Experimental and modeling study of reactive core mats to reduce bioavailability of persistent organic compounds in aquatic sediments.

摘要

Sediment remediation techniques to limit the bioavailability of contaminants are of special interest due to related acute or chronic toxicities associated with sediment contaminants. Bioavailability in aquatic sediments can be particularly problematic due to their accessibility to food chain biota, and interactions with surface and ground water which makes the long-term effective isolation necessary. This dissertation summarizes an experimental and numerical study to assess, characterize and model the effectiveness of Reactive Core Mats (RCM) for isolation, filtering, long term remediation and reducing bioavailability of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in aquatic sediments.;Bench-scale consolidation-coupled contaminant transport column tests provided a measure of short-term effectiveness under rapid consolidation-induced advective flux simulating active capping in field. The consolidation columns consisted of underlying contaminated sediment, caps consisting of combinations of RCM, sand and organic material (biouptake layer) and overlying water column. Analyses of overlying water and pore fluid concentrations, and contaminant bioavailability in the sediment and biouptake layer using freshwater worms L. variegatus, following sediment capping were used to evaluate isolation and filtering efficacy of the RCM. Upflow column tests with various capping configurations were performed to evaluate cap efficacy under constant upward submarine groundwater discharge. Effluent concentrations in upflow column tests were monitored continuously to quantify breakthrough peak time and concentration. A numerical model, RCM-XPORT2K, was developed to use experimental results from the column tests to estimate long term performance in the field. The model was in some cases integrated with commercial surface water quality models to perform conceptual site models for remediation.;Based on this work, it is concluded that RCM can effectively isolate rapid advective flux occurring following cap deployment, and the filtering capacity of RCM significantly reduces the resuspension of particulate-bound contaminants into overlying layers. The bioavailability tests resulted in up to 4 orders of magnitude reduction in bioavailability of contaminants compared to direct exposure and up to 3 orders of magnitude reduction compared to thin sand caps. Finally, long term modeling indicated application of RCM can significantly improve surface water quality and serves as an effective remediation/isolation tool.