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Environmental Assessment

National and Regional Air and Deposition Modeling of Stationary and Mobile Source Emissions of Dioxins Using the Relmap Modeling System

Objective/Intended Use

The purpose of this study is to estimate the atmospheric transport, fate and deposition flux of air releases of CDDs and CDFs from known sources activities within the continental United States using the Regional Lagrangian Model of Air Pollution (RELMAP).

Technical Information Staff
  • by phone at:   703-347-8561
  • by fax at:   703-347-8691
  • by email at:  nceadc.comment@epa.gov

Project Abstact

The purpose of this study is to estimate the atmospheric transport, fate and deposition flux of air releases of CDDs and CDFs from known sources within the continental United States using the Regional Lagrangian Model of Air Pollution (RELMAP). RELMAP is a Lagrangian air model that has been enhanced and modified to simulate atmospheric concentrations and wet and dry deposition patterns of CDDs and CDFs. Source emissions estimates from the Inventory of Sources of Dioxin-Like Compounds in the United States provides emission estimates for mobile, area and stationary sources. Stationary and mobile source emissions estimates for the 1995 time frame have been evaluated with RELMAP. These emissions were obtained from congener-specific emission factors contained in the Dioxin Inventory. Actual stationary source locations are added to the model as indicated in EPA databases of sources of air pollution. Annual releases from each stationary source are used as inputs to the model. Mobile source emission estimates were developed from EPA data on vehicle miles traveled per year by geographical region in the U.S. Meteorological data from 48 conterminous states is contained within the model. GIS software is used to display the RELMAP modeling results. Specifically, estimates of annual and seasonal average dioxin/furan air concentrations, total wet deposition, total dry deposition over the continental U.S. for stationary and mobile sources emission are depicted as an output to each RELMAP analysis. Ongoing work on RELMAP include: 1. Verification of RELMAP predictions to CDD/CDF monitoring data from the National Dioxin Air Monitoring Network; 2. Comparison of RELMAP to other regional-scale air models; 3. Updated analyses of sources of CDD/CDF emissions using the inventory of sources of dioxin-like compounds for reference year 2000.

Project Status

Preliminary analysis of CDD/CDF emission sources for reference year 1995 has been completed.
Next steps include:
1. Model verification using the National Dioxin Air Monitoring Network measurements;
2. Comparative analysis of model performance against other Regional-scaled air models: e.g., HYSPLT.
3. Refinement of RELMAP for dioxin source analysis;
4. Evaluation of source emissions of CDDs, CDFs for reference year 2000.

Project Dates

Project Start Date
  10/01/2000
Project Completion Date (Actual/Projected)
  09/30/2003

Related Links

Future Products

  • A Journal Article, "Evaluation of the Potential Atmospheric Deposition and Air Concentrations of Pcdds and Pcdfs from Air Emission of Pcdds and Pcdfs from Known Source Activities in the United States Using the Relmap Modeling System.

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