Modeling polychlorinated biphenyl mass transfer after amendment of contaminated sediment with activated carbon
- University of Newcastle upon Tyne, Newcastle (United Kingdom)
The sorption kinetics and concentration of polychlorinated biphenyls (PCBs) in historically polluted sediment is modeled to assess a remediation strategy based on in situ PCB sequestration by mixing with activated carbon (AC). The authors extend their evaluation of a model based on intraparticle diffusion by including a biomimetic semipermeable membrane device (SPMD) and a first-order degradation rate for the aqueous phase. The model predictions are compared with the previously reported experimental PCB concentrations in the bulk water phase and in SPMDs. The simulated scenarios comprise a marine and a freshwater sediment, four PCB congeners, two AC grain sizes, four doses of AC, and comparison with laboratory experiments. The modeling approach distinguishes between two different sediment particles types: a light-density fraction representing carbonaceous particles such as charcoal, coal, coke, cenospheres, or wood, and a heavy-density fraction representing the mineral phase with coatings of organic matter. A third particle type in the numerical model is AC. The model qualitatively reproduces the observed shifts in the PCB distribution during repartitioning after AC amendment but overestimates the overall effect of the treatment in reducing aqueous and SPMD concentrations of PCBs by a factor of 2-6. For the AC application in sediment, competitive sorption of the various solutes apparently requires a reduction by a factor of 16 of the literature values for the AC-water partitioning coefficient measured in pure aqueous systems. With this correction, model results and measurements agree within a factor of 3. After AC amendment is homogeneously mixed into the sediment and then left undisturbed, aqueous PCB concentrations tend toward the same reduction after 5 years. 19 refs., 5 figs., 4 tabs.
- OSTI ID:
- 20772694
- Journal Information:
- Environmental Science and Technology, Vol. 40, Issue 13; Other Information: luthy@stanford.edu; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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