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Measuring low levels of pollutants in sea water samples

WED scientists have developed a procedure for measuring very low concentrations of potentially toxic petroleum residues in small water samples. Many of these toxic compounds, called polycyclic aromatic hydrocarbons or PAHs, are included on EPA’s list of priority pollutants. Because the procedure involves the sampling of only one-half liter of water, it is useful with specialized equipment such as an instrument placed on the sea floor to determine the rates of release of particular sediment contaminants. The technique, which employs the use of a mass spectrometer, is sensitive enough to measure PAH concentrations less than one nanogram (one trillionth of a gram) per liter. The WED researchers, along with a colleague from the U.S. Navy’s Environmental Science Division, tested the technique at the U.S. Naval Shipyard in Puget Sound, Washington, where relatively high concentrations of PAHs were measured in surface sediments. During sampling periods of one to two days, the scientists observed clearly discernable rates of loss of toxic PAH compounds from the sediments to overlying water. Measures of toxic concentrations in the water were at least one thousand times less than levels reported to have any effect on marine organisms. (Contact D.R. Young, 541-867-4038; young.david@epa.gov)

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