A Method For Measuring The Vapour Pressures Of Pah'S Adsorbed On The Surface Of Soot

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Abstract
A new method is reported that utilizes a low-temperature quartz microbalance in combination with Knudsen cells to obtain adsorption isotherms for substances with very low equilibrium pressures (< 10−5 Pa). The method allows for the first time to measure directly thermodynamic properties of important aerosol/pollutant systems at typical environmental temperatures. Application is demonstrated by an investigation of fluoranthene and pyrene adsorbed on carbon aerosol particles (T = 293.15 K−302.13 K). Both PAHs are unable to form extended multilayers on the surface. Slightly above monolayer coverage the three-dimensional crystalline solid phase is thermodynamically more stable.