The oxidation of volatile organic compounds (VOCs) is an important step in the formation of photochemical smog in urban areas, but the rate at which VOCs are oxidized has been difficult to quantify. A reliable way to measure this rate would lead to improved prediction of smoke/fog events.
Volkamer et al. used differential optical absorption spectroscopy (DOAS) to make direct measurements of atmospheric glyoxal concentrations over Mexico City in the spring of 2003. They show that VOC oxidation, of which glyoxal is a product, begins about an hour after sunrise and continues throughout the day. These observations allow a lower limit to be placed on the rate of VOC oxidation and reveal that VOC chemistry is active throughout sunlit hours. On the basis of these results, satellite measurements of glyoxal appear to be feasible, which would support the identification of photochemical hot spots in the atmosphere. -- HJS
Geophys. Res. Lett. 32, 10.1029/2005GL022616 (2005).
