Total and Methyl Hg in Sediment Adjacent to Offshore Platforms of the Gulf of Mexico

Abstract

Distribution of total Hg and methyl Hg in surface sediment with distance from the three legs of two offshore oil production platforms was studied. Concentration of both total Hg and methyl Hg decreased with distance (0 to 800 m) from two platforms. Average methyl Hg content in sediment near the platform was 1.15 ppb, decreasing to 0.44 at 800 m. Average total Hg content in surface sediment measured at the two platforms was 63.40 ppb, decreasing to 29.45 at 800 m. The mercury level paralleled decrease in sediment organic matter with distance from the platform. Results of this study showed low levels of mercury in vicinity of the platform. Increased methyl Hg was likely associated with the higher organic matter content of sediment near the platform rather than mercury levels in sediment.