MRI-R2: Acquisition of a Proton Transfer Reaction Time-of-Flight Mass Spectrometer for Atmospheric Chemistry

Amherst College, Amherst MA

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This award supports acquisition of a state-of-the-art high-resolution proton-transfer time-of-flight mass spectrometer (PTR-ToF-MS) that will be used to further understanding of the atmospheric chemistry of biogenic volatile organic compounds (BVOCs). This instrument has the important advantage over the more common quadrupole PTR-MS of a much better mass resolution, which allows isobaric ions of different elemental composition to be separated. Research will include measurements of BVOC emissions from forests and study of BVOC reactions with atmospheric oxidants in the context of their ozone-forming potential and production of secondary organic aerosols as well as the susceptibility of BVOC emissions to changing biological and climatological factors. The studies will utilize a combination of field measurements and laboratory reaction chamber experiments. While many previous studies have looked at the formation of BVOCs, significant gaps in understanding still exist. In particular, chemical models currently underpredict the organic loading of atmospheric aerosols by factors of 4 to 8. It is hypothesized that this 'missing organic mass' consists of as-yet unidentified BVOC precursors originating from plant emissions. The PTR-ToF-MS will be used to search for and identify these compounds and quantify their emissions. Measurements will be made at Harvard Forest, which was established as a Long Term Ecological Research (LTER) site more than 20 years ago, and the Harvard environmental chamber. The results will be of great importance in the context of both air quality and climate forcing. In addition, the instrument will be used in the context of a new consortium for studies of biogenic emissions and production of aerosols. Four New England institutions are proposed as initial components of a regional center: Amherst College, Harvard University, Boston College, and the University of Vermont. A focus of the center will be enhanced research opportunities for undergraduates. Activities will include monthly group meetings, summer and academic-year research opportunities that will focus on undergraduate students, social activities to enhance mentoring and networking, and biennial research symposia.