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(M/EH042) Application of biosensors for assessment of toxicity of chlorophenol interactions in soil. Tiensing, Tinnakorn1, Preston, Sara1, Strachan, Norval1, Paton, Graeme1, 1 ABSTRACT- The assessment of toxicity of chlorophenols was studied by using luminescence-based microbial biosensors. These sensors act as a monitoring tool for determining the bioavailable fraction of contaminants and offer an ecological relevant toxicity test. For this study Escherichia coli HB101 pUCD607 and Pseudomonas fluorescens 10586r pUCD607 were selected as microbial biosensors, each representing contrasting different ecological niches (Preston et.al., Environ. Tox. Chem., 19(3), 775, 2000). Individual and combination of chlorophenol compounds; 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP), were added to field moist soil of sandy loam and loamy sand textures and then extracted by methanol-water mixture. The luminescence response of microbial biosensors was compared with standard solution in deionised water at pH 5.5. The prediction of interaction effects was investigated. Pollutant interactions were predicted using a suitable model. Results showed that the predicted level of toxicity was greater than the observed level at high concentrations of all mixture combinations hence the interaction was synergistic. Soil characteristic mediated the actual toxicity response hence high performance liquid chromatography (HPLC) was used to quantify the actual burden of toxicity. The median effective concentration (EC50) of individual compounds varied with the matrix of solution and was influenced by soil physicochemical characteristics. Legislation deals with the pressure of individual contaminants regardless of their association with 10-contaminants and indeed metabolites. This work highlights the need to consider multicontaminant impacts and interaction therefore developing a thorough understanding of risk assessment. Key words: micorbial biosensor, interactions, chlorophenols, bioavailability |
