DISTRIBUTION AND BIOACCUMULATION OF HEAVY-METALS FROM PRODUCED WATER DISCHARGES TO THE GULF-OF-MEXICO

Produced water, the largest volume waste generated during production o f offshore gas and oil, is typically discharged into the ocean at the sea surface. Concentrations of some heavy metals, such as Cd, Ph, Fe a nd 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, c oncentrations 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 platform s was addressed by analyzing mollusks collected within 10 m of the dis charge pipe. No statistically significant differences in tissue levels of Ba, Cd, Hg, Ni, Pb or V were identified for clams (Chama macerophy lla) or oysters (Crassostrea virginica) collected from production plat forms with variable loadings of heavy metals. Sediment in discharge ar eas from the Gulf of Mexico often had elevated levels of Pb and Ba rel ative to Al; however, such enhancement is unlikely to be solely relate d to produced water.