Distribution coefficients of potentially toxic elements in soils from the eastern Amazon

Abstract

The solid-solution distribution or partition coefficient (Kd) is a measure of affinity of potentially toxic elements (PTE) for soil colloids. Kd plays a key role in several models for defining PTE guideline values in soils and for assessing environmental risks, and its value depends on edaphic and climatic conditions of the sites where the soils occur. This study quantified Kd values for Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn from representative soil samples from Brazil's eastern Amazon region, which measures 1.2 million km(2). The Kd values obtained were lower than those set by both international and Brazilian environmental agencies and were correlated with the pH, Fe and Mn oxide content, and cationic exchange capacity of the soils. The following order of decreasing affinity was observed: Pb>Cu>Hg>Cr>Cd≈Co>Ni>Zn.

Phytoextraction of heavy metals from a landfill in the metropolitan region of Belém-Pará-Brazil

“…The negative correlations of the OM content with Pb and Zn may be related to the formation of organometallic complexes with polymerized Fe or with the insoluble compounds of high molecular mass. Moreover, the positive correlation with available Cu (p < 0.05) may be attributed to the formation of chelates from the material synthesized from residues of microbial metabolism or immobilized by material originating from live or recently dead cells (Souza Braz et al, 2013). The pH was positively correlated (p < 0.05) with Al, but there were no significant correlations with any other analyzed metal.…”

“…In weathered soils, such as that considered in this study, with predominantly kaolinitic and oxide mineralogies in the clay fraction, there is an increased affinity of metal cations to the reactive surfaces of these components through physical-chemical reactions (Souza Braz et al, 2013).…”

“…The solubility of metallic oxides, mainly the bivalent species, decreases with increasing pH; hence, there are high positive correlations between the coefficients of adsorption of heavy metals (with the exception of Cr and Hg) and the value of soil pH (Souza Braz et al, 2013).…”

“…The lack of correlation between the available Cd level and the clay content can be explained by the selectivity of the cations to the compounds in the soil; the adsorption selectivity for Cd is always smaller than the selectivity for Cu, Pb and Cr for weathered soils with a predominance of Fe and Al oxides (Souza Braz et al, 2013). This condition can increase the mobility of this element, enabling its movement into water resources.…”

Adsorption of lead (Pb) in strongly weathered tropical soil (Ribeira Valley region - Brazil)

“…Metal mobility in the soil also depends on soil conditions and the chemical form of the metal (Alloway 1995;Rieuwerts 2007). Several studies have addressed metal behavior in different soils, such as Zuquette et al (2008); Korf (2011);Braz et al (2013); Odukoya et al (2013); Diagboya et al (2015), Zia et al (2018); Gabarrón et al (2018); Colzato et al (2018). Other researchers specifically studied the use of tropical soils as liners for waste disposal (Boscov et al 1999;Afolayan and Nwaiwu 2005;Knop et al 2008;Boscov et al 2011;Morandini and Leite 2015;Agbenyeku et al 2016;Miguel et al 2017;Onyelowe et al 2019;Ehrlich et al 2019).…”