Organic species in the atmosphere are typically present in two phases; gas and aerosol. Some of these organic species are in equilibrium between gas and aerosol phase depending on several factors, hence the name semi-volatile organic compounds (SVOC). These factors include temperature, concentration and chemical form. A few examples are hydrocarbons, aromatics, pesticides and oxygenated aldehydes.
Models to determine the phase distribution of organic species in the atmosphere are at best an approximation of their true phase distribution. The phase distribution of SVOCs is used to determine the fate of SVOCs and their transport pathways in the atmosphere.
Recent developments with XAD coated annular denuders now make it possible to isolate, separate and analyze the gas phase SVOCs and condensed phase organic compounds. This new measurement technology can provide the true phase distribution of SVOCs and provide data to model the fate and transport mechanisms of these important pollutants.