Geochemical Background for Potentially Toxic Elements in Forested Soils of the State of Para, Brazilian Amazon

The objectives of this study were to establish geochemical background values of aluminum (Al), iron (Fe), arsenic (As), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) for eastern Amazon soils and to assess the relationship between soil chemical and granulometric attributes using univariate and multivariate procedures. Samples from the topsoil (0-0.2 m) were collected in several areas with minimal or no human intervention. Pseudo total concentrations of potentially toxic elements were extracted via acid digestion and quantified via inductively coupled plasma optical emission spectrometry (ICP-OES). The results revealed that the soils present high acidity, low levels of cations and organic carbon, and highly heterogeneous geomorphological characteristics. The elements Fe (9300 mg kg(-1)) and Al (8200 mg kg(-1)) showed the highest mean concentrations in the study, while As (0.8 mg kg(-1)) and Cd (0.1 mg kg(-1)) presented the lowest levels. The results of this study indicate that the 90th percentile can be used to formalize quality reference values for the State of Para and that the 98th percentile can be considered for areas rich in mineral deposits.