Trends in sediment trace metal concentrations around six petroleum drilling platforms in the northwest Gulf of Mexico

Abstract

From the Abstract: “Sediments within 500 m of 6 offshore drilling sites in the northwestern Gulf of Mexico were studied. The objective was a detailed characterization of sediment gradients of elements known to be major constituents of drilling fluids e.g. Ba, and of trace elements of environmental concern, e.g. Cd, Cr, Cu, Hg, Pb, Zn, which may be released during drilling…Using a high sampling density (36 samples within 500 m) complete discharge history and analysis of subsurface sediments, a detailed three-dimensional barium mass balance was calculated which showed that only a small fraction of the total barium used, i.e. <1.5% nearshore, >12% offshore, and presumabley similarly behaving drilling mud components, are retained in near-site sediments. …Statistically significant elevations in surficial sediment Hg and Zn concentrations, i.e. with 125 m of the site, Hg 4–7 fold above background, Zn 5–10 fold were observed at these two deep water sites. Significant elevations, e.g. 3–5 times background, in other trace metals (Cd, Cu, Pb, Zn) were not common and generally restricted to sediments within 125 m of the drilling site.”