Bioavailability and degradation of phenanthrene in compost amended soils Edoardo Puglisi a , Fabrizio Cappa b , George Fragoulis a , Marco Trevisan a, * , Attilio A.M. Del Re a a Istituto di Chimica Agraria ed Ambientale, Universita ` Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29100 Piacenza, Italy b Istituto di Microbiologia, Universita ` Cattolica del Sacro Cuore, Via Emilia Parmense 84, 29100 Piacenza, Italy Received 31 May 2006; received in revised form 15 September 2006; accepted 21 September 2006 Available online 27 November 2006 Abstract Bioavailability in soil of organic xenobiotics such as phenanthrene is limited by mechanisms of diffusion of the xenobiotics within soil micropores and organic matter. The agricultural utilization of compost may reduce the risk connected to organic xenobiotic contami- nation by means of: (i) a reduction of the bioavailable fraction through an increased adsorption and (ii) an enhanced degradation of the remaining bioavailable fraction through an inoculum of degrading microorganisms. Aim of this work is to test this hypothesis by assessing the effects of compost amendment on the bioavailability and degradation of phenanthrene in soil. Experiments were carried out in both sterilized and non-sterilized conditions, and chemical and microbiological analyses were carried out in order to determine the extent of degradation and bioavailability and to monitor the evolution of the soil micro flora in time. Bioavailability was assessed in sterilized microcosms, in order to assess the physical effects of compost on aging processes without the influence of microbial degra- dation. Results showed that bioavailability is significantly reduced in soils amended with compost, although no differences were found at the 2 doses of compost studied. In non-sterilized soils the amount of phenanthrene degraded was always higher in the amended soils than in the non-amended one. Microbiological analyses confirmed the presence of a higher number of phenanthrene degraders in the amended soils and in samples of compost alone. These results suggest that compost induces the degradation in soils of easily degradable compounds such as phenan- threne, when the proper bacteria are in the compost; more resistant xenobiotics may instead be trapped by the compost organic matter, thus becoming less available. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Bioavailability; Degradation; Phenanthrene; Non-exhaustive extraction techniques; Compost 1. Introduction Polycyclic aromatic hydrocarbons (PAHs) are amongst the most widespread organic contaminants in soils, natural waters and wastewater. PAHs are formed as by-products of incomplete combustion of organic materials and are emit- ted in the environment mainly by anthropogenic sources such as oil spills, automobile exhausts and coal refining processes (Means et al., 1980). They are ubiquitous, highly hydrophobic and, due to their affinity for fatty tissues, tend to be bioaccumulated in food chains (Van der Oost et al., 2003). Great concern is associated with their presence in the environment, since some of them were demonstrated to be carcinogenic (Santodonato, 1997). Although several hundred PAHs exist, most studies focus on a limited num- ber of them, namely the 16 PAHs listed by the US Environ- mental Protection Agency and the European Community as priority pollutants. Phenanthrene is one of the 16 PAHs on the EPA’s pri- ority list. It is a tricyclic aromatic hydrocarbon, which is 0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.09.058 * Corresponding author. Tel.: +39 (0) 523 599218; fax: +39 (0) 523 599217. E-mail address: marco.trevisan@unicatt.it (M. Trevisan). www.elsevier.com/locate/chemosphere Chemosphere 67 (2007) 548–556