Watershed-scale assessment of environmental background values of soil potential toxic elements from the Caatinga and Atlantic forest ecotone in Brazil

• Published in: Chemosphere (Oxford) Vol. 338; p. 139394
• Main Authors: Cardoso, Kaíque Mesquita, Boechat, Cácio Luiz, Nascimento, Clístenes Williams Araújo do, Escobar, Maria Eugenia Ortiz, Silva, Douglas Gonçalves da, Lins, Simone Aparecida da Silva, Oliveira, Raiane Lima, Morais, Pâmalla Graziely Carvalho
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-10-2023
• Subjects: Environmental monitoring; Environmentally available; Heavy metals; Oxisols; Trace-elements; Ultisols; Ultisols; Environmental monitoring; Oxisols; Heavy metals; Trace-elements; Environmentally available
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2023.139394

The evaluation of the concentration of a potentially toxic element (PTE) in soils under native vegetation is the base study to obtain the quality reference values (QRVs), and the watershed is the strategic planning unit for decision making. The objective of this study was to determine the natural concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn and to establish QRVs for the Verruga river basin. Soils with no or minimal anthropic intervention from the surface layer (0.0–0.2 m) were collected and processed, and PTEs were extracted according to the USEPA 3051A method and determined by ICP‒OES. The quality of the analyses was checked by blank tests and soil samples certified SRM 2709 - San Joaquin Soil. The data set was subjected to exploratory analysis and multivariate statistics. The mean background concentrations of PTEs in soils showed high variability compared to other locations in Brazil and in the world and were (mg kg−1) Fe (24,300) > Mn (211.10) > Cr (40.98) > Zn (28.28) > Cu (10.68) > Ni (9.44) > Pb (4.95) > Co (4.08) > As (3.48) > Cd (0.09). The QRVs for the PTEs were established based on the 75th percentile, where (mg kg−1) Mn (124.59) > Cr (54.51) > Zn (31.66) > Cu (7.89) > Ni (7.20) > Pb (5.98) > As (4.05) > Co (3.40) > Cd (0.10). The chemical attributes and topography variation along the watershed are very heterogeneous and influence the dynamics of the PTEs. This survey will support future research on the impact of human activities on soil contamination in the watershed. This survey will support future research on environmental monitoring and the impacts caused by increased human activities on soil contamination in the Verruga river watershed, in the state of Bahia, Brazil.
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•Parent material, relief and grain size affect potential toxic element distribution.•Background values of the studied elements differ from other watersheds and countries.•Quality reference values were established based on the 75th and 90th percentiles.•To maintain soil health, this assessment can help government agencies.