United States Environmental Protection Agency Office of Research and Development National Exposure Research Laboratory Research Abstract Government Performance Results Act (GPRA) Goal 4, Healthy Communities and Ecosystems Annual Performance Measure # 549 Significant Research Findings: Modeling the Distribution of Non-point Nitrogen Sources and Sinks Scientific Excessive nitrogen (N) loading is considered the critical factor for Problem and stimulating algal growth and eutrophication in estuarine and coastal marine Policy Issues waters. Symptoms of excessive N loading to estuarine and coastal systems include phytoplankton and algal blooms, which increase biological oxygen demand (BOD) through decomposition processes, leading to bottom water hypoxia and, under extreme conditions, can culminate in fish kills. In the Neuse River Basin (NRB), N loading has increased coincident with increases in chemical fertilizer use in the early-1960s and animal feeding operations in the early-1970s. The proportion of non-point source (NPS) N from fertilizer applications, animal feeding operations, and atmospheric deposition that actually enters the aquatic system (watercourses), is an ongoing research question of significance for evaluating the relative importance of NPS-N sources. The amended Clean Water Act of 1987 (section 319) requires states to perform an assessment of water quality problems, including those associated with diffuse (non-point) sources. Currently, high priority NPS issues are focused on nutrient and sediment transport from the landscape to receiving streams. These NPS loadings are used to support the development of Total Maximum Daily Loads (TMDLs) determinations for streams and rivers. Emerging technology and data integration issues include how to integrate remote sensing data into distributed non-point source nitrogen modeling capabilities to protect estuarine and near coastal waters. Research This study quantified NPS-N sources and sinks across the 14,582 km2 Approach Neuse River Basin located in North Carolina, to provide tabular data summaries and graphic overlay products. These were used to support the development of management approaches to best achieve established N reduction goals. First, a remote sensor derived land-cover classification was performed to support modeling needs. Modeling efforts included the development of a mass-balance model to quantify potential N sources and sinks, followed by a precipitation event driven hydrologic model to effectively transport excess N across the landscape to individual stream reaches to support subsequent labeling of transported N values corresponding to their source of origin. ------- Results indicated that agricultural land contributed 55% of the total annual NPS-N loadings, followed by forested land at 23% (background), and urban areas at 21%. Average annual N source contributions were quantified for agricultural (1.4 kg/ha), urban (1.2 kg/ha) and forested cover types (0.5 kg/ha). NPS-N source contributions were greatest during the winter (40%), followed by spring (32%), summer (28%), and fall (0.3%). Seasonal total N loadings shifted from urban and forest dominated sources during the winter, to agricultural sources in the spring and summer. A quantitative assessment of the significant NRB land-use activities indicated that high (>70%) impervious) and medium (>35% impervious) density urban development were the greatest contributors of NPS-N on a unit area basis (1.9 and 1.6 kg/ha/yr, respectively), followed by row crops and pasture/hay cover types (1.4 kg/ha/yr). Research This effort was performed in collaboration with Charles Garten and Collaboration Thomas Ashwood, Department of Energy, Oak Ridge National Laboratory, and Research Environmental Sciences Division, Oak Ridge, TN; Richard Greene, Products National Research Council (NRC), RTP, NC; and Chris Roessler, North Carolina Department of Environment and Natural Resources, Division of Water Quality, Raleigh, NC. Products developed under this work unit include the following report and publications. Garten, Jr., C.T., and T.L. Ashwood, 2000. Landscape Based Modeling of Nonpoint Source Nitrogen Loading in the Neuse River Basin, North Carolina. Oak Ridge National Laboratory, Environmental Sciences Division, Publication No. 5044, Oak Ridge, TN, 39 p. + Appendices. Garten, Jr., C.T., and T.L. Ashwood, 2003. A landscape level analysis of potential excess nitrogen in east-central North Carolina, USA. Water, Air, and Soil Pollution, 146,3-21. Lunetta, R.S., J. Ediriwickrema, J. Iiames, D. Johnson, J.G. Lyon, A. McKerrow, and D. Pilant, 2003. A quantitative assessment of a combined spectral and GIS rule-based land-cover classification in the Neuse River Basin of North Carolina. Photogrammetric Engineering & Remote Sensing, 69(3), 299-310. Results and Impact Lunetta, R.S., R.G. Greene, and J.G. Lyon, 2005. Modeling the distribution of diffuse source nitrogen sources and sinks in the Neuse River Basin of North Carolina, USA JAWRA, 41(5), October 2005. These are the final products developed under this research effort. ------- Future No future research is currently planned on this topic. Research Contacts for Questions and inquiries regarding NERL's work on Modeling the Additional distribution of NRB non-point N sources and sinks can be directed to: Information Ross S. Lunetta U.S. EPA National Exposure Research Laboratory Environmental Sciences Division Landscape Characterization Branch 109 TW. Alexander Drive, RTP, NC 27711 Phone: 919-541-4256 E-mail: lunetta.ross@epa.gov Federal funding for this project was through the U.S. EPA's Office of Research and Development, National Exposure Research Laboratory, and the work was conducted by the Environmental Sciences Division; Oak Ridge National Laboratory (Interagency Agreement No. DW 89938154-01- 0); and National Research Council (Cooperative Agreement No. CR- 826388-01-0). ------- |