Uranium phases in contaminated sediments below Hanford's U tank farm.
Uranium phases in contaminated sediments below Hanford's U tank farm.
复制标题
汉福德 U 储罐场下方受污染沉积物中的铀相。
DOI：
10.1021/es900203r
复制
发表时间：
2009
影响因子：
11.4
通讯作者：
A. Francis
中科院分区：
文献类型：
--
作者：
W. Um;Zhemin Wang;R. Serne;B. Williams;Christopher F. Brown;C. Dodge;A. Francis
宏观和光谱调查（XAFS，XRF和TRLIF）汉福德污染的包气带沉积物的U-罐农场表明，U（VI）存在不同的表面相作为地下深度的函数（BGS）。U（VI）硅酸盐沉淀物的次级沉淀物（钼铀矿和铀矿）主要存在于浅深度沉积物（15-16 m bgs）中，而吸附U（VI）相和多核U（VI）表面沉淀物被认为在中深度沉积物（20-25 m bgs）中占主导地位。在较深的沉积物（> 28 m bgs）中仅观察到天然铀，没有与含汉福德铀（VI）的罐废物接触的迹象。在所有深度，大部分的U（VI）优先与沉积物的粉砂和粘土粒度级。U（VI）和Ca之间的强相关性被发现在浅层沉积物中，特别是沉淀的U（VI）硅酸盐。由于U（VI）硅酸盐沉淀在浅部沉积物中占主导地位，宏观（重）碳酸盐淋滤释放的U（VI）浓度是解吸和溶解过程的结果。在汉福德污染的沉积物中具有不同的U（VI）表面相表明U（VI）释放机制可能是复杂的，并且需要使用几种不同的方法对沉积物进行详细表征，以正确估计U（VI）在包气带中的命运和运输。
Macroscopic and spectroscopic investigations (XAFS, XRF, and TRLIF) on Hanford contaminated vadose zone sediments from the U-tank farm showed that U(VI) exists as different surface phases as a function of depth below ground surface (bgs). Secondary precipitates of U(VI) silicate precipitates (boltwoodite and uranophane) were present dominantly in shallow-depth sediments (15-16 m bgs), while adsorbed U(VI) phases and polynuclear U(VI) surface precipitates were considered to dominate in intermediate-depth sediments (20-25 m bgs). Only natural uranium was observed in the deeper sediments (> 28 m bgs) with no signs of contact with tank wastes containing Hanford-derived U(VI). Across all depths, most of the U(VI) was preferentially associated with the silt and clay size fractions of sediments. Strong correlation between U(VI) and Ca was found in the shallow-depth sediments, especially for the precipitated U(VI) silicates. Because U(VI) silicate precipitates dominate in the shallow-depth sediments, the released U(VI) concentration by macroscopic (bi)carbonate leaching resulted from both desorption and dissolution processes. Having different U(VI) surface phases in the Hanford contaminated sediments indicates that the U(VI) release mechanism could be complicated and that detailed characterization of the sediments using several different methods would be needed to estimate U(VI) fate and transport correctly in the vadose zone.