Abstract
Lateritic soils have been widely used in the construction of landfill base liners for municipal and industrial waste. On the other hand, there is little practice in the use of strongly weathered residual soils for this finality. The use of local soil for the construction of liners in order to waterproof and retain contaminants represents an alternative to control this type of contamination. Thus, the objective of this study was to determine the physical and chemical properties of a strongly weathered tropical soil (residual soil) collected in the city of Eldorado Paulista (Ribeira Valley), and to evaluate the abilityof this soil to adsorb lead (Pb). The contamination of soil and water by Pb due to inadequate mining waste disposal is common in this region. The Pb was adsorbed by the residual soil, mainly at the lowest initial concentrations. When the initial concentration of 20 mg L-1 was used, the adsorption percentage of Pb was 92.5% and when the initial concentration was 100 mg L-1, the adsorption rate was 81.7%. In addition to the retention of Pb, this soil presented the following characteristics which are favorable for using soils in the construction of liners: fine granulometry, liquid limit (LL) of 57%, plasticity index (PI) of 33%, oxidizing medium and the predominance of negative charges on the surface of the colloidal particles. Thus, it is concluded that the weathered tropical residual soil exhibits characteristics that allow it to be used as a liner in the disposal of residues containing Pb.
Highlights
Lead (Pb) is a nonessential potentially toxic element (PTE) that naturally occurs at low concentrations in the environment (Adriano 1986; Alloway 1995)
The clay fraction obtained in the soil when applying sodium hexametaphosphate (SHMP) was 26.12% (Table 1), while the percentage of clay was lower (20.19%) without SMHP
The results of the test with dispersant show higher clay content and lower silt content. This is explained by flocculation of small clay particles when there was no dispersant
Summary
Lead (Pb) is a nonessential potentially toxic element (PTE) that naturally occurs at low concentrations in the environment (Adriano 1986; Alloway 1995). The excess of Pb is common in the soil due to anthropogenic activities These activities are related to the use of this metal in industrial applications, mainly in the automotive industry, the improper disposal of mining and smelting wastes; air-borne sources; use of pesticides; biosolids and manure (Alloway 1995; Skerfving and Bergdahl 2007; Wuana and Okieimen 2011). The contamination by Pb is a global concern due to its high toxicity and bioaccumulative properties It can cause severe biological effects, increasing anemia, cancer and mortality rates (Lustberg and Silbergeld, 2002; Papanikolaou et al, 2005; Skerfving and Bergdahl 2007; Jin et al 2008; Hegazy et al 2010). There is no known safe blood level for Pb, concentrations as low as 5 μg/dL may be associated with decreased intelligence in children, behavioral difficulties and, learning problems (WHO 2018)
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