Abundance of mass 47 CO2 in urban air, car exhaust, and human breath

Changes in mixing ratio and isotopic composition of CO2 in urban air from the Los Angeles basin, California, between 1972 and 2003

“…The estimated d 13 C values of CO 2 produced by natural gas combustion and human breath exhalation were À40.2 ± 0.5% and À20.9 ± 0.4%, respectively; the d 18 O of CO 2 from natural gas combustion and human exhalation were À21.3 ± 0.4% and À5.2 ± 0.3%, respectively. Although this d 18 O value for human breath is higher than that reported for Paris, France, by Widory and Javoy [2003] (À24.5%), it is similar to that reported by Epstein and Zeiri [1988] (À18.7 -À23.5%) and Affek and Eiler [2006] (À22.3 ± 0.2%) for subjects in the San Gabriel valley and probably reflects a larger proportion of C 4 plants in the Californian diet relative to that in France. Possible relationships of these potential sources of CO 2 to the trends displayed by our analyses of Pasadena air are discussed below.…”

“…6% for 1972-1973 and À13.9% for 2002 -2003) are similar to average values observed for plant respiration, $À14% [e.g., Farquhar et al, 1993aFarquhar et al, , 1993bFlanagan et al, 1997]. The 1972The -1973 value is similar to and the 2002 -2003 value more enriched than the À17% estimated for soil respiration in Pasadena [Affek and Eiler, 2006]. Given the significant uncertainties in the d 18 O values of CO 2 generated by burning of various fossil fuels and the effects of biological activity, we have not attempted to model the change in the oxygen isotope composition of the polluted end-member through time, and simply note that there has not been a significant change.…”

“…However, Affek and Eiler [2006] found much more 18 O-enriched oxygen in CO 2 emitted by an automobile burning gasoline (À11.0 ± 0.2%), even more enriched in d 18 O than the intercept for our gasoline exhaust measurements (À14.2 ± 0.3%; Figure 5). They attributed this elevated d 18 O (i.e., relative to atmospheric O 2 ) to exchange equilibration between CO 2 and H 2 O (both produced in the combustion process) in the exhaust tail pipe [Affek and Eiler, 2006]. The intercept we obtained for CO 2 generated by burning of natural gas (À21.3 ± 0.4%; Figure 5) also differs from atmospheric O 2 , but it is more depleted in 18 O than atmospheric O 2 .…”

“…The d 18 O of CO 2 produced by combustion is generally assumed to be the same as that of the atmospheric O 2 that is consumed in the combustion process [Ciais and Meijer, 1998;Kroopnick and Craig, 1972;Pataki et al, 2003;Zimnoch et al, 2004;Zondervan and Meijer, 1996]. However, Affek and Eiler [2006] found much more 18 O-enriched oxygen in CO 2 emitted by an automobile burning gasoline (À11.0 ± 0.2%), even more enriched in d 18 O than the intercept for our gasoline exhaust measurements (À14.2 ± 0.3%; Figure 5). They attributed this elevated d 18 O (i.e., relative to atmospheric O 2 ) to exchange equilibration between CO 2 and H 2 O (both produced in the combustion process) in the exhaust tail pipe [Affek and Eiler, 2006].…”

Temperatures of aqueous alteration and evidence for methane generation on the parent bodies of the CM chondrites

“…The extent of 13 C-18 O clumping in a carbonate mineral is determined through the measurements of anomalous enrichment of mass 47 CO 2 (mainly 13 C 18 O 16 O) in the CO 2 derived from phosphoric acid digestion of that mineral Eiler and Schauble, 2004;Affek and Eiler, 2006).…”