A hidroquímica do Rio Solimões - Amazonas

Umberto de Menezes Santos Maria de Nazaré Góes Ribeiro About the authors

This work presents the results for the physical and chemical studies of the Solimões-Amazon River in eleven (11) places and in thirty-one (31) tributaries and branches from the Brasil-Peru Colombia border, in Tabatinga, to the town of Santarém, in the State of Para. It was covered a total distance of 2457 km.

The tributaries and branches of the Solimões-Amazon River are reduced to small streams in their high courses; only the rivers Jurua, Purus, Negro and Madeira can present a 2 - meter water level in navigable regions, depending on the behavior of the dry season.

All the muddy water rivers form várzeas* which are rich in mineral nutrients and present along their whole area lakes, paranas*, igapós*, and a large amount of floating in formed. Part of this grass is decomposed and produces toxic gases, such as H2S, CH4, CO2. The lakes and the várzea work as a sponge the river absorbing suspended sediments, mineral and organic nutrients, and relieving part of them during the dry season.

The dark water rivers do not form várzeas, but beaches (dry season), and igapos (rainy season), due to their low amount of sediments. The dark color is due to colorful substances, such as humic material, that limit the production of phytoplankton.

The clear water rivers do not form várzeas, either, but beaches with a few igapós. They show a bluis-green color due to large formations of algae of the type Cyanophyta.

The muddy water rivers that present higher concentrations of sediments during the period from November to April, have their mobility supplying them with re-suspension of sediments due to an increase in flow and partially due to the phenomenon of "falling land".

It is possible that the Solimões-Amazon river receives mineral and organic supplies from muddy water rivers, small rivers barraged in its mouth, rivers with small flushes of limestone, and rivers with a high amount of colorful substances.

The lowest temperatures in the Solimões-Amazon River occur in the period of flooding of the main channel, while the highest ones occur in the Summer. The lowest concentrations of oxygen take place during the period from April to July, and th.y are due to oxidized water coming from várzeas and lakes.

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