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(254) Cyclodextrins as a mimic for the microbial availability of hydrophobic organic contaminant in soils. Semple, Kirk1, Reid, Brian2, Stokes, Joanna1, Jones, Kevin1, 1 2 ABSTRACT- Traditionally, assessment of contaminanted land has been concerned with the determination of total organic contaminant concentrations in soils, using exhaustive extraction techniques. However, in light of the increasing body of knowledge relating to temporal decreases in contaminant availability in soils, such methods may have little relevance to the amount of contaminant, which may pose an ecological risk or be available for degradation, i.e. the bioavailable fraction. An extraction method using cyclodextrins has been developed to determine contaminant availability to microbes in soils. Cyclodextrins are a group of macrocyclic compounds comprising a taurus of Key words: microorganisms, bioavailability, PAHs, mineralisation |
-1,4-linked glucose units. These molecules have a high aqueous solubility, but also possess a hydrophobic cavity in the interior and are much like a bucket in structure. Because of these physico-chemical properties, it is possible to form a 1 to 1 inclusion complex between the cyclodextrin macromolecule and a hydrophobic organic contaminant (HOC). In recent work, polycyclic aromatic hydrocarbon (PAH) extractability using traditional solvent extractions (dichloromethane and butanol) was compared to cyclodextrin (HPCD) extraction against the amount of the contaminant that could be degraded in soils by a known PAH degrader. In all cases, the correlations between extractability and degradability with a known phenanthrene degrader, Pseudomonas fluorescens, were high. However, only the HPCD extractions gave a 1 to 1 comparison between PAH extractability and biodegradability in soil. Recently, we have investigated the feasibility of using the HPCD extraction technique on a PAH-contaminated soil from a disused coke plant to determine the putative bioavailability of the PAHs present in the soil. As before, a strong 1 to 1 relationship was found between the mass extracted and degraded (following a 6 week incubation) for 16 PAHs in the soil. It is anticipated that by using cyclodextrin extraction procedures, assessments for the success of bioremediation as well as risk, can be made in soils contaminated with HOCs.