Quality reference values and background concentrations of potentially toxic elements in soils from the Eastern Amazon, Brazil

Abstract

Concentration quality reference value (QRV) concentrations are calculated based on the background of potentially toxic elements (PTEs) in their natural state, absent from human influences. QRVs are essential for ensuring that environmental legislation is consistent with the local conditions and they are also important for monitoring potential changes in the chemical compositions soils that can affect soil quality. The objective of this study was to obtain background concentrations to set QRVs for the PTEs in the soils of the state of Pará. The background concentrations and QRVs of the PTEs were obtained from 132 surface soils (0–0.2 m) and 132 subsurface (0.8–1.0 m) soils in the state of Pará, Eastern Amazon, Brazil. Under natural conditions, the values found for the QRVs and the background values of the PTEs were low, indicating low risk of environmental contamination and hazard to human health. The exception was Hg, whose content was higher than the prevention level defined by Brazilian law. The concentrations of Al, Cu, Cd, Cr, Fe, Hg, and Mn were positively correlated with the clay, Fe, Si, Ti, Al, and Mn oxide contents, whereas As, Ba, Ni, Pb, and Zn were positively correlated with the organic matter, Mn oxide and silt concentrations.Analysis of the main soil components indicated that Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn showed similar geochemical behaviors and common lithogenic origins. In the surface layers, Hg did not behave similarly to the other PTEs indicating that it can originate from different lithogenic sources or become or have elevated levels from anthropogenic sources. The results of this study serve as a basis for the monitoring of environmental contamination, prevention, and control of PTE pollution by authorities of the state of Pará and may serve as a reference for all Amazonian soils with similar soil characteristics.