Abstract
During the INSTAC-I flight campaign in March 1989, 21 air samples were collected and 8 light nonmethane hydrocarbons were measured with an FID-gas chromatograph. The mean concentrations of the hydrocarbons measured were 1.30 ppb (ethane), 0.372 ppb (propane), 0.175 ppb (n-butane), 0.075 ppb (iso-butane), 0.139 ppb (n-pentane), 0.039 ppb (iso-pentane), 0.006 ppb (neo-pentane), and 0.179 ppb (acetylene). All hydrocarbons showed a slight tendency to increase over the tropics. No marked difference was recognized between the samples obtained during the southbound and northbound flights. The sum of relative reactivities of these light hydrocarbons to methane was estimated to be about 26% of methane, which signifies that the effect of light hydrocarbons on atmospheric chemistry in the unpolluted troposphere can not be ignored.
