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 bottom-moored 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 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.

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Using mussels as monitoring tools we measured water quality in Sydney Harbour during a large scale, multi-year remediation project of the Sydney Tar Ponds (STPs); one of Canada's most contaminated sites. Chemical contaminants were measured in blue mussels (Mytilus edulis) in Sydney Harbour, which were used as monitoring tools to assess the spatio-temporal distribution of polycyclic aromatic hydrocarbons (PAHs); polychlorinated biphenyls (PCBs); metals (As, Cd, Cu, Hg, Pb, Zn) and lipid content during baseline and 3 years of remediation. The overall spatio-temporal distribution of chemicals in mussels was also compared to contaminants in other marine indicators (e.g., sediment, water and crab tissue). Measured metal concentrations in mussels showed some minor temporal variability (4 years), but these did not appear to be directly related to remediation activities, with the highest concentrations of As, Hg and Zn measured at reference stations. Most measured contaminants showed stable or potentially decreasing concentrations during the study, except Pb and Zn. Individual PAH compounds were mostly undetected during baseline and remediation, except for fluoranthene and pyrene. Concentrations of fluoranthene in mussels and deep water samples were moderately related. Generally, PCBs were undetected (<0.05 μg g(-1)), except during year 2 remediation at some near-field stations. Contaminants measured during this study were at much lower concentrations than previously reported in other studies of mussels in Sydney Harbour and eastern Canada. This is likely due to the ongoing natural recovery of Sydney Harbour and to a lesser extent because of the environmental mitigation protection measures implemented during remediation activities at the STPs. The lack of detection of most individual PAHs and PCBs, plus relatively low bio-accumulation of metals observed during baseline and remediation attest to the effectiveness of using mussels as monitoring tools for environmental quality.

Contaminants were measured in blue mussels (Mytilus edulis) in Sydney Harbour (SH) during remediation of the Sydney Tar Ponds (STPs) to assess the spatio-temporal distribution of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and metals during baseline and remediation. Overall distribution of chemicals in mussels was compared to contaminants in other marine indicators. Metal concentrations in mussels showed some minor temporal variability, but did not appear to be directly related to remediation activities. Contaminants showed stable or decreasing concentrations, except Pb and Zn. Individual PAH compounds were mostly undetected, except for fluoranthene and pyrene. Concentrations of fluoranthene in mussels and water were weakly related (R2 = 0.72). PCBs were undetected, except during year 2 remediation at some near-field stations. Contaminants measured during this study were much lower than previously reported in other studies of mussels in SH, likely due to ongoing natural recovery and because of environmental mitigation measures implemented during remediation activities at the STPs. The lack of detection of most individual PAHs, PCBs, and low bioaccumulation of metals during baseline and remediation using mussels as bioindicators reveal subtle improvements in environmental quality in SH.

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