Impact of arbuscular mycorrhizal fungi on phytoremediation of benzo[a]pyrene polluted soils

Details

Supervisors

Declerck, Stephan ; Garces Ruiz, Monica Cristina

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences et technologies de l'environnement, à finalité spécialisée

Abstract

A third of the world's polluted soils are contaminated by petroleum. In addition to degrading soil quality, petroleum is toxic to living organisms, with benzo[a]pyrene (B[a]P) being one of its most harmful components. Phytoremediation is gaining attention as an environmentally friendly, cost-effective technique for managing polluted soils, and its effectiveness can be enhanced by using arbuscular mycorrhizal fungi (AMF). In a greenhouse experiment, a grass mix of Festuca rubra (82%) and Poa pratensis (18%) was inoculated with three different AMF strains: Rhizophagus sp. PHE 121001-P2 and Acaulospora sp. PHE121303-6-P2-0, isolated from crude oil-polluted soils in Ecuador, and Rhizophagus irregularis MUCL 4183, isolated from a non-polluted environment. After five months, the developed grass mat was transferred onto a substrate contaminated with 50 μg B[a]P/g of soil or uncontaminated for two additional months. Afterwards, the effects of AMF on shoot growth, oxidative stress (measurement of malondialdehyde), and the dissipation and accumulation of B[a]P were evaluated. Root colonization by AMF was effective, with a tendency for higher colonization in the contaminated substrate. This effect was significant for R. irregularis, indicating the plant modulated its colonization in response to B[a]P stress. Rhizophagus sp. enhanced shoot growth, while Acaulospora sp. enhanced shoot growth only with B[a]P. No effect of AMF or B[a]P was found on oxidative stress. B[a]P dissipated significantly in all treatments but none of the AMF strains significantly affected B[a]P degradation. R. irregularis enhanced accumulation of B[a]P in the upper roots and shoots, while Acaulospora sp. enhanced accumulation in the lower roots and seemed to have excluded it from the rest of the plant. The two Ecuadorian strains associated with F. rubra and P. pratensis are promising for revegetating soils polluted with B[a]P, while Acaulospora sp. is also a good candidate for phytostabilization of B[a]P. A future study evaluating oxidative stress over six months would be useful to ensure the success of this method. The concentration of B[a]P in grass mats shoots associated with R. irregularis is not high enough to propose a phytoextraction method.