Pacific Northwest National Laboratory, P.O. Box 999, K3-62, 902 Battelle Boulevard, Richland, Washington 99354, USA.
Environ Sci Technol. 2010 Nov 1;44(21):8089-94. doi: 10.1021/es903223x.
We investigated the effects of water saturation and secondary precipitate formation on Sr and Cs transport through quartz sand columns under saturated and unsaturated flow. Column experiments were conducted at effective water saturation ranging from 0.2 to 1.0 under steady-state flow using either 0.1 M NaNO(3) or simulated tank waste leachate (STWL; 1 M NaNO(3) and 1 M NaOH) mimicking Hanford (Washington, USA) tank waste. In 0.1 M NaNO(3) columns, Sr transported like a conservative tracer, whereas Cs was retarded relative to Sr. The transport of Sr and Cs in the 0.1 M NaNO(3) columns under all water saturations could be described with the equilibrium convection-dispersion equation (CDE). In STWL columns, Sr mobility was significantly reduced compared to the 0.1 M NaNO(3) column, because Sr was incorporated into or sorbed to neo-formed secondary precipitates. Strontium sequestration by precipitates was confirmed by additional batch and electron micrograph analyses. In contrast(,) the transport of Cs was less affected by the STWL; retardation of Cs in STWL columns was similar to that found in 0.1 M NaNO(3) columns. Analysis of STWL column data revealed that both Sr and Cs breakthrough curves showed nonideal behavior that suggest nonequilibrium conditions, although nonlinear geochemical behavior cannot be ruled out.
我们研究了水饱和度和次生沉淀形成对 Sr 和 Cs 在饱和和非饱和流通过石英砂柱的传输的影响。在稳态流条件下，有效水饱和度范围为 0.2 至 1.0 时，使用 0.1 M NaNO3 或模拟乏燃料池浸出液（STWL；1 M NaNO3 和 1 M NaOH）进行了柱实验，以模拟美国华盛顿汉福德（Hanford）乏燃料池。在 0.1 M NaNO3 柱中，Sr 作为保守示踪剂传输，而 Cs 相对于 Sr 则被延迟。在所有水饱和度下，Sr 和 Cs 在 0.1 M NaNO3 柱中的传输可以用平衡对流-弥散方程（CDE）来描述。在 STWL 柱中，与 0.1 M NaNO3 柱相比，Sr 的迁移性显著降低，因为 Sr 被纳入或吸附到新形成的次生沉淀中。沉淀物对 Sr 的螯合作用通过额外的批处理和电子显微镜分析得到证实。相比之下，Cs 的传输受 STWL 的影响较小；在 STWL 柱中，Cs 的延迟与在 0.1 M NaNO3 柱中发现的相似。对 STWL 柱数据的分析表明，Sr 和 Cs 的穿透曲线均表现出非理想行为，表明存在非平衡条件，尽管不能排除非线性地球化学行为。
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