Factors involved in uptake of lead by some edible crops grown in agricultural soils of Central Italy.

This study was organized to investigate the bioavailability of Pb in soil, as affected by soil type and crop species. The four most representative forms of Pb in soil (exchangeable, bound to carbonates, bound to the Fe-Mn oxides, and bound to organic matter) were considered, and their respective contribution to the uptake of this metal was determined. Four edible crops (lettuce, radish, tomato, and Italian ryegrass) were grown in four soil types, both nonspiked and spiked with 200 mg Pb kg-1. Chemical analyses were carried out to determine the amount of Pb sorbed from the soil and stored in the different plant organs. The bioaccumulation factor (BAF) and the translocation factor were derived and used to compare plant species. Results showed that all the test plants sorbed 10 to 30 times more Pb from spiked soils, as compared with nonspiked soils. The BAF and translocation factor showed that, excluding Italian ryegrass, all the crops sorbed less Pb from the soils containing Ca carbonate. On the basis of BAF, lettuce, tomato, and Italian ryegrass could be classified as crops with high Pb uptake ability in all soils. Concerning the distribution of Pb within the plant, all species showed the tendency to store this metal mainly in roots. The translocation to above-ground organs was the highest with lettuce, tomato (with reference to non edible above-ground organs) and Italian ryegrass, whereas radish showed the lowest translocation ability, together with the lowest uptake ability.