UC Riverside

Indoor environmental chambers have been widely used to simulate the Secondary Organic Aerosol (SOA) generation processes in the atmosphere. Experimental data is used to optimize atmospheric models, contribute to scientific predictions, and policy making. However, the measured data, such as the quantified aerosol yield, can be biased due to the interactions between the gas-particle system and chamber walls. Minimizing uncertainties of particle- and vapor-wall deposition corrections thus become critical. This dissertation crystalizes the journey to review and explore the particle-wall interactions and to make responsible corrections in multi-generations of environmental chambers at UCR.Size-dependency of particle wall-loss varies between Teflon environmental chamber designs. The measured particle wall-loss rates in UCR previous-generation dual 90-m3 collapsible chambers were relatively insensitive to particle size with the rates exceeding those reported for some smaller volume chambers. Coagulation-free monodisperse seed injection experiments were performed and the particle wall-loss behaviors were experimentally observed to be dominated by electrostatic effect via charged chamber walls. Particles in the chamber were found to approach chamber-specific charge equilibrium, driven by size-dependent preferential loss of charged particles and bidirectional diffusion charging. The traditional particle wall-loss correction model has been modified into a new system to investigate the significance of particle-particle coagulation and dynamic change of particle wall-loss rates within experiments for previous-generation collapsible chambers. The modified model re-visited particle wall-loss corrections for thousands of historical runs over the past two decades, creating a massive data pool with increased correction accuracy. Dynamic change of particle wall-loss rate was observed within individual experiments. Final particle mass can be over-corrected due to coagulation, dependent on the particle number loadings present in the chamber. Mitigation strategies to minimize the electrostatic impact have been applied on UCR new-generation 120-m3 fixed-volume chamber. Size-dependent particle wall-loss patterns were characterized with monodisperse seed injection experiments with negligible coagulation. The observed trend was found to be more sensitive to particle size and much lower than previous-generation chambers. A three-component particle loss correction model has been developed to account for chamber dilution, particle coagulation and wall-loss. Performance evaluation shows good agreement between the new correction method with the modified traditional method.