surprisingly short equilibration time scales (1-60 days for log K(ow) < 7) were observed for the exposures to sediment slurries. This was a result of a profound decrease in transport resistance, due to the presence of particles in the aqueous boundary layer. Concentrations in the pore water were calculated from the initial uptake rates and the dissipation rates of performance reference compounds. Good correspondence existed with concentrations estimated from the equilibrium amounts in the strips and LDPE-water partition coefficients. Sediment-water partition coefficients for PAHs were higher than for PCBs and chlorobenzenes by approximately 1 order of magnitude. A one-dimensional diffusion model was used to describe contaminant uptake by LDPE strips from stagnant sediments. The results indicated that 95% of the PAHs and 50% of the PCBs were immobile on a time scale of two months. A comparison of concentrations in pore waters and water columns indicated that a fair degree of equilibrium existed for PCBs and that one sediment was a potential source of PAHs. Concentrations of HCB near a former discharge site were higher by a factor of 6 compared to reference locations.