# Presentation: 018431

## 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**
**Longer-lived isotopes (****241****Am,****137****Cs, ****238****Pu, ****239****Pu, ****90****Sr, Uranium)**
**Less water column testing**
**Complemented by fish testing**

**LA-UR-04-7342**

## Monitoring Stations

**Monitoring Stations**

**LA-UR-04-7342**

## Sources of Radioactivity in Rio Grande

**World-wide fallout**
**Natural uranium**
**Old Manhattan Project Site (mostly ****239****Pu)**
**Traced 40+ km from site into Rio Grande and Cochiti Reservoir**

**LA-UR-04-7342**

## 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**

## Cerro Grande Fire Accelerated Transport of Radioactivity 

**Fallout ****137****Cs and ****90****Sr in ash **
**Old Manhattan Project ****239****Pu**

- Source: Gallaher and Koch, 2004

**LA-UR-04-7342**

## Trends in Cochiti Reservoir Sediments

- Cesium-137

- Plutonium-239,240

**Background Limit**

**LA-UR-04-7342**

## 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 (****137****Cs, 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**

## 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**

## 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**

## 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**

## 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**