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Bioavailability assessment of trace metal contaminants in urban soils and partitioning of zinc, cadmium, lead, nickel, and copper in the roots, shoots, foliage, and seeds of Chenopodium quinoa Thomas, Elisabeth Chere


This paper presents two studies on urban soils in Vancouver – the first is a case study for assessment of trace metals in urban soils, with particular emphasis on brownfield reclamation and food production. Three single-extraction procedures are evaluated for their usefulness for identifying the bioavailable fractions of trace metals in soil. Plant-available Zn, Cd, Pb, Ni, and Cu were estimated using elemental analysis, pH, organic matter, and soil texture. Specific geochemical factors such as oxidizing conditions and the presence of Fe-, Al-, and Mn-oxides suggest trace metal mobility in the soils. The use of 0.1M HCl for estimating the risk of trace metal bioaccumulation in crop urban plants is recommended. The second study assesses selected phytoremediation technology for removing trace metals from soil through successive cultivation of trace metal-accumulating crop plants. A pot study was conducted using Chenopodium quinoa (quinoa) to extract Zn, Cd, Pb, Ni, and Cu from variously spiked brownfield soil. Chenopodium quinoa is a grain that may be a high-value specialty crop in British Columbia. Previous research suggested that Chenopodium quinoa may be a useful plant for phytoextraction of trace metals. The reasons for using quinoa in the present experiment are twofold – (1) to evaluate potential human health risks involved with growing a metal-accumulating crop in potentially contaminated urban soils, and (2) to assess the above-ground partitioning and accumulation of trace metals for evaluating the usefulness of Chenopodium quinoa for phytoextraction in Vancouver, British Columbia. It was found that quinoa is a hyperaccumulator and there is a potential concern that grains may contain harmful levels of trace metals for human consumption.

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