HR: 0830h
AN: H51C-1076    [PDF]
TI: Possible Processes For Acidity And Metal Contaminant Attenuation In A Polluted Estuarine Aquifer
AU: Patrick, E
EM: patricia.enot@ed.ac.uk
AF: University of edinburgh, Crew Bulding, the King\\\'s Buildings, West Mains Road, edinburgh, EH9 3JN United Kingdom
AU: Xiaomin, M
EM: xmao@ed.ac.uk
AF: University of edinburgh, Crew Bulding, the King\\\'s Buildings, West Mains Road, edinburgh, EH9 3JN United Kingdom
AU: * Andrew, B
EM: d.a.barry@ed.ac.uk
AF: University of edinburgh, Crew Bulding, the King\\\'s Buildings, West Mains Road, edinburgh, EH9 3JN United Kingdom
AU: Ling, L
EM: ling.li'ed.ac.uk
AF: univeristy of queensland, xxx, queensland, xxx Australia
AU: Andrew, B
EM: a.binley@lanc.ed.ac.uk
AF: university of Lancaster, xxx, lancaster, xxx United Kingdom
AB: Geochemical data obtained from an estuarine sandy aquifer situated below an old industrial landfill (Ayrshire, Scotland) indicated that acidic groundwater (pH $<$2) exists 100 meters from the estuary bank. Associated with this acidic plume, elevated concentrations of dissolved heavy metals (Al, Zn, Cu, Cr, Cd) were observed. Water table monitoring and chemical data showed that the groundwater is intruded by estuarine water and is tidally influenced. While geochemical processes associated with acidic plumes and related metal contamination have been widely studied in inland aquifer systems, they have received much less attention in near shore aquifers. Rarely have processes taking place in tidally influenced acidic aquifers been investigated in detail in the field. The aim of the study was to identify the key processes controlling the migration of the acidic plume and reactive transport of contaminants on the path from the aquifer to the estuary. More specifically, the research work has focused on the role played by estuarine water intrusion on the geochemical processes occurring in the aquifer. Through integration of intense geophysical, hydrogeological and hydrogeochemical Investigations, a comprehensive field-monitoring program and laboratory experiments have been carried out. Data obtained were analysed using a geochemical modelling code, PHREEQC-2. In parallel, a model for multi-components reactive transport with density dependent flow was developed and applied to the site. Results from the field, laboratory, and modelling work indicated that oxidation of sulphurous waste located in the landfill at the pollution source is the origin of the groundwater acidity. The low pH plume and associated contaminants are slowly migrating towards the estuary. Retardation of the plume and pH buffering processes are clearly occurring in the aquifer. Ion exchange, precipitation, buffering mineral dissolution, and tidal forcing on the advective-dispersive transport were identified as the main factors influencing contaminant migration and behaviour in the aquifer.
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2003 Fall Meeting