Measuring black carbon mixing states using a tandem centrifugal particle mass analyzer and single particle soot photometer system

  • Author / Creator
    Naseri, Arash
  • This work aimed to improve the evaluation of atmospheric black carbon (BC) mixing states by using a tandem Centrifugal Particle Mass Analyzer (CPMA), and Single Particle Soot Photometer (SP2) system. To derive a BC mixing state using the CPMA SP2 system, the measurements should be deconvolved with a proper inversion scheme that accounts for multiple charging of particles and physical constraints. Four objectives were followed to improve the accuracy of the method: (i) developing a novel deconvolution scheme; (ii) determining optimum measurement configurations for the CPMA SP2 system response collection; (iii) experimentally characterizing the CPMA transfer function; and (iv) incorporating CPMA-SP2 system into real-world applications to demonstrate its performance.

    The first objective was achieved by developing a novel inversion scheme for determining the two-dimensional number distribution of non-refractory materials on black carbon, taking into account both physical constraints and a lack of knowledge about black carbon particle mobility. The novel approach was tested with several well-established regularization methods to determine which method outperforms the other. The results revealed that the exponential distance method outperformed other regularization methods tested. Also, to derive the optimum sampling settings of the CPMA SP2 responses, Monte Carlo sampling was utilized to examine the sensitivity of reconstruction error to experimental inputs. Based on the aerosol concentration and measuring time, general recommendations for typical aged atmospheric aerosols are: (i) large numbers of SP2 bins per decade (ns' = 64, (ii) a preference for higher SP2 sampling counts per CPMA setpoint (Ns>10000), (iii) a moderate number of CPMA setpoints per decade (nc' = 3 to 8), (iv) CPMA resolution around 1.0, and (v) a high CPMA flow rate (1.5 L/min).

    For improving the evaluation of the mathematical model of the CPMA-SP2 system, which directly impacts the reconstruction accuracy of particle mass-BC mass distribution, the transfer function of CPMA was experimentally evaluated and approximated with a triangular transfer function. Deviation of the idealized transfer function from the actual case was measured, and it was found that the actual CPMA transfer function is generally a little bit narrower than expected, while the losses are much higher than expected.

    Finally, the improved CPMA-SP2 system was demonstrated for the measurement of wildfire BC mixing states and compared to other measurement techniques established in the literature. The comprehensive comparison between methods indicates that while the CPMA-SP2 measurement may suffer from poor temporal resolution, it enjoys higher counting statistics to retrieve information, thus the reconstructed results are less uncertain, and also information is retrieved on a larger validated detection size range.

  • Subjects / Keywords
  • Graduation date
    Spring 2023
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • 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.