Pore-scale modelling of dynamic interaction between SVOCs and airborne particles with lattice Boltzmann method

Semivolatile organic compounds (SVOCs) can be easily adsorbed on the suspended particulate matter (PM), and the exchange of SVOCs across the air-particle interface is crucial for the determination of their exposure on human. In the present study, an airborne particle with a diameter of 2.5 μm is fully reconstructed and applied to investigate the SVOCs transport mechanism and the adsorption/desorption process. The pore size distribution of the particle is statistically estimated, based on which Knudsen and Fick diffusion mechanisms are considered. The sorption process between the adsorbed SVOCs on the element carbon (EC) and SVOCs in organic matter (OM) is performed with Langmuir-isotherm model. The effective diffusivity in particle is numerically predicted and compared with the existing empirical study. The influences of the equilibrium sorption constant and the volume fraction of organic matter and carbon on the dynamic interaction process are also explored. Results show that the effective diffusivity of the PM particle with low porosity predicted with the present model is much lower than that adopted by the Bruggeman equation. The amount of adsorbed di-2-ethyhexyl phthalate (DEHP) on EC is predominant compared with the gas phase in pores and dissolved phase in PM. The total amount of DEHP transporting from air to the PM particle is highly influenced by the equilibrium sorption constant and the volume fraction of EC. The influence of volume fraction of OM on the total amount of adsorbed DEHP is slight.