Speciation And Reactivity Of Uranium And Organic Matter In Abandoned Mine Wastes From Laguna - New Mexico

We applied spectroscopy, microscopy, and water chemistry techniques to investigate the speciation and reactivity of organic matter on uranium (U) binding from abandoned U mine waste from the Jackpile Mine in Laguna Pueblo, New Mexico. Preliminary studies using fixed angle X-ray fluorescence (XRF) analysis show 3.14% carbon (C). Results from microprobe mapping suggest that uranium particles are surrounded by carbon inclusions. We hypothesize that the presence of carbon in the mine waste influences the uranium binding and therefore its release to the environment. Loss on ignition (LOI) analysis showed that 12.98±0.25% mass was lost. The change on mass after the LOI might be due to the loss of organic content of the samples. Analyses with Xray photoelectron spectroscopy (XPS) show changes on the carbon binding after the LOI experiments and the oxidation of U (IV) to U(VI). The mean concentration of acid extractable for mine waste was 0.54±0.1% U before LOI and 0.64±0.01% U after LOI. Basic Extractions of the Particulate Organic Matter (BEPOM) and Excitation Emission Matrix (EMM) show the presence of humic and fulvic-like groups in the mine waste. Findings from this study are relevant to identify how the binding of U and C in mine wastes can influence U mobilization in order to inform risk assessment and reduction strategies.