UNCLASSIFIED

UNCLASSIFIED

Transport of Radionuclides to the Rio Grande

Bruce Gallahergallaher@lanl.gov

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

Monitoring Stations

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

LA-UR-04-7342

UNCLASSIFIED

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

UNCLASSIFIED

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

LA-UR-04-7342

UNCLASSIFIED

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.

LA-UR-04-7342

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

LA-UR-04-7342

UNCLASSIFIED

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

LA-UR-04-7342

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