Possible impact of sodium species on ClO and O₃ in the upper stratosphere

Abstract

Recent measurements of the rates for tion (4) was first recognized by Murad et al.reactions of NaO2 and NaOH with HC1 and of the (1981) who suggested that the species MC1 could photoabsorption cross section of NaC1 allow for act as an important reservoir of chlorine if its realistic estimates of the impact of sodium chem-stratospheric abundance is comparable to that of istry on chlorine partitioning in the upper strat-HC1. On the other hand, reactions (4) and (5) osphere. When sodium chemistry is incorporated into our one-dimensional model of the upper atmosphere, the results indicate that the calculated C10 concentrations near 50 km could increase by up to a factor of two with a corresponding decrease in calculated O3 abundances of as much as 15 percent.The impact on C10 and O3 depends crucially on the assumed meteoritic source of sodium, on transport from the mesosphere, and on transformation and removal of gaseous sodium in the stratosphere.Since the fluctuations in the abundance of gaseous sodium could induce O3 variations comparable to those caused by changes in temperature and solar UV, consideration of the chemistry of sodium and other metals may be an important element in efforts toward early detection of trends in upper stratospheric 03 . Future increases in stratospheric chlorine will magnify the impact of sodium species on ozone.

Antarctic ozone: Meteoric control of HNO3

“…Formation of metal nitrates and sulfates is likely to occur in PSCs, and these neutralized salts remain in the aerosol phase after the clouds evaporate, irrevocably removing HNO 3 from the gas phase. On a global average, meteoric metals are expected to be present in the middle stratosphere at concentrations much less than a part per billion [Rodriguez et al, 1986b], insufficient to neutralize fully the acidity of the Junge sulfate layer [Junge et al, 1961;Rosen, 1971]. Over polar regions, however, meteoric debris accumulates in winter and early spring as a result of the pole-to-pole mesospheric circulation illustrated here in three-dimensional tracer simulations.…”

“…Subsequent oxidation of CI to CIONO 2 or HOCI can lead to further conversion of HCI to active CI x. The atmospheric chemistry of sodium has been studied recently [Rodriguez et al, 1986b, and references therein]. Magnesium and iron, however, are predicted to be the dominant metals deposited in the upper atmosphere by meteors, with sodium and other metals present in much lesser abundances.…”

Atmospheric Chemistry of Meteoric Metals

“…The seasonal meridional circulation in the mesosphere (Figure ) should result in a large flux of meteoric smoke descending into the winter polar vortex. Interestingly, the downward flux of essentially alkaline smoke from the mesosphere approximately balances the nitric acid removed when the lower stratosphere becomes denitrified by the formation of polar stratospheric clouds during the polar night . Finally, the transport of this material, which is probably rich in water-soluble iron, may have a significant impact in fertilizing the Fe-deficient Southern Ocean around Antarctica, which is far removed from sources of continental aeolian dust. , …”

Rate coefficient for the gas phase reaction of NaOH with CO2

“…Their model is based on the polar nature of NaC1 and therefore can be extended to NaOH and other polar Na species. The effect of this polymerization on the efficiency of (2)-(5) is discussed by Rodriguez et al [1986]. They predict that if the Lamb and Benson [1986] mechanism and estimated rate coefficients are valid, (2)-(5) could still catalytically destroy 0 3 at altitudes above 50 km.…”

“…(1) was first proposed by Murad and Swider [1979] as a possible sink for Na species in the stratosphere. NaOH is a reservoir species for Na, since only photolysis and reaction with H atoms can return it to more reactive forms (Na, NaO, and NaO2) [Rodriguez et al, 1986]. On the other hand, NaOH has been shown to react rapidly with HC1 to form NaC1 [Silver et al, 1984a].…”