Soil can trap radioactive toxins.

• Position: Nuclear Waste

Soil particles lock up contaminants hundreds to thousands of times faster under the caustic conditions found beneath leaking toxic waste tanks at the Hanford Nuclear Reservation than under normal soil conditions, researchers report. Understanding more about how contaminants such as radioactive cesium and strontium move through the soil under real-world conditions will help clean-up efforts at Hanford and other sites fraught with nuclear waste. Previous work on the movement of soil contaminants had not replicated the extreme conditions found in the state of Washington.

At Hanford, high-level nuclear waste from the manufacture of weapons is stored in 177 tanks buried in the soil. The waste contains toxic and highly radioactive elements, including plutonium, cesium 137, and strontium 90 mixed in with other materials that make the liquids in the tanks extremely caustic. Weapons production began at Hanford in 1944. Since then, 67 of the tanks have leaked, releasing liquid radioactive waste into the soil. Some of the contaminants have been found in the groundwater. Cost estimates for cleaning up the venue run into the tens of billions of dollars.

Figuring out how the wastes move through the soil is difficult because the tanks' contents are complex mixtures of chemicals. Moreover, the contaminated soils and toxic waste materials are too dangerous for the scientists to handle. "If we were working with the concentrations of radioactivity that are out there, it would be lethal doses," indicates Jon Chorover, an...