Prediction of [3-C-14] phenyldodecane biodegradation in cable insulating oil-spiked soil using selected extraction techniques

This study investigated the use of an aqueous hydroxypropyl-p-cyclodextrin (HPCD) shake extraction in predicting microbial mineralisation and total loss of [3-C-14]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-C-14]phenyldodecane (10 mg kg(-1)) 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 C-14-activity in soils under composting and non-composting conditions. Methods included determination of total C-14-activity remaining, dichloromethane (DCM) and HPCD extractions. Mineralisation assays were also carried out to quantify the fraction of C-14-phenyldodecane associated activity available for degradation in the soil at each time point. DCM and HPCD extractability were compared to contaminant mineralisation and to totalloss of C-14-phenyldodecane associated activity from the microcosms, after 153 d incubation. Poor relationships were found between (i) the amount of C-14-activity mineralised and the fraction removed from the soils using DCM extraction and (ii) DCM extraction and total loss of [C-14]phenyldodecane associated activity from the soil systems. Good relationships were observed between (i) the amount of C-14-activity mineralised and the fraction removed from the soils using the HPCD extraction and (ii) HPCD extraction and total loss Of [C-14] 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. (c) 2005 Elsevier Ltd. All rights reserved.