Use of bioaccumulation test results to evaluate treatment efficacy of a reactive core mat on contaminated subaqueous sediments.

摘要

A multi-stage research approach was developed to assess the ability of an organoclay-based reactive core mat (RCM) to prevent the breakthrough and uptake of hydrophobic organic contaminants by overlying biota. Through sorption to this organoclay layer, the RCM offers the potential to sequester contaminants as well as provide a stable foundation for clean overlying sediment. In the field the RCM is covered by a 10 cm layer of clean sand to provide stability for the RCM and also to provide substrate for biota regeneration. Bench-scale testing of the RCM was performed in the Integrated Contaminated Sediment Testing Apparatus Column (ICSTAC), a coupled consolidation and contaminant transport device. In the device, contaminated sediments were placed beneath the RCM and an overlying 10 cm thick layer of layer of clean sand. Initial tests were conducted with polychlorinated biphenyl (PCB)-contaminated sediments sampled from the Neponset River, Milton, MA. To evaluate the RCM's ability to prevent biouptake of polycyclic aromatic compounds (PAH), naphthalene-spiked sediment was used in ICSTAC experiments. After inducing advective-diffusive processes to occur in the sediment-RCM-sand column, the sand was removed and deposit-feeding, freshwater oligochaete worms Lumbriculus variegates were exposed to the sand in 28-day bioaccumulation tests.;Breakthrough of PCBs through the reactive core mat was not observed in the ICSTAC and biouptake experiments. Bioaccumulation of contaminants occurred during both PCB and naphthalene exposure tests, as L. variegatus concentrations were significantly higher than those of the sand. The results of these bioaccumulation experiments as well as efforts to characterize the PCB contaminant profile within the tested worms, sands, and sediment are presented. Results of PCA analysis provided insight as to the differential partitioning of PCB congeners within worms, sands, and sediments; the exposed oligochaetes displayed preferential uptake of tetra- and pentachlorobiphenyls.;RCM-ICSTAC testing performed with naphthalene-spiked and associated bioaccumulation experiments were less conclusive as to the efficacy of the RCM to sequester contaminants; this may be due to the inadequacy of the substitute organic matter to adequately sorb breakthrough contaminants. Biota-sediment accumulation factor (BSAF) calculation revealed trout-chow amended sand to more readily release naphthalene to exposed biota than the spiked-sediment. Chemical analysis of the ICSTAC's overlying water column during naphthalene tests indicate that the RCM significantly reduced contaminant breakthrough as compared to control tests with only a sand layer and no RCM. While further analysis and testing is necessary to clarify the results, contaminants were sequestered within the RCM during these preliminary tests.