Monitoring Gas Concentrations in Pollutant Exposure Systems: Defining Exposure Concentrations

Several reasons have been offered in the recent literature toexplain the disagreement in experimental results on the effectsof SO² on plants. The tacit assumption that each research groupis monitoring exposure concentration in a comparable manneris challenged. For example, in well-stirred chambers exposureconcentrations are identical with outlet concentrations, yetseveral studies have interpreted plant response in terms ofsupply (i.e. inlet) concentrations. Experiments are presentedthat illustrate the extent to which supply concentrations canbe depleted within chambers, and the magnitude of error in assumingsupply to represent exposure concentrations. Definitions forexposure concentration in chamber, wind tunnel, and glasshousesystems are suggested.