Effect of Medicago sativa L. and compost on organic and inorganic pollutant removal from a mixed contaminated soil and risk assessment using ecotoxicological tests

ABSTRACT

Several Gentle Remediation Options (GRO), e.g., plant-based options (phytoremediation), singly and combined with soil amendments, can be simultaneously efficient for degrading organic pollutants and either stabilizing or extracting trace elements (TEs). Here, a 5-month greenhouse trial was performed to test the efficiency of Medicago sativa L., singly and combined with a compost addition (30% w/w), to treat soils contaminated by petroleum hydrocarbons (PHC), Co and Pb collected at an auto scrap yard. After 5 months, total soil Pb significantly decreased in the compost-amended soil planted with M. sativa, but not total soil Co. Compost incorporation into the soil promoted PHC degradation, M. sativa growth and survival, and shoot Pb concentrations [3.8 mg kg⁻¹ dry weight (DW)]. Residual risk assessment after the phytoremediation trial showed a positive effect of compost amendment on plant growth and earthworm development. The O₂ uptake by soil microorganisms was lower in the compost-amended soil, suggesting a decrease in microbial activity. This study underlined the benefits of the phytoremediation option based on M. sativa cultivation and compost amendment for remediating PHC- and Pb-contaminated soils.

KEYWORDS:

• cobalt
• petroleum hydrocarbon
• phytoremediation
• polycyclic aromatic hydrocarbon
• lead

Acknowledgments

The authors would like to thank NoDesign AB for their technical support and giving us access to the site of study, Bernth Noren for providing useful information of the site and assistance on oil sampling. The authors are grateful to Dr. Michel Mench, UMR Biogeco INRA 1202, University of Bordeaux, France for his writing assistance. We also thank two anonymous reviewers for their helpful comments.

Funding

This work was supported by funds provided by the Industrial Development Centre in Kalmar County (IUC), the Regional Council of Kalmar County, Genome Quebec and Genome Canada who are greatly acknowledged. CH received a traveling fund from the Quebec Centre for Biodiversity Science (QCBS).