There is a growing need to recover degraded soils to restore their essential ecosystem services and limit damages of anthropic activities onto these systems. Safe and sustainable solutions for long-term recovery must be designed, ideally by recycling existing resources. Using ash from combustion of residual forest biomass at the pulp and paper industry is an interesting and sustainable strategy to recover mining soils. However, formulations must be found to limit the potential toxicity associated with soluble salts and chloride that ash contains. Here, we assessed the effectiveness of three field ash-based amendments for the recovery of three highly acidic soils from Portuguese abandoned mines. Three amendments were tested: an un-stabilized mixture of ash and biological sludge, granulated ash, and granulated ash mixed with composted sludge. One year after application in open field plots (in the scope of LIFE No_Waste project), soil health restoration was evaluated through (i) soil physico-chemical characterization and (ii) soil habitat functions though standardized ecotoxicological tests.

This study highlights that stabilized materials provided nutrients, organic matter and alkalinity that corrected soil pH and decreased metal bioavailability, while controlling the release of soluble salts and chloride from ash. This soil improvement correlated with improved soil model organisms’ reproduction and survival. For similar amendment, the native soil properties studied (as soil native electrical conductivity) affected the level of organism response.

This work provides evidence that ash stabilization, formulation and supplementation with organic matter could be sustainable strategies to restore highly degraded mining soils and to recover their ecological functions. It further highlights the importance of analyzing combined effects on soil physico-chemical properties and ecological function recovery to assess restoration strategy efficiencies in complex multi-stressor environments.

越来越需要恢复退化的土壤，以恢复其基本的生态系统服务，并限制人类活动对这些系统的破坏。必须设计安全和可持续的长期恢复解决方案，最好是通过回收现有资源。在纸浆和造纸工业中使用剩余森林生物质燃烧产生的灰是恢复采矿土壤的一种有趣且可持续的策略。然而，必须找到能够限制与灰分中的可溶性盐和氯化物相关的潜在毒性的配方。在这里，我们评估了三种基于现场灰分的改良剂对从葡萄牙废弃矿山中恢复三种高酸性土壤的有效性。测试了三种改良剂：灰和生物污泥的不稳定混合物、颗粒灰以及与堆肥污泥混合的颗粒灰。(i)土壤理化特性和(ii)通过标准化生态毒理学测试的土壤栖息地功能。

这项研究强调，稳定的材料提供了营养物质、有机质和碱度，可以纠正土壤 pH 值并降低金属生物有效性，同时控制灰烬中可溶性盐和氯化物的释放。这种土壤改良与改良的土壤模式生物的繁殖和存活相关。对于类似的修正，所研究的原生土壤特性（如土壤原生电导率）影响生物体反应的水平。

这项工作提供的证据表明，灰烬稳定、配制和补充有机物质可能是恢复高度退化的采矿土壤并恢复其生态功能的可持续策略。它进一步强调了分析土壤理化特性和生态功能恢复的综合影响以评估复杂多压力环境中恢复策略效率的重要性。