Importance of DOC in sediments for contaminant transport modelling

Contaminants in the interstitial waters are not only dissolved but also associated with a filterable colloidal phase such as DOC. The DOC plays an important role regulating the distribution of chemicals between particulate and dissolved phases since it binds chemicals and makes them unavailable for vertical diffusive exchange. A three-phase partitioning model that consists of free-dissolved, DOC-bound, particulate-bound components of the chemicals involved is used for the contaminant transport model in order to include the effect of DOC on the partition coefficient. The contaminant model is linked to WASP modeling framework to predict remobilization of PCBs in sediments and the fate and transport of the contaminant in overlying waters of the New Bedford Harbor where the harbor has been contaminated with PCBs and heavy metals released from electronic capacitor manufacturers. Simulation of remedial controls indicates that if no action is taken, PCB concentrations will continue to be at elevated levels. Several scenarios for the removal of contaminated sediments have been performed to reduce the elevated PCB concentrations to background levels.