Mobilization of PAHS and PCBs from in-place contaminated marine resuspension events

A particle entrainment simulator was used to experimentally produce represe ntative estuarine resuspension conditions to investigate the resulting tran sport of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarb ons (PAHs) to the overlying water column. Contaminants were evaluated in bu lk sediments, size fractionated sediments, resuspended particulate material and in some cases, dissolved phases during the experiments. The two types of sediments used in the experiments, dredged material and bedded estuarine sediment, represented gradients in contaminant loadings and sediment textu ral characteristics. For the bedded sediment, resuspension tended to winnow the sediments of finer particles. However, in the case of the more highly contaminated dredge material, non-selective resuspension was most common. R esuspension resulted in up to orders of magnitude higher particle-bound org anic contaminant concentrations in the overlying water column. Dissolved ph ase PAH changes during resuspension were variable and at most, increased by a factor of three. The sifting process resulted in the partitioning of fin e and coarse particle contaminant loading. For bedded sediments, accurate p redictions of PAH and PCB loadings on resuspended particles were made using the mass of resuspended particles of different sizes and the concentration s of contaminants in the particle pools of the bulk sediment. However, due possibly to contributions from other unmeasured particles (e.g. colloids), predictions were not possible for the dredge material. Thus, knowledge of t he redistribution and fate of colloids may be important. The partitioning o f PAHs between the dissolved and particulate phases during resuspension eve nts was predicted to within a factor of two from the amount: of organic car bon in each of the resuspended samples. These experiments show that contami nant transport is a function of the chemistry and textural characteristics of the bulk sediment and the winnowing action during resuspension events. E xisting relationships of resuspension and settling velocity are probably us eful in predicting chemical redistribution.