Toxic effects of iron ore tailings and the response of watercress from tailings at high concentrations of Fe, Zn and Mn

Watercress Nasturtium officinale was found growing on the iron ore tailings at Ma On Shan which had high total metal contents (Fe 46792 μg g⁻¹, Mn 2063 μg g⁻¹ and Zn 423 μg g⁻¹). Samples of the plant were collected from this heavy metal contaminated site (Ma On Shan), a cultivated area (Tai Po) and non-cultivated land (Lam Tsuen). It was found that the heavy metal contents (Fe, Zn, Mn) of the plant tissue collected from Ma On Shan were significantly (P/0·05) higher than those collected from the other two sites.
Seeds of Brassica chinensis used to study the effect of water extracts of soil samples collected from the three sites on seed germination and root elongation showed that 5, 10 and 15% (w/v) extracts reduced seed germination and root elongation of the crop.
When the three different populations of N. officinale collected from the three sites were tested for metal tolerance by examination of root growth in a series of concentrations of manganese, iron and zinc separately, it was found that the tailings population had significantly higher values of tolerance to each of the three metals despite the fact it had only been growing on the site for three years. Copyright © 1985 Published by Elsevier Ltd.