Bioremediation of hydrocarbon degradation in a petroleum- contaminated soil and microbial population and activity determination Manli Wu a , Wei Li a , Warren A. Dick b , Xiqiong Ye a , Kaili Chen a , David Kost b , Liming Chen b, * a School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, No.13 Yanta Road, Xi'an, Shaanxi Province 710055, China b School of Environment and Natural Resources, The Ohio State University, Ohio Agricultural Research and Development Center,1680 Madison Avenue, Wooster, OH 44691, USA highlights  Biostimulation and bioaugmentation achieved 48% and 58% hydrocarbon degradation.  Hydrocarbon degradation rate correlated with degrader population increase.  The degradation rate correlated with degrader activity increase in Biolog assay.  MPN and Biolog were efficient methods for assessing hydrocarbon degradation rate. article info Article history: Received 10 June 2016 Received in revised form 28 October 2016 Accepted 11 November 2016 Handling Editor: X. Cao Keywords: Bioremediation Petroleum-contaminated soil Hydrocarbon degradation efficiency Microbial population Biolog assay abstract Bioremediation of hydrocarbon degradation in petroleum-polluted soil is carried out by various micro- organisms. However, little information is available for the relationships between hydrocarbon degra- dation rates in petroleum-contaminated soil and microbial population and activity in laboratory assay. In a microcosm study, degradation rate and efficiency of total petroleum hydrocarbons (TPH), alkanes, and polycyclic aromatic hydrocarbons (PAH) in a petroleum-contaminated soil were determined using an infrared photometer oil content analyzer and a gas chromatography mass spectrometry (GC-MS). Also, the populations of TPH, alkane, and PAH degraders were enumerated by a modified most probable number (MPN) procedure, and the hydrocarbon degrading activities of these degraders were determined by the Biolog (MT2) MicroPlates assay. Results showed linear correlations between the TPH and alkane degradation rates and the population and activity increases of TPH and alkane degraders, but no cor- relation was observed between the PAH degradation rates and the PAH population and activity increases. Petroleum hydrocarbon degrading microbial population measured by MPN was significantly correlated with metabolic activity in the Biolog assay. The results suggest that the MPN procedure and the Biolog assay are efficient methods for assessing the rates of TPH and alkane, but not PAH, bioremediation in oil- contaminated soil in laboratory. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Petroleum spills often occur by accidents during pumping, transportation, and refining. Petroleum is a complex mixture including aliphatic and aromatic hydrocarbons, which are known to have negative effects on human health and the environment. Thus, the US Environmental Protection Agency (U.S. EPA, 1986) considers these hydrocarbons as priority environmental pollutants. Bioremediation has been considered an efficient, cost-effective, and environmentally sound method to degrade hydrocarbons in petroleum-contaminated soils (Salanitro and Dorn, 1997; Liebeg and Cutright, 1999; Margesin and Schinner, 2001; Zhang et al., 2008; Chiu et al., 2009; Wu et al., 2013; Kharusi et al., 2016; Ma * Corresponding author. E-mail address: chen.280@osu.edu (L. Chen). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.11.059 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 169 (2017) 124e130