Phytotoxicity of branched cyclohexanes found in the volatile fraction of diesel fuel on germination of selected grass species

Abstract

During a larger study to screen candidate plant species for phytoremediation of diesel fuelcontaminated soils, it was observed that at relatively low levels of diesel fuel contamination, delayed shoot/root emergence and reduced germination was observed for the majority of plant species investigated. It was theorised that these effects were the result of acute phytotoxicity, caused by the volatile fraction of diesel fuel, with results supporting this theory. This finding was investigated further in the current study. Headspace analysis of diesel fuel showed that between 5-10% of diesel fuel consisted of compounds that would volatilise at 20°C, with the most predominant compounds identified being the isomers of xylene (m-, o-and p-), n-alkanes (C9-C12) and alkylbenzenes. There were also low levels of toluene, branched cyclohexanes (methyl-, to butylcyclohexane) and alkenes. Of particular interest were branched cyclohexanes as little work has previously been reported on these compounds. To explain the phytotoxic effect of the volatile fraction of diesel fuel and attribute the effect to a specific compound or group of compounds within diesel fuel, seeds were germinated in petri dishes contaminated with a number of pure branchedcyclohexanes. An unusual pattern of germination was apparent, with results varying depending on grass species and the length of cyclohexane branching. Results showed ethyl-and butylcyclohexane had a significant effect on the germination rate of selected grass species whereas methyl-and propylcyclohexane had little effect.

Differentiation between physical and chemical effects of oil presence in freshly spiked soil during rhizoremediation trial

“…This reduction in seed germination might be explained by the physical and chemical effects posed by diesel oil addition. This fact is well established in literature that different constituents of diesel fuel (alkanes, aromatics and polycyclic aromatic hydrocarbons) are toxic to many tested plant species (Chaîneau et al 1997 ; Adam and Duncan 2002 ; Huang et al 2004 ; MacKinnon and Duncan 2013 ; Macoustra et al ( 2015 ); Panchenko et al 2016 ). It appears that reduced germination of Birdsfoot trefoil is mainly due to chemical toxicity of diesel fuel, while reduced germination of Italian ryegrass seeds was affected mainly by physical effects caused by oil contaminants in soil.…”

Endophytic bacteria: Prospects and applications for the phytoremediation of organic pollutants

“…The presence of organic compounds in soil, such as hydrocarbons, polyaromatic hydrocarbons, polychlorinated biphenyls, phenols, chlorophenols, toluene, trinitrotoluene, benzene, herbicides and pesticides, inhibits growth and metabolic activities of soil-associated microbes, even at very low concentrations (Oleszczuk, 2006;Porteous Moore et al, 2006;MacKinnon and Duncan, 2013;Sun et al, 2013). Furthermore, organic compounds can enter the food chain, and due to their toxic nature they can cause mutagenicity and carcinogenicity in animals and humans (Mahanty et al, 2011;Guo et al, 2012;Havelcová et al, 2014).…”

Enhanced Degradation of Diesel in the Rhizosphere of Lupinus luteus after Inoculation with Diesel-Degrading and Plant Growth-Promoting Bacterial Strains

“…This technique can be applied in situ and is inexpensive, clean, and socially accepted and has a low impact on the environment. In particular, rhizoremediation (phytoremediation assisted with rhizosphere microorganisms) has emerged as one of the most effective techniques to degrade petroleum contaminants (MacKinnon and Duncan, 2013) and can even be improved with the inoculation of carefully selected bacterial inoculants. Many authors have isolated bacteria from petroleum‐contaminated sites with hydrocarbon‐degrading potential for use in soil rhizoremediation (Das and Mukherjee, 2007; Obayori et al, 2009; Tanase et al, 2013).…”