Zeno Karl Schindler Award 2014 - Yuheng Wang
MOBILE URANIUM(IV)-BEARING COLLOIDS IN A MINING-IMPACTED WETLAND AND GEOCHEMICAL CONTROLS ON THEIR FORMATION, Project director: Prof. Rizlan Bernier-Latmani
"For his contribution to uranium geochemistry and for uncovering naturally occurring yet novel reduced uranium species and their impact on the uranium mobility in natural and engineered systems."
Wetlands often act as sinks for toxic heavy metals of natural and anthropogenic origin. We investigated the mobility of uranium in a natural wetland adjacent to a former U mine in central France. A fraction of the U accumulated in the wetland was released into a nearby stream. This is unexpected because the reducing conditions prevalent in such wetlands usually immobilize large amounts of uranium very effectively. The investigation led to the identification of two factors enhancing the mobility of U in this wetland. First, the presence of a clay layer with U concentrations up to 1.4% (w./w.). Locations without the clay layer showed limited U mobility. Second, the presence of mobile colloids (small particles on the order of 5nm) containing Fe(II) and organic matter that also harbor U. The role of the clay layer is to serve as a source of relatively reactive reduced U and that of the colloids is to ‘carry’ U and render it highly mobile. This is the first time that colloids containing reduced U are identified in nature and it has implications for the remediation of U contaminated sites and for the use of wetlands to remove uranium from mining and industrial waste streams.
