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TitleMarine environmental impacts of historical gold mining activities, Isaacs, Seal, and Wine harbours, Nova Scotia
AuthorParsons, M B; Milligan, T G; Yeats, P A; Smith, J N; Little, M E; Parrott, D R
SourceACCESS Conference 2008, Atlantic Canada Coastal and Estuarine Science Society, abstracts volume; 2008 p. 21-22
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20080132
MeetingAtlantic Canada Coastal and Estuarine Science Society 2008 Workshop and General Meeting (ACCESS 2008); Dartmouth, NS; CA; May 14-16, 2008
Mediaon-line; digital
ProvinceNova Scotia
AreaIsaacs Harbour; Seal Harbour; Wine Harbour
Lat/Long WENS-62.0000 -61.5000 45.2500 45.0000
Subjectsenvironmental geology; marine geology; Health and Safety; gold; mining; mining activities; mining history; environmental analysis; environmental impacts; environmental studies; tailings; tailings analyses; arsenic; mercury; marine sediments; human health
ProgramEnvironment and Health
AbstractFrom 1861 to the mid-1940s, gold mines in Nova Scotia generated more than 3,000,000 tonnes of tailings containing high concentrations of both arsenic (As) and mercury (Hg). Tailings from these operations were generally slurried into local rivers, swamps, lakes, and the ocean. Recent land-use changes (e.g. industrial development, recreational activities, shellfish harvesting) in some historical mining districts are increasing the likelihood of human exposure to these mine wastes. This study examines the dispersion, speciation, and fate of metal(loid)s from historical gold mines in water, sediment, and biota from Isaacs, Seal, and Wine harbours in Guysborough County, NS. From 2003-2006, mine tailings, waters, and marine sediment samples were collected downstream of former milling operations, and in nearshore areas impacted by tailings. Marine sediments were collected using both a grab sampler (n = 53) and a gravity corer (n = 20), and analyzed for metals, carbon, and grain size. In-situ temperature and salinity measurements were made at selected stations using a CTD instrument, and marine water samples were collected for analyses of nutrients, and dissolved and particulate metals. The distribution of As and Hg in marine sediments confirms that most areas of all three harbours have been impacted by historical gold milling activities. Chemical analyses of 800 marine sediment subsamples show a wide range in both As (1 to 1500 ppm; median 20 ppm) and Hg (5 to 9500 ppb; median 102 ppb) concentrations. Radiometric dating of sediment cores using 210Pb and 137Cs indicates that the most tailings were deposited in Isaacs Harbour between 1900 and 1950, and in Wine Harbour between 1880 and 1920. The highest As and Hg values are located close to known stamp mill structures along the shores of Wine Harbour, and in an intertidal tailings flat in Seal Harbour. In general, the most contaminated sediments are deeper than the zone of active bioturbation (~0-15 cm); however, near-surface concentrations of As and Hg still exceed Canadian Sediment Quality Guidelines in many areas. Water analyses show that West Brook is a significant source of dissolved As to Seal Harbour, but that concentrations drop off rapidly with distance from the mouth of West Brook. Large quantities of orange, Fe-rich floc are present on the seafloor of Seal Harbour, which likely serve as a significant source of As to suspension-feeding organisms like clams and mussels. Biological sampling by project partners in 2004 and 2005 demonstrated that both As and Hg have bioaccumulated to various degrees in clams, mussels, and seaweed from Seal Harbour. A bivalve shellfish closure is now in effect for Seal and Isaacs harbours to prevent harvesting of As-contaminated clams. Results from this study have led to the formation of a Provincial-Federal Historic Gold Mines Advisory Committee, which is evaluating the ecological and human health risks associated with gold mines throughout Nova Scotia, and developing recommendations for management of these tailings sites.