Atmospheric chemistry, sources and sinks of carbon suboxide, C₃O₂

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 D(2.6±0.5)X10^-12 cm³ molecule^{-1 s-1} at 295K (independent of pressure between ∼25 and 1000 mbar) and k_O3 1.5 10^-21cm³ molecule^-1-1 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.