A Novel Method of Measuring Refractory Black Carbon Mass and Number Distributions by Inversion of CPMA-SP2 Data

• Author / Creator

  Broda, Kurtis N

• A new method of examining mass and number distributions of nanoscale refractive black carbon (rBC) particles has been developed. This method will be useful for atmospheric scientists conducting semi-continuous measurement of atmospheric rBC. The new method uses a Centrifugal Particle Mass Analyzer (CPMA) and Single Particle Soot Photometer (SP2), coupled with a novel inversion algorithm. The CPMA classifies particles by total mass to charge ratio, and the SP2 measures the mass of rBC in each individual particle. To recover the true rBC and total particle mass and number distributions, an inversion is required which accounts for multiple charging of particles and the CPMA transfer function. The inversion solves an inverse problem characterized by a Fredholm integral equation, where the true number and mass distribution of the aerosol is unknown, however both the system response and mathematical model of the CPMA-SP2 system are known. The inverse problem was solved using iterative methods, and a two variable number distribution was used to represent number concentration as a function of both rBC and total particle mass. The inversion was tested and validated using laboratory experiments, where the CPMA-SP2 sampled from a smog chamber. Sampling populations of uncoated, coated, and mixed coated-uncoated rBC particle populations was conducted. Finally the inversion was tested on data gathered in the real world during a field campaign in Shanghai, China. The results for three cases of high, medium, and low pollution levels, showed distinct populations of rBC particles, which are a function of rBC released from different sources and having different atmospheric residence times. The real world results showed this method can give valuable insights for atmospheric scientists using semi-continuous data logging. Future work will involve packing the software into a convenient form for use by CPMA-SP2 users.

• Subjects / Keywords

  • Black Carbon
  • Single particle soot photometer
  • Inversion
  • Centrifugal particle mass analyzer

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3JD4Q35X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.