The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Spokane St, PO Box 642710, Pullman, WA 99164-2710, United States.
Water Res. 2012 Sep 1;46(13):3989-98. doi: 10.1016/j.watres.2012.05.027. Epub 2012 May 23.
Regions within the U.S. Department of Energy Hanford 300 Area (300 A) site experience periodic hydrologic influences from the nearby Columbia River as a result of changing river stage, which causes changes in groundwater elevation, flow direction and water chemistry. An important question is the extent to which the mixing of Columbia River water and groundwater impacts the speciation and mobility of uranium (U). In this study, we designed experiments to mimic interactions among U, oxic groundwater or Columbia River water, and 300 A sediments in the subsurface environment of Hanford 300 A. The goals were to investigate mechanisms of: 1) U immobilization in 300 A sediments under bulk oxic conditions and 2) U remobilization from U-immobilized 300 A sediments exposed to oxic Columbia River water. Initially, 300 A sediments in column reactors were fed with U(VI)-containing oxic 1) synthetic groundwater (SGW), 2) organic-amended SGW (OA-SGW), and 3) de-ionized (DI) water to investigate U immobilization processes. After that, the sediments were exposed to oxic Columbia River water for U remobilization studies. The results reveal that U was immobilized by 300 A sediments predominantly through reduction (80-85%) when the column reactor was fed with oxic OA-SGW. However, U was immobilized by 300 A sediments through adsorption (100%) when the column reactors were fed with oxic SGW or DI water. The reduced U in the 300 A sediments fed with OA-SGW was relatively resistant to remobilization by oxic Columbia River water. Oxic Columbia River water resulted in U remobilization (∼7%) through desorption, and most of the U that remained in the 300 A sediments fed with OA-SGW (∼93%) was in the form of uraninite nanoparticles. These results reveal that: 1) the reductive immobilization of U through OA-SGW stimulation of indigenous 300 A sediment microorganisms may be viable in the relatively oxic Hanford 300 A subsurface environments and 2) with the intrusion of Columbia River water, desorption may be the primary process resulting in U remobilization from OA-SGW-stimulated 300 A sediments at the subsurface of the Hanford 300 A site.
美国能源部汉福德 300 区（300A）内的部分地区会受到附近哥伦比亚河周期性水文变化的影响，包括河流水位变化导致的地下水抬升、流向和水化学变化。一个重要的问题是，哥伦比亚河水与地下水的混合在多大程度上影响了铀（U）的形态和迁移性。在这项研究中，我们设计了实验来模拟 U、含氧地下水或哥伦比亚河水与汉福德 300A 地下环境中的 300A 沉积物之间的相互作用。目的是研究以下机制：1）在含氧条件下 300A 沉积物中 U 的固定化；2）含氧哥伦比亚河水暴露下从 U 固定化的 300A 沉积物中重新释放 U。首先，在柱式反应器中，用含氧 1）合成地下水（SGW）、2）含有机添加剂的 SGW（OA-SGW）和 3）去离子（DI）水喂养 300A 沉积物，以研究 U 的固定化过程。之后，将沉积物暴露于含氧的哥伦比亚河水中以进行 U 的再移动研究。结果表明，当柱式反应器中含氧 OA-SGW 时，300A 沉积物主要通过还原（80-85%）固定 U。然而，当柱式反应器中含氧 SGW 或 DI 水时，U 则通过吸附（100%）固定在 300A 沉积物中。在 OA-SGW 喂养的 300A 沉积物中还原的 U 相对不易受含氧哥伦比亚河水中的再移动。含氧哥伦比亚河水通过解吸导致 U 的再移动（∼7%），并且在 OA-SGW 喂养的 300A 沉积物中保留的大部分 U（∼93%）是以铀矿纳米颗粒的形式存在。这些结果表明：1）通过 OA-SGW 刺激 300A 沉积物中土著微生物的还原固定 U，在相对含氧的汉福德 300A 地下环境中可能是可行的；2）随着哥伦比亚河水的入侵，解吸可能是导致汉福德 300A 地下 300A 沉积物中由 OA-SGW 刺激的 U 重新迁移的主要过程。
