Variação espacial das concentrações de metais-traço no solo e liteira de uma área de floresta natural

Abstract

To consider that a certain soil is free of contamination, it is necessary to know the metal contents in this soil in natural conditions, without anthropic introduction, as well as in the vegetation, due to the importance of the biogeochemical cycle in the Amazon. Therefore, the determination of natural levels of metals in soil and litter is essential for the construction of a parameter that serves as a basis for the monitoring and remediation of contaminated areas and that is adequate to the local pedological and floristic reality. In this context, the objective of this research was to determine the natural calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), aluminum (Al), boron (B), barium (Ba), cobalt Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), silicon (Si), strontium (Sr), titanium V), zinc (Zn) and cadmium (Cd), as a reference base of quality for soils and for litter in a forest in central Amazonia, in the State of Amazonas. According to the results, the concentrations of the exchangeable or assimilable chemical elements in the soil followed the order: Al> Ca> Mg> K> Na, in which, in general, the majority was found in greater concentration in the Plateau / Slope. For the metallic elements a PCA was obtained, in which the main components 1 and 2, explained 89.12% and 10.87%, respectively, of the total variability of the data. The loadings of the main component 1 correlated positively with the majority of the metals, except for B, Cr, Mo, Ni, and these were positively correlated in the main component 2 (lower representativity). The mean macronutrient contents in the litter in decreasing order for plateau and valley area were Ca> K> Mg> Na. For the micronutrients, the order was from Al> Mn> Fe> Sr> Zn> Cu> Ba> Cr> Ni> Co> Cd for Plateau and Al> Mn> Fe> Sr> Zn> Cu> Ba> Cr> Ni > Cd> Co for the valley. Among the fractions, Ca had its highest concentration in the woody material; the K in the reproductive material, while the Mg, Na and Al had higher concentrations in the leaf fraction. The other elements were in very low concentrations in all compartments of the litter. It was also observed that the return to the soil of the metallic elements via litter, were higher in the dry season. Ca and Al differed significantly within the same area. Al and Zn differed significantly among the studied areas, with higher returns for both elements in the plateau area.