Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone

Pressure and temperature dependence of Freon-12 absorption coefficients for CO(2) waveguide laser radiation

Freon-12 absorption coefficients for the P(22) through P(48) CO(2) waveguide laser transitions of the 00 degrees 1-(10 degrees 0, 02 degrees 0)(I) band are presented. For pressures below 10 Torr and a spectral resolution of 0.1 MHz, the absorption coefficients show considerable spectral structure within +/-250 MHz of the CO(2) laser line center; but individual absorption lines are only resolved for pressures below 100 microm. The absorption coefficients around the CO(2) waveguide laser lines are shown to be spectrally structureless as well as pressure independent above 20 Torr. The temperature dependence of the absorption coefficients are presented for the first time, and they are shown to be linearly dependent on temperature.

Atomic Chlorine and the Chlorine Monoxide Radical in the Stratosphere: Three in situ Observations

Three simultaneous observations of atomic chlorine (Cl) and the chlorine monoxide radical (ClO) are reported which encompass the altitude interval between 25 and 45 kilometers. Together, Cl and ClO form a gas-phase catalytic cycle potentially capable of depleting stratospheric ozone. Observed Cl and C1O densities, although variable, imply that chlorine compounds constitute an important part of the stratospheric ozone budget. The results are compared with recent models of stratospheric photochemistry which have been used as a basis for predicting ozone depletion resulting from fluorocarbon release.

Ozone Monitoring with an Infrared Heterodyne Radiometer

Measurements of the total burden and of the concentration versus altitude profiles of ozone have been made with a ground-based heterodyne radiometer at Pasadena, California. The measurements were made in the 9.5-micrometer wavelength region, where a strong ozone infrared absorption band exists. The radiometer measured solar absorption at selected wavelengths, with a spectral resolution of 0.001 reciprocal centimeter, equivalent to the half-width of an ozone absorption line at the 10-millibar altitude level. A carbon dioxide laser served as the local oscillator. This technique can be used to gather important data on both tropospheric and stratospheric ozone, which are not readily accessible with other remote-sensing techniques.

The sampling and determination of halocarbons in ambient air using concentration on porous polymer

The levels of halocarbons have been determined in rural air in central Michigan using a sampling procedure employing pre-concentration on a porous polymer. The samples were analyzed by gas chromatography (GC) with an electron capture detector. Both qualitative and quantitative confirmation of the results were achieved by GC-mass spectrometry. Trichlorofluoromethane, chloroform, 1,1,1-trichloroethane, carbon tetrachloride, trichloroethylene and perchloroethylene were determined in the range of 30-130 parts per trillion. These concentrations agree well with data obtained by others in Washington state and Ireland indicating even distribution of the halocarbons in these latitudes.

Energetic Radiation Belt Electron Precipitation: A Natural Depletion Mechanism for Stratospheric Ozone

During geomagnetically disturbed periods the precipitational loss of energetic electrons from the outer radiation belt of the earth can readily provide the major ionization source for the mesosphere and upper stratosphere. One particularly intense manifestation of this interaction between the radiation belts and the lower atmosphere is the relativistic electron precipitation (REP) event which occurs at subauroral latitudes during magnetospheric substorm activity. At relativistic energies the precipitating electrons produce copious fluxes of energetic bremsstrahlung x-rays, the major portion of which penetrate deep into the stratosphere before undergoing excitation and ionization collisions with the neutral atmosphere. If such REP events occur more than a few percent of the time, they can, on an annual basis, provide a local source of upper stratospheric nitric oxide molecules (via the dissociation of molecular nitrogen) comparable to that from either galactic cosmic rays or energetic solar proton events. Since nitric oxide plays a major role in the removal of stratospheric ozone, it appears that the influence of REP events must also be considered in future photochemical modeling of the terrestrial ozone layer.

Greenhouse Effects due to Man-Mad Perturbations of Trace Gases

Nitrous oxide, methane, ammonia, and a number of other trace constituents in the earth's atmosphere have infrared absorption bands in the spectral region 7 to 14 microm and contribute to the atmospheric greenhouse effect. The concentrations of these trace gases may undergo substantial changes because of man's activities. Extensive use of chemical fertilizers and combustion of fossil fuels may perturb the nitrogen cycle, leading to increases in atmospheric N(2)O, and the same perturbing processes may increase the amounts of atmospheric CH(4) and NH(3). We use a one-dimensional radiative-convective model for the atmospheric thermal structure to compute the change in the surface temperature of the earth for large assumed increases in the trace gas concentrations; doubling the N(2)O, CH(4), and NH(3) concentrations is found to cause additive increases in the surface temperature of 0.7 degrees , 0.3 degrees , and 0.1 degrees K, respectively. These systematic effects on the earth's radiation budget would have substantial climatic significance. It is therefore important that the abundances of these trace gases be accurately monitored to determine the actual trends of their concentrations.

Man-Made Carbon Tetrachloride in the Atmosphere

The emissions of man-made carbon tetrachloride and the rates of its removal from the atmosphere by natural sinks are evaluated. A large fraction, perhaps all of the carbon tetrachloride observed in the atmosphere, could be man-made, and carbon tetrachloride is a global atmospheric pollutant.

Atmospheric ozone and man-made pollution

Atmospheric photochemistry and transport processes, related to the ozone layer, are discussed. Natural or man-made changes of the biosphere, variations of radiation, or general circulation as well as anthropogenic release of ozone-destroying catalysts are likely to alter the earth's ozone shield. The possible effects of ozone depletion caused by supersonic aircraft, nuclear weapons, nitrogen fertilizers, and chlorofluoromethanes are discussed.