Optimisation of XAD extraction methodology for the assessment of biodegradation potential of 14C-phenanthrene in soil

This study investigated the use of a hydrophobic resin, amberlite XAD, as a tool for assessing the biodegradation potential of 14C-phenanthrene in soil. The method was optimised in terms of soil/XAD ratio, shaking, extraction time and eluting solvent. The most effective method was then tested on selected XADs, and the performance compared with cyclodextrin (HP-β-CD) and dichloromethane (DCM) extractions suitability to predict phenanthrene biodegradation in soil over 100 d. Results showed that the optimum conditions for the XAD extraction technique are a 2:1 soil/XAD ratio, 100 rpm mixing for 22 h and elution using a DCM:methanol solution (1:1). Mineralisation of 14C-phenanthrene was accurately predicted by HP-β-CD (r2=0.990, slope = 0.953, intercept = 1.374) and XAD-4 extractions (r2=0.989, slope = 0.820, intercept = 6.567), while DCM overestimated the bioaccessibility of  14C-phenanthrene (r2=0.999, slope = 1.328, intercept =−49.507). This investigation showed that XAD extraction can be considered a suitable non-exhaustive technique for estimating biodegradability of phenanthrene in soil.