Monitoring effects of remediation on natural sediment recovery in Sydney Harbour, Nova Scotia
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Monitoring effects of remediation on natural sediment recovery in Sydney Harbour, Nova Scotia Tony R. Walker & Devin MacAskill & Theresa Rushton & Andrew Thalheimer & Peter Weaver
Received: 29 May 2012 / Accepted: 28 February 2013 / Published online: 20 March 2013 # Springer Science+Business Media Dordrecht 2013
Abstract Chemical contaminants were assessed in Sydney Harbour, Nova Scotia during pre-remediation (baseline) and 3 years of remediation of a former coking and steel facility after nearly a century of operation and historical pollution into the Sydney Tar Ponds (STP). Concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, metals, and inorganic parameters measured in sediments and total suspended solids in seawater indicate that the overall spatial distribution pattern of historical contaminants remains unchanged, although at much lower concentrations than previously reported due to natural sediment recovery, despite remediation activities. Measured sediment deposition rates in bottommoored traps during baseline were low (0.4–0.8 cm year−1), but during dredging operations required for construction of new port facilities in the inner Sydney T. R. Walker (*) : T. Rushton : A. Thalheimer Dillon Consulting Limited, 137 Chain Lake Drive, Halifax, NS B3S 1B3, Canada e-mail: [email protected] D. MacAskill Dillon Consulting Limited, 275 Charlotte Street, Sydney, NS B1P 1C6, Canada P. Weaver Sydney Tar Ponds Agency, 1 Inglis Street, Sydney, NS B1P 6J7, Canada
Harbour, sedimentation rates were equivalent to 26– 128 cm year−1. Measurements of sediment chemical contaminants confirmed that natural recovery rates of Sydney Harbour sediments were in broad agreement with predicted concentrations, or in some cases, lower than originally predicted despite remediation activities at the STP site. Overall, most measured contaminants in sediments showed little temporal variability (4 years), except for the detection of significant increases in total PAH concentrations during the onset of remediation monitoring compared to baseline. This slight increase represents only a short-term interruption in the overall natural recovery of sediments in Sydney Harbour, which were enhanced due to the positive impacts of large-scale dredging of less contaminated outer harbor sediments which were discharged into a confined disposal area located in the inner harbor. Keywords Sediment contaminants . Remediation . Monitoring . Natural recovery . Sydney Tar Ponds
Introduction Sydney Harbour, Nova Scotia has long been subject to effluent and atmospheric inputs of contaminants, including metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs), from a large coking and steel plant which operated
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in Sydney from 1901 until it closed in 1988 (Lambert and Lane 2004). Contaminants comprised of coal tar residues were discharged from coking ovens into Coke Ovens Brook, which in turn were discharged into the Sydney Tar Ponds (STP) (Furinsky 2002). The STP forms a small tidal tributa
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