HR: 0800h
AN: H21C-1029    [Abstracts]
TI: Aqueous and Mineralogical Analysis of Arsenic in the Reduced, Circumneutral Groundwaters and Sediments of the Fraser River Delta, British Columbia
AU: Bolton, M
EM: mbolton@eos.ubc.ca
AF: Department of Earth and Ocean Sciences University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4 Canada
AU: * Beckie, R
EM: rbeckie@eos.ubc.ca
AF: Department of Earth and Ocean Sciences University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4 Canada
AB: The aqueous and mineralogical geochemistry of the groundwaters and sediments of the Fraser River delta, BC is investigated. Groundwater and sediment samples were collected from two sites. The DND site is located in an upland area of Richmond BC, approximately 3 km upgradient from the north arm of the Fraser River. The Kidd2 site is located adjacent to the north arm of the Fraser River. A saline water wedge extends inland from the bed of the Fraser River to the subsurface beneath the Kidd2 site. Concentrations of dissolved arsenic (As) are relatively low at the DND site, while concentrations of approximately 30 ug/L dissolved As are present in the vicinity of the saline water wedge, at the Kidd2 site. The aqueous geochemical data for the Kidd2 site suggest that dissolved As is generated by the reduction of hydrous ferric oxide minerals. Sediment samples from both sites were analysed using a sequential extraction procedure (SEP) that was designed to target specific pools of solid-phase As. Results of the SEP analyses indicate that solid-phase As is present in the sediments at trace concentrations (<8 ppm). Processes such as sorption and the precipitation of arsenical sulphide minerals do not appear to be sufficient to mitigate the relatively elevated concentrations of dissolved As that are present at the Kidd2 site.
DE: 1806 Chemistry of fresh water
DE: 1045 Low-temperature geochemistry
DE: 1065 Trace elements (3670)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting