Comparison of plants with C3 and C4 carbon fixation pathways for remediation of polycyclic aromatic hydrocarbon contaminated soils

Anithadevi Kenday Sivaram,Suresh R Subashchandrabose,Robin Lockington,Ravi Naidu,Mallavarapu Megharaj,Panneerselvan Logeshwaran

doi:10.1038/s41598-018-20317-0

Abstract

The phytoremediation technique has been demonstrated to be a viable option for the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated sites. This study evaluated the potential applicability of plants with C3 and C4 carbon fixation pathways for the phytoremediation of recalcitrant high molecular weight (HMW) PAHs contaminated soil. A 60 and 120-day greenhouse study was conducted which showed higher degradation of HMW PAHs in soil grown with C4 plants when compared to C3 plants. Also, no PAHs were detected in the maize cobs, sunflower, wallaby, and Sudan grass seeds at the end of the experiment. The effect of plants in modifying the microbial community and dynamics in the rhizosphere was also examined by measuring soil biochemical properties such as dehydrogenase activity and water-soluble phenols. The results demonstrate a substantial difference in the microbial populations between planted and unplanted soils, which in turn facilitate the degradation of PAHs. To the best of our knowledge, this study for the first time evaluated the phytoremediation efficacy through the A. cepa cyto- and genotoxicity assay which should be considered as an integral part of all remediation experiments.

Highlights

Polycyclic aromatic compounds are a group of organic compounds that are categorized worldwide as priority pollutants of terrestrial and aquatic ecosystems, and sediments, primarily because they can cause mutation, cancer and interfere with the reproduction of higher organisms[1]
The proportion of the dominant compounds in the root exudates especially sugars and organic acids may differ among the C3 and C4 plants depending on the type of plants[11]
After 120 days of experimental period the relationship was in the order of maize (r2 = 0.95) > Sudan grass (r2 = 0.92) > vetiver (r2 = 0.94) > sunflower (r2 = 0.89) > wallaby grass (r2 = 0.89) at P ≤ 0.05. These results revealed that Hydroxypropyl-β- cyclodextrin (HPCD) extraction reasonably predicted the bioavailable concentration to the plants in the polycyclic aromatic hydrocarbons (PAHs) contaminated soils

Summary

Introduction

Polycyclic aromatic compounds are a group of organic compounds that are categorized worldwide as priority pollutants of terrestrial and aquatic ecosystems, and sediments, primarily because they can cause mutation, cancer and interfere with the reproduction of higher organisms[1]. Plants can be classified according to their carbon fixation pathways, like C3, C4 and CAM (Crassulacean Acid Metabolism) Of these C3 and C4 plant species are mainly employed in phytoremediation studies[9]. Success was monitored only by the amounts of parent compounds removed while their metabolites were largely ignored These metabolites are primarily responsible for the toxicity seen in biological organisms. A. cepa root cells are used in the single cell gel electrophoresis (SCGE) system, often referred to as the comet assay This is regarded as a simple, cost-effective and sensitive tool for examining the genotoxicity of organic pollutants present in the environment[18]

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