Indoor air quality (IAQ) has a direct impact on our health, as more than half the air we inhale throughout our lifetimes is indoor air. With an increasing trend in dampness in modern buildings due to urban expansion into wetland environments and increased use of gypsum board in construction, hydrolysis in indoor surface films has been suggested to be an important chemical process in the indoor environment. Several synthetic esters (SEs) found in building materials, electronics, and consumer products may undergo hydrolysis to produce harmful volatile organic compounds (VOCs) to which building occupants may be exposed. In this dissertation, the impact of hydrolysis on indoor air quality is explored by experiments on alkaline hydrolysis kinetics and ventilation, followed by simulations of VOC production from hydrolysis.
Alkaline hydrolysis kinetics of four SEs, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TMPD-MIB), butylparaben (BP), bis (2-ethylhexyl) adipate (DEHA), and butyl benzyl phthalate (BBzP), in bulk solutions are investigated in chapter 2. With concentration decay profiles following pseudo first-order kinetics, the second order-rate constants were determined from measured pH values. The determined rate constants of the aforementioned SEs are compared with those of respective ester categories (e.g., parabens, phthalates), and the steric/polar effects of the ester substituents are discussed in detail. The results of this study contributed to the completion of the indoor chemistry box model GAMMA-CIE which was used for simulation studies in chapter 4.
Room-level ventilation measurements in educational spaces across different US regions (e.g., Northeastern, Southeastern, Western) are presented in chapter 3. In the wake of COVID-19 pandemic, ventilation data on a room-by-room basis were critical in planning a safe reopening in schools and universities. Three major approaches to ventilation measurements are outlined in this chapter: direct flow measurement, controlled release, and passive/in-situ monitoring. The application of these approaches is presented in case studies across various educational institutions, showcasing their advantages and disadvantages. The frequently observed range of 0.5-5.5 ACH in this study is taken into account in simulation conditions in chapter 4.
The predicted indoor generation of VOCs from alkaline hydrolysis of SEs occurring in surface aqueous films is discussed in chapter 4. Simulations were performed using GAMMA-CIE, which considers aqueous hydrolysis kinetics, interphase mass transport, and loss by ventilation. Three different scenarios were studied: (1) installation of PVC flooring on concrete; (2) coating of latex paint on concrete; and (3) uptake of airborne SEs by surface aqueous films. The simulation results suggested that: (1) the rate of hydrolysis of DEHA and DEHP from PVC flooring is not fast enough to generate high concentrations of 2-ethylhexanol observed during episodes of sick building syndrome (SBS); (2) fresh application of latex paint may cause acute exposure to 2,2,4-trimethyl-1,3-pentanediol (TMPD); and (3) hydrolysis of SEs diffused from indoor air is unlikely to produce significant amounts of alcohols associated with SBS.
| Identifer | oai:union.ndltd.org:columbia.edu/oai:academiccommons.columbia.edu:10.7916/w5yf-m841 |
| Date | January 2023 |
| Creators | Maeng, Do Young |
| Source Sets | Columbia University |
| Language | English |
| Detected Language | English |
| Type | Theses |
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