Phytoremediation of soil contaminated with petroleum hydrocarbons and trace elements

Abstract: The rapid urbanization and industrialization has led to an increase of disposal petroleum hydrocarbons (PHC) and trace elements (TE) into the environment. These pollutants are considered as the most toxic contaminants in the world due to their persistence in the environment, and the long range of toxicological effects for living beings.Recent concerns regarding the environmental contamination have initiated the development of several remediation technologies, including physical, chemical, and biological approaches. In this thesis, gentle soil remediation options (GRO) were investigated at different scales for the reclamation of PHC and TE co-contaminated soil. In the first part of this thesis, laboratory experiments were performed to characterize PHC and TE contaminated soil as well as the indigenous microorganisms (bacteria and fungi) present inside these contaminated soil. It was found that the studied aged contaminated soil had a negative effect on earthworm’s development and L. sativum biomass. Moreover, a high respiration of microorganisms attributed to the transformation/ mineralization of organic matter or/and organic pollutants was observed. This presence of viable microorganisms suggested an adaptation of microorganisms to the contaminant. Further results showed that the long-term exposure of soil microorganisms to high PHC concentration and the type of isolation culture media did not influence the ability of isolates to effectively degrade PHC. However, phylogenic affiliation had a strong on PHC biodegradation. In the second part of this thesis, preliminary studies in greenhouse were assessed to investigate the ability of M. sativa assisted by compost in the greenhouse aided-phytoremediation of PHC and TE. It was found that compost incorporation into the soil promoted PHC degradation, M. sativa growth and survival, and phytoextraction of TE. Residual risk assessment after the phytoremediation trial also showed a positive effect of compost amendment on plant growth and earthworm development. Pilot scale ecopile experiment carried out in the third part of this thesis allow a reduction of up to 80% of PHC and 20% of metals after 17 months. This research demonstrated that M. sativa and H. annus were suitable for phytodegradation of PHC and phytoextraction of TE.  Results from this thesis are helpful for further full-scale phytoremediation studies. 

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