Articles | Volume 17, issue 14
Atmos. Chem. Phys., 17, 8789–8804, 2017

Special issue: The Modular Earth Submodel System (MESSy) (ACP/GMD inter-journal...

Atmos. Chem. Phys., 17, 8789–8804, 2017

Research article 20 Jul 2017

Research article | 20 Jul 2017

Atmospheric chemistry, sources and sinks of carbon suboxide, C3O2

Stephan Keßel1, David Cabrera-Perez1, Abraham Horowitz1, Patrick R. Veres1,a,b, Rolf Sander1, Domenico Taraborrelli1,c, Maria Tucceri1, John N. Crowley1, Andrea Pozzer1, Christof Stönner1, Luc Vereecken1,c, Jos Lelieveld1, and Jonathan Williams1 Stephan Keßel et al.
  • 1Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, Mainz, Germany
  • anow at: NOAA ESRL Chemical Sciences Division, Boulder, CO, USA
  • bnow at: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  • cnow at: Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich, Jülich, Germany

Abstract. Carbon suboxide, O  =  C  =  C  =  C  =  O, has been detected in ambient air samples and has the potential to be a noxious pollutant and oxidant precursor; however, its lifetime and fate in the atmosphere are largely unknown. In this work, we collect an extensive set of studies on the atmospheric chemistry of C3O2. Rate coefficients for the reactions of C3O2 with OH radicals and ozone were determined as kOH =  (2.6 ± 0.5)  ×  10−12 cm3 molecule−1 s−1 at 295 K (independent of pressure between  ∼  25 and 1000 mbar) and kO3  <  1.5  ×  10−21 cm3 molecule−1 s−1 at 295 K. A theoretical study on the mechanisms of these reactions indicates that the sole products are CO and CO2, as observed experimentally. The UV absorption spectrum and the interaction of C3O2 with water (Henry's law solubility and hydrolysis rate constant) were also investigated, enabling its photodissociation lifetime and hydrolysis rates, respectively, to be assessed.

The role of C3O2 in the atmosphere was examined using in situ measurements, an analysis of the atmospheric sources and sinks and simulation with the EMAC atmospheric chemistry–general circulation model. The results indicate sub-pptv levels at the Earth's surface, up to about 10 pptv in regions with relatively strong sources, e.g. influenced by biomass burning, and a mean lifetime of  ∼  3.2 days. These predictions carry considerable uncertainty, as more measurement data are needed to determine ambient concentrations and constrain the source strengths.

Short summary
In this study we identify an often overlooked stable oxide of carbon, namely carbon suboxide (C3O2), in ambient air. We have made C3O2 and in the laboratory determined its absorption cross section data and the rate of reaction with two important atmospheric oxidants, OH and O3. By incorporating known sources and sinks in a global model we have generated a first global picture of the distribution of this species in the atmosphere.
Final-revised paper