Mechanisms and observations for isotope fractionation of molecular species in planetary atmospheres

Abstract

Chemical and physical processes which may give rise to isotope fractionation of molecular species in the atmospheres of both Earth and other planets are reviewed, along with observations of isotopically substituted molecules in planetary atmospheres. Mechanisms for production of isotope fractionation considered include escape and effect of isotope substitution on equilibrium constants (including those of phase changes), photolysis rates, and chemical reaction rates. The isotopes considered for compounds in

Probing stratospheric transport and chemistry with new balloon and aircraft observations of the meridional and vertical N<sub>2</sub>O isotope distribution

“…3.5). This was demonstrated for the reaction-diffusion system (Kaiser et al, 2002a;Kaye, 1987;Morgan et al, 2004), but is still valid even if advection is included due to the linearity of the corresponding differential equation (Kaiser and Röckmann, 2006 1 ). As noted in most previous publications on stratospheric N 2 O isotopes (e.g., Rahn et al, 1998;Röckmann et al, 2001;Toyoda et al, 2001), the stratospheric measurements clearly fall below the δ−µ relationship defined by the intrinsic isotope effect, which is due to transport and mixing effects.…”

“…However, this calculation does not take into account that transport effects prevent the full intrinsic photochemical isotope fractionation from being expressed in the stratosphere, as Toyoda et al (2004) acknowledge in the subsequent section of their paper. In a simple one-dimensional reaction-diffusion scheme, the effective fractionation constant can be calculated from the intrinsic fractionation constant and the reaction and transport time-scales as follows (Kaye, 1987;Kaiser, 2002;Kaiser et al, 2002a;Brenninkmeijer et al, 2003):…”

A one‐dimensional simulation of the water vapor isotope HDO in the tropical stratosphere

“…•D=-500%0 to -600%0, and at 50 km we expect a action; according to Kaye [1987] this reaction is about 1% slower; …”

Carbon dioxide in the atmosphere: Isotopic exchange with ozone and its use as a tracer in the middle atmosphere

“…0148-0227/97/97JD-00528509.00 [Kaye, 1987]. Hence there remains a fundamental challenge to the physical chemist to explain the isotopic fractionation factors.…”

“…It is now well established both in the atmosphere and in the laboratory that when ozone is formed from O and 02 via the three-body (Chapman) reaction, there is a preference for the formation of heavy ozone. Let [Kaye and Strobel, 1983;Kaye, 1986Kaye, , 1987. Another important aspect of this fractionation is that the enrichments in 170 and 180 are related to each other with a slope of 1 [Thiemens and Heidenreich, 1983] rather than 0.5, a value that is characteristic of equilibrium processes Copyright 1997 by the American Geophysical Union.…”