Comparative analysis of remediation efficiency and ultrastructural translocalization of polycyclic aromatic hydrocarbons in Medicago sativa , Helianthus annuus, and Tagetes erecta

Polycyclic aromatic hydrocarbons (PAHs) are semi-volatile anthropogenic contaminants that can damage soil fertility and threaten the environment due to their hazardous effects on various ecological parameters. The experimental objective was divided into two parts because PAHs are always present in mixtures. The toxicity of anthracene, phenanthrene, pyrene, and fluoranthene was examined and investigated the potential of three phytoremediator plants species viz Tagetes erecta, Helianthus annuus, and Medicago sativa for remediation and translocation of individual PAH. PAHs were shown to have inhibitory or stimulating effects on growth, antioxidant properties, and impact on the structure of plant cells. The result showed that M. sativa significantly enhances the removal rate of PAHs in the soil. The dissipation rate reached 96.2% in M. sativa planted soil, followed by H. annuus and T. erecta. Among the plant species, M. sativa exhibited the highest root and shoot concentrations (314.37 and 169.55 mg kg-1), while the lowest concentration was 187.56 and 76.60 mg kg-1 in T. erecta. SEM-EDX and fluorescence micrographs confirmed that pyrene altered plant tissue's ultrastructure and cell viability and was found to be the most toxic and resistant. M. sativa was proven to be the most effective plant for the mitigation of PAHs.The novelty of our work situates phytoremediation into a practical viewpoint as to whether the process can be achieved within a measurable amount of time. In conclusion, Medicago sativa behaved as the more tolerant plant species in PAH-contaminated soil. While to the best of our knowledge, researchers have yet to study single contamination of PAH together, especially for phenanthrene and pyrene. We hope our study is fundamental and will help assess M. sativa as a potential phytoremediator plant for hydrocarbon-contaminated soil. Furthermore, this work is novel because the plant can remediate PAHs from industrial soil and agricultural fields. The harvested plant material can later be used for various purposes, such as biodegradable paper production. The higher dissipation of hydrocarbons measured in soil cultivated with M. sativa may be related to a large amount of soil bacteria stimulated explicitly by the M. sativa fibrous root system. Further studies are in progress to evaluate the possible degradation of PAH using microorganisms.