Abstract The cost of sourcing material for cover material is often a barrier to implementation of multilayer covers to reclaim mined waste or other disturbed land. This study investigated the use of municipal biosolids blended with stabilizing materials as a low-permeability material in covers with capillary barrier effects (CCBEs) for reactive mine tailings. A blended biosolids referred to as Custom Reclamation Mix or CRM (1:1 volumetric mix of anaerobically digested biosolids and leaf and yard waste) was evaluated as a candidate low-permeability layer in a CCBE using material characterization, physical simulation of the CCBE in columns, and unsaturated flow modelling. The CRM exhibited low saturated hydraulic conductivities (k = 4 × 10 −7 cm/s @ e = 4.0) and an air-entry value of approximately 300 kPa. During laboratory column testing comparing a monolayer biosolids cover to a biosolids CCBEs, biosolids layers within the CCBEs remained highly saturated, acting as a barrier to oxygen diffusion and water flux. Pore-water samples in the tailings of the monolayer cover show some evidence of increased concentrations of nitrate relative to CCBEs columns. No significant change in pH was observed in any of the columns. Numerical models showed reduction in water flux at the tailings surface by 98% and a reduction in oxygen diffusion by up to three orders of magnitude when using biosolids CCBEs relative to uncovered tailings. Cover function was not significantly impacted by the characteristics of the underlying tailings. Whereas substantial cracking occurred in the biosolids monolayer cover, the low-permeability layers in the CCBEs remained sufficiently intact to remain both saturated and apparently retained low hydraulic conductivity. The use of amended biosolids as a low-permeability layer in a CCBE therefore appears promising and should be evaluated at larger scales.

中文翻译：

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具有毛细管屏障效应的覆盖物中生物固体的初步评估

摘要 覆盖材料的采购成本通常是实施多层覆盖以回收开采废物或其他受干扰土地的障碍。本研究调查了城市生物固体与稳定材料混合用作反应性尾矿的毛细管屏障效应 (CCBE) 覆盖层中的低渗透性材料。混合生物固体称为定制回收混合物或 CRM（厌氧消化的生物固体和树叶和庭院废物的 1:1 体积混合）被评估为 CCBE 中的候选低渗透层，使用材料表征、柱中 CCBE 的物理模拟和非饱和流动建模。CRM 表现出低饱和水力传导率（k = 4 × 10 -7 cm/s @ e = 4.0）和大约 300 kPa 的空气进入值。在将单层生物固体覆盖物与生物固体 CCBE 进行比较的实验室柱测试期间，CCBE 内的生物固体层保持高度饱和，充当氧气扩散和水通量的屏障。单层覆盖层尾矿中的孔隙水样品显示出一些证据表明硝酸盐浓度相对于 CCBEs 柱增加。在任何柱子中都没有观察到 pH 值的显着变化。数值模型显示，与未覆盖的尾矿相比，使用生物固体 CCBE 时，尾矿表面的水通量减少了 98%，氧扩散减少了三个数量级。覆盖层功能不受底层尾矿特性的显着影响。而生物固体单层覆盖层发生了大量开裂，CCBE 中的低渗透层保持足够完整，以保持饱和并明显保持低水力传导率。因此，在 CCBE 中使用改良的生物固体作为低渗透层似乎很有前景，应该在更大的范围内进行评估。