Optical instrumentation to understand the chemistry of the atmospheric chlorine budget

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A complete understanding of oxidation chemistry is essential to our ability to manage environmental issues such as smog formation, climate change, and contaminant long-range transport. Chlorine atoms have recently been recognized as important to atmospheric oxidation globally. However, our understanding of the chemistry of chlorine atom formation is inadequate. By undertaking a complete study of the important species hypothesized to be involved in chlorine atom formation, we can better understand and predict the importance of chemical formation processes. The proposed equipment for this research is state-of-the-science optical instrumentation for in situ measurements of key species hydrochloric acid, nitrogen oxides, and ozone. Hydrochloric acid will be measured using a cavity ring-down spectroscopy and will be the first instrument of its kind applied to atmospheric measurements in Canada. Nitrogen oxides and ozone will be measured using chemiluminescence and absorption, respectively. The requested instrumentation will be used along with existing infrastructure to provide the complete set of measurements required to study this chemistry. Initially, these instruments will be deployed simultaneously in the polluted marine boundary layer of St. John’s, Newfoundland and Labrador at an existing urban sampling site. This location provides the ideal location for study of these processes, as it is rich in chloride sources (including sea spray and road salt), and the anthropogenic pollution known to activate unreactive chloride into reactive chlorine. The proposed measurements will be the first to close the chlorine budget comprehensively, by including measurements of particulate chloride in all particle sizes, along with gas-phase hydrochloric acid. Follow-up field work in other locations and laboratory flow tube studies will allow us to fully address the chemistry of this important system to scale-up for inclusion in global models. Without the requested equipment, the chemistry of this important system that is central to my research program cannot be studied. This work is expected to attract highly qualified personnel and to contribute to training. All personnel involved in this work will gain highly marketable skills in field work, instrument maintenance, instrumental analysis, and analysis of large data sets.