| Abstrakt: |
Sediments in Halifax Harbour have accumulated contaminant metals Hg, Cu, Zn, and Pb as a result of discharge of untreated sewage and industrial waste, leaching of land fill waste, and surface drainage. Concentrations of contaminants in210Pb dated sediment cores became significant about 1880 and rose rapidly after 1900, reaching maximum concentrations in the decades between 1950 and 1980. Mean concentrations of Hg increased from 0.2 μg g−1 in pre 1890 sediments to 1.6 μg g−1 in the 20th century. Similar enrichments for Cu changed the concentration from 26 to 88 μg g−1; for Zn from 90 to 250 μg g−1, and for Pb the increase was from 12 to 206 μg g−1 Statistical factor analyses of geochemical data have been used to identify: (1) primary contaminants directly associated with waste discharge, these include total and organic-bound forms of Cu, Zn, and Pb; (2) secondary contamination attributed to leaching and modification of primary contaminants include acid labile forms of Zn, Ni, and Cu; (3) diagenetic modification of buried sediments are identified by total and labile forms of Mn; (4) dispersion of contaminants from land surface drainage are characterized by fine-grained aluminosilicates. Historical trends in the changing dominance of these environmental factors reflect changes in industrial activity, urban growth, and changes in the use of metals in paints, domestic and industrial chemicals, and in the combustion of fuels. |
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