Development of Soft-Ionization for Particulate Organic Detection with the Aerodyne Aerosol Mass Spectrometer

75716S Aerosol particles in the atmosphere have important effects on visibility, acid deposition, climate, and human health. A significant amount of anthropogenic aerosols is generated from energy-related activities, and organic compounds are known to constitute a significant fraction of ambient aerosol mass in many locations. However, there is a lack of are real-time, size-resolved, quantitative instruments for measuring the chemical composition of organic aerosols. This project will develop soft ionization technology for a recently-developed aerosol mass spectrometer that will enable better identification of organic species in ambient aerosol particles. (Soft ionization causes less fragmentation of molecular species than the currently used electron impact ionization.) During Phase I, two different soft ionization techniques were successfully demonstrated, Vacuum Ultra Violet (VUV) photoionization and Li+ ion attachment. A custom lamp to produce VUV photons was designed and coupled to the aerosol mass spectrometer. Selective detection of organic test aerosols was accomplished. A Li+ ion source was integrated into the aerosol mass spectrometer and successfully used to detect organic particles. Designs for prototype soft ionization modules that couple to the aerosol mass spectrometer were completed. Phase II will include further development of both the VUV photoionization and Li+ attachment modules. Improvements to the VUV photoionization module will include increasing the photon flux, designing a more suitable power supply, and using different gases for the lamp fill. For the Li+ attachment module, sources with more flux and fewer impurities will be investigated. The soft ionization modules will be deployed in the field on aerosol mass spectrometer instruments. Data analysis software to classify organic particles will also be developed. Commercial Applications and Other Benefits as described by the applicant. This instrument should have application in ambient pollution monitoring, chemical and biological warfare agent identification, and the characterization and control of aerosol emissions from a variety of industrial and energy production processes. These processes, which produce aerosol laden gaseous exhaust or waste streams, include semiconductor manufacturing, gas turbines, and the diesel combustors and conventional furnaces used for electrical power.