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Research Highlights
Gauging the Effectiveness of Riparian BuffersPodcastsListen to or download the podcast to learn more about how NRMRL research helps to support the protection of human health and the environment.   Heavy loads of nutrients, sediments, pesticides, and other materials can be harmful to delicate aquatic ecosystems. Riparian buffers—vegetated regions adjacent to streams and wetlands— are a common means of intercepting and controlling these pollutants as they enter water bodies. EPA considers nitrogen one of the top stressors to aquatic ecosystem health. To determine how to better protect these environments from excess nitrogen, National Risk Management Research Laboratory's (NRMRL’s) Ground Water and Ecosystems Restoration Division (GWERD) conducted a comprehensive review of riparian buffer practices. Researchers evaluated the importance of riparian buffer width on nitrogen control and surveyed the effectiveness of current state and federal regulations. Background
Riparian zone near Blackwater Falls State Park, West Virginia.
Although nitrogen is an important nutrient to living organisms, surplus nitrogen from fertilizers, animal wastes, leaky sewer lines, highway runoff and other sources is a hazardous pollutant to both surface and subsurface water systems. For instance, excess nitrogen levels in surface water often cause toxic algal blooms, oxygen depletion, fish deaths, and a loss of biodiversity. In ground water, the nitrate form of nitrogen often contaminates drinking water sources and poses a threat to human health, especially in infants. Riparian buffers are considered an effective, sustainable method of protecting against these dangerous effects of excess nitrogen. Buffers reduce nitrogen levels through plant uptake, microbial immobilization and denitrification, soil storage, and ground water mixing. To better identify the relationship between buffer width and nitrogen removal capacity, EPA researchers reviewed data from 60 riparian buffer studies, including comprehensive and regional studies and peer-reviewed research papers. Researchers employed linear and nonlinear models to combine and analyze the data, identifying patterns in nitrogen removal related to buffer width. Current regulatory policies were also surveyed by researching state and federal regulation codes, peer reviews of government guidelines, and recommendations by state and federal agencies. ConclusionsThough riparian buffer efficiency varied widely across individual studies, EPA meta-analysis found important trends. While some narrow buffers (up to 25 meters) proved effective, buffers wider than 50 meters more consistently removed significant amounts of nitrogen. Buffers of various vegetation types were equally effective at removing nitrogen, but buffers with grassy vegetation were more effective when wider. Another strong trend in the data showed that subsurface removal of nitrogen was far more efficient than removal at or near the soil surface. Important patterns observed among the studies reviewed indicated that nitrogen control peaks when:
However, due to the limited capacity of streams and other watersheds to process nitrogen, watershed managers must control point and nonpoint sources of nitrogen in addition to maintaining buffers. For best results, buffer integrity must be protected against soil compaction, loss of vegetation, and stream incision. On average, state guidelines were found to correspond with the minimum effective buffer width necessary to improve water quality only if conditions are conducive to denitrification. Federal recommendations for buffer width vary from 7 to 100 meters, encompassing the range expected to remove significant amounts of nitrogen. EPA’s research effort is the most current, comprehensive review of nitrogen removal in riparian buffers. Since its publication, the data has been accessed more than 50,000 times by resource managers, policy makers, and local governments as a guide for developing effective management plans. For further information, the full report can be found here: "Riparian Buffer Width, Vegetative Cover, and Nitrogen Removal Effectiveness: A Review of Current Science and Regulations." A related article, "Meta-Analysis of Nitrogen Removal in Riparian Buffers," published in the Journal of Environmental Quality, is also available on the Web site. ContactJane Ice, NRMRL Office of Public Affairs (513) 569-7311
Hot Off the Presses—NRMRL PublicationsJournal Articles Boyd, G. R., K. M. Dewis, G. V. Korshin, S. H. Reiber, M. R. Schock, A. M. Sandvig, and R. Giani. (2008). “Effects of Changing Disinfectants on Lead and Copper Release—A Review.” Journal of the American Water Works Association. American Water Works Association, Denver, CO, 100,11. Gift, D., P. M. Groffman, S. Kaushal, and P. M. Mayer. (2008) “Denitrification Potential, Root Biomass, and Organic Matter in Degraded and Restored Urban Riparian Zones.” Restoration Ecology. Blackwell Publishing, Malden, MA. Hayes, S. L., M. Sivaganesan, K. M. White, and S. L. Pfaller. (2008) “Assessing the effectiveness of low-pressure ultraviolet light for inactivating Mycobacterium avium complex (MAC) micro-organisms.” Letters in Applied Microbiology. Society for Applied Microbiology, 47, 5:386–392. Nadagouda, M. N. and R. S. Varma. (2008) “Green Synthesis of Ag and Pd Nanospheres, Nanowires, and Nanorods Using Vitamin B2: Catalytic Polymerisation of Aniline and Pyrrole.” doi:10.1155/2008/782 Journal of Nanomaterials. Hindawi Publishing Corporation, New York, NY. Rastogi, A., S. R. Al-Abed, and D. D. Dionysiou. (2009) “Sulfate Radical-Based Ferrous-Peroxymonosulfate Oxidative System for PCBs Degradation in Aqueous and Sediment Systems.” Applied Catalysis B: Environmental. Elsevier BV, Amsterdam, Netherlands, 85, 3-4:171–179. You will need Adobe Reader to view some of the files on this page. |
