UNCLASSIFIED Transport of Radionuclides to the Rio Grande Bruce Gallaher [email protected] Middle...
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Transcript of UNCLASSIFIED Transport of Radionuclides to the Rio Grande Bruce Gallaher [email protected] Middle...
UNCLASSIFIED
UNCLASSIFIED
Transport of Radionuclides to the Rio Grande
Bruce [email protected]
Middle Rio Grande Water Quality Summit
October 25, 2004
LA-UR-04-7342
UNCLASSIFIED
UNCLASSIFIED
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
UNCLASSIFIED
UNCLASSIFIED
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
UNCLASSIFIED
UNCLASSIFIED
Concentrations in Rio Grande Influenced Largely by Sediment Loads
Source: Graf 1994
Flow diagram for the annual budget for suspended sediment in the northern and middle Rio Grande
LA-UR-04-7342
UNCLASSIFIED
UNCLASSIFIED
Cerro Grande Fire Accelerated Transport of Radioactivity
0
5
10
15
20
25
30
Cs-137 (mCi) Sr-90 (mCi) Pu-239,240 (mCi) SuspendedSediment (MT x
1000)
Analyte
Tra
nsp
ort
(m
Ci
or
Th
ou
san
d M
T) Prefire Avg.
2000
2001
2002
2003
–Fallout 137Cs and 90Sr in ash –Old Manhattan Project 239Pu
Source: Gallaher and Koch, 2004
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UNCLASSIFIED
Trends in Cochiti Reservoir Sediments
Cs-137 in Cochiti Lake
0
0.5
1
1.5
2
2.5
3
Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03
Date
Co
nc
en
tra
tio
n (
pC
i/g)
Cochiti Lower
Cochiti Middle
Cochiti Upper Cerro Grande Fire
Pu-239,240 in Cochiti Sediment
0
0.05
0.1
0.15
0.2
0.25
1995 1996 1999 2000 2003 2004Co
ncen
tratio
n (p
Ci/g
)
Cochiti Upper
Cochiti Middle
Cochiti Lower
Cerro Grande Fire
Cesium-137 Plutonium-239,240
Background Limit
LA-UR-04-7342
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UNCLASSIFIED
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
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UNCLASSIFIED
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.
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UNCLASSIFIED
UNCLASSIFIED
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
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UNCLASSIFIED
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
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UNCLASSIFIED
UNCLASSIFIED
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