Stable history for OH radical

The hydroxyl radical is the main atmospheric component that oxidizes pollutants, so pinpointing its activity is crucial to understanding how the atmosphere cleanses itself. But because of its short lifetime in the atmosphere, measuring OH concentration wasn't possible until the 1990s. Now, the first long-term measurements of hydroxyl radical concentration in the troposphere have been reported by Franz Rohrer of Germany's Jülich Research Center and Harald Berresheim of the German National Meteorological Service (Nature 2006, 442, 184). By measuring atmospheric OH concentration in southern Germany over a period of five years, they find that 99% of the fluctuation in OH concentration can be accounted for by solar radiation; the two variables are related in a strong linear correlation. The researchers say the findings are surprising because the surrounding meteorological conditions and atmospheric chemical composition ranged widely over the same period. Although its interactions with pollutants aren't well-understood, the hydroxyl radical's lack of response to changes in pollution suggests that it is a limited commodity that may be overwhelmed.