Faculty of Graduate Studies
Graduate Programme in Chemistry
ORAL EXAMINATION PROSPECTUS
Christine Facca
A Candidate for the Degreee of
Master of Science
Title of Thesis:
Method Development of a Denuder Based Technique for the Determination of the Partitioning of Nitrophenols
August 30, 2013 @ 9:30 am – 10:15 am
317 Petrie Science and Engineering Bldg.
York University
ABSTRACT
The formation of secondary organic matter (SOM), from the photooxidation of aromatic volatile organic compounds (VOCs) is currently quite poorly understood. One class of these secondary organic species are nitrophenols, which are toxic, semi-volatile compounds formed in the atmosphere from the hydroxyl (HO) radical initiated photooxidation of aromatic hydrocarbons, such as toluene, benzene and xylene. Due to their semi-volatile nature, these nitrophenols can exist in the atmosphere in both the gas phase and in particulate matter (PM), which makes understanding the partitioning of these nitrophenols important in order to gain a better understanding of the formation, yields and processing of SOM. In recent years, methods have been developed for the collection of nitrophenols using high volume air sampling, employing uncoated quartz fibre filters for PM collection and XAD-4TM coated quartz fibre filters for PM and gas phase collection (Busca, 2010; Moukhtar et al., 2011; Saccon et al., 2013). Results from these high volume, filter-based techniques tend to be biased due to sampling artifacts, therefore they do not necessarily give a completely accurate depiction of the partitioning of these nitrophenols.
In this work, a method has been developed and tested using the IOGAPS (Integrated Organic Gas and Particle Sampler) system, which employs an eight channel annular diffusion denuder and both uncoated and XAD 4TM coated quartz fibre filters, to determine separate concentration measurements for both gas phase and PM for a group of five nitrophenols found in the atmosphere. From atmospheric measurements made over the course of a year at York University, these nitrophenols were found to exist predominately in the gas phase, with their partitioning between the two phases showing only slight dependences on ambient temperature. Comparison of the results obtained from this denuder-filter based technique to both high volume and low volume filter based techniques was performed, and all three methods were found to give similar results, although there was some evidence suggesting that the denuder measurements slightly overestimate the gas phase concentrations. This work was able to gain significant insight into the performance of denuders and low volume uncoated and XAD 4TM coated quartz fibre filters.