Application of different organic amendments in a gasoline contaminated soil: Effect on soil microbial properties M. Tejada a, * , J.L. Gonzalez b , M.T. Hernandez c , C. Garcia c a Departamento de Cristalografı ´a, Mineralogı ´a y Quı ´mica Agrı ´cola, E.U.I.T.A. Universidad de Sevilla, Crta de Utrera km. 1, 41013 Sevilla, Spain b Departamento de Quı ´mica Agrı ´cola y Edafologı ´a, Universidad de Co ´ rdoba, Campus de Rabanales, Edificio C-3, Crta N-IV-a, km. 396, 14014 Co ´ rdoba, Spain c Departamento de Conservacio ´ n de Suelos y Agua y Manejo de Residuos Orga ´ nicos, Centro de Edafologı ´a y Biologı ´a Aplicada del Segura, CEBAS-CSIC, P.O. Box 4195, 30080 Murcia, Spain Received 3 May 2007; received in revised form 11 June 2007; accepted 11 June 2007 Available online 26 July 2007 Abstract The effects of four organic wastes, including cotton gin crushed compost (CC), poultry manure (PM), sewage sludge (SS) and organic municipal solid waste (MSW) on some biological properties of a Xerollic Calciorthid soil polluted with gasoline at two loading rates (5% and 10%) were studied in an incubation experiment. Three hundred grams of sieved soil (<2 mm) were polluted with gasoline and mixed with PM at a rate of 10%, CC at a rate of 17.2%, SS at a rate of 23.1%, or MSW at a rate of 13.1%, applying to the soil the same amount of organic matter with each organic amendment. An unamended soil, non polluted (C) and polluted with gasoline at 5% (G1) and 10% (G2) rate were used as reference. Soil samples were collected after 1, 30, 60, 90, 120, 180 and 270 d of incubation and analyzed for micro- bial biomass carbon, respiration and dehydrogenase, urease, b-glucosidase, phosphatase and arylsulfatase activities. At the end of the incubation period, soil biological properties were higher in organic amended soils than in C, G1 and G2 treatments. In particular, soil microbial biomass carbon and dehydrogenase, urease, b-glucosidase, phosphatase and arylsulfatase activities increased 87.1%, 92.9%, 88.7%, 93.2%, 78.2% and 85.3%, respectively for CC-amended soils respect to G2, 85.7%, 82.3%, 87.3%, 92.2%, 76.7% and 83.6%, respec- tively for PM-amended soils; 82%, 90%, 84.8%, 89.9%, 74.1% and 80%, respectively for SS-amended soils; and 71.3%, 78.3% 26.2%, 38.2%, 79.7% and 88.6%, respectively for MSW-amended soils. Since the adsorption capacity of gasoline was higher in CC than the PM, SS and MSW-amended soils, it can be concluded that the addition of organic wastes with higher humic acid concentration is more beneficial for remediation of soils polluted with gasoline. Ó 2007 Published by Elsevier Ltd. Keywords: Gasoline; Organic wastes; Soil biochemical properties 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) have been recognised as a potential health risk due to their intrinsic chemical stability, high recalcitrant to different types of degradation and high toxicity to living microorganisms (Alexander, 1999; Andreoni et al., 2004; Eibes et al., 2006). Soil microorganisms, being in intimate contact with soil environment, are very sensitive to any ecosystem per- turbation, and therefore are considered to be the best indi- cators of soil pollution (Andreoni et al., 2004). Soil pollution with PAHs influences microbiota, producing changes in enzyme activity, soil respiration, biomass and microbial counts (Margesin et al., 2000; Baran et al., 2004; Labud et al., 2007). It should be noted that PAHs (64 rings) are moderately toxic and degradable by micro- organisms, whereas the remaining group (>4 rings) has a strongly toxic, mutagenic and carcinogemic character, and their decomposition is only possible via cometabolism (Cernigilia, 1984; Kanaly and Harayama, 2000). The mea- surement of microbial parameters, such as soil respiration, 0960-8524/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.biortech.2007.06.002 * Corresponding author. E-mail address: mtmoral@us.es (M. Tejada). Available online at www.sciencedirect.com Bioresource Technology 99 (2008) 2872–2880