In this Major Research Instrumentation (MRI) project, the investigators will acquire a new shared, multi-user instrument at the University of Minnesota – Twin Cities. This instrument will enable new observations of both concentrations and fluxes of a wide variety of chemical compounds by the project team, which will enhance their ability to study urban air pollution, nitrogen cycling, indoor and outdoor air quality, plant-microbe interactions, and chemical exchange between surfaces and the atmosphere. This instrument will be used to train a new generation of scientists and experimentalists including graduate and undergraduate students. Additionally, the instrument will enable research projects that include a range of outreach activities including a partnership with the University of Minnesota Urban Outreach-Engagement Center.<br/><br/>The instrument to be acquired is a dual-reagent chemical ionization mass spectrometer with high-resolution time-of-flight detection, specifically an Aerodyne Vocus 2R CI-TOF, which is unique in that it is the only instrument that can take field measurements with both hydronium and iodine reagent ions. The CI-TOF will enable a broad range of chemical observational coverage and will be used by a multidisciplinary research team with a broad range of career levels and research projects. There are four key issues that this instrument acquisition will address: (1) the air quality effects of urban fluxes of volatile organic compounds; (2) the cycling and fate of reactive nitrogen in the atmosphere of the agricultural Midwest; (3) the indoor air quality impacts of photocatalytic and ionization purification technologies; and (4) the volatile organic compound mediation of plant-microbe interactions and plant growth.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.