APRIL 2001: Atmospheric budget of acetone

Monthly mean acetone concentrations in surface air in January and July simulated by the GEOS-CHEM global 3-D model of atmospheric chemistry including an inverse model analysis of sources and sinks. Acetone is of major interest for atmospheric chemistry as a precursor of hydrogen oxide radicals (HO_x) in the upper troposphere and as an agent for conversion of nitrogen oxide radicals (NO_x) to peroxyacetylnitrate (PAN). In this work we used the best available a priori estimates of sources and sinks to constrain a global 3-D simulation of acetone, and then applied atmospheric observations from 14 surface sites and 5 aircraft missions to improve these estimates through an inversion analysis. Matching the high acetone concentrations observed over the South Pacific requires a large photochemical ocean source, while matching the low concentrations observed at European sites in winter-spring and in the Arctic in summer implies a large microbial ocean sink (seawater saturation ratio in the range 0.7-0.85). The seasonal decrease in concentrations observed in Europe from summer to fall argues against a large acetone source from plant decay. Continental observations in the tropics and at northern midlatitudes in summer indicate a large acetone source from terrestrial vegetation, while observations in the northern hemisphere outside summer imply a large source from atmospheric oxidation of isoalkanes (propane, isobutane, isopentane). This work was carried out by Daniel J. Jacob, Brendan D. Field, and Emily Jin. For further details and a quantitative budget of atmospheric acetone see Jacob et al. [2001].