Hexachlorocyclohexane (HCH) isomers are toxic and persistent pollutants that pose serious risks to the environment and human health. Here we tested the capacity of various nature-based solutions to degrade HCH in contaminated soils of O Porriño area (Galicia, Spain). To this end, eight microcosms were established using combinations of tailor-made biostabilized organic amendments, nanoscale zero-valent iron (nZVI), and an autochthonous microbial inoculum. Throughout a 60-day experiment, we conducted HCH quantification, leachability tests, bacterial community analysis, and soil health assessment. Our results showed that landfarming alone achieved a reduction of up to 83 % in ∑HCH concentrations, demonstrating its cost-effectiveness, facilitated by the physical disruption of HCH aggregates and the presence of HCH-degrading bacteria as Sphingobium, Mesorhizobium and Cupriavidus. Organic amendments did not improve the HCH degradation rate of landfarming, but, notably, reduced HCH leachability and improved soil properties
the combination of the inoculum with the organic amendments revealed the same positive effects but a higher HCH depletion similar to that of landfarming. Thus, the synergistic effects of organic amending and inoculum in an integrated landfarming allows a reduction of the environmental risk and a potential long-term soil restoration, while a landfarming without amendments appear as a cost-effective option but only to reduce HCH contents. These findings aim to provide valuable insights into integrated approach for HCH large-scale landfarming remediation.