Chemical and Mineralogical Attributes of an Eutroferric Red Latosol and Their Interactions with Lead Sorption.

The ferric RED LATOSOLS derived from basalt comprise much of the soils present in the state of Paraná (PR). These soils have been called attention by their high natural fertility, provided by their physical, chemical and mineralogical properties. However, the large amounts of heavy metals added daily to the system, may cause damage to plants and animals. Thus, this study aimed to evaluate the chemical and mineralogical attributes of two eutroferric RED LATOSOLS derived from basalt of the Serra Geral formation, and their relations with the lead sorption (Pb). For this purpose, two profiles of an eutroferric RED LATOSOL were sampled with A, Bw, C1, C2 horizons and the parent rock and assessed their chemical and mineralogical properties. Besides the complete chemical and mineralogical characterization of the different horizons it was also evaluated the sorption of Pb in the different horizons and powder rocks. The results showed that the chemical and mineralogical properties are directly affected by the weathering process. Several minerals phases changed within the profile, and the accumulation of more resistant minerals to weathering (kaolinite and iron oxides) were found in the surface horizons. We also evaluated the remaining (Pb_rem) and adsorbed Pb (Pb_ads) to the soil using a dose of 3000 mg Pb mg  L^-1 solution in a 5:40 soil: solution ratio, and desorption of Pb⁺² using Mehlich-1 acid extractor. Chemical characteristics that correlated significantly with the adsorption of Pb were Ca^{2 +}  and organic carbon contents. The mineralogical attributes that have higher correlations with the remaining Pb were the magnetic susceptibility of the non-magnetic fraction of sand and clay fractiois. Desorption of lead was directly influenced by organic matter and 2:1 clay minerals.