Geoquímica de elementos-traço em sólidos em suspensão no alto rio Madeira, Rondônia, Brasil

Abstract

The objective this work is to evaluate the suspended solids load and the traceelements concentrations in suspended solids (Cd, Cr, Cu, Zn, Pb, Fe, Co, Mn and Hg)through principal components analysis (PCA) in the Upper Madeira River and some ofits tributaries. The Upper Madeira River presents a natural flow of trace elementsexcept for the Hg, which clearly shows anthropogenic influence. The largestconcentrations were of Fe and Mn, due to the dominant soils types of the basin, whereoxisoils prevail. The trace elements considered as industrial tracers (Cd, Cr and Pb)presented low concentrations due to their low natural concentrations and lack ofindustrial sources. The principal components analysis of the geochemical variables insuspended solids demonstrates the different influences in trace elements flow arerelated to marginal soils, agricultural activities, extension of flood-plains and theinfluence of tributaries. Suspended solids in the Madeira River originate from tertiaryAndean rocky formations and receive marginal soils runoff along of the river extension.In the case of Hg, marginal soils and tributaries closer to the gold mining areas are thepossible sources related to the increase in Hg concentrations in suspended solids.