Metal concentrations in mussels from St. John's Harbour, Newfoundland

Leawood, Nancy E. (2002) Metal concentrations in mussels from St. John's Harbour, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

St. John's Harbour is an estuarine environment that has been at the centre of much of Newfoundland and Labrador's industrial, commercial and social activity since the settlement of the province's first immigrants. Historical practices such as atmospheric discharges from coal burning and current activities such as high-volume municipal sewage dumping and frequent ocean vessel trafficking has thus lead to contamination of this environment by a range of pollutants associated with such activities. Surprisingly there is little published quantitative information regarding seawater metal abundance and distribution within the harbour. In this study, the concentrations of 12 metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Cd and Pb) were determined in the soft tissue of indigenous blue mussels that were collected from 6 sites within St. John's Harbour and 5 outer harbour sites, including one control site. The tissue was dissolved in a closed-vessel microwave system and analyzed by ICPMS. -- Statistical analysis indicated significant differences (p < 0.005) of median concentrations for most metals between inner and outer harbour regions. Zinc and Pb concentrations were an order of magnitude higher at the inner harbour sites, while Cd was an order of magnitude lower at the inner sites. Median inner and outer region values were 149 and 87 µg⋅g⁻¹ for Zn, 1.74 and 0.58 µg⋅g⁻¹ for Pb, 398 and 1133 µg⋅g⁻¹ of Cd, respectively. The magnitude of between-region concentration differences was not as great for the other analytes. Like Cd, concentrations of As and Se were significantly higher in the outer harbour region, all other metals being significantly higher in the inner region, except Cr and Ni, for which no significant concentration differences between regions was indicated (p > 0.05). The 85th percentile Zn concentration from the inner region and that of Se from both regions were higher than 85th percentile mussel concentrations reported by the NOAA National Status and Trends program. The spatial distribution of metals within each region was uniform, excepting one site on the south side of the harbour that showed elevated concentrations for several analytes. No indication of a correlation between the metal concentrations in mussels and proximity to sewage and storm drain outflows was found.

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