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 sedime nts in the Amazon ecosystem by comparing bottom samples from the shelf with those from the floodplain of the Rio Amazonas. Trace elements me asured by neutron activation analysis were used. The system is divided into three parts: the basin, including tributaries from the pre-Andea n region to Obidos; the delta-plain region between Obidos and the mout h; and the continental shelf. Significant correlation was found betwee n the shelf and floodplain sediments, especially those samples close t o the mouth. In the shelf surface samples, Ta, Eu, La, and Ce (in this order) have the lowest coefficients of variation in concentration, wh ereas Hf, Br, and Cs have the greatest.