Thesis
Measuring nitrogen trichloride in an indoor swimming pool with proton-transfer-reaction mass spectrometry
Washington State University
Master of Science (MS), Washington State University
05/2020
DOI:
https://doi.org/10.7273/000004109
Handle:
https://hdl.handle.net/2376/124894
Abstract
Nitrogen trichloride (NCl3) in indoor pool air can cause acute ocular, nasal, and respiratory discomfort. Long term effects of NCl3 exposure is still being studied, and bronchial hypersensitivity is suspected, which is of concern for elite swimmers and lifeguards. Most measurement methods use grab sampling and lab analysis that limits sample number and temporal analysis. Proton transfer reaction mass spectrometry (PTR-MS) is an in-situ measuring technique that employs soft chemical ionization of target compounds by a proton transfer reaction, the charged compounds are then measured using mass spectrometry. The PTR-MS was calibrated for VOCs, NCl3, and the other chloramines (NH2Cl and NHCl2) using gas standards, permeation tubes, and liquid volatilization and dynamic dilution with zero-air. Gas standard calibrations were used to compare the accuracy of the dynamic dilution system for VOCs, and the tests concluded that the dynamic dilution system was successful in calibrating the PTR-MS. Volatilized NCl3 was measured at the WSU Rec Center indoor pool PTR-MS for 13 days in September 2019. The PTR-MS sensitivity to NCl3 was 0.21 + 0.03 ncps ppbv-1. Due to the low sensitivity, a water vapor dependence was difficult to obtain. The proton affinity (PA) of NCl3 (721.5 kJ mol-1) is close enough to that of water vapor (697 kJ mol-1) that the protonated H+(NCl3) ion measured by the mass spectrometer is deprotonated by water vapor in the drift tube. Formaldehyde and H2S were used as model compounds due to the similar PA values. Using these compounds, a NCl3 sensitivity for pool humidity (~45%) was determined at 0.064 + 0.059 ncps ppbv-1. The average NCl3 concentration of the pool, 114 + 33 ppbv, was about 10 times higher than the next highest concentration of the compounds measured that came from acetaldehyde. From the diel variation of NCl3 it is shown that the concentration increases with the pool occupancy, reaching its lowest concentration before the pool opened in the morning; and the maximum concentration near the end of the pool operating hours when the occupancy is highest.
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Details
- Title
- Measuring nitrogen trichloride in an indoor swimming pool with proton-transfer-reaction mass spectrometry
- Creators
- Brian Grimm
- Contributors
- Bertram Thomas Jobson (Advisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890785601842
- Language
- English
- Resource Type
- Thesis