, Volume 17, Issue 5, pp 683-697

Drilling fluids and the arctic tundra of Alaska: Assessing contamination of wetlands habitat and the toxicity to aquatic invertebrates and fish

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Drilling for oil on the North Slope of Alaska results in the release of large volumes of used drilling fluids into arctic wetlands. These releases, usually come from regulated discharges or seepage from reserve pits constructed to hold used drilling fluids. A study of five drill sites and their reserve pits showed an increase in common and trace elements and organic hydrocarbons in ponds near-to and distant from reserve pits. Ions elevated in water were Ba, Cl, Cr, K, SO4 and Zn. Concentrations of Cu, Cr, Fe, Pb, and Si in sediments were higher in near and distant ponds than in control ponds. The predominant organics in drill site waters and sediments consisted of aromatic and paraffinic hydrocarbons characteristic of petroleum or a refined product of petroleum. In 96-hr exposures in the field, toxicity toDaphnia Middendorffiana was observed in water from all reserve pits, and from two of five near ponds, but not from distant ponds. In laboratory tests withDaphnia magna, growth and reproduction were reduced in dilutions of 2.5% drilling fluid (2.5 drilling fluid: 97.5 dilution water) from one reserve pit, and 25% drilling fluid from a second. Growth and reproduction were not affected at these dilutions of fluid from the other three reserve pits. Additional regulations—such as an upper limit on aromatic hydrocarbon content and toxicity to sensitive organisms —are needed to improve safety for aquatic organisms in habitats receiving used drilling fluids.