Grain size and trace metal concentrations on the Scotian Shelf : results from the Thebaud offshore gas production platform and Gully MPA / by Vanessa S. Zions, Brent A. Law and Timothy G. Milligan. : Fs97-6/3415E-PDF

"Core samples were collected for sediment grain size and trace metal analysis from the Scotian Shelf in the summers of 2006 and 2007 from the vicinity of Thebaud gas production platform and the Gully Marine Protected Area (MPA). At Thebaud samples were collected along transects radiating from the platform in east, west, north-east and south-east directions. In the Gully, transects followed the canyon axis in a north-west to south-east orientation. All bottom sediment core samples were collected using a slow-corer which preserved the sediment-water interface. Cores were sectioned into 2 cm layers for sediment grain size and trace metal analysis. Sediment analysis from Thebaud revealed a median diameter (d50) that ranged from 158.14-385.03 μm with 0.20-6.04% of material residing in the mud fraction (<63 μm). The Gully had median diameters between 131.06-408.10 μm where mud made up 0.11-5.50% of material. For metals of interest (Zn, Fe, Mn, Ba, and Sr) concentrations were plotted against aluminum for grain size normalization and compared to background concentrations collected from sandy sediments throughout the Scotian and Newfoundland Shelfs. Elevated metal concentrations were measured at Thebaud throughout the sampling program, which may be indicative of drilling waste and produced water impacts. Elevated levels of metals were not detected in the Gully suggesting there was little evidence of hydrocarbon activities in the MPA"--Abstract, page vii.

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