O-17 O-16 AND O-18/O-16 ISOTOPE MEASUREMENTS OF ATMOSPHERIC CARBON-MONOXIDE AND ITS SOURCES/

Simultaneous O-17/O-16 and O-18/O-16 measurements of atmospheric carbo n monoxide (CO) and two of its major sources are presented. CO was col lected in situ at ground level in La Jolla, CA, Pasadena, CA and White Mountain, CA, altitude 3.8 km. Samples were also taken directly from engine exhaust and during a local wild brushfire. Results indicate tha t atmospheric carbon monoxide has a significant mass independent compo nent, which increases as carbon monoxide concentrations decrease. The origin of the observed mass independent fractionation is discussed. CO samples from engine exhaust and brushfires are clearly mass dependent , but with a wide variation in O-18 values from different engines.