Atmospheric lifetimes of most organic micropollutants are poorly constrained. In this research project we are using a combination of field observations and laboratory measurements to measure lifetimes of several organic micropollutants in the atmsophere.
In the field, we are measuring the variability in concentrations of organic pollutants and applying the Junge variability-lifetime relationship. The Junge relationship is an empirical relationship between lifetime in the atmosphere and spatial or temporal variability in concentrations measured at remote locations. Conceptually, the Junge relationship is a consequence of incomplete mixing of gases in the global atmosphere. Gases with very long lifetimes approach a homogenous distribution, and thus concentrations of such gases measured at remote locations show very little variability. Gases with shorter lifetimes are not as homogeneously distributed and arrive at remote locations as a result of specific, transient transport events. Therefore the variability in atmospheric concentrations of gases with shorter lifetimes measured at remote locations will be greater than variability of gases with longer lifetimes.
The Junge relationship must be calibrated with observations of substances with known atmospheric lifetimes that have similar sources and sinks as the pollutants of interest. We are conducting new laboratory measurements of degradation rates of organic micropollutants by the hydroxyl radical in the gas phase for a set of chemicals that we will use to calibrate the Junge relationship.