Heavy Metals Uptake From Contaminated Soils as Affected by Peat, Lime, and Chelates

Heavy metal contamination of soils may reduce yields as well as the suitability for consumption of crop growth (Keeney et al., 1977; Leeper, 1978). In an effort to find possible ways to counter this danger, the effect of lime, chelating agents, and peat applied to Zn‐, Cu‐and Pb‐contaminated soils on the uptake of metal ions were studied. Pot experiments with barley ( Hordeum vulgare L.), perennial ryegrass ( Lolium perenne ) and Italian ryegrass ( Lolium multiflorum ) plants and soils, humic podzols (haplohumads) contaminated with Zn (3030 mg kg −1 ) and with Pb, Zn and Cu (110, 630, and 40 mg kg −1 , respectively) were carried out. The concentration of the acid extracts of soils and plants were determined with the aid of the simultaneous direct reading spectrograph and atomic absorption. In all cases, raising the pH of the soil by liming appeared to be the most efficient method for reducing plant absorption of toxic micronutrients and heavy metals. However, the uptake of Fe and Mn was more markedly dependent on pH than that of Zn and Cu. The lowest pH level to which an acid soil has to be limed in order to overcome heavy metal contamination is a function of both the type and the concentration of the metal. Contamination of the soil by heavy metals influenced plant growth as well as mineral composition and quality for a pasture crop. Perennial ryegrass, Lolium perenne (R.v.P.) was more tolerant than Bent grass, Agrostis tenuis , to high levels of Pb, Zn and Cu in soils. While the addition of lime reduces the uptake of heavy metals, the addition of the investigated chelating agents increased the uptake.