Application potential of Chrysopogon zizanioides (L.) Roberty for the remediation of red mud-treated soil: an analysis via determining alterations in essential oil content and composition

The study was undertaken to determine the effects of different red mud treatments (0, 5, 10, and 15% w/w) in sewage-sludge amended soil (soil:sludge:2:1 w/w) on quantity, quality, and safety of essential oil extracted from the roots of Chrysopogon zizanioides (vetiver), when used for the phytoremediation of red mud. Garden soil without red mud and sewage-sludge served as control and there were 10 replicates for each treatment. Essential oil content in roots increased under all soil treatments except maximum red mud addition in sludge-amended soil compared to the control. Gas chromatography and mass spectroscopic analysis of oil revealed that 36, 35, 33, and 31 compounds contributed nearly 87.7, 90, 92.1, and 87% of total volatiles under 0, 5, 10, and 15% red mud treatments, respectively. Contents of rosifoliol, α-muurolol, farnesol, γ-costol, isovalencene, and vetivone increased, while selina-6-en-ol, cadin-4-en-10-ol, vetiselinenol, and aristolone decreased with increasing red mud treatments. In essential oil, contents of metals were within the safe limits for food by Food Safety and Standard Authority of India. The study insinuate utilization of 5 and 10% red mud in sludge-amended soil for improved quantity and quality of essential oil, without any metal contamination coupled with enhanced phytoremediation potential of vetiver. The present study is of significant importance because phytoremediation of metals in red mud using essential oil-bearing plants such as Chrysopogon zizanioides (commonly known as vetiver) is a potential alternative for on-site management of the waste in most economical and sustainable way. Vetiver is a potential metal tolerant plant with high economic value; therefore the present study was accomplished to evaluate the impacts of metals in red mud on essential oil content and composition, used for remediation and stabilization of dumps. Novelty of the study is that, it aimed to utilize red mud along with sewage-sludge to cultivate vetiver which offers twin benefits, i.e. phytoremediation of metals in red mud coupled with improved quantity and quality of high valued essential oil without metal contamination.