Remediation of Organically Contaminated Soil Through the Combination of Assisted Phytoremediation and Bioaugmentation

Mikel Anza,José María Becerril,Oihane Salazar,Carlos Garbisu,Itziar Alkorta,Lur Epelde

doi:10.3390/app9224757

Abstract

Here, we aimed to bioremediate organically contaminated soil with Brassica napus and a bacterial consortium. The bioaugmentation consortium consisted of four endophyte strains that showed plant growth-promoting traits (three Pseudomonas and one Microbacterium) plus three strains with the capacity to degrade organic compounds (Burkholderia xenovorans LB400, Paenibacillus sp. and Lysinibacillus sp.). The organically contaminated soil was supplemented with rhamnolipid biosurfactant and sodium dodecyl benzenesulfonate to increase the degradability of the sorbed contaminants. Soils were treated with organic amendments (composted horse manure vs. dried cow slurry) to promote plant growth and stimulate soil microbial activity. Apart from quantification of the expected decrease in contaminant concentrations (total petroleum hydrocarbons, polycyclic aromatic hydrocarbons), the effectiveness of our approach was assessed in terms of the recovery of soil health, as reflected by the values of different microbial indicators of soil health. Although the applied treatments did not achieve a significant decrease in contaminant concentrations, a significant improvement of soil health was observed in our amended soils (especially in soils amended with dried cow slurry), pointing out a not-so-uncommon situation in which remediation efforts fail from the point of view of the reduction in contaminant concentrations while succeeding to recover soil health.

Highlights

Bioremediation, or the use of microorganisms to detoxify or remove contaminants, has great potential for the remediation of contaminated soils [1,2,3]
Statistically significant differences in contaminant concentrations were detected for the “Plant x Amendment” interaction: in planted pots, the addition of dried cow slurry resulted in higher values of total-PAHs with respect to (i) pots amended with composted horse manure and (i) unamended controls
All the applied treatments failed at achieving a reduction in the concentration of the target contaminants (TPHs, PAHs), but some did succeed at improving soil health

Summary

Introduction

Bioremediation, or the use of microorganisms to detoxify or remove contaminants, has great potential for the remediation of contaminated soils [1,2,3]. (i) natural attenuation, or the natural process of contaminant degradation; (ii) biostimulation, or the modification of the environmental conditions to stimulate the biodegradation ability of indigenous microorganisms; and (iii) bioaugmentation, or the introduction of exogenous microorganisms with the capacity to degrade the target contaminants [4,5,6]. Industrial soils are most frequently affected by the presence of more than one contaminant, hindering the application of biological remediation techniques. In petroleum contaminated soils, aliphatic and aromatic hydrocarbons [including polycyclic aromatic hydrocarbons.

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