Similarity between trace-element composition of river and seabed sediments in the Amazon system

The aim of this paper was to study the elemental composition of sediments in the Amazon ecosystem by comparing bottom samples from the shelf with those from the floodplain of the Rio Amazonas. Trace elements measured by neutron activation analysis were used. The system is divided into three parts: the basin, including tributaries from the pre-Andean region to Óbidos; the delta—plain region between Óbidos and the mouth; and the continental shelf. Significant correlation was found between the shelf and floodplain sediments, especially those samples close to the mouth. In the shelf surface samples, Ta, Eu, La, and Ce (in this order) have the lowest coefficients of variation in concentration, whereas Hf, Br, and Cs have the greatest.