A multiscale method for predicting the long-term emission behaviors of semivolatile organic compounds

Abstract

Characterizing the emission behaviors of the gaseous, particulate, and adsorbed semivolatile organic compounds (SVOCs) in indoor environments is critical for exposure assessments and control strategies. A long-term multiscale model was developed to predict the emission profiles of the SVOC concentrations in different phases with the macroscale model, and the dynamic gas/particle partitioning process via the mesoscale model. The mesoscopic method can fully consider the detailed microstructures of the indoor airborne particles, and the macroscale model considers their residence time. The dynamic SVOC concentration in a particle predicted with the mesoscale model was upscaled to the macroscale model. Results show that the difference of the critical equilibrium times predicted with the simulated and the existing dynamic partitioning model is attributed to the surface area per unit volume of the particle. The critical equilibrium time increases with the partition coefficient, while decreases with the mass transfer coefficient at gas/particle surfaces. If the residence time is far lower than the critical equilibrium time, the difference of the gaseous, particulate and adsorbed SVOC concentrations of low volatility obtained with the present model and the existing models becomes more significant. Parameter sensitivity analyses of the relative deviations of different SVOC phases predicted with the present model and the existing models on several critical model parameters such as the ventilation rate, the residence time, the total suspended mass concentration particles and the partition coefficient, demonstrate the possible large errors that may be introduced.