Over 4 million liters of mixed acidic (∼pH 2.5), high ionic strength (∼5 M nitrate) plutonium (Pu) processing waste were released into the 216-Z-9 (Z-9) trench at the Hanford Site, USA, and trace Pu has migrated 37 m below the trench. In this study, we used flowthrough columns to investigate Pu transport in simplified processing waste through uncontaminated Hanford sediments to determine the conditions that led to Pu migration. In low pH aqueous fluids, some Pu breakthrough is observed at pH < 4, and increased Pu transport (14% total Pu breakthrough) is observed at pH < 2. However, Pu migrates in organic processing solvents through low pH sediments virtually uninhibited with approximately 94 and 86% total Pu breakthrough observed at pH 1 and pH 3, respectively. This study demonstrates that Pu migration can occur both with and without organic solvents at pH < 4, but significantly more Pu can be transported when partitioned into organic processing solvents. Our data suggest that under acidic conditions (pH < 4) in the vadose zone beneath the Z-9 trench, Pu present in organic processing solvents moved relatively unhindered and may explain the historical downward migration of Pu tens of meters below the Z-9 trench.

中文翻译：

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美国汉福德工厂有机和含水酸性加工废物中钚的地下传输


超过 400 万升混合酸性（~pH 2.5）、高离子强度（~5 M 硝酸盐）钚 (Pu) 加工废物被排放到美国汉福德工厂的 216-Z-9 (Z-9) 沟槽中，微量Pu已迁移到海沟以下37 m处。在这项研究中，我们使用流通柱来研究简化加工废物中钚通过未受污染的汉福德沉积物的迁移，以确定导致钚迁移的条件。在低 pH 水性流体中，在 pH < 4 时观察到一些 Pu 突破，在 pH < 2 时观察到 Pu 传输增加（总 Pu 突破的 14%）。然而，Pu 在有机加工溶剂中通过低 pH 沉积物的迁移几乎不受抑制，大约为在 pH 1 和 pH 3 时分别观察到 94% 和 86% 的总 Pu 突破。这项研究表明，在 pH < 4 的情况下，无论有无有机溶剂，Pu 迁移都会发生，但当分配到有机加工溶剂中时，可以传输更多的 Pu。我们的数据表明，在 Z-9 海沟下方渗流区的酸性条件下（pH < 4），有机加工溶剂中存在的 Pu 移动相对不受阻碍，这可能解释了历史上 Z-9 海沟下方数十米处的 Pu 向下迁移。