Ultrafine Aerosol Research Group

Web pages for the Ultrafine Aerosols group were archived in May 2019.

UA Group News

February 2015: This month the UA Group hosted Prof. Peter McMurry from the University of Minnesota. Peter was here to discuss a collaborative project, funded by the US Department of Energy, to explore the mechanisms by which nanoparticles grow in the atmosphere.
January 2015: This month the UA Group hosted a member of Prof. Delphine Farmer's research group from Colorado State University. Prof. Farmer's graduate student, Patrick Brophy, set up an experiment to study the penetration of aerosol particles through the sampling inlet of a chemical ionization mass spectrometer.
5-9 January 2015: The UA Group welcomed Prof. Chris Hogan from the Dept. of Mechanical Engineering at the University of Minnesota Twin Cities. Prof. Hogan shared his expertise on ion mobility measurements. His visit was funded by the ACD Visitor Program.
15-19 December 2014: At the Fall Meeting of the American Geophysical Union, Jim Smith delivered a platform talk entitled Mechanisms for the formation and growth of nanometer-sized particles in the Amazon: Insights from GoAmazon2014 and the Tapajós Upwind Forest Flux Study (TUFFS). Jeong-Hoo Park presented a poster based on his postdoc work in the UA Group entitled Deposition fluxes of oxygenated volatile organic compounds (OVOCs) above FLONA Tapajós in central Amazon rainforest, Brazil. Postdoc Mike Lawler presented a poster entitled Nanoparticle composition at a rural U.S. forest site: evidence for diverse sources.
27 November 2014: Jim Smith received a Special Visiting Researcher scholarship from the Government of Brazil for a 3-year project entitled "Ultrafine particle formation and impacts in the Amazon." The scholarship will provide funding for postdoc and graduate student exchanges between the UA Group and Brazilian research groups, and in addition will fund Jim for collaborative research visits to Brazil.
October-November 2014: Researchers from Aerodyne Research Inc. set up experiments in our laboratory using a chemical ionization mass spectrometer for quantifying gas phase amine levels in ambient air. Much fun was had by all.
1 October 2014: Dr. Jeong-Hoo Park, an NCAR Advanced Study Program postdoc in the UA Group, departed to start his new position as a Senior Researcher in the Climate and Air Quality Research Department of the Air Quality Forecasting Center of the National Institute of Environmental Research in Incheon, Korea.

Forget the spray can!
Aerosol = Particles + Air

Many of us think of spray cans when we hear the word aerosol but we think of aerosol as particles suspended in air. Aerosol is a system that includes both particles and the air in which they are suspended; we treat this as a system because typically molecules move constantly from the air into particles and vice versa. We need to understand the behavior of both gases and particles in order to understand atmospheric aerosol, so in the Ultrafine Aerosol Research Group ("UA Group") we focus on measuring both. Why do we care about atmospheric aerosol? Particles suspended in the air are the main constituent of the haze that we perceive as smog. They can impact human health through afflictions like asthma, bronchitis, as well as climate by directly scattering sunlight and modifying cloud properties.

smog over Tecamac, Mexico

Smog in Tecamac, Mexico, on a day when air from Mexico City was blowing into town. On this day the sunlight was scattered so much by aerosol particles that it looked like a foggy day!


The main goals of the UA Group are to understand the chemical species and mechanisms by which ultrafine aerosol particles form and grow in the atmosphere. Specific questions include:

  • What possible roles do organic compounds play in the formation of the stable clusters and for the growth of these clusters into "new particles"?
  • Are the compounds responsible for the birth and growth of aerosol particles formed in the atmosphere or within the particles themselves?

Another interest that we have is in the impacts of ultrafine aerosol. Particles of this size form the inner "seed" upon which water may condense to form cloud and fog droplets. When we change the composition of ultrafine aerosols through the pollutants we emit, we may be impacting cloud droplet formation, which in turn could affect the amount of sunlight we receive as well as precipitation.

To study these phenomena, the UA Group has teamed with university investigators to develop a unique set of instruments. Among these is the Thermal Desorption Chemical Ionization Mass Spectrometer, or TDCIMS, which can characterize the chemical composition of particles as small as 5 nm.




ACOM | Atmospheric Chemistry Observations & Modeling