Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99354, United States.
Environ Sci Technol. 2011 Oct 1;45(19):8313-20. doi: 10.1021/es2010368. Epub 2011 Sep 2.
Leaching behavior of Sr and Cs in the vadose zone of Hanford site (Washington) was studied with laboratory-weathered sediments mimicking realistic conditions beneath the leaking radioactive waste storage tanks. Unsaturated column leaching experiments were conducted using background Hanford pore water focused on first 200 pore volumes. The weathered sediments were prepared by 6 months reaction with a synthetic Hanford tank waste leachate containing Sr and Cs (10(-5) and 10(-3) molal representative of LO- and HI-sediment, respectively) as surrogates for (90)Sr and (137)Cs. The mineral composition of the weathered sediments showed that zeolite (chabazite-type) and feldspathoid (sodalite-type) were the major byproducts but different contents depending on the weathering conditions. Reactive transport modeling indicated that Cs leaching was controlled by ion-exchange, while Sr release was affected primarily by dissolution of the secondary minerals. The later release of K, Al, and Si from the HI-column indicated the additional dissolution of a more crystalline mineral (cancrinite-type). A two-site ion-exchange model successfully simulated the Cs release from the LO-column. However, a three-site ion-exchange model was needed for the HI-column. The study implied that the weathering conditions greatly impact the speciation of the secondary minerals and leaching behavior of sequestrated Sr and Cs.
采用模拟放射性废物储存罐下真实条件的实验室风化沉积物，研究了汉福德场址（华盛顿州）包气带中 Sr 和 Cs 的淋滤行为。使用聚焦于前 200 个孔隙体积的背景汉福德孔隙水进行了非饱和柱淋滤实验。风化沉积物是通过 6 个月与含有 Sr 和 Cs 的合成汉福德罐废物浸出液（分别代表 LO- 和 HI-沉积物的 10(-5)和 10(-3)摩尔浓度的替代物）反应制备的。风化沉积物的矿物组成表明沸石（片沸石型）和类沸石（方钠石型）是主要的副产物，但取决于风化条件，含量不同。反应迁移模型表明，Cs 的淋滤受离子交换控制，而 Sr 的释放主要受次生矿物溶解的影响。HI 柱中 K、Al 和 Si 的后期释放表明更结晶矿物（方沸石型）的额外溶解。两站点离子交换模型成功模拟了 LO 柱中 Cs 的释放。然而，HI 柱需要三站点离子交换模型。研究表明，风化条件会极大地影响次生矿物的形态和被固定的 Sr 和 Cs 的淋滤行为。
