The soil contamination of petroleum hydrocarbons is a widespread problem requiring an environmentally friendly and cost-effective solution. This study aimed to test the leguminous plant resistance to heavy fuel oil (HF) soil contamination and to evaluate their phytoremediation efficiency and potential to maintain the soil nutrient content. Eight legume species were selected for the study. The selected legumes were grown in a growth chamber in HF-contaminated soil (2.5 and 4 g kg⁻¹) for 90 days. After the soil treatment, the changes in the soil HF contamination, nutrient concentrations, and plants morphology were monitored. The HF pollution significantly affected the dry weight of the shoots and roots of seven of the eight tested plant species. M. sativa, M. albus, and L. corniculatus had the highest phytoremediation potential with the efficiency of the HF removal up to 95 %. The leguminous plant-assisted HF remediation resulted in an increase in the ammonium and inorganic phosphorous soil content, with the highest increase in the case of L. corniculatus and O. viciifolia. The cultivation of Phaseolus vulgaris, L. corniculatus, and M. albus helped to maintain the soil nitrates close to the constant level. The study demonstrated that M. sativa, L. corniculatus, and M. albus were the most efficient in HF removal.

This study aims to assess the impact of HydroBreak PLUS biosurfactant on the phytoremediation of diesel-contaminated soil by three legume plant species: Medicago sativa, Lotus corniculatus, and Melilotus albus. Legumes were grown in soil contaminated with diesel (4.0 g kg⁻¹, 6.0 g kg⁻¹) for 90 days, and the changes in soil diesel and nutrient concentrations, plant growth, and physiological parameters were measured. Diesel negatively affected the biomass production of all legumes, though the reduction in growth rate was observed only in L. corniculatus and M. albus. L. corniculatus had the highest diesel removal rate of 93%, M. albus had the lowest of 87.9%, and unplanted treatments had significantly lower diesel removal rates (up to 66.5%). The biosurfactant mitigated diesel-induced reduction in plant shoot and root weight and an increase in L. corniculatus root biomass (24.2%) were observed at 4.0 g kg⁻¹ diesel treatment. The use of biosurfactant accelerated diesel removal from the soil, though the effect was diesel soil concentration and plant species-dependent. In unplanted treatments, the diesel removal rates increased by 16.4% and 6.9% in the treatments with 4 and 6 mg kg⁻¹, respectively. The effect of biosurfactants on diesel removal by plants was less pronounced and reached 4.6% and 3.2% in the treatments with 4 and 6 mg kg⁻¹, respectively. The study revealed that the phytoremediation efficiency could not be directly linked to plant physiological parameters as only M. sativa changes in plant growth corresponded well with photosystem II performance. Implementation of legumes and biosurfactants has a positive effect on soil quality by its enrichment with inorganic P and soluble phenols, while no enrichment in NO₃⁻ and NH₄⁺ was observed.

Due to the large number of areas contaminated with TPH, there is significant interest in biological remediation technology research, offering a comprehensive and sustainable approach to soil decontamination and health recovery at the same time. This study aimed to investigate the effectiveness of remediating TPH-contaminated soil (6120 mg kg⁻¹) using Lotus corniculatus along with a microorganism consortium (GTC-GVT/2021) isolated from historic TPH-contaminated sites. This study evaluated the removal of TPH and soil health recovery through changes in soil nutrient content, soil enzymatic activity, and the microbiological community. The growth of L. corniculatus was reduced in TPH-contaminated soil, particularly affecting root biomass by 52.17%. Applying inoculum positively affected total plant biomass in uncontaminated (51.44%) and contaminated (33.30%) soil. The GTC-GVT/2021 inoculum significantly enhanced the degradation of TPH in contaminated soil after 90 days by 20.8% and in conjunction with L. corniculatus by 26.33% compared to the control. The soil enzymatic activity was more pronounced in TPH-contaminated soil treatments, and in most cases, the presence of L. corniculatus and inoculum led to a significantly higher soil enzymatic activity. The cultivation of L. corniculatus and the inoculum resulted in an increased concentration of inorganic P, NH₄⁺, and water-soluble phenols in the soil, while no rise in NO₃⁻ was observed.