Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA.
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA.
Talanta. 2021 May 1;226:122096. doi: 10.1016/j.talanta.2021.122096. Epub 2021 Jan 13.
Hydrated secondary mineralization readily forms on the surface of UO particles exposed to humidity in an oxidizing environment. The oxygen stable isotope composition of the secondary uranium oxide may reflect that of the water vapor, as well as the hydrogen and oxygen stable isotopic composition of the mineral hydration water. The geospatial organization of δH and δO values of atmospheric humidity and precipitation is increasingly well understood, which suggests that the hydrogen and oxygen stable isotopes in secondary mineral hydration water may yield information on the environment in which the mineralization formed. UO powders were exposed to air with constant 30%, 61%, and 91% relative humidity, and constant H and O stable isotope composition. Aliquots were sampled from the UO materials at intervals of 1-10 days through the total humidity exposure duration of 180 days. Scanning electron microscopy, transmission electron microscopy, and x-ray diffraction analysis of the humidity-exposed UO indicates that schoepite/metaschoepite [(UO)•2HO] secondary phases had formed on the underlying UO. The δH and δO values of mineral hydration waters were determined by thermogravimetry-enabled isotope ratio infrared spectroscopy (TGA-IRIS). Results indicate that hydrogen in the surface sorbed and mineral hydration waters is exchangeable and thus their δH values are difficult to interpret. However, oxygen in these waters is less exchangeable, and thus the oxygen stable isotope composition of the schoepite/metaschoepite hydration water is likely to be related to that of the exposure water vapor. After formation of schoepite/metaschoepite, the δO values of the hydration water in schoepite/metaschoepite does not change in response to changes in exposure vapor δO values, which suggests that the δO values of the hydration water is relatively durable. These findings suggest that information about the origin and storage history of a UO sample may be discernable from δO values of schoepite/metaschoepite hydration water.
水合次生矿物在暴露于氧化环境中的湿度的 UO 颗粒表面上很容易形成。次生氧化铀的氧稳定同位素组成可能反映了水蒸气以及矿物水合水的氢和氧稳定同位素组成。大气湿度和降水的氢和氧稳定同位素的地理空间组织越来越被理解，这表明次生矿物水合水中的氢和氧稳定同位素可能提供有关成矿形成环境的信息。UO 粉末暴露于相对湿度恒定为 30%、61%和 91%的空气中，且氢和氧稳定同位素组成恒定。在总共 180 天的湿度暴露期间，每隔 1-10 天从 UO 材料中取样。湿度暴露的 UO 的扫描电子显微镜、透射电子显微镜和 X 射线衍射分析表明，在基础 UO 上已经形成了水羟铀矿/准水羟铀矿[（UO）•2HO]次生相。矿物水合水的δH 和δO 值通过热重法同位素比红外光谱（TGA-IRIS）确定。结果表明，表面吸附和矿物水合水中的氢是可交换的，因此它们的δH 值难以解释。然而，这些水中的氧交换性较小，因此水羟铀矿/准水羟铀矿水合水的氧稳定同位素组成可能与暴露水蒸气有关。形成水羟铀矿/准水羟铀矿后，水羟铀矿/准水羟铀矿中水合水的δO 值不会随暴露水蒸气δO 值的变化而变化，这表明水合水的δO 值相对稳定。这些发现表明，UO 样品的起源和储存历史的信息可能可以从水羟铀矿/准水羟铀矿水合水中的δO 值中辨别出来。
