The particle associations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were studied in both the water column and the surface sediments of a marine fiord system and were found to poorly obey expectations from the organic matter partitioning (OMP) paradigm. The field observations were instead consistent with the presence of a stronger sorbent subdomain such as pyrogenic soot-carbon (SC) playing an important role in affecting the environmental distribution and fate of PCDD/Fs. Solid-water distribution coefficients (Kd) of PCDD/ Fs actually observed in the water column were several orders of magnitude above predictions from a commonly used OMP model. Even when these elevated Kd values were normalized to the particulate organic carbon (POC) content (i.e., K(OC)), the variability in K(OC) for individual PCDD/ Fs at different fjord locations and seasons of factors 100-1,000 suggested that bulk organic matter was not the governing sorbent domain of the suspended particles. Further, POC-normalized particle concentrations of PCDD/ Fs (C(OC)) in a vertical profile (surface water-bottom water-surface sediment) revealed a strong increasing trend with depth. Factors of about 100 higher Coc for all PCDD/Fs in the sediment than in the surface water could not be explained by higher fugacity in the surrounding deep water nor with C:N or delta13C indexes of selective aging of the bulk organic matter. Instead this was hypothesized to reflect selective preservation of a more recalcitrant and highly sorbing, but minor, subdomain such as soot. The extent of enhanced PCDD/F sorption, above the OMP predictions, was positively correlated with the SC:POC ratio of the suspended particles in surface and deep waters. Finally, the geographical distribution of sedimentary PCDD/F concentrations were better explained by the SC content than by the bulk OC content of the sediment. Altogether, these field-based findings add to recent laboratory-based sorption studies to suggest that we need to consider both amorphous OC partitioning domains and SC particles as carriers of planar aromatic contaminants if we are to explain the environmental distribution and fate of pollutants such as PCDD/Fs.

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Multimedia environmental fate models are useful tools to investigate the long-term impacts of remediation measures designed to alleviate potential ecological and human health concerns in contaminated areas. Estimating and communicating the uncertainties associated with the model simulations is a critical task for demonstrating the transparency and reliability of the results. The Extended Fourier Amplitude Sensitivity Test(Extended FAST) method for sensitivity analysis and Bayesian Markov chain Monte Carlo (MCMC) method for uncertainty analysis and model calibration have several advantages over methods typically applied for multimedia environmental fate models. Most importantly, the simulation results and their uncertainties can be anchored to the available observations and their uncertainties. We apply these techniques for simulating the historical fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Grenland fjords, Norway, and for predicting the effects of different contaminated sediment remediation (capping) scenarios on the future levels of PCDD/Fs in cod and crab therein. The remediation scenario simulations show that a significant remediation effect can first be seen when significant portions of the contaminated sediment areas are cleaned up, and that increase in capping area leads to both earlier achievement of good fjord status and narrower uncertainty in the predicted timing for this.