Atmospheric Measurement Techniques

Abstract. This paper presents a theoretical and experimen-tal investigation of thermodenuders that addresses two con-troversial issues: (1) equilibration time scales and (2) the need for an activated carbon (AC) denuder in the cooling sec-tion. We describe a plug flow model for transport phenom-ena in a TD, which can be used to simulate the rate of vapor build-up in the gas phase and the corresponding change in particle size distribution. Model simulations were found to have excellent agreement with experiments performed with pure and mixed dicarboxylic acid aerosols. Both simula-tions and experiments showed that the aerosols approached equilibrium within reasonable residence times (15 s–30 s) for aerosol concentrations and size distributions typical for lab-oratory measurements, and that volatility studies at suffi-ciently high aerosol loadings, therefore, need not resort t