Agronomic strategies for remediation of hydrocarbon-contaminated soils: Turfgrass coverage, compost amendment, and bacterial inoculation

The presence of contaminants in the soil, such as hydrocarbons, potentially toxic elements and pesticides, represents one of the major threats to human and natural ecosystem health. Remediation techniques, including biological and physico-chemical methods, are often very expensive and not particularly efficient, so safety measures could be applied for reducing or limiting the movement of these contaminants towards other environmental compartments. In this mesocosm study, the efficacy of different phytoremediation systems (i.e. turfgrass mixtures, amendment and microbial biostimulation) was evaluated to prevent the dispersion and resuspension of particles of a soil artificially contaminated with hydrocarbons. The turfgrass mixture containing Festuca arundinacea, Poa pratensis and Lolium perenne reached about 80 % soil cover within three months, whereas the mixture based on two F. arundinacea cultivars showed slower initial establishment but achieved complete cover after 11 months, confirming the later growth of this species. Compost amendment consistently enhanced plant growth and nitrogen uptake and accelerated canopy closure, improving early soil coverage. After 11 months, total hydrocarbons in the soils decreased on average by about 60 %, with significantly greater removal in inoculated than in non-inoculated soils. Compost amendment and sampling time strongly shaped bacterial community composition, while inoculation with the selected PGPR consortium modified microbial diversity patterns without impairing turfgrass performance. Overall, turfgrass phytocapping, particularly when combined with compost and selected PGPR strains, proved effective in stabilizing diesel-contaminated soil by rapidly securing the surface and stimulating hydrocarbon biodegradation while supporting soil microbial communities. These results highlight compost-assisted, microbe-enhanced turfgrass systems as a low-input and scalable strategy to reduce human and environmental exposure to hydrocarbons in contaminated industrial and peri-urban soils.