Total chlorine content in the lower stratosphere

Abstract

A cryogenic whole air sampler and a filter sampler were used, simultaneously, on a balloon platform to capture and preserve all significant stratospheric chlorine species with the exception of Cl and ClO at altitudes of 15, 20, 25, and 30 km. The whole air samples were analyzed by gas chromatography to determine mixing ratios of CF2Cl2, CFCl3, CH3Cl, CH3CCl3, and CCl4. Liquid extractions of the filter samples were analyzed for acidic and particulate chlorine content using neutron activation and wet chemistry techniques. Summation of the contributions from the major species produced total chlorine mixing ratios that decreased from 2.6 ppbv at 15 km to 2.2–2.5 ppbv for the higher altitudes. Omission of Cl and ClO introduced about a 3–7% error at 25–30 km and negligible error at 15 and 20 km. The combined contributions of all other omitted species introduced 1–2% error to the total chlorine values for all altitudes investigated. The increase in total acidic species content with increasing altitude correlates with the decrease in the mixing ratios of the chlorine species of tropospheric origin.

The 1985 chlorine and fluorine inventories in the stratosphere based on ATMOS observations at 30� north latitude

“…Earlier investigations in the stratosphere (at = 33" N in 1976) by Lazrus et al (1977) by means of base-impregnated filters, revealed significant variation with altitude in their (HCl + ClONO,) VMRs, with values of 0.8, 0.5, and 1.0 ppbv at 24,32, and 36 km altitude, respectively. Subsequently, Berg et al (1980) using activated charcoal traps and neutron activation analysis, found values of total chlorine at = 33" N on 5 October 1978, ranging from 2.8 to 3.0 ppbv at 21.5 km altitude, while Gallagher et al (1985) reported total Cl values of 2.58,2.17 to 2.51, and 2.46 ppbv at 15, 20, and 25-30 km altitudes, respectively, obtained by cryogenic whole air and filter sampling at = 33" N during the spring of 1981 and 1982. Within their respective relative uncertainties, the Berg et al (1980) and the Gallagher et al (1985) results encompass the present Cl inventory, but the absolute uncer~nties of the various techniques involved have been insu~cientiy assessed through intercompa~son exercises for these in-situ measurements to be used for validation purposes here.…”

“…Subsequently, Berg et al (1980) using activated charcoal traps and neutron activation analysis, found values of total chlorine at = 33" N on 5 October 1978, ranging from 2.8 to 3.0 ppbv at 21.5 km altitude, while Gallagher et al (1985) reported total Cl values of 2.58,2.17 to 2.51, and 2.46 ppbv at 15, 20, and 25-30 km altitudes, respectively, obtained by cryogenic whole air and filter sampling at = 33" N during the spring of 1981 and 1982. Within their respective relative uncertainties, the Berg et al (1980) and the Gallagher et al (1985) results encompass the present Cl inventory, but the absolute uncer~nties of the various techniques involved have been insu~cientiy assessed through intercompa~son exercises for these in-situ measurements to be used for validation purposes here. To our knowledge, no stratosphe~c fluorine budget dealing with both organic and inorganic gas measurements has been reported except for this ATMOS/SL3 inventory.…”

Halogen ions and NO+ in the mass spectra of aerosols in the upper troposphere and lower stratosphere

“…Clearly, these amounts are small compared to the total amounts of fluorine and chlorine . I,,,,11,,,I,,,,I, previous null measurement of aerosol F and C1 in filter samples [Gandrud et al, 1989] as well as the good closure obtained for the stratospheric chlorine budget [Gallagher et al, 1985;Zander et al, 1996]. However, we cannot quite exclude the possibility that aerosols could be a Given the ease of forming negative ions from halogens, the fraction of Br ions is probably an upper limit to the mole fraction of Br in aerosols.…”