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Transport of Radionuclides to the Rio Grande

Transport of Radionuclides to the Rio Grande. Bruce Gallaher gallaher@lanl.gov Middle Rio Grande Water Quality Summit October 25, 2004. LA-UR-04-7342. LANL Monitoring History. Regular LANL testing of Rio Grande sediments started in 1970s Emphasis on radioactivity

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Transport of Radionuclides to the Rio Grande

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  1. Transport of Radionuclides to the Rio Grande Bruce Gallaher gallaher@lanl.gov Middle Rio Grande Water Quality Summit October 25, 2004 LA-UR-04-7342

  2. LANL Monitoring History • Regular LANL testing of Rio Grande sediments started in 1970s • Emphasis on radioactivity • Longer-lived isotopes (241Am,137Cs, 238Pu, 239Pu, 90Sr, Uranium) • Less water column testing • Complemented by fish testing LA-UR-04-7342

  3. Monitoring Stations LA-UR-04-7342

  4. Sources of Radioactivity in Rio Grande • World-wide fallout • Natural uranium • Old Manhattan Project Site (mostly 239Pu) • Traced 40+ km from site into Rio Grande and Cochiti Reservoir LA-UR-04-7342

  5. Concentrations in Rio Grande Influenced Largely by Sediment Loads Flow diagram for the annual budget for suspended sediment in the northern and middle Rio Grande Source: Graf 1994 LA-UR-04-7342

  6. Cerro Grande Fire Accelerated Transport of Radioactivity • Fallout 137Cs and 90Sr in ash • Old Manhattan Project 239Pu Source: Gallaher and Koch, 2004 LA-UR-04-7342

  7. Trends in Cochiti Reservoir Sediments Cesium-137 Plutonium-239,240 Background Limit LA-UR-04-7342

  8. Human Health Risks • Three separate teams assessed combined risks to post-fire users of Rio Grande • Over 100 chemicals and radioactive substances studied • Drinking water and eating fish primary exposure (137Cs, RDX, benzo(a)pryene) • Conclusions • Risks within EPA acceptable levels • Below international radiological dose guides • Not significantly higher than pre-fire risk levels LA-UR-04-7342

  9. Risks to Aquatic Organisms • No known detailed studies of radiological impacts on Rio Grande aquatic populations • We can estimate risks • Screening values • Whole effluent toxicity tests • Fish tissue analyses • NMED/FWS Intensive Surveys, etc. LA-UR-04-7342

  10. Estimate Radioactivity Risk To Aquatic Organisms • We assembled concentration data for 9 key radionuclides for Rio water and sediment • 25 to 60 results for each radionuclide since 1990 • Compared data to DOE screen values • DOE Biota Concentration Guides (DOE-STD-1153-2002) • Based on dose exposure of < 1 rad/d • Deleterious effects in aquatic populations not expected below this dose • All results below the screening values LA-UR-04-7342

  11. Whole Effluent Toxicity Testing • No tests on Rio Grande waters • LANL/NMED tested Los Alamos surface waters for one year after fire • No acute toxicity • Two of 15 samples showed chronic toxicity (ash-ladened samples.) Daphnia Fat head minnow LA-UR-04-7342

  12. Summary • Probably already have seen highest concentrations in Rio Grande • Long-term radionuclide concentrations in Rio Grande should stabilize near or slightly above fallout or natural levels • For human health, rad concentrations within EPA acceptable levels • For aquatic organisms, rad concentrations below DOE screening values • No tests of rad toxicity in Rio Grande on aquatics LA-UR-04-7342

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