The efficiency of capping to control air emissions from exposed contaminated sediments and dredged material

Experiments were conducted to ascertain the effects of the use of two diffe rent types of capping materials on the air emissions of semivolatile organi c compounds from exposed, contaminated dredged material such as those occur ring in a CDF. A 4-cm sand cap and a 2-cm fine-grained sediment cap were us ed to reduce emissions from sediment inoculated with dibenzofuran, phenanth rene, and pyrene. The experiments were performed in a flux chamber. The sed iment was sectioned after the experiment to obtain the spatial concentratio n profiles in the contaminated layer and the cap layer. The fluxes of diben zofuran, phenanthrene, and pyrene showed reductions of 90, 94, and 95%, res pectively, after 3 months in the presence of a sediment cap compared to unc apped sediment. The model prediction of the flux and the concentration prof iles was satisfactory. The porosity of the cap and the partitioning of the organic compound between the pore air and the cap material had the largest effect on flux through the cap. The model can be used to evaluate cap selec tion.