CARBON ISOTOPIC COMPARISONS OF OIL PRODUCTS USED IN THE DEVELOPMENTALHISTORY OF ALASKA

Studies of the fate of oil released into Prince William Sound, AK, as a result of the 1989 Exxon Valdez oil spill, have led to an unexpected discovery. In addition to oil-like residues attributed to the spill, the ubiquitous presence of flattened tar balls, the carbon isotopic co mpositions of which fall within a surprisingly narrow range [delta(13) C(PDB) = -23.7 +/- 0.3 parts per thousand (n = 65)], were observed on the shorelines of the northern and western parts of the sound. These c ompositions are similar to those of some all products [-23.7 +/- 0.7 p arts per thousand (n = 35)] that were shipped from California and used in Alaska for fuel, lubrication, construction, and paving before simi lar to 1970. These products include fuel oil, asphalt, and lubricants [-23.8 +/- 0.5 parts per thousand (n = 11)], caulking, sealants, and r oofing tar [-23.7 +/- 0.7 parts per thousand (n = 16)], and road pavem ents and airport runways [-23.5 +/- 0.9 parts per thousand (n = 8)]. F uel oil and asphalt [-23.5 +/- 0.1 parts per thousand (n = 3)], stored at the old Valdez town site and spilled during the 1964 Alaskan earth quake, appear to be the source of most of the beached tar balls. Oil p roducts with lighter carbon isotopic compositions, between -25 and -30 parts per thousand (n = 18), appear to have been used more recently i n Alaska, that is, after - 1970. The source of some of the products us ed for modern pavement and runways [-29.3 +/- 0.2 parts per thousand ( n = 6)] is likely Alaskan North Slope crude oil, an example of which w as spilled in the 1989 oil spill [-29.2 parts per thousand (n = 1)]. ( C) 1998 Elsevier Science B.V. All rights reserved.