FROM IMPACTED TO REUSABLE: DEFINING THE ECOLOGICAL POTENTIAL OF BIOREMEDIATED SOILS

Bioremediation is a sustainable, low-impact approach to managing contaminated soils, enabling the restoration of ecological functionality and supporting their integration into the circular economy. However, the safe reuse of remediated soils requires assessment frameworks that go beyond chemical compliance and integrate physicochemical properties with biological responses. This study presents an integrated approach for evaluating the quality and reuse potential of bioremediated soils by combining agronomic characterization with a structured ecotoxicological framework. The aim is to develop a reproducible, stepwise methodology for classifying soil quality into six levels (Classes A–F), each associated with potential reuse applications in urban green infrastructure, landscape design, and ecological restoration. Agronomic characterization includes pH, texture, total and organic carbon, nitrogen, total, organic and available phosphorus, and calcium carbonate, providing information on soil properties that may influence biological responses and ecological performance. The ecotoxicological workflow consists of two sequential phases using the standard soil indicator species Eisenia fetida and Folsomia candida. The first phase comprises avoidance tests to identify unsuitable soil conditions and assign a preliminary quality class. The second phase uses reproduction tests to assess chronic sub-lethal effects and refine the classification into the final Classes A–F, providing a more comprehensive indication of ecological functionality. The first phase was applied to soils collected from two sites undergoing dynamic biopile remediation. The tested soils showed a broad range of biological responses, from compatibility with both indicator species to moderate or strong avoidance. The integration of these biological endpoints with soil physicochemical characteristics provides the basis for distinguishing soils with different ecological suitability for reuse. Overall, the proposed classification framework aims to translate physicochemical and ecotoxicological information into practical reuse categories, supporting the safe integration of bioremediated soils into circular-economy strategies and promoting sustainable land management.