two students using an outdoor rainfall simulator

CU students using rainfall simulator to conduct experiments near the "903 Pad" at the Rocky Flats site, July 1993.


Starting with a set of field experiments piggybacked on a soil flow path tracer experiment at the Rocky Flats site in 1993, we have been investigating the mobilization and transport of particles in the unsaturated zone.  Our interest in particles in soils stems from the strong association between some contaminants (e.g., plutonium) and particles and the potential for particle-facilitated transport of these contaminants.  We've emphasized the role of rainfall intensity and soil structure (preferential flow paths, macropores) on particle mobilization.


  • Tracer Experiments in the Vadose Zone at the Rocky Flats Plant Site
    co-PIs: T.H. Illangasekare, M. Nachabe, J.N. Ryan, J. White, M. Williams.
    EG&G Rocky Flats/U.S. Department of Energy, 1993
  • Mobilization and Transport of Particles and Particle-Associated Contaminants in the Unsaturated Zone
    PI: Joe Ryan
    National Science Foundation, EAR Hydrologic Sciences (EAR-9909553), 2000-2003


  • Prof. Tissa H. Illangasekare, Colorado School of Mines, Golden, Colorado
  • Prof. M. Iggy Litaor
  • Robert Shannon, PACE Analytical Laboratory


  • Nicole DeNovio, PhD in progress, Particle Mobilization by Rainfall in Macroporous Soils.  Nicole's research will focus on the effects of rainfall intensity and duration and the structure of soils, both model and natural, in controlling the mobilization of particles in the unsaturated zone.  Experimental systems are now being developed to test the hypotheses laid out for the NSF EAR Hydrologic Sciences project listed above.


(with links to PDF files; some PDF files are large -- 2-4 MBytes)

  • Ryan J.N., Illangasekare T.H., Litaor M.I., and Shannon R., 1998. Particle and plutonium mobilization in a macroporous soil during rainfall simulations. Environmental Science & Technology 32, 476-482.

sketch of instrument

Sketch of instrumented soil pits installed by Iggy Litaor and colleagues for the study of plutonium transport near the "903 Pad" at the Rocky Flats site.


  • Simulating the Effects of Rainfall on Particle and Plutonium Transport in Rocky Flats Soils.  Colorado School of Mines, Environmental Engineering Sciences Division, Golden, Colorado, 1998. 
  • Mobilizing Particles (and Plutonium) in Macroporous Soils during Rainfall Simulations at Rocky Flats, Colorado.  Ohio State University, Joint Geological Sciences-Civil and Environmental Engineering Seminar Series, Columbus, Ohio, 1998.
  • Role of Particles in Actinide Transport Through Soils during Simulated Rainfall.  American Society of Agronomy Annual Meeting, Indianapolis, Indiana, 1996.