| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4436745 | Applied Geochemistry | 2011 | 12 Pages |
Naturally occurring As in the groundwater and Holocene sediments of the lower Fraser River delta was studied. At each of two sites in the delta, vertical profiles of groundwater geochemistry were characterized and sediment cores were collected for petrographic analysis, quantification of elemental abundances, and sequential extraction analysis to characterize the pools of solid-phase As. Total solid-phase As concentrations were similar to those found in other deltaic environments, ranging from 2.2 to 2.6 μg/g at a site of groundwater recharge with approximately 4 m of peat at the surface, to 2.7–4.1 μg/g at a site adjacent to the Fraser River where saline water is encountered within the aquifer at depth. Arsenic that was weakly bound or could be mobilized by reduction of Fe oxides constituted between 20% and 50% of the total As in the sediments. Groundwater As concentrations showed distinct vertical trends, and peaked at 9 μg/L at the peat-influenced site and between 29 and 32 μg/L at the site with saline water at depth. At both sites, reduction of dissolved organic matter appears to be responsible for reducing conditions, high dissolved Fe (up to 230 mg/L), high HCO3-, and the presence of NH4+ and PO43-. The peat-impacted site implies that a direct source of dissolved organic C from peat is not a sufficient condition for significant As release into groundwater in the Fraser River delta.
Research highlights► Naturally occurring arsenic in Fraser River delta aquifer. ► Dissolved concentrations peak at 32 μg/L. ► Solid phase concentrations average between 2.2 and 4.1 μg/g. ► Influx of natural organic matter from peat not sufficient to release significant arsenic to solution.
