MRI Track 1: Acquisition of a Vocus Mass Spectrometer for Atmospheric Chemistry Research

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

This Major Research Instrumentation (MRI) project provides for the purchase of an Aerodyne Vocus Proton Transfer Reaction-Mass Spectrometer (Vocus PTR-MS) that will enable the ability to simultaneously measure hundreds to thousands of different gas and particle-phase organic compounds in the atmosphere. The Vocus PTR-MS will be housed in the Center for Atmospheric Particle Studies (CAPS) laboratories at Carnegie Mellon University, complementing other state-of-the-art equipment there. Among other capabilities, the instrument is designed to measure extremely polar constituents that nucleate and grow to form atmospheric nanoparticles that can be harmful to human health. In addition to resolving differences between atmospheric carbon, oxygen, hydrogen, sulfur, and nitrogen atoms in molecules of the same nominal mass, this mass spectrometer has the sensitivity to measure highly reactive, critical free radicals such as organic peroxy radicals. The instrument design also reduces wall losses of those species as well as other sticky compounds. The Vocus is a factor of over a hundred times more sensitive than the instrument that the CMU group previously has been using for research. The new instrument will enable detection of the most lightly oxidized first-generation products at concentrations encountered in the atmosphere, radical species such as organic peroxy radicals, and gas-phase intermediate volatility organic compounds that play a central role in organic aerosol formation and aging. The high time resolution will permit sampling of source plumes in real-world conditions. Junior faculty, postdocs, and students will be trained to use the new instrument. This MRI project is funded by the NSF Atmospheric Chemistry Program. 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.