An estimation of the <sup>18</sup>O / <sup>16</sup>O ratio of UT/LMS ozone based on artefact CO in air sampled during CARIBIC flights

Abstract

Abstract. An issue of O 3 -driven artefact production of O 3 in the upper troposphere/lowermost stratosphere (UT/LMS) air analysed in the CARIBIC-1 project is being discussed. By confronting the CO mixing and isotope ratios obtained from different analytical instrumentation, we (i) reject natural/artificial sampling and mixing effects as possible culprits of the problem, (ii) ascertain the chemical nature and quantify the strength of the contamination, and (iii) demonstrate successful application of the isotope mass-balance calculations for inferring the isotope composition of the contamination source. The δ 18 O values of the latter indicate that the oxygen is very likely being inherited from O 3 . The δ 13 C values hint at reactions of trace amounts of organics with stratospheric O 3 that could have yielded the artificial CO. While the exact contamination mechanism is not known, it is clear that the issue pertains only to the earlier (first) phase of the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) project. Finally, estimated UT/LMS ozone δ 18 O values are lower than those observed in the stratosphere within the same temperature range, suggesting that higher pressures (240-270 hPa) imply lower isotope fractionation controlling the local δ 18 O(O 3 ) value.

Wildfire smoke in the lower stratosphere identified by in situ CO observations

“…where p is the atmospheric pressure in bar. The coefficients a, b, and c are fit to combined datasets from Röckmann et al (1998), Stevens et al (1980), and Smit et al (1982), are obtained from Gromov (2013), and can be found in Table 2. k minor and k major are the reaction rates of the rare and abundant isotopologues respectively.…”

Lifetimes and decay mechanisms of isotopically substituted ozone above the dissociation threshold: matching quantum and classical dynamics

“…82 It is now well established [4][5][6] that the ozone MIF is not a minor and exotic phenomenon of a limited impact: its effect is photochemically transferred to many oxygen-bearing species including atmospheric CO 2 , O 2 , and water in the early solar system. 6,91,92 There is a wide area of interdisciplinary scientific fields, including atmospheric physics, geo-and cosmochemistry or climate research, 5,[93][94][95][96][97] where the ozone isotope composition, or molecular effects of isotope fractionation, plays a major role. [98][99][100] The state-of-the art of the MIF studies and possible impacts across various branches of science have been described in recent exhaustive reviews by Thiemens and Lin, 5 Thiemens et al, 20 Dauphas and Schauble, 4 and Carlstad and Boering, 6 who have concluded that ''The origin in chemical physics of the large, robustly measured mass-independent enrichments in ozone resulting from the three-body ozone formation reaction remains elusive and represents an intriguing chemical physics puzzle that deserves further study''.…”

“…It is now well established 4–6 that the ozone MIF is not a minor and exotic phenomenon of a limited impact: its effect is photochemically transferred to many oxygen-bearing species including atmospheric CO 2 , O 2 , and water in the early solar system. 6,91,92 There is a wide area of interdisciplinary scientific fields, including atmospheric physics, geo- and cosmochemistry or climate research, 5,93–97 where the ozone isotope composition, or molecular effects of isotope fractionation, plays a major role. 98–100…”