Abstract
The contamination of soil with total petroleum hydrocarbons (TPH) may result in dramatic consequences and needs great attention, as soil rehabilitation would need more effort from a sustainability perspective. However, there is still no known general method since the remediation technology is strictly site-specific. Adaptive biological system dynamics can play a key role in understanding and addressing the potential of situ-specific biological combinations for soil pollutants removal. The potential worst-case of TPH contamination reflects soil affected by heavy industrial activities, such as oil refineries. Therefore, the experimental trial was conducted on a 2,000 m2 area from a contaminated site located in northern Italy. We evaluated the remediation potential over time (270 days) assessing (i) the phytoremediation efficiency of two species of Poaceae (Festuca arundinacea Schreb. and Dactylis glomerata L.) and two species of Fabaceae (Medicago sativa L. and Lotus corniculatus L.) and (ii) the role of the indigenous bacteria flora and endo-mycorrhizae consortium addition in plant growth promotion. We also induced resistance to contamination stress in a field experiment. Thirty-three indigenous bacteria selected from the contaminated soils showed marked plant growth promotion. Moreover, functional metagenomics confirmed the metabolic capability of hydrocarbon-degrading microorganisms living in the polluted soil. Our data showed that soil enzymatic activities increased with hydrocarbon degradation rate after 60 days. Both Poaceae and Fabaceae resulted in remarkable remediation potential. Stress markers and antioxidant activity indicated that the selected plant species generally need some time to adapt to TPH stress. In conclusion, our evaluation implied both the rhizosphere effects and functional features of the plant and suggested that plants should (i) have marked tolerance to specific contaminants, (ii) be characterized by an extensive root system, and (iii) be susceptible to arbuscular mycorrhizal fungi (AMF) infection.
Highlights
The soil pollution produced by total petroleum hydrocarbons (TPH), as aliphatic, aromatic, heterocyclic, and asphaltene/tar hydrocarbons are together termed, constitutes a serious issue worldwide due to eco-toxicity caused by their strong persistence in the environment (Hussain et al, 2019)
The lower N levels in APH may be imputed to the uptake of N and P by vegetation, and to their storage function, which could have been enhanced by the arbuscular mycorrhizal fungi (AMF) activity
In order to estimate the level of oxidative stress, the malandialdehyde content (MDA), Glutathione S-Transferase (GST), Phenylalanine Ammonia Lyase (PAL), and Proline content were determined, and our results indicate a decreasing pattern over the experimental time
Summary
The soil pollution produced by total petroleum hydrocarbons (TPH), as aliphatic, aromatic, heterocyclic, and asphaltene/tar hydrocarbons are together termed, constitutes a serious issue worldwide due to eco-toxicity caused by their strong persistence in the environment (Hussain et al, 2019). Plant-Soil-Microbiota Combination TPH Removal well as via the lack of waste oil recycling and the disposal of hazardous oil wastes into landfill areas without sufficient management (Khudur et al, 2019; Grifoni et al, 2020) All these anthropic activities have further increased the number of contaminated sites (Koshlaf and Ball, 2017). Growth promoters, and ecto- and endophytic fungi are the protagonists (together with plants and, in particular, roots) of interesting degradation co-metabolic processes (Pawlik et al, 2017) In this context, plants play a key role as they shape the conditions for a specific microbial colonization through root exudation (Guyonnet et al, 2018). Root colonizing symbiotic microorganisms, such as arbuscular mycorrhizal fungi (AMF), can play a crucial role in (i) improving the growth stages of the plant, (ii) increasing the biodegradation activity in the rhizosphere, and (iii) enhancing hydrocarbons’ uptake at the root level (Rajtor and Piotrowska-Seget, 2016)
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