The first gasworks were developed in the early 19th Century and their usage increased until the 1970's when the manufacture of town gas was phased out owing to the new natural gas supply. Consequently, gasworks often have a long history of potentially contaminative use. The main process utilised on these sites, coal carbonization, produced a broad range of potential contaminants including phenols, benzene, toluene, ethylbenzene and xylene (BTEX), polycyclic aromatic hydrocarbons (P AH's), ammonium, and cyanides. This study has focused largely on ammonium and phenol migration and attenuation in the Chalk aquifer and overlying sediments, following the extensive characterisation of a former gasworks at St Albans, Hertfordshire, UK. Invasive and non-invasive techniques, including borehole construction, enabling core- retrieval, "- and geophysical investigation methods respectively, have been used to characterise the nature and extent of contamination and the possible migration pathways in the Chalk aquifer. Chalk pore-water quality analyses indicate that the aquifer is contaminated at depth, but attenuation of ammonium and phenol is sufficient to reduce .- 'concentrations to an acceptable level in the nearby Holywell Hill pumping station. Concentrations of ammonium, phenols and the BTEX compounds in fissure-derived water beneath the former gasworks are well above drinking water• standards, and long- term monitoring has shown that their distribution is closely related to fluctuations in water levels and changes in pumping regimes at the pumping station. Excavation and drilling work has highlighted the variability in the depth of the Chalk surface over the study area, and this has a significant influence on groundwater flow and contaminant --- distribution. Batch adsorption experiments on unsaturated and saturated zone sediments suggest that _phenol is only adsorbed by topsoil samples owing to the presence of specific fractions of organic matter. Ammonium adsorption was highest in unsaturated zone sediments and is closely related to surface area and cation exchange capacity. Leaching through cores suggests that the Chalk matrix has little potential for the attenuation of ammonium. Biodegradation appears to control the attenuation of phenol in the Chalk.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553096 |
| Date | January 2000 |
| Creators | Burton, Jonathan Mark |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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