Uranium munitions contaminate the groundwater

Long-term study on the weathering of uranium munitions proves leaching

Uranium-bearing ammunition UNEP
Read out

It has long been suspected, but now it is official: uranium ammunition, which remains in the ground, is decomposed relatively quickly and uranium compounds reach the groundwater. This is the result of a study in which scientists have for the first time studied the weathering and leaching of uranium containing projectiles.

Depleted uranium is actually a by-product of nuclear power generation. Due to its high density, it is used in the weapons industry for the production of high-impact armor-piercing projectiles. Uranium ammunition has already been deployed in large numbers in Iraq and Kosovo. The leftovers of the ammunition will eventually weather in the ground. Whether or not uranium compounds dissolve in the groundwater or in the plants has been completely unclear.

In a so far unique study, scientists from the GSF Research Center for Environment and Health in cooperation with the Forschungszentrum Dresden-Rossendorf (FZD) have investigated what happens to armor-piercing uranium munitions, which are stored in the ground for a long time and thus exposed to weathering and leaching processes. With the data now obtained, the scientists can make an initial risk assessment and plan next experimental studies.

Chemical modification by "weathering"

To study the weathering process, GSF scientists filled test tubes with different soils and buried uranium ammunition in them. In addition, the soils were treated with normal fertilizer from agriculture and sown with grass. In an air-conditioned laboratory, the test tubes were irrigated weekly with a synthetic rain and the leachate was tested for existing uranium compounds. In total, six test columns were measured in three years under controlled conditions.

The formation of a patina layer on copper roofs is well known. Depending on the chemical composition of the rain, copper minerals with a greenish blue color are formed there. This formation of minerals also occurs during the weathering of uranium munitions. However, uranium minerals are produced there. For example, scientists found sabugalite on the surface of uranium ammunition, an aluminum uranyl phosphate that is poorly soluble in water. This process is relatively fast. According to researchers, a projectile could have completely transformed itself into sabugalite within 50 years. The poisonous uranium is firmly bound in this mineral. display

Leaching takes place in the long term

In parallel with this relatively rapid reaction, a leaching process occurs over a much longer period of time. This results in new carbonated uranium compounds that are very soluble in water. In the unique experiment of GSF and Forschungszentrum Dresden-Rossendorf these uranium compounds could now be detected in the leachate.

The good water solubility is also the reason why uranium compounds from uranium ammunition can enter the groundwater or the plants. Although in the experiment, the growth of the plants in the vicinity of the uranium projectile decreased, the question of the agricultural use of the contaminated soil can not yet be answered with certainty.

High uranium concentrations in the leachate

Checking the leachate for possible uranium compounds is a major challenge in metrological terms. Gerhard Geipel from the FZD's Institute of Radiochemistry is one of only a few experts worldwide who can detect and determine a specific uranium compound even in the smallest amounts. The highly sensitive method of time-resolved laser-induced fluorescence spectroscopy was used.

In this method, one uses the different afterglow of the different uranium compounds when they are irradiated with pulsed laser light. Each of these compounds has a characteristic fluorescence spectrum, which can be accurately attributed to a reference sample.

The leachate contained, according to the current results, a high concentration of uranium compounds: "We have detected concentrations in the leachate, which otherwise can only be found in former uranium mining areas, such as the mines at Schlema in Saxony, " says Geipel. For sure prognoses over a longer period, further investigations are necessary.

(Research Center Dresden - Rossendorf, 19.06.2007 - NPO)