Use of Isotope Effects to Understand the Present and Past of the Atmosphere and Climate and Track the Origin of Life

Mass‐independent isotope effect is a new type of isotopic chemistry that does not follow the traditional isotope fractionation rule. It has been widely used in understanding the origin and evolutions of our solar system, Earth, Mars, life, and modern Earth's atmospheric and environmental physics and chemistry. This Minireview presents the history and most recent advances on this isotope effect, from quantum level understanding to its application in nature.

Abstract

Stable isotope ratio measurements have been used as a measure of a wide variety of processes, including solar system evolution, geological formational temperatures, tracking of atmospheric gas and aerosol chemical transformation, and is the only means by which past global temperatures may be determined over long time scales. Conventionally, isotope effects derive from differences of isotopically substituted molecules in isotope vibrational energy, bond strength, velocity, gravity, and evaporation/condensation. The variations in isotope ratio, such as ¹⁸O/¹⁶O (δ¹⁸O) and ¹⁷O/¹⁶O (δ¹⁷O) are dependent upon mass differences with δ¹⁷O/δ¹⁸O=0.5, due to the relative mass differences (1 amu vs. 2 amu). Relations that do not follow this are termed mass independent and are the focus of this Minireview. In chemical reactions such as ozone formation, a δ¹⁷O/δ¹⁸O=1 is observed. Physical chemical models capture most parameters but differ in basic approach and are reviewed. The mass independent effect is observed in atmospheric species and used to track their chemistry at the modern and ancient Earth, Mars, and the early solar system (meteorites).

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