Hydrocarbon contaminants regularly leach into groundwater because of human activities and accidental chemical spills. Here, the contaminants pose a threat to the environment and valuable drinking water resources. Many subsurface environments are able to purify the groundwater of such contaminants, thus lowering the cost of remediation. This has sparked an interest in the use of naturally occurring processes to degrade contaminants in the subsurface and has opened up an area of research focusing on „natural attenuation‟. For the successful application of natural attenuation and in order to obtain regulatory approval a reliable assessment of the mechanisms responsible for the removal of contaminants in an aquifer is essential. This thesis presents evidence to support the natural attenuation of isoproturon (IPU) and sulphanilamide (SULPH) in a chalk aquifer and assesses in-situ biodegradation by: (a) analysing historical monitoring data to identify and support biodegradation processes at the contaminated field site; (b) the development of in-situ microcosm approaches, (c) determining the catabolic activity present across the site using ex-situ microcosm studies that replicate in-situ aquifer conditions and, (d) identifying and quantifying biodegradation in the aquifer (of SULPH) using compound specific isotope analysis. Based on the historical data and ex-situ microcosms IPU biodegradation was found to be occurring at the site; albeit at very low levels (2 %). It is suggested that the high concentrations of other contaminants at the site (up to 650 mg L-1), compared to the low IPU concentrations (9 μg L-1) may have impeded IPU biodegradation. However, even these low levels of IPU biodegradation may be important in aquifers exhibiting long residence times. The historical data and ex-situ microcosms further indicated the biodegradation of around 50% of the SULPH present at the site. The development of novel compound specific isotope analysis indicates 56 % of the SULPH has undergone biodegradation at the site. These three approaches; historical data, ex-situ microcosms and compound specific isotope analysis, provide strong evidence to support the occurrence of natural attenuation at the site. Of particular originality, is the identification of natural attenuation of SULPH in a chalk aquifer and the quantification of its biodegradation using compound specific isotope analysis.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:590747 |
| Date | January 2013 |
| Creators | Hampson, Karen |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://ueaeprints.uea.ac.uk/47908/ |
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