Abstract
The abundance variations of near surface atmospheric CO2 isotopologues (primarily 16O12C16O, 16O13C16O, 17O12C16O, and 18O12C16O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, and stratospheric photochemistry. Oxygen isotopes, in particular, are affected by the carbon and water cycles. Being a useful tracer that directly probes governing processes in CO2 biogeochemical cycles, Δ17O (=ln(1 + δ17O) − 0.516 × ln(1 + δ18O)) provides an alternative constraint on the strengths of the associated cycles involving CO2. Here, we analyze Δ17O data from four places (Taipei, Taiwan; South China Sea; La Jolla, United States; Jerusalem, Israel) in the northern hemisphere (with a total of 455 measurements) and find a rather narrow range (0.326 ± 0.005‰). A conservative estimate places a lower limit of 345 ± 70 PgC year−1 on the cycling flux between the terrestrial biosphere and atmosphere and infers a residence time of CO2 of 1.9 ± 0.3 years (upper limit) in the atmosphere. A Monte Carlo simulation that takes various plant uptake scenarios into account yields a terrestrial gross primary productivity of 120 ± 30 PgC year−1 and soil invasion of 110 ± 30 PgC year−1, providing a quantitative assessment utilizing the oxygen isotope anomaly for quantifying CO2 cycling.
Highlights
The net growth rate and level of CO2 in the atmosphere represents a dynamic balance between anthropogenic activities and natural sources and sinks[1]
We show that the terrestrial flux can be quantified using the Δ17O values of CO2, where
Equilibrium processes are the major controllers in oxygen isotope dynamics; we show below in the Box model section that kinetic fractionations are insignificant
Summary
In addition to using data available in the literature from Jerusalem[11], La Jolla[12], and western Pacific regions[10], we have continuously collected air for isotopic analysis of CO2 in three locations: (1) Academia Sinica campus (abbreviated AS; 121°36′51′′ E, 25°02′27′′ N; ~10 m above ground level or 60 m above sea level) in Taipei, Taiwan and (2) the campus of National Taiwan University (NTU; 121°32′21′′ E, 25°00′53′′ N; ~10 m above ground level or 20 m above sea level; ~10 km southwest of Academia Sinica). To check the reported Δ17O values in the eastern Pacific[12], we have collected and analyzed CO2 from Los Angeles, California at a latitude slightly higher than La Jolla, along the coast on Palos Verdes peninsula (118°10.9′ W, 33° 44.7′ N; PVD). Air from western Pacific regions for isotope analysis was collected in pre-conditioned 1-liter Pyrex bottles, achieved by passing dry, high purity nitrogen through the bottles overnight. The sampling bottles used for concentration (~350-ml bottle) and isotope (1-liter) analyses were connected in series. Carbon dioxide was separated from the air samples cryogenically and measured, following the method described in Newman et al.[38]. The CO2-O2 oxygen isotope exchange method developed previously[36,37] was used to measure the Δ17O of CO2 samples. The analytical precision obtained for a single measurement of the Δ17O value of CO2 is better than 0.01‰ (1-σ standard deviation)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
