An examination of metal inputs to the southern Beaufort Sea by disposal of waste barite in drilling fluid

Barites often contain trace metal impurities. Oil exploration in the Beaufort Sea will require barite as a major component of drilling fluid, most of which will be disposed after drilling. The trace metal impurities Hg, Pb, Zn and Cu have been examined by considering the natural budget and residence time of these elements for the Beaufort Shelf compared to projected scale of barite disposal. The form of metal, its solubility and bioavailability, and dispersion during ocean disposal have also been considered. Measurable effects of trace metals on the water column are not likely to extend much beyond hundreds of meters from the disposal. Elevated metal concentration in sediments will be most noticeable within about 100 m of disposal but detectable to perhaps 1 km depending on currents, sedimentation, and time since disposal. It is unlikely that much of the metal will enter the biosphere, and effects on the biota are more likely to arise from smothering or from other components used to make drilling fluid. Options such as land disposal or extraction of trace metal impurities from barite may not improve the overall environmental aspect of disposal.