Trace-elements Behavior in the Sedimentary Transport Regime of the Blue Amazon, Brazil

Abstract

Trace elements or trace metals are of great interest in environmental studies due to their toxic and cumulative properties in the biological and sedimentary compartments. The discharge area of the Amazon River mouth receives an immense volume of suspended material with adsorbed trace elements, which mostly ends up depositing in the shelf area influenced by the fluvial-marine currents and physical-chemical properties of the water and sediment. This research aims to quantify and to discuss the routes of trace elements (Cr, Pb, Ni, Zn and Hg), associated with sedimentary transport and deposition in the Amazon Continental Shelf (ACS). The results showed a sediment distribution by zone, with a non-continuous range of erosive processes and areas of deposition for mud and sand sediments. The trace elements contents in the sediments are strongly influenced by the pH, salinity, organic compounds, clay minerals and CaCO3content. Fluvial-marine currents were important drive forces for deposition and accumulation of fine sediments in the shelf, especially the North Brazilian Coastal Current (NBCC). Statistical analysis and hypothesis testing confirmed the trend of sediment accumulation by zone, influenced by the physical-chemical parameters.