Phytoremediation of soil contaminated with used lubricating oil using Jatropha curcas

Abstract

Soil contamination by used lubricating oil from automobiles is a growing concern in many countries, especially in Asian and African continents. Phytoremediation of this polluted soil with non-edible plant like Jatropha curcas offers an environmental friendly and cost-effective method for remediating the polluted soil. In this study, phytoremediation of soil contaminated with 2.5 and 1% (w/w) waste lubricating oil using J. curcas and enhancement with organic wastes [Banana skin (BS), brewery spent grain (BSG) and spent mushroom compost (SMC)] was undertaken for a period of 180 days under room condition. 56.6% and 67.3% loss of waste lubricating oil was recorded in Jatropha remediated soil without organic amendment for 2.5% and 1% contamination, respectively. However addition of organic waste (BSG) to Jatropha remediation rapidly increases the removal of waste lubricating oil to 89.6% and 96.6% in soil contaminated with 2.5% and 1% oil, respectively. Jatropha root did not accumulate hydrocarbons from the soil, but the number of hydrocarbon utilizing bacteria was high in the rhizosphere of the Jatropha plant, thus suggesting that the mechanism of the oil degradation was via rhizodegradation. These studies have proven that J. curcas with organic amendment has a potential in reclaiming hydrocarbon-contaminated soil.

Introduction

Contamination of soil by organic chemicals (mostly hydrocarbons) is prevalent in oil producing and industrialized countries of the world, but pollution of soil by used lubricating oil is a common phenomenon in every major city across the globe. This may pose a great threat to the environment and human being at large. Different treatment methods have been employed to reclaim contaminated soil. Phytoremediation, a strategy that uses plant to degrade, stabilize, and/or remove soil contaminants [1] can be an alternative green technology method for remediation of hydrocarbon-contaminated soil. It offers an environmentally friendly, cost-effective and carbon neutral approach for the remediation of toxic pollutant in the environment [2].

Phytoremediation has now emerged as a promising strategy for in situ removal of many contaminants [3], [4], [5]. Microbe-assisted phytoremediation, including rhizoremediation appears to be particularly effective for the removal and/or degradation of organic contaminants from contaminated soil [1]. Furthermore, according to Palmroth et al. [6], root exudates from plants do help to degrade toxic organic chemicals and acts as substrates for soil microorganisms in the soil which directly results in increased rate of biodegradation of the organic contaminants.

Different types of plants have been found useful for phytotreatment of soil contaminated by hydrocarbons. Alfalfa and horse radish was found to reduce concentration of kerosene-based jet fuel by 57–90% in 5 months [7]. Peng et al. [8] observed 41.61–63.2% total petroleum hydrocarbons (TPH) removal by Mirabilis jalapa L. in 127 days. Euliss et al. [9] found out that Carex stricta, Pannicum virgatum and Tripsacum dactyloides significantly reduced TPH by 70% after 1 year of growth. Studies by various authors show Jatropha curcas as a potential plant for remediation of heavy metals-contaminated soil. The plant (J. curcas) has been implicated in remediation of soil contaminated by heavy metals (Al, Fe, Cr, Mn, Ar, Zn, Cd and Pb) due to its bioaccumulation potential [10], [11], [12].

In this study J. curcas was selected due to its hardiness, its characteristics as non-edible plant which can grow in tropical areas and its commercial viability for the production of biodiesel, therefore the objective of this study is to determine the potential of J. curcas in removing hydrocarbons from soil and to investigate effects of different organic amendments on the ability of Jatropha in removing hydrocarbons. In addition, the mechanisms of removal of hydrocarbon will be determined.