The reactive transport of U from co-occurring U(IV) and U(VI) mineral phases in mine waste sediments from the Jack pile mine, in Laguna Pueblo, NM was investigated using laboratory experiments, reactive transport modelling (PFLOTRAN) and advanced spectroscopy, microscopy and diffraction techniques. Concentrations exceeding 7000 mg/Kg U were measured in mine waste sediments using X-ray fluorescence. Furthermore, XPS results suggest that these sediments contain 80% U(VI) and 20% U(IV). These results agree with the XRD and electron microprobe data which identified coffinite and U-phosphates minerals. The reactive transport of U was tested using continuous flow through column experiments where the unreacted sediments were sequentially reacted with 18MΩ water (pH 5.4), 10mM HCO3- (pH 7.9) and 10mM CH3COOH (pH 3.4). Our results suggest U desorption and dissolution of coffinite and U-phosphates are key mechanisms controlling the release of U. These results are relevant to better understand the transport of U in surface and hyphoreic zone waters adjacent to abandoned mine waste sites.

Reactive transport of U from co-occurring U(IV) and U(VI) phases in abandoned U mine waste sites

253rd National Meeting (2017)

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