The aim of the study was to carry out a much needed field investigation on the physical and chemical processes affecting contaminant movement in the groundwater of coastal aquifers, prior to their discharge to coastal waters. The study site located in Ayrshire, UK, was selected as it contains a low-pH acidic and metal-contaminated plume migrating to the Garnock estuary. The tidal estuary is characterised by a very low relief sandy beach. A key research motivation was to determine the mechanisms of contaminant attenuation on the transport pathway, which significantly reduced the impact of groundwater contamination on the estuary. It was found that near to the shore, the groundwater flow was very responsible to changes in the tidal stage. The amplitude of the tidally induced water table fluctuations was rapidly dampened as it propagated inland due to the mild sloping beach. A zone of brackish groundwater of marine origin was found at depth and identified as part of the saltwater intrusion wedge. Little spatial and temporal changes observed during the monitoring period suggest that the saline water was at a quasi-steady state. Mixing between upper acidic and deep alkaline saline groundwaters was unlikely in the monitoring transect. The migration of the acidic plume towards the estuary was limited to the upper section of the aquifer, and was considerably affected by buffering processes involving mainly carbonates, AI and Fe oxy-hydroxides. In turn, the fate of metal contaminants was mainly controlled by pH, however the effect of sediment heterogeneity on the distribution of dissolved metals was shown to be significant. In addition, the results suggested that tide-induced fluctuations in the groundwater flow would have an impact on the distribution of metal contaminants near the shore.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:650027 |
| Date | January 2005 |
| Creators | Enot, Patricia |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13801 |
Page generated in 0.0024 seconds