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Nanometer-sized Aerosol Particles in the Atmosphere: Measurement, Analysis, and Impact


Kong, Weimeng (Stephanie) (2021) Nanometer-sized Aerosol Particles in the Atmosphere: Measurement, Analysis, and Impact. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/893j-7x60.


New particle formation (NPF) from gaseous precursor vapors is frequently observed in the ambient environment and contributes to a major source of global cloud condensation nuclei (CCN). The survival and CCN activation of newly formed particles are highly dependent on particle growth below 10 nm. Characterizing and understanding nanoparticle early growth will therefore help to quantify the impact of NPF on cloud reflectivity and global energy budget. In this work, I first present a recently developed instrument, the Caltech nano-Scanning Electrical Mobility Spectrometer (nSEMS), which consists of a charge conditioner, a novel differential mobility analyzer (DMA), and a two-stage condensation particle counter (CPC). This new design, coupled with a data inversion method that combines empirical calibration and COMSOL simulation, can help to measure nanoparticle size distributions from 1.5 nm to 25 nm more accurately. This instrument was employed in the experiments conducted in the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN) to better understand NPF, particle growth and survival. Multiple experimental parameters were varied to study the influence of different highly oxygenated molecules (HOMs) and inorganic trace gases, such as ammonia and nitrogen oxides on particle early growth. Experiment results have suggested a novel mechanism that may help to explain nanoparticle formation and growth in highly polluted urban environments or in the cold free troposphere. In as little as a few minutes, freshly nucleated particles as small as 2 nanometers in diameter can grow very rapidly due to simultaneous condensation of nitric acid and ammonia. This can help them to survive through the so-called "valley of death" where they would otherwise be lost to larger particles, and instead allow them to grow to sizes where they are less vulnerable to loss and can continue on to sizes where they influence local air quality or climate. Further, the laboratory results of nanoparticle growth were incorporated into the Global Model of Aerosol Processes (GLOMAP) model to study the impact of this extremely rapid growth on the global CCN budget. Having realized the importance of conducting well-controlled chamber experiments and of using chamber experimental data, we established an online data infrastructure, the Index of Chamber Atmospheric Research in the United States (ICARUS), for storing, sharing, and using chamber data. A combined effort of the described works contributes to better measuring the size distribution of nanoparticles and to understanding their impact on global climate.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:New particle formation; atmospheric aerosol; instrumentation; climate; CERN CLOUD Experiment
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Awards:Advocating Change Together (ACT) Award, 2018.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Seinfeld, John H. (co-advisor)
  • Flagan, Richard C. (co-advisor)
Thesis Committee:
  • Seinfeld, John H.
  • Flagan, Richard C.
  • Wang, Zhen-Gang (chair)
  • Okumura, Mitchio
Defense Date:19 June 2020
Non-Caltech Author Email:stephaniewkong (AT)
Funding AgencyGrant Number
NSFAGS 1602086
NSFAGS 1801329
NSFAGS 1740552
Projects:CERN CLOUD Project
Record Number:CaltechTHESIS:09272020-215437294
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 3. A. B. C. D. E. F. G.
Kong, Weimeng (Stephanie)0000-0002-9432-2857
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13968
Deposited By: Weimeng Kong
Deposited On:29 Sep 2020 23:08
Last Modified:03 Nov 2021 00:00

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