Optimization of a Single Particle Soot Photometer for Metallic Particle Detection and Differentiation

Metallic particles can be detrimental when present in the atmosphere, because they could contribute to global climate change through direct atmospheric absorption and reduction of snow albedo. There have also been links between the presence of iron-oxide particles in the brain and Alzheimer’s diseaseA, suggesting metallic particles as a potentially important air pollutant that is not currently well-characterized. The ability to detect these particles in real time will help further our understanding of them. Single particle soot photometers (SP2) are primarily used to measure black carbon, but can be modified to measure and characterize metallic particles, as indicated in a previous studyB. Modifications to the SP2, including the addition of optical filters to the incandescent channels, were made in an attempt to better distinguish metallic particles and black carbon. The addition of the optical filters appears to be unnecessary for distinguishing metallic particles. The incandescence efficiencies of different metallic particles were also analyzed to assess the practicality of measuring these particles in the atmosphere. Ambient air sampled in Boulder, CO showed a small amount of metallic pollution, between 2±2% of the total mass of measured incandescent particles. Reliable measurements of metallic particles would help us better understand the quantity and type of metallic particles in the atmosphere, which can then be used to study their effects on climate and human health. A. Maher, Barbara A., et al. “Magnetite pollution nanoparticles in the human brain.” Proceedings of the National Academy of Sciences 113.39 (2016): 10797-10801. B. Yoshida, Atsushi, et al. “Detection of light-absorbing iron oxide particles using a modified single-particle soot photometer.” Aerosol Science and Technology50.3 (2016): 1-4