Barium is an alkaline-earth metal that occurs naturally in soils. It is present in soil in carbonates, sulphates and silicates as well as in the isomorphic substitution of calcium and magnesium in clay minerals. When available at high soil concentrations, Ba is toxic to several living organisms. To rule out the possibility of metal contamination of a particular soil, the natural metal concentrations of this soil must be known. Therefore, the natural soil concentrations of metals must be determined for soil monitoring and remediation, taking the local soil conditions into account. This study determined the natural Ba concentrations as threshold levels of this metal in reference soils of the state of Pernambuco. Samples from the two upper horizons of the 35 benchmark soil profiles were submitted to microwave-assisted acid digestion using method 3051A. Afterwards, the Ba concentration in extracts was obtained by ICP-OES. Ba concentrations above the prevention and investigation values according to the Brazilian guidelines (CONAMA, 2009) were observed. This corroborates the importance of a deeper knowledge of the regional soil diversity underlying national guidelines. The natural Ba concentrations determined in the soils can be used to define the Reference Quality Levels (natural concentration) in soils of Pernambuco, according to the Brazilian legislation.
soil contamination; ecotoxicity; trace element; heavy metal
