A case study for SOA formation by glyoxal processing in aqueous aerosol in Mexico City

The role of heterogeneous chemistry as a source of Secondary Organic Aerosol (SOA) remains difficult to quantify. SOA is the portion of organic aerosol that forms in the atmosphere as a result of atmospheric transformations. Glyoxal is a building block for SOA formation as a result of heterogeneous chemistry. Measurements from the MCMA-2003 campaign in Mexico City showed that the gas phase glyoxal concentrations were lower by a factor of two to three than predicted by the Master Chemical Mechanism, and that this missing gas phase glyoxal was equivalent to the formation of about 5 μg/m3 of organic aerosol mass over the course of eight hours [Volkamer et al., 2007]. Numerous recent laboratory studies have found that glyoxal can form significant amounts of SOA due to uptake, by both dark (equilibrium) processes and by rapid photochemical uptake to aerosols. These processes have recently been reviewed, and a model framework has been developed based on these laboratory experiments to numerically describe glyoxal processing in aqueous aerosol particles [Ervens and Volkamer, 2010]. Here this model is applied to predict SOA formation due to glyoxal processing in Mexico City. We present an initial case study where the model was constrained with measurements from Mexico City during MCMA 2003 in a first attempt to bridge between laboratory and field observations, and an early assessment of our understanding of the processes and parameters that determine the amount of SOA formed from glyoxal. Volkamer, R., F. San Martini, L. T. Molina, D. Salcedo, J. L. Jimenez, M. J. Molina (2007), A missing sink for gas-phase glyoxal in Mexico City: Formation of secondary organic aerosol, Geophys. Res. Lett., 34, L19807, doi:10.1029/2007GL030752. Ervens, B. and R. Volkamer (2010), Glyoxal processing by aerosol multiphase chemistry: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles, Atmos. Chem. Phys., 10, 8219-8244, doi:10.5194/acp-10-8219-2010