An environmental monitoring study to assess the impact of drilling discharges in the mid-Atlantic. III. Chemical and physical alterations in the benthic drilling environment

Abstract

From the Abstract: “Two benthic surveys werer conducted to monitor the possible accumulation of trace metals resulting from the discharge of drilling muds and drill solids during exploratory drilling in theMid-Atlanti Bight. Increases in the concentrations of lead, barium, nickel, vanadium, and zinc in bottom sediments were detected during the Post-Drilling survey. Increase in the concentrations of lead and zinc were within the ranges of natural variability…for the same general area. Based on the concentrations of nickel and vanadium in drilling discharges, the likelihood that these increases resulted from the discharges alone seems remote. Incrased concentrations of barium in the bottom sediments were detected within the southern hemisphere of the sampling grid. Brittle stars, mollusks, and polychaetes collected during the Post-Drilling Survey had significantly higher barium and mercury content than those collected during the Pre-Drilling Survey. Increased mercury content in the organisms was detected despite the fact that negligible quantities of mercury were discharged and that mercury concenterations in the sediment were below the detection limit of 0.05 ug/g. Concentration gradients of barium in each organism group were not correlated to bottom sediment gradients. No simple correlation between the metal concentrations in the sediment samples and tissue samples was detected.”