Oxygen isotopes, atmospheric oxidation

The 8 N- and 8 0-values of atmospheric N2O today, range from 6.4 to 7.0%c and 43 to 45.5%c (Sowers 2001). Terrestrial emissions have generally lower 8-values than marine sources. The 8 N and 8 0-values of stratospheric N2O gradually increase with altitude due to preferential photodissociation of the lighter isotopes (Rahn and Wahlen 1997). Oxygen isotope values of atmospheric nitrous oxide exhibit a mass-independent component (Cliff and Thiemens 1997 Clifif et al. 1999), which increases with altitude and distance from the source. The responsible process has not been discovered so far. First isotope measurements of N2O from the Vostok ice core by Sowers (2001) indicate large and 0 variations with time (8 N from 10 to 25%c and 8 0 from 30 to 50%c), which have been interpreted to result from in situ N2O production via nitrification. 

Clayton RN, Goldsmith JR, Karel KJ, Mayeda TK, Newton RP (1975) Limits on the effect of pressure in isotopic fractionation. Geochim Cosmochim Acta 39 1197-1201 Clayton RN, Onuma N, Grossman C, Mayeda TK (1977) Distribution of the presolar component in Allende and other carbonaceous chondrites. Earth Planet Sd Lett 34 209-224 Clayton RN, Goldsmith JR, Mayeda TK (1989) Oxygen isotope fractionation in quartz, albite, anorthite and caldte. Geochim Cosmochim Acta 53 725-733 Cliff SS, Thiemens MH (1997) The 0/ 0 and 0/ 0 ratios in atmospheric nitrous oxide a mass independent anomaly. Science 278 1774-1776 Cliff SS, Brenninkmeijer CAM, Thiemens MH (1999) First measurement of the 0/ 0 and ratios in stratospheric nitrous oxide a mass-independent anomaly. J Geophys Res 104 16171-16175... 

Stein LY, Yung YL (2003) Production, isotopic composition, and atmospheric fate of biologically produced nitrous oxide. Ann Rev Earth Planet Sci 31 329-356 Stem LA, Chamberlain CP, Reynolds RC, Johnson CD (1997) Oxygen isotope evidence of climate change from pedogenic clay minerals in the Himalayan molasse. Geochim Cosmochim Acta 61 731-744... 

Oxygen Isotopic Study of the Oxidation of S02 by H202 in the Atmosphere... 

Considerable interest has been shown in the possibility of using oxygen isotopy to elucidate the role of H2O2 in the oxidation of SO2 to sulfates in the atmosphere (1). Oxygen isotopic studies are useful in distinguishing between... 

J. Kaiser, T. Rockmann, C.A.M. Brerininkmeijer, Contribution of mass-dependent fractionation to the oxygen isotope anomaly of atmospheric nitrous oxide, /. Geophys. Res.-Atmos. 109 (D3) (2004), D03305. 

The causes of the anomalies of sulfate and other oxygen-bearing materials in the atmosphere and in extraterrestrial materials are the topic of active research. Aqueous-phase oxidation of S(IV) causes an MIF in sulfate only if the oxidant has an MIF oxygen isotopic composition (Lee et al., 2001). Hence, the anomalous values of... 

The discovery of the anomalous oxygen isotopic compositions of atmospheric sulfate provides a new means for identifying sulfate of atmospheric origin. Rainwater and aerosols from southern California were found to have A O values in the range of 0%o to -K.5%o (Lee et al., 2001). The average A O of snow sulfate in the Rocky Mountains (Colorado, USA) was - -1.3%o. Sulfate in ice cores, massive sulfate deposits, and Dry Valley soils from various locations also have MIF (Bao et al., 2000 Lee et al., 2001). There appears to be seasonality in the A O of sulfate in precipitation, with higher values in the winter and lower values in the summer, probably due to seasonal changes in climatic elfects that favor aqueous phase S(IV) oxidation in winter relative to summer (Lee and Thiemens, 2001). 

The high iron concentrations are difficult to explain. The stoichiometry of the 02/FeS2 oxidation reaction (Eq. 12.39a) indicates that 3.5 moles of O2 are consumed to produce a mole of Fe. Given the atmospheric O2 solubility of 8.4 mg/kg at 25°C, for example, oxidation of pyrite by O2 can produce a Fe concentration of only 4.2 mg/kg. The low Eh values in the pools make it doubtful that measureable DO is present in any case. Based on the foregoing discussion of sulfur and oxygen isotopes and bacterial oxidation, pyrite oxidation in the pools is probably largely abiotic with ferric iron as the oxidant. Oxidation rates must be slow, given the fact that Fe(III) Fe(II) at these Eh values. 

Baxter, J.E. and M.E. Hobbs Investigation of some physico-chemical aspects of cigarette smoke using oxygen isotopes. CO and COj from atmospheric oxidation Tob. Sci. 11 (1967) 65-71. 

The interstitial air trapped during this process preserves a largely unaltered record of the composition of past atmospheres on time scales as short as decades and as long as several hundred thousand years. Such records have provided critical information about past variations in carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), and the isotopic composition of some of these trace species. In addition, studies of the major elements of air nitrogen, oxygen, and argon, and their isotopic composition, have contributed... 

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