Dynamics of metals in lacustrine sediments: case study of the Madeira River, Amazon region

Abstract

The studies on metals in Madeira River’s principal flow show high variability of Co, Cr, Cu, Fe, Ni, Pb and Zn concentrations. However, the transfer of these metals from the main river channel, whose physical and chemical characteristics differ from those of lakes, has not been fully characterized. The objective of this study was to discuss how the transfer of Madeira River’s metals changes the spatial dynamics of these metals in sediments of the Puruzinho Lake (AM). The principal component analysis pointed to differences in the order of the data, creating two distribution zones of metals. The average concentrations of Co, Cu, Cr, Mn and Fe are higher in the area under the influence of the suspended solids coming from the Madeira River. The zoning of metals in lakes is structured by the forces acting across the river’s course at the same time as plains flood and generates ecotones.

Distribution of Metals in the Waters and Sediments of Rivers in Central Amazon Region, Brazil

“…Determined values for total Pb, Cr, Ni, Al, Fe, Cu and Zn in the surface sediment samples collected in November 2015 Pb / (mg kg -1 ) Cr / (mg kg -1 ) Ni / (mg kg -1 ) Al / (g kg -1 ) Fe / (g kg -1 ) Cu / (mg kg -1 ) Zn / (mg kg -1 ) and Cu concentrations did not change (57.2 to 58.6 mg kg -1 , and 13.0 to 13.8 mg kg -1 , respectively), indicating that these elements occur naturally. 9 However, the concentrations determined in the present study were higher and varied among the sampling sites, indicating anthropogenic influence on the contents of Zn, Cu, Ni, Cr and Pb. The determination of metals in the surface sediments of the Amazonas River (Amazonas 1 and 2) near Itacoatiara region provides evidence that the sampling points closest to the urbanized areas presented higher Pb, Cr, Ni, Cu and Zn contents, which may be of anthropogenic origin.…”

“…6 Several studies of metal transport have been conducted in the Amazon region, but most have been centered on the main rivers, especially the Negro, Solimões, Madeira and Amazonas River. 2,3,[7][8][9][10][11][12][13] Considering the land use in this region and since the Amazon River carries annually around 600 million tons of sediment to the ocean, the evaluation of metals transportation in the main tributaries of white and blackwaters from under-investigated regions are of great relevance to monitor the vulnerability of aquatic life and because these shall contribute to a significant fraction of metals exported to the ocean. This study aimed determination of total, dissolved and particulate metals concentration in freshwater and sediments of the rivers from Central Brazilian Amazon.…”