Atmospheric Methyl Ethyl Ketone (MEK): Global Budget and Source Attribution

Methyl ethyl ketone (MEK) is one of the most abundant ketones in the atmosphere.  MEK can be emitted directly into the atmosphere from both anthropogenic and natural sources, and it is also formed during the gas-phase oxidation of volatile organic compounds (VOCs). MEK is lost via reaction with OH, photolysis and deposition to the surface.  Though it has been observed across a wide range of atmospheric environments, MEK has received little attention, particularly in a global sense. Similar to the other atmospheric ketones, the photolysis of MEK may represent a source of HO_x (OH + HO₂) radicals in the upper troposphere. The degradation of MEK also leads to the atmospheric formation of acetaldehyde and formaldehyde.

Many uncertainties remain regarding the global distribution of MEK. Simulation of MEK is a challenge because of the complex VOC sources and chemistry.  We use the GEOS-Chem 3-D CTM (version 10-01, www.geos-chem.org) to investigate spatial distribution, seasonality, and relative importance of the various sources of MEK represented in the model. GEOS-Chem incorporates direct emissions of MEK from anthropogenic and pyrogenic sources, but not currently from the terrestrial biosphere.  Primary emitted species that contribute to MEK formation in the model are isoprene and >C₃ alkanes.  We evaluate the simulation against a suite of aircraft and surface observations.