Ecological implications of motor oil pollution: Earthworm survival and soil health Kavitha Ramadass a, b , Mallavarapu Megharaj a, b, * , Kadiyala Venkateswarlu a, c , Ravi Naidu a, b a Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095, Australia b Cooperative Research Centre for Contamination and Remediation of the Environment (CRC CARE), Australia c Sri Krishnadevaraya University, Anantapur 515055, India article info Article history: Received 7 September 2014 Received in revised form 20 February 2015 Accepted 24 February 2015 Available online 9 March 2015 Keywords: Used motor oil Nontarget effects Earthworm survival Hydrocarbon accumulation Soil health abstract The nontarget effects of fresh and used motor oil were studied in a soil test system involving such criteria as earthworm survival, response of soil dehydrogenase and urease, and nitrification. When earthworms were exposed to motor oil-contaminated soil for 4 weeks, the observed median lethal concentrations (LC 50 ) were 40.33 and 3.88 g kg 1 soil for fresh and used oil, respectively. Only fresh motor oil application increased earthworms' body weight even at the higher dose of 19 g kg 1 soil. Gas chromatography/mass spectrometry revealed that used motor oil contained more of aromatic hydrocarbons and heavy metals than fresh oil. This disparity in the chemical composition might be the factor responsible for the sig- nificant toxicity of used motor oil towards earthworms. Activities of soil dehydrogenase and urease were significantly enhanced in presence of both the motor oils, while there was a significant inhibition in nitrification by the used motor oil even at a low concentration of 0.2 g kg 1 soil. This study clearly demonstrated that earthworm survival and nitrification could serve as suitable indices to assess motor oil pollution in soil. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Lubricants in the form of motor oil or engine oil are consumed largely in automobiles to protect the internal combustion engines. Generally, motor oil consists of 90% petroleum fractions and 10% additives. Different brands of engine oils have different additives that belong to several groups such as antioxidants, detergents, anti- wear agents, dispersants, corrosion inhibitors and viscosity index improvers (Caines and Haycock, 2004). The internal combustion engine acts like an oxidator and the hydrocarbons in the engine oil are partially oxidized when contacted with oxygen at elevated temperatures for long periods. Metals like iron (Fe), copper (Cu), lead (Pb), nickel (Ni), etc. used in the manufacture of the engine are effective oxidation catalysts and increases the rate of oxidation of the engine oil. The oxidation process produces acidic bodies within the motor oil which are corrosive to typical Cu, Pb, and cadmium (Cd) engine bearings. Furthermore, oxidation products contribute to the formation of sludges within the motor oil and an overall breakdown of viscosity characteristics of the lubricant. Used motor oil contains minute quantities of gasoline or diesel, additives, nitrogen and sulphur compounds, a broad range of aro- matic and aliphatic hydrocarbons with chain lengths ranging from C 15 to C 50 , and metals that arise from normal wear of engine components and from heating and oxidation of lubricating oil (Vazquez-Duhalt, 1989; Dominguez-Rosado, and Pichtel, 2003; Singh et al., 2006). Thus, US EPA (2001) defined used motor oil as “any petroleum-based or synthetic oil that has been used for vehicle lubrication and as a result of normal use, motor oil becomes contaminated with various impurities such as dirt, water, chemicals or metals from vehicle engine”. Once degraded motor oil escapes the engine, it has the potential to pollute waterways in the form of runoff and soil. The US Environmental Protection Agency (EPA) reported that 1.0 gallon of used motor oil can contaminate 1.0 million gallons of fresh water. If used motor oil reaches sewage treatment plants, even small concentrations of 50e100 ppm can foul the water treatment process. One litre of used motor oil can pollute up to 3784 m 2 of soil, making it non-productive for farming or plant growth for up to * Corresponding Author. Centre for Environmental Risk Assessment and Reme- diation, University of South Australia, X Building, Room X1-14, Mawson Lakes Campus, Mawson Lakes, South Australia, SA 5095, Australia. Tel.: þ61 8 8302 5044 (W); fax: þ61 8 8302 3057. E-mail address: Megharaj.Mallavarapu@unisa.edu.au (M. Megharaj). Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio http://dx.doi.org/10.1016/j.soilbio.2015.02.026 0038-0717/© 2015 Elsevier Ltd. All rights reserved. Soil Biology & Biochemistry 85 (2015) 72e81