ABSTRACT
Soil contamination by lead in the town of Santo Amaro, in the state of Bahia, Brazil, originated with the installation of a metal plant in the city in the 1960s, and poses a serious risk to the local population. Determination of the available Pb levels in the soil is an important tool in monitoring the risks of this contamination. However, different methods are used to determine the available Pb content of the soil, resulting in differing values for the extractants. The aim of the present work was to compare the efficiency of extraction using Mehlich 1, DTPA and CaCl2solutions in the evaluation of Pb availability in soil treated with different soil amendments. The soil sample used in the experiment was collected near the metal plant. The dosages of soil amendments were set up based on the carbon content of the materials (compost humic acid, commercial humic acid and charcoal), being: 0, 0.75, 1.5, 3 and 7.5 g C kg-1. The available Pb content was extracted by Mehlich 1, DTPA pH 7.3 and CaCl2 10 mmol L-1. Soil fractionation was carried out to determine the metal attached to the exchangeable and organic matter fractions of the soil. The addition of AHv reduced the Pb content of the soil by 60, 89 and 47% for extractions carried out with Mehlich 1, CaCl2 and DTPA respectively. The Pb content of the organic matter fraction was directly proportional to the dosages of soil amendments. The three extractants under evaluation were efficient in predicting the available Pb content.
Key words:
Soil pollution; Heavy metals; CaCl2; Mehlich 1; DTPA
