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Remediation strategies for metal(loid)-polluted soils vary among the wide range of approaches, including physical, chemical, and biological remediation, or combinations of these. In this study, we assessed the effectiveness of a set of soil remediation treatments based on the combined application of inorganic (marble sludge) and organic amendments (vermicompost, and dry olive residue [DOR] biotransformed by the saprobic fungi Coriolopsis rigida and Coprinellus radians) and inoculation with arbuscular mycorrhizal fungi (AMFs) (Rhizophagus irregularis and Rhizoglomus custos). The treatments were applied under greenhouse conditions to soil residually polluted by potentially toxic elements (PTEs) (Pb, As, Zn, Cu, Cd, and Sb), and wheat was grown in the amended soils to test the effectiveness of the treatments in reducing soil toxicity and improving soil conditions and plant performance. Therefore, we evaluated the influence of the treatments on the main soil properties and microbial activities, as well as on PTE availability and bioaccumulation in wheat plants. Overall, the results showed a positive influence of all treatments on the main soil properties. Treatments consisting of a combination of marble and organic amendments, especially biotransformed DOR amendments, showed the greatest effectiveness in improving the soil biological status, promoting plant growth and survival, and reducing PTE availability and plant uptake. Furthermore, AMF inoculation further enhanced the efficacy of DOR amendments by promoting the immobilization of PTEs in soil and stimulating the phytostabilization mechanisms induced by AMFs, thus playing an important bioprotective role in plants. Therefore, our results highlight that biotransformed DOR may represent an efficient product for use as a soil organic amendment when remediating metal(loid)-polluted soils, and that its application in combination with AMFs may represent a promising sustainable bioremediation strategy for recovering soil functions and reducing toxicity in polluted areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The present study focuses on the remediation of diesel-polluted soil using modified Fenton treatment coupled with inorganic NPK fertilizer ("Fenton+NPK"). Studies were carried out in a pilot plant containing 1 m(3) of sandy soil contaminated with 20,000 mg kg(-1) of diesel, placed outdoors at a temperature ranging between 5 and 10 °C. Results showed that NPK-fertilizer as post-treatment stimulated culturable degrading bacteria and enhanced dehydrogenase activity. Fenton+NPK treatment increased total petroleum hydrocarbon (TPH) removal efficacy. Natural attenuation removed 49% of TPH in the surface layer, 23% of TPH in the non-saturated layer and 4% of the TPH in the saturated layer, while the percentage removed of TPH after Fenton+NPK treatment was 58%, 57% and 32% respectively. The results from our study showed that, immediately after soil contamination, occurred a specialization and differentiation of the bacterial community, but after this initial modification, no significant changes of bacterial diversity was observed under natural attenuation conditions. In contrast, when the Fenton's reagent was applied a reduction of the bacterial biodiversity was observed. However, the post-biostimulation did enhance the degrading microbiota and stimulated their degrading biological activity. In conclusion, biostimulation, as a post-treatment step in chemical oxidation, is an effective solution to remediate hydrocarbon-polluted sites., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Biodegradation is one of the primary mechanisms for elimination of petroleum and other hydrocarbon pollutants from the environment. It is considered an environmentally acceptable way of eliminating oils and fuel because the majority of hydrocarbons in crude oils and refined products are biodegradable. Petroleum hydrocarbon compounds bind to soil components and are difficult to remove and degrade. Bioemulsifiers can emulsify hydrocarbons enhancing their water solubility and increasing the displacement of oily substances from soil particles. For these reasons, inclusion of bioemulsifiers in a bioremediation treatment of a hydrocarbon polluted environment could be really advantageous. There is a useful diversity of bioemulsifiers due to the wide variety of producer microorganisms. Also their chemical compositions and functional properties can be strongly influenced by environmental conditions. The effectiveness of the bioemulsifiers as biostimulating agent in oil bioremediation processes has been demonstrated by several authors in different experimental assays. For example, they have shown to be really efficient in combination with other products frequently used in oil bioremediation such as they are inorganic fertilizer (NPK) and oleophilic fertilizer (i.e. S200C). On the other hand, the bioemulsifiers have shown to be more efficient in the treatment of soil with high percentage of clay. Finally, it has been proved their efficacy in other biotechnological processes such as in situ treatment and biopiles. This paper reviews literature concerning the application of bioemulsifiers in the bioremediation of soil polluted with hydrocarbons, and summarizes aspects of the current knowledge about their industrial application in bioremediation processes.