AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
A Dynamic Method to Measure Partition Coefficient and Mass Accommodation Coefficient for Gas/Particle Interaction of Phthalates in Indoor Environments
Jianping Cao, CLARA EICHLER, Yaoxing Wu, John Little, Virginia Tech
Abstract Number: 900 Working Group: Indoor Aerosols
Abstract The particle/gas partition coefficient Kp and the mass accommodation coefficient a are two parameters characterizing the gas/particle interaction of semi-volatile organic compounds (SVOCs). Most of the available methods for measuring Kp require equilibrium at the chamber outlet, implying substantial preliminary testing. The need to separate gas- and particle-phase SVOCs also reduces method accuracy. Few studies measuring a for indoor-related SVOCs are available, and they usually ignore the wall loss of SVOCs, resulting in reduced measurement accuracy. To overcome these deficiencies, we developed a dynamic method coupling a laminar flow tube chamber and an SVOC mass transfer model. Using the interaction between gas-phase di-2-ethylhexyl phthalate (DEHP) and (NH4)2SO4 particles (with diameters in the range of 10-600 nm) as an example, experiments were performed to evaluate the effectiveness and accuracy of the dynamic method. For the experimental conditions investigated (temperature = 25 °C and relative humidity < 10%), gas-particle interaction between DEHP and (NH4)2SO4 particles is governed by surface adsorption because (NH4)2SO4 particles are in solid state. In this case, gas-particle partitioning should be characterized by the surface-area-normalized partition coefficient (KpA). KpA and a were measured to be 260 ± 80 m and 0.20 ± 0.05, respectively. Both are consistent with results reported in literature. The method applicability for other SVOC-particle combinations and the improvement of method accuracy require further study.