Distribution and bioaccumulation of heavy metals from produced water discharges to the gulf of mexico

Produced water, the largest volume waste generated during production of offshore gas and oil, is typically discharged into the ocean at the sea surface. Concentrations of some heavy metals, such as Cd, Pb, Fe and Ba, are enriched in produced water from the Gulf of Mexico relative to ambient seawater by factors of about 10 to >10,000. In contrast, concentrations of other metals in produced water, including Hg, Ni and V, are generally close to or less than those in seawater. Concern for enhanced bioaccumulation of metals from water surrounding oil platforms was addressed by analyzing mollusks collected within 10 m of the discharge pipe. No statistically significant differences in tissue levels of Ba, Cd, Hg, Ni, Pb or V were identified for clams (Chama macerophylla) or oysters (Crassostrea virginica) collected from production platforms with variable loadings of heavy metals. Sediment in discharge areas from the Gulf of Mexico often had elevated levels of Pb and Ba relative to AI; however, such enhancement is unlikely to be solely related to produced water.