RAPID: Online Single-particle Measurements of the Chemical Composition, Mixing State, and Ice Nuclei Residues During the FLAME IV Biomass Burning Experiment

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

This RAPID project involves performing online single-particle mass spectrometry (SP-MS) measurements of the chemical composition and mixing state of biomass particles during the fourth Fire Lab At Missoula Experiment (FLAME IV). FLAME IV affords a unique and important opportunity to better understand the evolution of biomass smoke more completely than is possible in the Carnegie-Mellon University (CMU) laboratory, by taking advantage of the collaborative simultaneous measurements conducted by a wide range of scientists. The SP-MS will determine how the aerosol mixing state evolves as the biomass smoke is photochemically aged in a novel twin environmental chamber system. The chambers will be filled with combustion smoke generated from a variety of globally relevant biomass fuels, and diluted to atmospheric concentrations. Atmospheric photochemistry will be simulated in the chambers for several hours using photo-simulator lights and the optional addition of oxidants such as hydroxyl radical and nitrogen oxides. The twin chamber design will provide an unperturbed control aerosol system to which aerosols in the perturbed chamber can be compared at any time during the multi-hour long experiments. Through tandem experiments with FLAME IV participants from Colorado State University, the SP-MS will also determine the chemical composition of ice nuclei present in fresh and aged biomass burning smoke. A novel suite of gas and aerosol instruments will be used to thoroughly characterize the biomass aerosol prior to, during, and after simulated photochemistry. The instrument package includes a High-Resolution Time-Of-Flight Aerosol Mass Spectrometer, Proton-Transfer-Reaction Mass Spectrometer, and a new single-particle mass spectrometer. This will be the first deployment of this new Laser Ablation Aerosol Particle Time-Of-Flight (LAAP-TOF) mass spectrometer in any collaborative experimental or field campaign. The LAAP-TOF will allow better understanding to be gained of the variations in individual particle composition and mixing state for the different fuels tested, how this mixing state evolves during photo-oxidation, and what role this mixing state might play in the partitioning of organic carbon between the gas and particle phases. The research cuts across multiple disciplines including chemistry, combustion, air quality engineering, atmospheric science, and climate change. Thus, this research will have immediate impacts on a wide range of interdisciplinary fields including forest management, atmospheric chemistry, cloud microphysics, and biogeochemistry. The project will compose a significant portion of at least two graduate student Ph.D. dissertations, and the research of one post-doctoral associate. The collaborative and multi-disciplinary nature of the FLAME IV experiment will provide our participants with the unique opportunity to work alongside a wider range of scientists than otherwise possible during their research at CMU.