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Soil contamination constitutes a significant threat to the health of soil ecosystems in terms of complexity, toxicity, and recalcitrance. Among all contaminants, aliphatic petroleum hydrocarbons (APH) are of particular concern due to their abundance and persistence in the environment and the need of remediation technologies to ensure their removal in an environmentally, socially, and economically sustainable way. Soil remediation technologies presently available on the market to tackle soil contamination by petroleum hydrocarbons (PH) include landfilling, physical treatments (e.g., thermal desorption), chemical treatments (e.g., oxidation), and conventional bioremediation. The first two solutions are costly and energy-intensive approaches. Conversely, bioremediation of on-site excavated soil arranged in biopiles is a more sustainable procedure. Biopiles are engineered heaps able to stimulate microbial activity and enhance biodegradation, thus ensuring the removal of organic pollutants. This soil remediation technology is currently the most environmentally friendly solution available on the market, as it is less energy-intensive and has no detrimental impact on biological soil functions. However, its major limitation is its low removal efficiency, especially for long-chain hydrocarbons (LCH), compared to thermal desorption. Nevertheless, the use of fungi for remediation of environmental contaminants retains the benefits of bioremediation treatments, including low economic, social, and environmental costs, while attaining removal efficiencies similar to thermal desorption. Mycoremediation is a widely studied technology at lab scale, but there are few experiences at pilot scale. Several factors may reduce the overall efficiency of on-site mycoremediation biopiles (mycopiles), and the efficiency detected in the bench scale. These factors include the bioavailability of hydrocarbons, the selection of fungal species and bulking agents and their application rate, the interaction between the inoculated fungi and the indigenous microbiota, soil properties and nutrients, and other environmental factors (e.g., humidity, oxygen, and temperature). The identification of these factors at an early stage of biotreatability experiments would allow the application of this on-site technology to be refined and fine-tuned. This review brings together all mycoremediation work applied to aliphatic petroleum hydrocarbons (APH) and identifies the key factors in making mycoremediation effective. It also includes technological advances that reduce the effect of these factors, such as the structure of mycopiles, the application of surfactants, and the control of environmental factors. [ABSTRACT FROM AUTHOR]

• Bioremediation failed to decontaminate a chronically oil-polluted soil. • Electrokinetic remediation (EKR) was combined with bioremediation. • Bioremediation was applied downstream of the EKR. • The sequential treatment exhibited high degradation performance. • The EKR induced a partial, albeit reversible, inhibition of the microbiota. This study focused on the remediation of a chronically diesel-polluted soil by combining an electrokinetic treatment with a variety of bioremediation approaches. Priority within the sequential treatment was given to electrokinetic remediation (EKR) since the application of natural attenuation (NA), biostimulation and site-specific bio-augmentation resulted in very low degradation performance for total petroleum hydrocarbons (TPH) and polycyclic hydrocarbons (PAH). The application of 20-day EKR (1.0 V cm−1 with polarity reversal) led to 47.2 % and 46.2 % removal of TPH and PAH, respectively, and exerted a negative impact on bacterial abundance, as determined indirectly by quantitative PCR of 16S rRNA genes and community function, as investigated by community-level physiological profiling. These adverse effects were transient and, after a 50-day NA treatment applied downstream from EKR, bacterial abundance was an order of magnitude higher than that found in the initial soil and TPH and PAH removals were significantly higher than those attained by EKR (64.1 % and 56.3 %, respectively). The combination of EKR with site-specific bioaugmentation led to the greatest TPH and PAH degradation (76.0 % and 78.6 %, respectively). The results indicate that bioremediation can be successfully applied downstream from EKR and that the adverse effects exerted by this physico-chemical approach on soil microbiota are reversible. [ABSTRACT FROM AUTHOR]

Fenton-like treatment (FLT) is an ISCO technique relying on the iron-induced H 2 O 2 activation in the presence of additives aimed at increasing the oxidant lifetime and maximizing iron solubility under natural soil pH conditions. The efficacy of FLT in the clean-up of hydrocarbon-contaminated soils is well established at the field-scale. However, a better assessment of the impact of the FLT on density, diversity and activity of the indigenous soil microbiota, might provide further insights into an optimal combination between FLT and in-situ bioremediation (ISB). The aim of this work was to assess the impacts of FLT on the microbial community of a diesel-contaminated soil collected nearby a gasoline station. Different FLT conditions were tested by varying either the H 2 O 2 concentrations (2 and 6%) or the oxidant application mode (single or double dosage). The impact of these treatments on the indigenous microbial community was assessed immediately after the Fenton-like treatment and after 30, 60 and 90 d and compared with enhanced natural attenuation (ENA). After FLT, a dramatic decrease in bacterial density, diversity and functionality was evident. Although in microcosms with double dosing at 2% H 2 O 2 a delayed recovery of the indigenous microbiota was observed as compared to those subjected to single oxidant dose, after 60 d incubation the respiration rate increased from 0.036 to 0.256 μg C CO 2 g −1 soil h −1 . Irrespective of the oxidant dose, best degradation results after 90 d incubation (around 80%) were observed with combined FLT, relying on double oxidant addition, and bioremediation. [ABSTRACT FROM AUTHOR]