Modeling the Formation of Organic Aerosol PM
From the 1970s to the Present:
Successes, Problems, and Next Steps

This page updated April 11, 2013

ARB Research Seminar



Wednesday, April 17, 2013
10:00 am, PDT
Sierra Hearing Room, Second Floor
1001 "I" Street, Sacramento

James F. Pankow, Ph.D.
Department of Chemistry
Department of Civil and Environmental Engineering
Portland State University

This study addresses a Gas/particle (G/P) partitioning is the process by which compounds distribute themselves between the gas phase and aerosol particles. In the case of organic compounds, the result is the formation/evaporation of organic particulate matter (OPM, aka organic aerosol). For each compound involved in the partitioning, there will be a governing partitioning constant Kp, with each Kp determined by the vapor pressure of the compound (which is strongly temperature dependent) and the composition of the particle phase into which the partitioning is occurring. The seminar will explore the fundamental chemistry governing the G/P partitioning process.

This seminar will trace the evolution of the field including: 

1)  1970s to early 1990s – early thinking;

2)  1994 – appearance of two papers describing the Pankow absorption model;

3)  1996 – simplification of the Pankow absorption model via the two-product model for secondary organic aerosol (SOA) by Odum et al. (1996);

4)  2006 – introduction by Donahue et al. (2006) the 1-D VBS (volatility-basis-set) framework for the Pankow absorption model; and

5)  2007 onward – appearance of subsequent papers by Pankow and others arguing for a return to modeling approaches more complex than the Odum 2-product model, especially as regards the consideration of the very important effects of water on OPM NO2 and PM10 exposures.

James F. Pankow, Ph.D., is a Professor of Chemistry and Civil & Environmental Engineering at Portland State University.  Dr. Pankow's research has involved the application of chemical principles to understanding how chemicals partition between important phases in the environment.  A primary focus of Dr. Pankow’s work has involved the study of the gas/particle (G/P) partitioning process.  This type of partitioning is of enormous fundamental importance in all contemporary model predictions of the amounts of particulate matter (PM) that form in urban and regional air, and in the global atmosphere.  His work on this theory, which is used in climate change research, resulted in his receipt of the 1999 American Chemical Society Award for Creative Advances in Environmental Science & Technology, and of the 2005 Haagen-Smit Prize (  G/P partitioning also affects the behavior and fate of individual toxic pollutants in the atmosphere, and theory developed by Pankow (1987) provides the foundation of the Junge-Pankow model used to predict how toxic compounds such as PCBs, pesticides, and dioxins behave in contaminated air, including how such compounds are transported to sensitive remote polar ecosystems (e.g.,  In addition G/P partitioning plays a fundamental role in controlling the delivery of the chemical doses of nicotine and carcinogens from cigarette smoke.  Dr. Pankow was elected to the National Academy of Engineering in 2009.  Dr. Pankow’s academic training combined basic chemistry (BA, SUNY, 1973) with engineering (Ph.D., Caltech, 1979).

For information on this Seminar please contact:
Ajith Kaduwela Ph.D., at (916) 327-3955 or send email to:

For information on this Series please contact:
Peter Mathews at (916) 323-8711 or send email to:

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