A major control on the attenuation of organic contaminants dissolved in groundwater is their sorption onto solid organic matter (OM) in the rock. Sorption modelling is currently based on the amount of solid organic carbon in the rock. However, there are very few available data on the total organic carbon (TOe) content in common UK geological materials. A significant new set of Toe measurements on a range of important formations is presented. Methods to measure TOe in geological, especially carbonate-rich, samples are reviewed and evaluated. The impact of the type of OM on its sorption capacity is not understood. Non-linear isotherms measured on seven samples (of Lincolnshire Limestone, Glacial Till from Norfolk and unconsolidated deposits) had a wide range of organic carbon normalised distribution coefficients (Koc from 7.85 l/g to 767 l/g at 0.01 gil trichloroethene). This indicates the impact of characteristics of the OM. Bulk geochemistry and micro-morphology characteristics of the OM that could be important predictors for sorption capacity are investigated and identified. Organic matter has been isolated, and the isolation technique evaluated. The major element composition of the isolated OM has been determined; elemental results were found to correlate with results of a pyrolysis analysis applied to whole rock samples. Morphological analysis of microscope slides of isolated organic matter provided information on the physical types (visually) and size (by image analysis) of the organic particles. Measured Koc values correlated with the elemental HlO content of the sample's OM and with the pyrolysis measurements, but not with morphological results. The effect of selected empirical isotherms on solute transport was simulated: use of an accurate distribution coefficient is essential, but non-linearity was found not to make a major impact on arrival results. Recommendations are made for the improvement of sorption modelling, and for appropriate analysis methods to supply relevant data on the type of OM in this context.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:552996 |
| Date | January 2001 |
| Creators | Steventon-Barnes, Hannah |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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