Background Levels of Petroleum Residues in the Waters and Surficial Bottom Sediments of the Labrador Shelf and Hudson Strait/Foxe Basin Regions

Background levels of petroleum residues in the form of particles floating on the sea and as substances extracted from the surface microlayer, the water column, and the surficial bottom sediments of the Hudson Strait/Foxe Basin and the Labrador shelf regions were measured during 1982 and 1983. No evidence of floating particulate oil was found in either region. Background levels of extractable petroleum residues in the surface microlayer were highly dependent on ambient sea conditions and ranged from 4.1 μg/L at the entrance to Hudson Strait to 28.3 μg/L on the southern Labrador shelf in 1982, and from 4.5 to 20.9 μg/L on the Labrador shelf in 1983 with the general background level at 8.13 μg/L. The background level in the water column in the Hudson Bay/Hudson Strait region was 0.46 μg/L in 1982 whereas that on the Labrador shelf was 0.42 μg/L during 1982 and 0.57 μg/L in 1983 (overall level of 0.51 μg/L). Concentration levels in the surficial bottom sediments depended primarily on the nature of the sediments and ranged from 1.9 μg/g at the eastern end of Hudson Strait to 52.5 μg/g on the continental slope east of Nain Bank with a general background level of 2.04 μg/g. These background levels are similar to those of other areas of the continental shelf off the east coast of Canada and are, presently, well below those known to have adverse biological consequences.