Prediction of [3- 14 C]phenyldodecane biodegradation in cable insulating oil-spiked soil using selected extraction techniques Nadia M. Dew a , Graeme I. Paton b , Kirk T. Semple a, * a Department of Environmental Science, Institute of Environmental and Natural Science, Lancaster University, Lancaster LA1 4YQ, UK b School of Biological Sciences, University of Aberdeen, Aberdeen AB24 3UU, UK Received 27 August 2004; accepted 17 March 2005 An aqueous-based cyclodextrin extraction can determine the amount of 3-phenyldodecane that is available for microbial degradation in soil. Abstract This study investigated the use of an aqueous hydroxypropyl-b-cyclodextrin (HPCD) shake extraction in predicting microbial mineralisation and total loss of [3- 14 C]phenyldodecane associated activity in soils spiked with cable insulating oil; phenyldodecane represents a major constituent of cable insulating oil. Direct comparisons were made between freshly spiked and aged soils, and following composting. Soil was spiked with [3- 14 C]phenyldodecane (10 mg kg ÿ1 ) and stored in microcosms and aged for 1, 23, 44, 65, 90 and 153 d. At each sample time point, a variety of analyses were performed to assess the relationship between chemical and biological techniques in determining mineralisation and loss of 14 C-activity in soils under composting and non-composting conditions. Methods included determination of total 14 C-activity remaining, dichloromethane (DCM) and HPCD extractions. Mineralisation assays were also carried out to quantify the fraction of 14 C-phenyldodecane associated activity available for degradation in the soil at each time point. DCM and HPCD extractability were compared to contaminant mineralisation and to total loss of 14 C-phenyldodecane associated activity from the microcosms, after 153 d incubation. Poor relationships were found between (i) the amount of 14 C-activity mineralised and the fraction removed from the soils using DCM extraction and (ii) DCM extraction and total loss of [ 14 C]phenyldodecane associated activity from the soil systems. Good relationships were observed between (i) the amount of 14 C-activity mineralised and the fraction removed from the soils using the HPCD extraction and (ii) HPCD extraction and total loss of [ 14 C]phenyldodecane associated activity from the soil systems. The results of this study indicate that an aqueous HPCD extraction may be a useful tool in assessing the microbial availability of phenyldodecane in freshly and aged spiked soils. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Cyclodextrin; Total contaminant loss; Bioavailability; Mineralisation; Phenyldodecane 1. Introduction Soils are repositories of organic contaminants, many of which are hydrophobic in nature (Wild and Jones, 1995; Jones et al., 1996; Semple et al., 2001). Hydro- carbons, including those found in insulating oils, are an important class of hydrophobic organic contaminants (HOCs) and have been the subject of detailed research due to their toxicity, environmental persistence and ubiquitous distribution (Wild and Jones, 1995). Cable insulating oils are used by electrical generation and transfer companies and are known to enter the soil * Corresponding author. Tel.: C44 1524 594534; fax: C44 1524 593985. E-mail address: k.semple@lancaster.ac.uk (K.T. Semple). 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2005.03.009 Environmental Pollution 138 (2005) 316e323 www.elsevier.com/locate/envpol