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An appraisal of NOx passive sampling

Cambal, Leah K (2015) An appraisal of NOx passive sampling. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Associated with chronic and short-term health effects, the public health consequences of ambient air pollution are considerable. Accurate measurement of air pollutants is critical for assessing exposure to pollutants as well as an essential step in reducing public health impacts through implementation of regulations and emission controls. Passive sampling devices are often used for the regional-scale determination of pollutants when knowledge of hourly fluctuations in concentrations is unnecessary. Often advantageously described as cost-effective and simple to use, passive samplers are increasingly utilized as an alternative to conventional active sampling. However, the accuracy of these descriptions is challenged by the findings of the subsequent research. The overall objective of this research was to assess the ability of a well-known passive sampler to accurately measure concentrations of nitrogen oxides (NOx) in the ambient environment. While the passive measurement of numerous pollutants is heavily studied, literature evaluating the use of passive sampling devices for the measurement of NOx is exceedingly limited. NOx is a generic term for a group of highly reactive gases composed of oxygen and nitrogen but most commonly NOx is defined as the sum of nitric oxide (NO) and nitrogen dioxide (NO2). The trapping of NOx using filters coated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) for quantitative analysis was investigated using various methods including ambient sampling, electronic absorption spectroscopy, mass spectrometry, and electron paramagnetic resonance. A first of its kind air sampling campaign in New Zealand measured ambient NOx concentrations at multiple locations using Ogawa passive samplers. High spatial variability in pollutant concentrations was found across the sampling area but accuracy of the concentrations was questioned. At low ambient NOx concentrations PTIO was found to contribute significantly to the analytical absorbance value. The fraction contributed by PTIO became increasingly difficult to quantitate as the contribution was not uniform across exposed filters. Degradation of PTIO during ambient exposure, evident by the loss of the filter color, was heavily dependent on the sampling environment. Intra- and inter-season variations in the magnitude of degradation are reported. Common limitations of various types of passive samplers are presented as well as challenges currently unaddressed in the literature.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Cambal, Leah Klec55@pitt.eduLEC55
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairPeterson, Jamesjpp16@pitt.eduJPP16
Committee MemberPearce, Lindalip10@pitt.eduLIP10
Committee MemberElliott, Emilyeelliott@pitt.eduEELLIOTT
Committee MemberSharma, Ravirks1946@pitt.eduRKS1946
Date: 29 June 2015
Date Type: Publication
Defense Date: 6 April 2015
Approval Date: 29 June 2015
Submission Date: 4 April 2015
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 138
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Environmental and Occupational Health
Degree: DrPH - Doctor of Public Health
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: air pollution, PTIO, NOx, passive sampling, photocatalyzed degradation
Date Deposited: 29 Jun 2015 16:27
Last Modified: 15 Nov 2016 14:27


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