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

摘要: During the Arctic Tropospheric Ozone Chemistry 1996 (ARCTOC 96) field campaign (March 29 to May 15, 1996), in situ measurements of C2-C8 hydrocarbons, selected C1-C2 halocarbons, and carbon monoxide were carried out at Ny Alesund, Svalbard (78°55′N, 11°56′E). Two major tropospheric ozone depletions observed during this period. In each case, concurrent depletion alkanes ethyne but no significant changes benzene, chloromethane, or CO mixing ratios detected. The change propane/benzene ratio can be used as evidence for presence chlorine radicals. Time integrated bromine atom concentrations calculated from concentration light ethyne, respectively. At background (O3 > 30 ppbv) our calculations yielded halogen (Cl: 5 ± 14 × 108 s cm−3, Br: 9 42 1010 cm−3). events, these values increase by more than a factor 10 about cm−3 (Cl) 1012 (Br). For such events losses explained quantitatively with data. Our results show that free atoms appear cause (more 92%). contribution loss is order 1% less. Highest found lowest reached up 1.4 1013 A closer analysis reveals event increases earlier remains high levels longer period time. starts when are below 15–20 ppbv reaches very <5 ppbv. appears anticorrelated (r2 = 0.811), whereas was logarithm 0.895).