ChemInform Abstract: OXYGEN‐18 EXCHANGE STUDIES OF AQUA AND OXO IONS

Laboratory oxygen isotopic study of sulfur (IV) oxidation: Origin of the mass‐independent oxygen isotopic anomaly in atmospheric sulfates and sulfate mineral deposits on Earth

“…SO3 exhibits a radically different behavior with regard to the related system, NO2 + H20, which is known to rapidly exchange oxygen isotopes [Gamsjager and Murmann, 1983]. This finding suggests that since the OH bond is broken in the transition state H2SO4 #, sulfuric acid is irreversibly formed.…”

Planetesimal sulfate and aqueous alteration in CM and CI carbonaceous chondrites

“…It is well established that sulfate, even in aqueous ionic form, is kinetically inhibited from oxygen isotope exchange with water unless temperature significantly exceed 100°C or the pH falls below a value of 2 (Gamsjager and Murmann, 1983;Van Stempvoort and Krouse, 1994). This is a significant difference in the behavior of sulfate relative to carbonate, because it means that the oxygen isotopic composition of sulfate will be preserved even if the sulfate minerals are dissolved, the sulfate ions are mobilized in aqueous phase, and reprecipitated as other sulfate minerals.…”

“…Sulfate is likely to have formed by oxidation reactions of sulfides in the presence of water, and once formed, the sulfate ion is slow to exchange oxygen with water and other oxygen-bearing species (Gamsjager and Murmann, 1983). The important distinction here between sulfate minerals and other oxygen-bearing species such as carbonate, is that they do not readily exchange oxygen with water at low to neutral pH and low temperature, even when this water causes the sulfate minerals to dissolve and reprecipitate.…”

Sulfate: A time capsule for Earth's O2, O3, and H2O

“…the Atacama Desert and Antarctica Dry Valleys (Bao and Gu, 2004;Michalski et al, 2004;Kounaves et al, 2010), and they are no older than Miocene. BrO 4 − (perbromate) may also be non-labile in terms of oxygen exchange with water at surface conditions (Gamsjäger and Murmann, 1983), but their natural occurrence is unknown. PO 4 3− does form highly insoluble minerals and chemical deposition of phosphorites can be dated back to the Paleoproterozoic Era (Holland, 2005).…”

“…This means that once formed, these oxyanions do not exchange their oxygen with ambient water oxygen under surface conditions. The first systematic study on oxyanionwater exchange was conducted by Hall and Alexander (1940) and the researches using 18 O to determine the rate of aqua-or oxo-ions exchange with water have been thoroughly reviewed by Gamsjäger and Murmann (1983). Sulfate (SO 4 2− ) is a tetrahedral polyatomic ion with a central sulfur atom surrounded by four equivalent oxygen atoms.…”