Assessment of surface and ground waters, stream and estuary sediments and other ecosystem receptors to determine long term impacts of surface PCB and heavy metal releases, Makinsons, Newfoundland

Bourgeois, Jason (1997) Assessment of surface and ground waters, stream and estuary sediments and other ecosystem receptors to determine long term impacts of surface PCB and heavy metal releases, Makinsons, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

As part of a National Contaminated Sites Remediation Program (NCSRP), FFC/BEAK (1992d) identified polychlorinated biphenyl (PCB) and heavy metal contamination from an old salvage yard at the top of a small drainage basin located in Makinsons, Newfoundland. Given the lack of understanding of how PCBs and heavy metals are distributed and attenuated in small drainage basins that consist of thin overburden underlain by fractured bedrock, a study was undertaken with the main objective of determining how PCBs and heavy metals are distributed in the surface waters, ground waters, soils, sediments within the stream and estuary, and bivalve bioreceptors (Mercenaria mercenaria). It was necessary to describe the spatial distribution of PCBs and heavy metals in order to determine the role that these waters, sediments, and bioreceptors, play in contaminant transport within this small drainage basin. -- There is evidence that the salvage yard is contributing PCBs, Cr, As, MnO, Fe₂O₃, and Pb to the Makinsons drainage basin. The major pathway is believed to be surface runoff carrying contaminants adsorbed on sedimentary and particulate matter from the salvage yard to the stream. However, PCBs were unexpectedly detected in stream sediments and soils located upgradient from the salvage yard, suggesting an additional source of PCB contamination. This additional source probably relates to the oiling of roads to control dust before they were paved. -- Based on the surface water and ground water chemistry described in this study, mobilization of dissolved metals from the salvage yard-bog area was found to be negligible. Relatively neutral pH (> 6) conditions detected in drainage basin ground waters most likely limited the aqueous solubility of metals and resulted in the predominant species being adsorbed to the soil framework. An additional source of contamination to the drainage basin is suspected to include domestic septic effluent. M. mercenaria collected from the South River estuary were enriched in Fe, Ni, Mn, Cd, Cr, and Pb, relative to average concentrations of M. mercenaria collected along the Atlantic coast of the US. However, PCBs were not present ≥ 0.05 ppm (wet weight) in M. mercenaria from the estuary. Therefore, PCBs adsorbed on suspended material are either being deposited closer to the salvage yard or are being diluted by uncontaminated suspended matter. Regardless, PCBs are not available to these relatively immobile bioreceptors in the estuary.

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