Hydrocarbon measurements during tropospheric ozone depletion events: Evidence for halogen atom chemistry

Abstract. During the Arctic Tropospheric Ozone Chemistry 1996 (ARCTOC 96) field campaign (March 29 to May 15, 1996), in situ measurements of C2-C s hydrocarbons, selected C•-C2 halocarbons, and carbon monoxide were carried out at Ny •lesund, Svalbard (78ø55'N, 11ø56'E). Two major tropospheric ozone depletions were observed during this period. In each case, concurrent depletion of alkanes and ethyne but no significant changes in benzene, chloromethane, or CO mixing ratios were detected. The change in the propane/benzene ratio can be used as evidence for the presence of chlorine radicals. Time integrated chlorine and bromine atom concentrations were calculated from the concentration changes of light alkanes and ethyne, respectively. At background ozon