Total soil lead (Pb) content along with the sorption capacity of Pb in soils are important parameters for risk assessment studies of Pb in the environment. This experiment used A-horizon samples of 17 Oxisols from all Brazilian regions to evaluate their total Pb content as well as their Pb maximum adsorption capacities (PbMAC). The total soil Pb content varied from 6.14 to 30.55 mg kg-1, averaging 18.00 mg kg-1. The highest total soil Pb contents were found for soils of the southern and southeastern regions, followed by the soils from the western Central and northern/Northeast regions. Values of the PbMAC varied from 2,215 to 19,465 mg kg-1, averaging 11,296 mg kg-1. Lead maximum adsorption capacity was positively correlated with sulfuric acid digestion-Si and -Fe, oxalate- and DCB-Fe, hematite, kaolinite and clay contents, CEC and specific surface area values and negatively correlated with Al2O3/Fe2O3 and Gt/(Gt + Hm). The results indicated that Oxisols can adsorb a great amount of Pb. In addition, it was observed that most Oxisols adsorbed more Pb than the amount expected from CEC values, which indicates the occurrence of inner-sphere complexation.
heavy metal; tropical soils; soil mineralogy