A modeling system for supporting assessments of exposure to contaminants released from forest fires in the vicinity of hazardous and nuclear waste sites
P.G. Georgopoulos, A.Chandrasekar, C. Efstafthiou (EOHSI, UMDNJ - R.W. Johnson
Medical School and Rutgers University)
K. Gurer (California Air Resources Board)
This work presents new developments in the implementation of a modeling system intended to provide tools for assessing population exposures from potential releases of gaseous and particulate phase contaminants into the atmosphere due to forest fire events in the vicinity of nuclear and hazardous waste sites. The above contaminants would include components resulting from the long term accumulation of toxicants (chemicals and radionuclides) originating from the site.
This prototype modeling system couples multiscale (through nested grids) prognostic atmospheric modeling (based on the Regional Atmospheric Modeling System, RAMS) with a new forest fire propagation and emission model. The coupling is "two-way" in the sense that, on one hand, the spread rate and the areal coverage of the forest fire are determined by the wind field whereas, on the other hand, the heart released from the fire affects the dynamic and thermodynamic structure of the Atmospheric Boundary Layer (ABL). The forest fire model calculates the amounts of heat, moisture and gaseous and particulate phase emissions released while the HPACT dispersion module of RAMS calculates the transport and deposition of contaminants released from the fire. The model also provides for dry deposition of gaseous as well as particulate phase contaminants. A large eddy simulation (LES) approach is used for the innermost nested grid to realistically simulate fire propagation and to introduce thermal effects of the forest fire into the coupled model. A set of GIS-based modules have been developed to process available databases (from USGS, Forest Service) and derive the inputs required for the forest fire model. Another GIS-based module is under development to facilitate the characterization of potential population exposures associated with the fire events.
Case studies presented here investigate the dynamics of transport and deposition of pollutants emitted into the atmosphere from forest fires in the vicinity of the Savannah River Site (SRS); historical data from controlled burns are used for model evaluation purposes. Discussion of the results addresses the effects of mesoscale phenomena, such as sea breezes, on fire and fire plume dynamics and discusses the data an model needs for emergency response planning and for exposure assessment studies.
ACKNOWLEDGEMENTS: Our research has been supported by a grant to the Institute for Responsible Management, Consortium for Risk Evaluation with Stakeholder Participation, from the US Department of Energy, Instrument DE-FG26-00NT 40938. The viewpoints expressed in this report are solely the responsibility of the authors and do not necessarily reflect the views of the US Department of Energy or its contractors.