United States Environmental Protection Agency Office of Research and Development National Exposure Research Laboratory Research Abstract Government Performance Results Act (GPRA) Goal 4 Annual Performance Measure 268 Significant Research Findings: A Tool for Estimating Climatological Seasonal and Annual Deposition of Sulfur and Nitrogen for Multimedia Management Sulfur oxides and reactive nitrogen are multimedia pollutants that contribute to significant deleterious effects on humans and ecosystems. Sulfur contributes to acidification of lakes and streams, which affects their viability to sustain fish populations. The oxidized forms of reactive nitrogen (from nitrogen oxide or NOx emissions) contribute to tropospheric ozone formation and acid rain. The reduced forms of reactive nitrogen (from ammonia or NH3 emissions) contribute to fine particle formation. Both forms of nitrogen contribute to coastal estuary eutrophication (including nuisance algal blooms). The air-water linkage needs to be integrated into strategies for effective management of the nation's lakes and streams and coastal water resources. For many air-water linkages, such as for Total Maximum Daily Load (TMDL) analyses, climatologically (multi- year) averaged deposition is desired. ORD has developed a method, termed the Aggregation method, to create climatological average fields of atmospheric deposition of sulfur and nitrogen across the United States. An archive of meteorology simulations of select transport cases are used to generate climatological average deposition estimates with the regional Community Multiscale Air Quality (CMAQ) model. The Aggregation method has been used extensively by the Chesapeake Bay Project for its nitrogen management planning that include an air-water linkages. The objective of this project is to make the Aggregation method available to the wider client community through an easy to use software tool. EPA's Office of Research and Development (ORD) developed the Aggregation method originally for integrated assessments of acidic deposition from sulfur and for visibility degradation from sulfate fine particles. The Aggregation method is based on the concept that the atmospheric chemistry, transport, and deposition at a given location is governed by recurring weather patterns that, in combination, produce a realistic estimate of annual and seasonal chemical climatology. Scientific Problem and Policy Issues Research Approach ------- Meteorological sequences are grouped by wind flow patterns and sampled proportionate to their frequency of occurrence. Weighted averages are used to derive the seasonal and annual average estimates. More recently with the advances provided by CMAQ, the aggregation outputs have been expanded to include nitrogen deposition from both NOx and NH3 emissions and visibility degradation from the full suite of fine particles. As part of this effort, the Aggregation method was upgraded to handle seasonality (four seasons) and spatially expanded to cover the continental U.S. in response to client requests. Also, to provide better resolution and accuracy for the simulations, the grid size was reduced from 80-km to 36-km over the continental U.S. and 12-km over the Chesapeake Bay/Mid-Atlantic region. The latest version of the meteorological model, MM5, was used to improve the meteorological predictions and provide a better seasonal and annual climatology. To date, ORD has been the only group using the Aggregation method. Wider use was limited because it was developed in SAS. To address this limitation, the upgraded Aggregation software program was converted from SAS to R, a widely used and supported open source statistical package. Also, the output was converted to the Models-3 / CMAQ format. An easy to understand front end to the package was developed, and documentation was written. This new Aggregation tool has met the objective to allow greater transferability and accessibility by the user community. Results and Making the Aggregation method available on the web will help expand and Impact move the user base over time beyond ORD/NERL/AMD. The method will be available for EPA's Chesapeake Bay Program and the Clean Air Markets Division of OAR, OAQPS and the Regional Planning Organizations (RPO's) and their contractors and be more available to the multimedia modeling community within and outside of EPA. The R statistical package is free, with no licensing issues. The R package is easier to use than the SAS approach, allowing less experienced users to be able to carry out the aggregation methodology. The output files can be viewed with PAVE, the Models-3 workhorse visualization tool that is publically available through CMAS, and is accessible to other Models-3 tools. The ability to use PAVE is very attractive and easy compared to mapping the results using SASGraph and enhances the users ability to display results. Nonetheless, the Aggregation package, RAGG, requires a fairly high degree of sophistication on the part of the users and they need to be very familiar with CMAQ and the development of emissions inputs for CMAQ. The degree of sophistication required is likely too high for water quality managers to derive benefit for TMDL and air nonpoint source estimation without help from their air quality colleagues in the State or RPO's. This makes a compelling argument that defines recommendations for future research to create additional help for the multimedia community. ------- This project was conducted by an outside contractor, who developed the original Aggregation method, with oversight by a team of NERL scientists. EPA's Chesapeake Bay Program and the Clean Air Markets Division of OAR provided client perspectives. The description of the new Aggregation method is summarized in a journal publication and an internal report: Peer Reviewed Publication: Cohn, Richard D., Brian K. Eder, Sharon K. Leduc and Robin L. Dennis, 2001. Development of an Aggregation and Episode Selection Scheme to Support the Models-3 Community Multiscale Air Quality Model, Journal of Applied Meteorology, 40, 210-228. Inhouse Contractor Report: "Work in Progress for the Development of an Episode Selection and Aggregation Approach to Achieve Meteorological Representation on Continental Scales," Report Prepared by Analytical Sciences, Inc. (now Constella Group), 2605 Meridian Parkway, Durham North Carolina 27713 for the U.S. Environmental Protection Agency, September 16, 1997, 216 pp. The R Aggregation Package, RAGG, documentation, and a test data set with inputs and the correct output answer are on EPA's anonymous ftp site for download. The ftp site can be reached from the AMD website page on Modeling Tools (www.epa.xov asmdnerl modeling.html) under the heading Climatological Deposition for Multimedia Modeling. A URL is also provided for the R website in case a user needs to install R. Future Research Future research will be directed towards development of a Deposition Mapping Tool that can take the aggregated fields of atmospheric deposition from the CMAQ grid cells and overlay them onto hydrological or ecosystem units with their own boundaries and define the average atmospheric deposition to these new boundaries. Such a tool will greatly facilitate the integration of air deposition nonpoint estimates in water quality management associated with TMDL requirements for watersheds. In addition, future work will extend the aggregation calculations to air concentrations for visibility calculations to support climatological assessments of haze. Questions and inquiries can be directed to Robin L. Dennis, Ph.D. US EPA, Mail Drop E243-01 National Exposure Research Laboratory Research Triangle Park, NC 27711 Research Collaboration and Research Products Contacts for Additional Information Phone: 919/541-2870 E-mail: Dennis.Robin@epa.gov ------- ------- |