Non-exhaustive extraction techniques (NEETs) for the prediction of naphthalene mineralisation in soil

Abstract

Non-exhaustive extraction techniques (NEETs) have been shown to measure the putatively bioavailable fraction of hydrophobic compounds in soil. To date, these studies have only considered bioavailability in a single soil type. In this study, naphthalene was amended into five different soil types and mineralisation, bacterial biosensor response and the number of indigenous microbial naphthalene degraders were determined. Two NEETs were used to extract the naphthalene from soil; hydroxypropyl-beta-cyclodextrin (HPCD) and XAD-4. The HPCD extractable fraction correlated closely (R2 = 0.917) with the portion that was mineralised, but the XAD-4 extract did not (R2 = 0.044). HPCD may be ideal for the rapid assessment of the fraction of a hydrophobic organic contaminant that is available for biodegradation. A NEET that complements environmental microbial analysis will enhance our understanding of soil pollution interactions and equip us better in designing risk assessment models that integrate biological parameters. This application, although refined for soil samples, should be transferable to other environmental matrices.

Pseudomonas fluorescens HK44: Lessons Learned from a Model Whole-Cell Bioreporter with a Broad Application History

“…The observation that bioreporter measurements of naphthalene concentrations are lower than concentrations derived by solvent extraction and chemical analysis are due to the fact that naphthalene is highly sorbed onto soil particles and thus it is not bioavailable to the bacteria for biotransformation [73]. In the mid-2000s a series of studies was performed that indicated biosensor performance can be improved using a non-exhaustive extraction technique (NEET) [73].…”

“…In the mid-2000s a series of studies was performed that indicated biosensor performance can be improved using a non-exhaustive extraction technique (NEET) [73]. In addition, this approach allowed for a determination of biodegradation potential of a PAH contaminated soil sample [58,73,79,80]. The main criteria for NEET to be compatible with biosensors is that the solvent should be primarily aqueous or if the extract is in an organic solvent it must be dilutable in an aqueous solution [79].…”

“…The main criteria for NEET to be compatible with biosensors is that the solvent should be primarily aqueous or if the extract is in an organic solvent it must be dilutable in an aqueous solution [79]. Initially, several chemicals were tested for their ability to extract PAHs from contaminated soil followed by testing in bioassays, including cyclodextrin (hydroxylpropyl-β-cyclodextrin), Amberlite XAD-4, and organic solvents (methanol and dimethylsulphoxide) [73]. Of these compounds, cyclodextrins, which consist of a hydrophobic cavity and a high aqueous solubility, were proven to be the most effective in extracting naphthalene from soils followed by either mineralization studies or coupling with biosensors [79].…”

Extraction and bioanalysis of the ecotoxicologically relevant fraction of contaminants in sediments

“…Tenax hydrophobic resins (Chrompack, Bergen op Zoom, The Netherlands) and cyclodextrins recently were proven to give a reliable estimation for the bioavailable fraction of contaminants [12,13]. Cyclodextrin extractions follow equilibrium kinetics, and these extractions were applied in several studies to estimate the bioavailable fraction of polycyclic aromatic hydrocarbons (PAHs) [18][19][20]. Cyclodextrin extractions follow equilibrium kinetics, and these extractions were applied in several studies to estimate the bioavailable fraction of polycyclic aromatic hydrocarbons (PAHs) [18][19][20].…”

Bacterial Biosensors for Measuring Availability of Environmental Pollutants

“…Chemically, bioaccessibility can be tested by using so called non-exhaustive extraction techniques (NEETs). NEETs employ, for instance, Tenax or cyclodextrins to rapidly retrieve a compound fraction from the sample that is similar to the fraction metabolized by (micro-) organisms during a much longer incubation period [29,30]. For example, Dick et al added [ 14 C]-labeled phenanthrene or pyrene to soils, and showed that the total fraction of PAHs metabolized by bacteria in the soil during thirty days as derived from [ 14 C]-CO 2 evolution was almost the same as the PAH-amount extracted by hydroxypropyl-beta-cyclodextrin [30].…”