Nanotechnology-Enabled Remediation of Contaminated Soils: Mechanisms, Soil Constraints, Environmental Risks, and Implications for Sustainable Land Management

Engineered nanomaterials have been increasingly proposed for the treatment of contaminated soils. Nevertheless, most available evidence has been obtained in water, artificial substrates or short-term laboratory experiments, and performance in real soil is substantially more variable. This review examines nanoscale zero-valent iron, photocatalytic metal oxides, carbon-based nanomaterials, and supported or hybrid formulations, with particular attention to the soil properties and contaminant characteristics that control their mobility, transformation, reactivity, and persistence. Nano-enabled treatments can decrease the mobility of arsenic, chromium, lead, and other potentially toxic elements and can promote the degradation of selected pesticides and hydrocarbons. However, opposite responses have also been reported, including mobilisation of non-target elements, nanoparticle aggregation and passivation, effects on microbial communities and plants, contaminant rebound, and potential transport beyond the treated zone. Environmental assessment should therefore consider both the target contaminant and the applied or transformed nanomaterial, together with ecological and occupational exposure pathways. Current evidence does not support nanoremediation as a general replacement for conventional technologies. Its main value lies in its use as a site-specific component of integrated remediation strategies selected according to soil properties, contaminant behaviour, treatment scale, cost, life-cycle impacts, and future land use. European field experience remains limited, particularly in unsaturated soils, and no harmonised EU-wide authorisation procedure specifically for soil nanoremediation currently exists. Wider implementation will require realistic field trials, long-term monitoring, safer and recoverable formulations, transparent regulatory assessment, and evaluation of soil functions and ecosystem-service recovery. A site-specific decision framework is proposed to support material selection, risk–benefit evaluation, and responsible implementation.