Sorption hypotheses and models are required for the prediction of ¹³⁷Cs migration in soils contaminated after nuclear reactor accidents and nuclear weapons tests. In assessment models, the K_d (distribution coefficient) hypothesis for sorption, which assumes that sorption is instantaneous, linear and reversible, has often been coupled with the convection-diffusion equation (CDE) to model ¹³⁷Cs migration. However, it fails to describe ¹³⁷Cs migration velocities which often decrease with time. Alternative equilibrium-kinetic (EK) hypotheses of ¹³⁷Cs sorption/desorption have been suggested by laboratory experiments but have not been fully validated in field conditions. This work addressed the influence and magnitude of non-equilibrium ¹³⁷Cs sorption in field conditions by reinterpreting, with an inverse approach, series of ¹³⁷Cs profiles measured in mineral soils of forest plots located in Fukushima Prefecture (2013–2018). Our results show that the inclusion of non-equilibrium sorption significantly improves, compared to the equilibrium hypothesis, the realism of simulated ¹³⁷Cs profiles. Fitted sorption parameters suggest a fast sorption kinetic (half-time of 1–7 h) and a pseudo-irreversible desorption rate (half-time of 3.2 × 10⁰–3.4 × 10⁶ years), whereas equilibrium sorption (4.0 × 10⁻³ L kg⁻¹ on average) only affects a negligible portion of ¹³⁷Cs inventory. By June 2011, such EK parameters fitted on our plots realistically reproduced profiles measured in the same forest study site (Takahashi et al., 2015). Predictive modeling of ¹³⁷Cs profiles in soil suggests a strong persistence of the surface ¹³⁷Cs contamination by 2030, with exponential profiles consistent with those reported after the Chernobyl accident. This study demonstrates that hypotheses and parameters of ¹³⁷Cs sorption can be partially inferred from in situ measurements. However, further experiments in controlled conditions are required to better estimate the sorption parameters and to identify the processes behind non-equilibrium sorption.

吸附假设和模型是预测在核反应堆事故和核武器试验后受污染的土壤中¹³⁷ Cs迁移所必需的。在评估模型中，假设吸附是瞬时的，线性的和可逆的，吸附的K _d（分布系数）假设通常与对流扩散方程（CDE）耦合在一起以模拟¹³⁷ Cs迁移。但是，它无法描述¹³⁷ Cs迁移速度，该速度通常会随着时间而降低。^137的其他平衡动力学（EK）假设实验室实验已经表明Cs的吸附/解吸，但在野外条件下尚未得到充分验证。这项工作通过反演方法，重新解释了在福岛县（2013–2018）森林地带的矿物土壤中测得的一系列¹³⁷ Cs剖面，从而解决了田间条件下非平衡¹³⁷ Cs吸附的影响和强度。我们的结果表明，与平衡假设相比，模拟的¹³⁷ Cs分布图的真实性与非平衡吸附的包含相比得到了显着改善。拟合的吸附参数表明吸附动力学快（半峰时间为1–7 h）和拟不可逆的解吸速率（半峰时间为3.2×10 ⁰ –3.4×10 ⁶年），而平衡吸附（平均4.0×10 ^-3  L kg ^-1）仅影响¹³⁷ Cs存量的可忽略部分。到2011年6月，在我们的样地上拟合的这些EK参数真实再现了在同一森林研究地点测得的剖面（Takahashi等人，2015）。对土壤中¹³⁷ Cs剖面的预测模型表明，到2030年，表面¹³⁷ Cs污染物的持久存在，其指数剖面与切尔诺贝利事故后报道的一致。这项研究表明，¹³⁷ Cs吸附的假设和参数可以从原位部分推断出来测量。但是，需要在可控条件下进行进一步的实验，以更好地估计吸附参数并确定非平衡吸附背后的过程。