PhD Oral Exam - Azad Bahrami, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Semi-volatile organic compounds (SVOCs) and particulate matter (PM) are considered indoor air pollutants. PM amplifies human exposure to SVOCs through particle-gas partitioning governed by physical intermolecular forces. This plays a critical role in both indoor fate-transport model studies and human inhalation exposure assessment; however, the influence of key indoor parameters such as ventilation rate (residence time), particle size, and competitive adsorption has been poorly documented.

This research addresses existing gaps in the particle-gas partitioning of phthalates, a subgroup of SVOCs, under indoor environmental conditions by using controlled laboratory experiments. The main purpose of this dissertation is to experimentally investigate how ventilation, particle size, and a binary mixture of phthalates affect the distribution of phthalates between their gas and particle phases. Sodium chloride (NaCl) as a model inorganic particle and four phthalates covering a wide range of vapor pressure were selected. A mixing chamber was used to combine particles and phthalates under isolated conditions. Moreover, the results were compared with an existing particle–gas partitioning model (adsorption), and its limitations were highlighted when applied to indoor environments.

Not only do findings enhance the scientific understanding of SVOC partitioning behavior in indoor air, but they also offer new empirical insights that can refine predictive adsorption models. Besides, this study provides new methodological approaches for generating gaseous phthalates (including heavier species), which can be used for future work. Results can be applied to exposure assessment, indoor air quality management, and the design of air remediation strategies, enabling the achievement of a healthier indoor environment through the provision of more realistic data and modeling approaches.