The Seasonal Variation of Light Nonmethane Hydrocarbons in the Antarctic Troposphere

About 80 samples of antarctic air were collected between 1982 and 1985 at the “Georg von Neumayer” station (70°36′S and 8°22′W) and analyzed for ethane, ethene, acetylene, propane, and propene. Yearly average mixing ratios were 0.37, 0.36, 0.011, 0.07, and 0.21 ppb, respectively. The seasonal cycles for ethane and acetylene showed minima around the late southern hemispheric summer and maxima in late winter. The phase of the seasonal cycle in ethane and acetylene can be explained by seasonal variation of atmospheric removal rates. Seasonal variation of one of the major southern hemispheric ethane and acetylene sources, biomass burning, would cause a similar seasonal change. Propane exhibits a much higher variability and shows no clear seasonal cycle. The atmospheric mixing ratios of ethene and propene peak around early austral fall and are most probably mainly determined by seasonal variation in emissions from the oceans surrounding Antarctica.