Atmospheric Effects on the Isotopic Composition of Ozone
The delta values of the isotope composition of atmospheric ozone is ~100‰ (referenced to atmospheric O<sub>2</sub>). Previous photochemical models, which considered the isotope fractionation processes from both formation and photolysis of ozone, predicted δ<sup>49</sup>O<s...
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MDPI AG
2021-12-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/12/12/1673 |
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| author | Mao-Chang Liang Yi-Chun Chen Yi-Qin Gao Xi Zhang Yuk L. Yung |
| author_facet | Mao-Chang Liang Yi-Chun Chen Yi-Qin Gao Xi Zhang Yuk L. Yung |
| author_sort | Mao-Chang Liang |
| collection | DOAJ |
| description | The delta values of the isotope composition of atmospheric ozone is ~100‰ (referenced to atmospheric O<sub>2</sub>). Previous photochemical models, which considered the isotope fractionation processes from both formation and photolysis of ozone, predicted δ<sup>49</sup>O<sub>3</sub> and δ<sup>50</sup>O<sub>3</sub> values, in δ<sup>49</sup>O<sub>3</sub> versus δ<sup>50</sup>O<sub>3</sub> space, that are >10‰ larger than the measurements. We propose that the difference between the model and observations could be explained either by the temperature variation, Chappuis band photolysis, or a combination of the two and examine them. The isotopic fractionation associated with ozone formation increases with temperature. Our model shows that a hypothetical reduction of ~20 K in the nominal temperature profile could reproduce the observations. However, this hypothesis is not consistent with temperatures obtained by in situ measurements and NCEP Reanalysis. Photolysis of O<sub>3</sub> in the Chappuis band causes O<sub>3</sub> to be isotopically depleted, which is supported by laboratory measurements for <sup>18</sup>O<sup>18</sup>O<sup>18</sup>O but not by recent new laboratory data made at several wavelengths for <sup>49</sup>O<sub>3</sub> and <sup>50</sup>O<sub>3</sub>. Cloud reflection can significantly enhance the photolysis rate and affect the spectral distribution of photons, which could influence the isotopic composition of ozone. Sensitivity studies that modify the isotopic composition of ozone by the above two mechanisms are presented. We conclude isotopic fractionation occurring in photolysis in the Chappuis band remains the most plausible solution to the model-observation discrepancy. Implications of our results for using the oxygen isotopic signature for constraining atmospheric chemical processes related to ozone, such as CO<sub>2</sub>, nitrate, and the hydroxyl radical, are discussed. |
| first_indexed | 2024-03-10T04:35:46Z |
| format | Article |
| id | doaj.art-77ca539dfd384ef28a9d04026ef317de |
| institution | Directory Open Access Journal |
| issn | 2073-4433 |
| language | English |
| last_indexed | 2024-03-10T04:35:46Z |
| publishDate | 2021-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj.art-77ca539dfd384ef28a9d04026ef317de2023-11-23T03:47:12ZengMDPI AGAtmosphere2073-44332021-12-011212167310.3390/atmos12121673Atmospheric Effects on the Isotopic Composition of OzoneMao-Chang Liang0Yi-Chun Chen1Yi-Qin Gao2Xi Zhang3Yuk L. Yung4Institute Earth Sciences, Academia Sinica, Taipei 115, TaiwanResearch Center for Environmental Changes, Academia Sinica, Taipei 115, TaiwanCollege of Chemistry and Molecular Engineering, Peking University, Beijing 100871, ChinaDepartment of Earth and Planetary Sciences, University of California, Santa Cruz, CA 92697, USADivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USAThe delta values of the isotope composition of atmospheric ozone is ~100‰ (referenced to atmospheric O<sub>2</sub>). Previous photochemical models, which considered the isotope fractionation processes from both formation and photolysis of ozone, predicted δ<sup>49</sup>O<sub>3</sub> and δ<sup>50</sup>O<sub>3</sub> values, in δ<sup>49</sup>O<sub>3</sub> versus δ<sup>50</sup>O<sub>3</sub> space, that are >10‰ larger than the measurements. We propose that the difference between the model and observations could be explained either by the temperature variation, Chappuis band photolysis, or a combination of the two and examine them. The isotopic fractionation associated with ozone formation increases with temperature. Our model shows that a hypothetical reduction of ~20 K in the nominal temperature profile could reproduce the observations. However, this hypothesis is not consistent with temperatures obtained by in situ measurements and NCEP Reanalysis. Photolysis of O<sub>3</sub> in the Chappuis band causes O<sub>3</sub> to be isotopically depleted, which is supported by laboratory measurements for <sup>18</sup>O<sup>18</sup>O<sup>18</sup>O but not by recent new laboratory data made at several wavelengths for <sup>49</sup>O<sub>3</sub> and <sup>50</sup>O<sub>3</sub>. Cloud reflection can significantly enhance the photolysis rate and affect the spectral distribution of photons, which could influence the isotopic composition of ozone. Sensitivity studies that modify the isotopic composition of ozone by the above two mechanisms are presented. We conclude isotopic fractionation occurring in photolysis in the Chappuis band remains the most plausible solution to the model-observation discrepancy. Implications of our results for using the oxygen isotopic signature for constraining atmospheric chemical processes related to ozone, such as CO<sub>2</sub>, nitrate, and the hydroxyl radical, are discussed.https://www.mdpi.com/2073-4433/12/12/1673ozonemass-independent effectHarley and Huggins bandsChappuis bandphotochemistrypollution chemistry |
| spellingShingle | Mao-Chang Liang Yi-Chun Chen Yi-Qin Gao Xi Zhang Yuk L. Yung Atmospheric Effects on the Isotopic Composition of Ozone Atmosphere ozone mass-independent effect Harley and Huggins bands Chappuis band photochemistry pollution chemistry |
| title | Atmospheric Effects on the Isotopic Composition of Ozone |
| title_full | Atmospheric Effects on the Isotopic Composition of Ozone |
| title_fullStr | Atmospheric Effects on the Isotopic Composition of Ozone |
| title_full_unstemmed | Atmospheric Effects on the Isotopic Composition of Ozone |
| title_short | Atmospheric Effects on the Isotopic Composition of Ozone |
| title_sort | atmospheric effects on the isotopic composition of ozone |
| topic | ozone mass-independent effect Harley and Huggins bands Chappuis band photochemistry pollution chemistry |
| url | https://www.mdpi.com/2073-4433/12/12/1673 |
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