The desire to characterize the trace gas composition and chemical reactivity of the troposphere has stimulated the development of various instrumental methods for the analysis of atmospheric gases at low part-per-billion and part-per-trillion concentrations. In order to assess the quantitative agreement between independent analysis methods, the atmospheric chemistry community has promoted the use of formal intercomparisons. The principal investigator of this award has developed a portable dynamic dilution system for the preparation of synthetic gas mixtures containing known pptv amounts of various sulfur gases. This system was recently employed successfully in an intercomparison focused on sulfur dioxide. An important step in extending the use of this system to non-sulfur compounds is the development of an enhanced measurement capability for testing and monitoring the different test gas streams prepared by the modified gas delivery system. This award is to develop such a capability based on an atmospheric pressure ionization/time-of-flight mass spectrometer (API-TOFMS). The API-TOFMS will provide rapid response time for simultaneous real-time monitoring of several analytes and relative design simplicity and robustness for dependable field operation. The instrument will extend the use of the gas dilution system to trace atmospheric compounds such as nitrogen gases, halogenated gases, aldehydes and ketones, and biogenic hydrocarbons. It will also contribute to the education and training of young scientists related to the importance of quality assurance for trace species measurements.
