Aerosol Time-of-Flight Mass Spectrometry (ATOFMS)

ATOFMS instruments perform real-time measurements of ambient particles and have been used in a wide variety of environments, including on aircraft (ICE-L, CARES, CalNex) and oceanic research vessel platforms during international field campaigns (CalNex, INDOEX, ACE-Asia, CalCOFI, CARES). Measurements of individual particle composition and size made by ATOFMS provide valuable insights into aerosol transformation processes and sources in both field and laboratory studies. Improvements to existing instruments and development of new instrumentation and data analysis methods are ongoing projects in our group. Procedures for quantification and scaling detected ATOFMS particle types to atmospheric concentrations appear in numerous publications. Comparison of source emission mass spectral "fingerprints" to atmospheric particle measurements has permitted source apportionment of ambient particles. ATOFMS data are also being used as inputs to improve atmospheric chemistry and climate models. Recently ATOFMS has seen increased use for the detection of bioaerosols and health effects studies.

ATOFMS development began in 1992 in the research laboratory of Prof. Kimberly Prather at the University of California, Riverside. Her research group moved in 2001 to the University of California, San Diego. Four generations of ATOFMS instruments have been developed in our group. The first generation (“The Beast”) is a stationary and single-polarity instrument used for lab studies and instrument development. The second generation instruments (“Jake” & “Elwood”) are field transportable, dual-polarity instruments. Jake is configured with an aerodynamic lens for detection of ultrafine particles (UF-ATOFMS) from 80-1000 nm. The third generation ATOFMS (“Laverne”) is also field transportable and dual-polarity and was the prototype for TSI’s commercial ATOFMS instrument, Model 3800. The commercially available ATOFMS is now available with an optional aerodynamic lens for detection of particles from 30-1000 nm (Model 3800-030). The ATOFMS User’s Group maintained by TSI is another valuable source of information and contains an extensive publications list of particle mass spectrometry. We are developing a chemical ionization version of the ATOFMS ("Clifford") that will soon be used in lab studies.  The newest (4th generation) ATOFMS is an aircraft-ATOFMS ("Shirley") who is much smaller and fits on airplanes and performs faster measurements that allow us to probe the particles seeding mixed phase clouds.  It is now possible to determine the sources of aerosols and cloud seeds "on the fly" using a library of major sources developed in our group over the past 20 years in funding provided by the California Air Resources Board.