Nonmethane hydrocarbon measurements in the North Atlantic Flight Corridor during the Subsonic Assessment Ozone and Nitrogen Oxide Experiment

Mixing ratios of nonmethane hydrocarbons (NMHCs) were not enhanced in whole air samples collected within the North Atlantic Flight Corridor (NAFC) dur ing the fall of 1997. The investigation was conducted aboard NASA's DC-8 re search aircraft, as part of the Subsonic Assessment (SASS) Ozone and Nitrog en Oxide Experiment (SONEX). NMHC enhancements were not detected within the general organized tracking system of the NAFC, nor during two tail chases of the DC-8's own exhaust. Because positive evidence of aircraft emissions was demonstrated by enhancements in both nitrogen oxides and condensation n uclei during SONEX, the NMHC results suggest that the commercial air traffi c fleet operating in the North Atlantic region does not contribute at all o r contributes negligibly to NMHCs in the NAFC.