Release of polychlorinated biphenyl congeners in a contaminated harbor and canal

The overall hypothesis of this thesis addresses the release of polychlorinated biphenyls (PCBs) in the sediments of a highly contaminated harbor. I collected, analyzed and quantified PCB congeners in more than 130 samples of air, water and sediment. Then I constructed a chemical fate model as function of chemical concentrations, physical-chemical properties, local meteorological and hydraulic conditions. Indiana Harbor and Ship Canal in East Chicago (IHSC), Indiana, was selected for its expected high levels of PCBs in the sediment and because of future plans for dredging. I found that PCB concentrations in air, water and sediment in this area were much higher than background levels in the Great Lakes region. PCB sediment concentrations were above the threshold limit to designate IHSC as a Superfund site (≥ 50 ppm), although it is not. The PCB signature in surficial sediment strongly resembles the original Aroclor 1248 but deeper layers show evidence of mixtures of Aroclors and weathering processes. The fate model showed that IHSC contaminated sediments are a continuous source of PCBs to the water and overlying air, and also produce a PCB input to Lake Michigan, even under quiescent conditions. The PCB signature in sediment, water, and air support my determination that the contaminated sediment is a major source of PCBs into the water and air above it. Simulations considering different surficial sediment concentrations post-dredging demonstrated that PCB concentrations in the sediment should be considered in the dredging operation to minimize the release of PCBs into the environment. Finally, I examined the role of the dissolved sediment porewater concentration in the prediction of sediment-water soluble fluxes, using a passive sampler technique (SPME PDMS-fiber) and calculated values from a one-parameter linear free energy relationship (op-LFER). I determined that the latter overestimates the freely dissolved porewater concentration but are nevertheless the most appropriate values for predicting PCBs soluble release from contaminated sediments.