Measurement of Carbon Suboxide (C3O2) with PTR-TOF-MS ? Atmospheric Sources and Sinks

KEßEL, STEPHAN; AULD, JANEEN ; CROWLEY, J. N.; HOROWITZ, ABRAHAM; SANDER, ROLF; MARIA EUGENIA TUCCERI; VERES, PATRICK R.; WILLIAMS, JONATHAN

Obergurgl

Conferencia; 6th. International Conference on Proton Transfer Reaction Massa Spectrometry and its Applications. Obergurgl, Austria. 3-8 Febrero de 2013.; 2013

There is a large volume of published studies describing the role of carbon dioxide and carbon monoxide in the atmosphere. The aim of this work was to analyze both source and sink terms of another carbon oxide, called carbon suboxide (C3O2), whose atmospheric relevance is yet relatively unknown. Therefore we started our studies by developing a simple method to synthesise C3O2 from malonic acid and phosphorous pentoxide. Afterwards a calibrated detection method was needed to identify and quantify C3O2 in the atmosphere. We used a proton transfer reaction time of flight mass spectrometer (PTR-TOF-MS) to monitor online in a tropical green house andambient air in Mainz, and offline a volcanic air sample from Stromboli (Italy). Only the ambient air measurement in Mainz showed evidence of C3O2 in the atmosphere. First looks in biomass fire experiments show evidence of C3O2 and will be evaluated soon. Furthermore we studied differentpossibilities for C3O2 losses in the atmosphere. To describe the behavior of C3O2 on aqueous surfaces the Henry-constant (kH = 1.56 ± 0.01 M atm -1 at pH = 6) and hydrolysis constant (kHyd = 0.039 ± 0.002 s-1 at pH = 6) were determined (PTR-TOF-MS). Hence, the lifetime of C3O2 in thepresence of fog and clouds is 7 to 10 days and in the presence of aerosols is 104 years. In addition, the rate constants of C3O2 at room temperature (298±3 K) and 1000 mbar with atmospheric oxidizing agents like ozone (kO3 = (1.5 ± 0.3)∙10-21 cm 3 s-1 molecules-1) and OH radicals (kOH =(2.6 ± 0.5)∙10-12 cm3 s-1 molecules-1) were determined via fourier transform infrared spectrometer (FTIR) measurements. The measured UV-spectrum was used to derive the photolysis rates, in the pressure range 10 mbar to 1000 mbar and zenith angles 10° to 90°, based on model calculations.