FATE AND TRANSPORT OF PCBS AT THE NEW-BEDFORD-HARBOR SUPERFUND SITE

A unique, holistic modeling approach, combining theoretical, empirical , and deterministic elements, was developed to define the ambient back ground transport of polychlorinated biphenyl (PCB) from New Bedford Ha rbor, to provide a baseline for remediation assessment of this Superfu nd site. Both empirical and deterministic elements characterized sedim ent processes. The deterministic section employed experimental data to describe flocculation through fluid shear, differential settling, and Brownian motion mechanisms, yielding a sediment settling velocity. Th e empirical portion of the model used this settling velocity, along wi th suspended solids, and flow field data to characterize sediment acti on. The remaining PCB transport mechanisms (volatilization and sorptio n) are theoretically considered to give a complete contaminant transpo rt assessment. The PCBs in New Bedford Harbor tend to volatilize at th e rate of 5.9 g/d; or sorb, with sorption coefficients increasing with percent chlorination from 10(-22) to 10(-0.4) m(3)/g for Aroclors 101 6 and 1260, respectively, rather than stay in solution. The determinis tic model showed that fluid shear was the most significant flocculatio n mass removal mechanism contributing to the settling velocity calcula tion. From the empirical model, the dominant sediment action mechanism s, resuspension and deposition, were driven by the change in suspended solids concentration and tides. The cycling of PCB-laden sediment, in dicated by the PCB sorption tendency and the presence and dominance of resuspension, and subsequent transport from the site, can lead to PCB contamination of the water column, atmosphere, or downstream (marine) areas.