Ozone and C2—C5 hydrocarbon observations in the marine boundary layer between 45°S and 77°S

During the austral summer of 1993, measurements of surface ozone (O₃), nonmethane hydrocarbons (NMHC), lead-212 and radon-222 activity were performed on board the vessel ANTARCTICA between 43°S and 77°S. The latitudinal variations of light C₂—C₅ alkanes reflect the relatively short photochemical lifetime of these compounds and their intensive photochemical destruction during summer. Average mixing ratios of ethane, propane and acetylene were 291 ± 76 pptv, 61 ± 53 pptv and 48 ± 35 pptv, respectively, in good agreement with published measurements previously undertaken in the Antarctic region.

O₃ mixing ratios ranged from 8.5 ppbv to 22.2 ppbv. The few relatively high values of ozone that have been observed during EREBUS94 campaign occurred simultaneously with high Rn-222 activities and possibly indicated continental influence through transport of air masses in the free troposphere. With the exception of these high O₃events, the O₃ and NMHC observations, in conjunction with air mass back trajectory analysis, radon-222 observations and a global 3-D model calculations, suggest that the troposphere/stratosphere exchanges play an important role on ozone budget at the high latitudes of the southern hemisphere.