Mise en évidence de silice à l'état colloïdal dans des cours d'eau d'Amazonie

Colloidal particles extracted from the waters of small Amazonian watersheds that drain different soils (podzols and ferrallitic soils) were observed and analyzed by means of analytical electron microscopy. Despite their diverse morphological aspects, colloids exhibit a mineral chemical composition very commonly dominated by silica. Comparison with the chemical composition of the waters before and after the extraction of the colloidal phase suggests that 40% of the silica could be in a colloidal state in waters draining the podzolic areas.