4.4. Metal concentrations in plants
Manure compost and sewage sludge reduced the DTPA-extractable Zn and Pb concentrations in Pb/Zn tailings (Table 7), but not DTPA-extractable Cu concentrations in Cu tailings. Both Pb and Cu uptake by vetiver and common reed were decreased in Pb/Zn tailings. It has been noted that refuse, pig manure, and cow manure are effective in reducing Pb availability, thus lowering the uptake of Pb by Brassica chinensis and Raphanus sativus by 7 and 5 times respectively ( Wong and Lau, 1985). It was suggested that soil had a relatively large capacity for the immobilization of ionic Pb, and that the precipitation of Pb was primarily through the fixation by organic matter ( Alloway, 1995). Hence, the high organic carbon content of amended Pb/Zn tailings contributed to the low uptake of Pb by both species. For Cu, although the metal could accumulate to high concentrations in the roots, it is much readily transported to the tops of the plants ( Mitchell et al., 1978 and Alloway, 1995). Therefore, Cu uptake was lower in both species, although the Pb/Zn tailings had elevated Cu levels.
4.4. Metal concentrations in plants
Manure compost and sewage sludge reduced the DTPA-extractable Zn and Pb concentrations in Pb/Zn tailings (Table 7), but not DTPA-extractable Cu concentrations in Cu tailings. Both Pb and Cu uptake by vetiver and common reed were decreased in Pb/Zn tailings. It has been noted that refuse, pig manure, and cow manure are effective in reducing Pb availability, thus lowering the uptake of Pb by Brassica chinensis and Raphanus sativus by 7 and 5 times respectively ( Wong and Lau, 1985). It was suggested that soil had a relatively large capacity for the immobilization of ionic Pb, and that the precipitation of Pb was primarily through the fixation by organic matter ( Alloway, 1995). Hence, the high organic carbon content of amended Pb/Zn tailings contributed to the low uptake of Pb by both species. For Cu, although the metal could accumulate to high concentrations in the roots, it is much readily transported to the tops of the plants ( Mitchell et al., 1978 and Alloway, 1995). Therefore, Cu uptake was lower in both species, although the Pb/Zn tailings had elevated Cu levels.
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