SEQUENTIAL EXTRACTION OF LEAD AND ZINC FROM SOILS OF HEAVY METAL MINING AND PROCESSING AREA

SEQUENTIAL EXTRACTION OF LEAD AND ZINC FROM SOILS OF HEAVY METAL MINING AND PROCESSING AREA Sequential extraction allows more detailed information about the origin of heavy metals in natural environments, their mode of occurrence, biological and physico-chemical availability, mobilization and transport. To study the Pb and Zn forms, eight soil profiles were selected at different sites within a Pb mining and metallurgy area in the city of Adrianopolis, state of Parana, in the Rio Ribeira valley. Samples were collected from the layers 00-10, 10-20 and 20-40 cm. The total Pb and Zn contents and their speciation in the forms: soluble, exchangeable, carbonate-bound, bound to organic matter, bound to Fe and Al oxides of low crystallinity; linked to crystalline Al oxides and phyllosilicates 1:1 and 2:1; and residual. Based on the percentage values of each fraction in the total contents, similar samples were grouped by principal component analysis (PCA). There were basically two contamination forms of soil profiles; the first was the result of particles from the chimneys and the second due to the accumulation of solid waste on the soil surface. The first was more environmentally damaging due to the higher total and soluble forms in the soil (in the exchangeable and in the solution forms). Overall, there was a greater association of Pb with carbonates, and residual fractions followed by Fe and Al oxides of low crystallinity. Zinc was found in more insoluble forms, increasing the participation in total contents of the residual fraction. The PCA is sensitive to different Pb forms in the soils, underlying the grouping of samples, mainly based on the participation of exchangeable forms, bound to Fe and Al oxides and to carbonates, in relation to the total content.