ACCUMULATION OF CONTAMINANT METALS IN MARINE-SEDIMENTS OF HALIFAX HARBOR, NOVA-SCOTIA - ENVIRONMENTAL-FACTORS AND HISTORICAL TRENDS

Sediments in Halifax Harbour have accumulated contaminant metals Hg, C u, Zn, and Pb as a result of discharge of untreated sewage and industr ial waste, leaching of land fill waste, and surface drainage. Concentr ations of contaminants in (210)pb dated sediment cores became signific ant about 1880 and rose rapidly after 1900, reaching maximum concentra tions in the decades between 1950 and 1980. Mean concentrations of Hg increased from 0.2 mu g g(-1) in pre 1890 sediments to 1.6 mu g g(-1) in the 20th century. Similar enrichments for Cu changed the concentrat ion from 26 to 88 mu g g(-1); for Zn from 90 to 250 mu g g(-1), and fo r Pb the increase was from 12 to 206 mu g g(-1). Statistical factor an alyses of geochemical data have been used to identify: (1) primary con taminants directly associated with waste discharge, these include tota l and organic-bound forms of Cu, Zn, and Pb; (2) secondary contaminati on attributed to leaching and modification of primary contaminants inc lude 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 characteri zed by fine-grained aluminosilicates. Historical trends in the changin g dominance of these environmental factors reflect changes in industri al activity, urban growth, and changes in the use of metals in paints, domestic and industrial chemicals, and in the combustion of fuels.