Comparison of ¹⁴CO₂, CO, and SF₆ as tracers for recently added fossil fuel CO₂ in the atmosphere and implications for biological CO₂ exchange

Abstract

[1] We use the nearly ideal tracer 14 CO 2 to estimate the fossil fuel CO 2 enhancement in boundary layer air at two sites in New England and Colorado. Improved D 14 C measurement precision of 1.6-2.6% provides fossil fuel CO 2 detection capability of 0.8-1.5 ppm. Using the indirect tracers CO and SF 6 , we obtain two additional independent estimates of the fossil fuel CO 2 component, and we assess the biases in these methods with respect to the 14 CO 2 -based estimates. The SF 6 -based estimates vary considerably from the 14 CO 2 -based estimates, and are at times implausibly large. The CO-based estimates are less variable, but show seasonally coherent biases with respect to the 14 CO 2 method.

Regional Δ14C patterns and fossil fuel derived CO2 distribution in the Beijing area using annual plants

“…Using flask measurements of 14 CO 2 , CO and SF 6 , Turnbull found that 14 CO 2 was the most appropriate of the three tracers, and found that 1 ppm of CO 2 added from fossil fuels caused a depletion of Δ 14 C by approximately 2.8‰ [13]. Another common sampling method is to use NaOH to absorb atmospheric CO 2 , but this method is more complicated and it can be difficult to collect CO 2 samples from a wide area [22] at the same time.…”

“…It showed an overall increasing trend that became more rapid during the last 5 years of research, but the extent to which this is caused by fossil fuel emissions could not be determined. Atmospheric 14 CO 2 is considered to be one of the most sensitive tracers for monitoring fossil fuel derived CO 2 [13].…”

Atmospheric Fossil Fuel CO2 Measurement Using a Field Unit in a Central European City During the Winter of 2008/09

“…There are more complex approaches described in the literature (Turnbull et al 2006) where they do not neglect the 14 C/C ratio difference between regional biogenic CO 2 and the mean background CO 2 . However, due to the large heterogeneity of the biosphere, the mean 14 C/C ratio of the regional biogenic component is rather difficult to measure and reliable estimates for this required parameter were not available for the Debrecen region in the studied term.…”

“…Adding fossil fuel CO 2 to the atmosphere, therefore, leads not only to an increase in the CO 2 content of the atmosphere, but also to a decrease in the 14 C/ 12 C ratio in atmospheric CO 2 (Suess 1955). From a 14 CO 2 measurement at a polluted sampling site, for example, near the ground level on the continent, we can directly calculate the regional fossil fuel CO 2 surplus (recently added fossil fuel CO 2 amount in air) if the undisturbed background 14 CO 2 level is known (Levin et al 2003;Turnbull et al 2006;Riley et al 2008). …”

“…CO 2 from burning of fossil fuels, due to their long storage time of several hundred million years, is essentially free of 14 C. 14 C observations in atmospheric CO 2 has been explored as an excellent tracer for recently added fossil fuel CO 2 in the atmosphere on the regional (Levin et al 1980(Levin et al , 1989(Levin et al , 2003Levin and Kromer 2004;Turnbull et al 2006), the continental (Tans et al 1979;de Jong and Mook 1982;Hsueh et al 2007;Kuc et al 2007), and also on the global scale (Stuiver and Quay 1981;Levin and Hesshaimer 2000). Adding fossil fuel CO 2 to the atmosphere, therefore, leads not only to an increase in the CO 2 content of the atmosphere, but also to a decrease in the 14 C/ 12 C ratio in atmospheric CO 2 (Suess 1955).…”