Trace element contents in soils on the banks of the Paraguay River, Pantanal de Cáceres/Mato Grosso

Abstract

Contamination of soil by trace elements threatens ecosystems and human health worldwide. Anthropogenic interferences in environments natural are becoming increasingly intense increasing the risks contamination of soil. Studies in environments natural with different types of soils and environmental conditions are necessary to establish quality guiding values ​​soil for each region, allowing the identification of contaminated areas and the evaluation of the potential risks of anthropic activities on contamination soil. The objective of this work was to determine contents trace element in soils with native vegetation along the margins of the Paraguay River, Pantanal de Caceres, region in the state of Mato Grosso. Soil samples were collect at a depth of 0.0 to 0.20 m in twelve areas with presence of the following soil classes: Argisol, Gleysol, Neosol and Planosol. The digestion of the samples was based on the method 3051-A,recommended by the United States Environmental Protection Agency, and the determination of the elements effected  by Inductively Coupled Plasma - Optic Emission Spectrometry (ICP-OES). The contents mean (mg kg^-1) of trace elements were: As (1.70); Ba (123.54); Cd (1.70); Co (5.37); Cr (36.66); Cu (41.60); Hg (8.26); Mo (0.25); Ni (9.47); Pb (7.45); Sb (32.18); Se (0.33) and Zn (26.26). Values ​​obtained through the 75th percentile indicate that the contents of Ba (166.97 mg kg^-1), Cd (2.19 mg kg^-1), Hg (11.41 mg kg^-1) and Sb (61.88 mg kg^-1), are above the prevention values - VP, recommended by Conama Resolution 420/2009. Among the trace elements was observed close correlation between Ba and Cr (r = 0.92). The contents of sand and clay, showed significantly correlated (p ≤ 0.05) with  the contents of Ba, Cd, Co, Cr, Cu, Ni, Pb and Zn, being that, the clay presented positive correlation and the sand negative correlation. The pH in water showed a significant correlation (p ≤ 0.05) with Se (r = 0.41). The CTC _{pH 7.0} showed a significant correlation with most of the trace elements, showing a close correlation with the Ba (r = 0.95). Considering that the contents verified for Ba, Cd, Hg and Sb from the 75th percentile are above the value of prevention established by national legislation, notes the need to stipulate quality reference values ​​for Pantanal soils, in order to establish measures for the prevention and preservation of the soil and the ecosystem.