Geochemical investigation of urban soils in Fredericton, New Brunswick, Canada
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Date
2016
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University of New Brunswick
Abstract
Fredericton, New Brunswick, overlies an aquifer that supplies potable water to ~95% of the city. This aquifer is confined by a discontinuous clay-silt aquitard which underlies floodplain/fluvial deposits. The aquitard contains erosion scours or ‘windows’, which could serve as pathways, allowing contaminants into the aquifer. A soil geochemical survey of Fredericton included 101 sampling sites with a focus on locations near the windows.
The urban centre occupies a large floodplain situated between the Saint John River and higher terrain to the west. Near-surface ‘A’ samples were collected at a depth of ~10-15 centimeters and, where possible, deeper ‘B’ samples were collected at a depth of >30 centimeters. Till samples were also collected from areas of higher elevation, where the soil has been less disturbed.
Subsamples <63 microns were analyzed by INAA or TD-ICP to determine elemental concentrations for 50 elements. Samples collected in the downtown area were found to surpass the Canadian Council of Ministers of the Environment (CCME) soil content guidelines for elements such as As, Cr, Pb, and Zn. It is interpreted that anthropologic factors have contributed to elevated elemental concentrations in the downtown area.
Weathering and elemental mobility are also interpreted to have facilitated the dispersion of elements. The ‘B’ till samples often displayed higher elemental concentrations than the ‘A’ samples. Unlike the till population, the urban centre population demonstrated higher elemental concentrations in the ‘A’ samples in comparison to the ‘B’ samples, suggesting anthropological contributions at ground surface. In an attempt to correlate human health with soil geochemical content, health statistics from the Fredericton area were investigated; fortunately, no illnesses or diseases seem to stand out in comparison with provincial and national statistics.