Predicting PAH bioremediation efficacy using bioaccessibility assessment tools: Validation of PAH biodegradation-bioaccessibility correlations

Abstract

Hydroxypropyl-β-cyclodextrin (HP-β-CD) may be utilised as a selective extractant to assesses the amount of PAHs in contaminated soil that are potentially available for biodegradation (i.e. the bioaccessible fraction). In this study, HP-β-CD extraction and PAH biodegradation (using enhanced natural attenuation) was assessed in 15 PAH-contaminated soils (dataset 1) in order to develop linear regression models to predict the extent of PAH degradation based on PAH bioaccessibility. Further studies were then undertaken to validate the HP-β-CD extraction-biodegradation relationships for individual PAHs using an independent dataset of 10 PAH-contaminated soils (dataset 2). Validated linear regression models were those where there was no significant difference ( P<0.05) in the slope and y intercept of the HP-β-CD extraction-biodegradation relationship for datasets 1 and 2. For acenaphthylene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, dibenz[a,h]anthracene and indeno[1,2,3-c,d]pyrene, validated linear regression models were developed with the slope of the relationships and goodness of fit ranging from 0.87 to 1.56 and 0.84-0.98 respectively. For benz[a]anthracene and benzo[a]pyrene, there was no significant difference ( P>0.05) in the slope of models 1 and 2, however, the y intercepts were significantly different ( P<0.05). For these compounds, a congruent model was developed using datasets 1 and 2 to derive a harmonised y intercept. Although linear regression models 1 and 2 were significantly different for benzo[b+k]fluoranthene and benzo[g,h,i]perylene, the more conservative linear regression model could be utilised for predicting the endpoints of PAH biodegradation. Linear regression models have the potential to be used as a screening tool to predict the efficacy of PAH bioremediation in contaminated soils. Predicted bioremediation endpoints may then be compared to clean up criteria to determine whether bioremediation is an appropriate technology for achieving these goals. This would advantage the remediation industry through the provision of a rapid, inexpensive method for determining the endpoints of PAH bioremediation.