Use of isotope effects to understand the present and past of the atmosphere and climate and track the origin of life

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 review. 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). The volcano, biomass burning, and oxidation histories of the Earth is stored in the ice core sulfate record and may be followed to more than 100,000 years. Photolytic reactions of sulfur and 4 sulfur isotope measurements in Earth's oldest rocks provide a quantitative way to observe the rise of oxygen on Earth starting at 3.8 until 2.3 billion years ago for deeper insight into the origins and evolution of our planet and life. Present day atmospheric sulfur isotope measurements (and with inclusion of radioactive 35S) have aided in understanding atmospheric gas/aerosol chemical transformation, physical transport (horizontally from local regions to equatorial‐polar and vertically from Earth's surface to Mt. Everest and the stratosphere), fundamental isotope effects, and relevant planetary processes that might have occurred since the early Earth.

from A via a.sfakia on Inoreader http://bit.ly/2FmxCFt