Atmospheric Aerosol Structure And Chemistry Exposed

Combining femtosecond X-ray pulses with mass spectrometry reveals the structural morphology and chemical composition of individual airborne particles, according to experiments done at SLAC National Accelerator Laboratory in Menlo Park, Calif. (Nature, DOI: 10.1038/nature11222). A better understanding of the structure and chemistry of atmospheric aerosol particles, such as soot emitted from vehicles or factories, will help unravel the roles they play in health, weather, and climate. The X-ray pulses have enough intensity to yield nanometer-resolution diffraction patterns before destroying the particles, and the ion fragments ejected by the X-ray beam can be funneled into a mass spectrometer. An international research team led by SLAC’s Michael J. Bogan and Duane Loh studied standard soot particles generated by an electric field focused between two carbon rods and was able to map the density variation across individual particles. They also used mass spectrometry to identify [Na(NaCl)]⁺ and [Na(NaCl)₂]⁺ species in soot particles exposed to salt, similar to what might happen if engine exhaust encounters sea air. The researchers plan to use to the technique to study real-world aerosols and how they change in response to their environment.