Sediments characteristics and rate of phosphorous release from two Argentinean reservoirs”

L. BORGNINO, C. ORONA, M. AVENA, A. RODRÍGUEZ, C. P. DE PAULI.

Foz de Iguazú, Brasil

Congreso; 1st International Conference of Surface and Colloid Science.; 2003

Eutrophication is the process by which an aquatic environment gradually ages due to the input of nutrients (phosphorous, nitrogen, carbon, etc.) that stimulate algae growth.. Although the harmful consequences of eutrophication have been recognized long time ago and many studies have been carried out worldwide to understand and control this process, very little information is available about South American lakes, especially information regarding the behavior of sediment material. Sediments can become very important in controlling the flux of nutrients from the solid phase to the water body and vice versa. Depending on the conditions and composition of the sediment-water interface, sediments could behave as a source or sink of nutrients, releasing or capturing them from the water column.  In this article, the general characteristics of sediments from two Argentinean lakes are presented; and their colloidal characteristics and kinetics of phosphate release are evaluated. The data indicate that sediments are constituted by a mix of  coarse sized and clay sized material with high organic matter content. The clay sized material has a high surface area and important phosphate adsorption-desorption properties. The desorption rate of phosphate is relatively low between pH 4 and 7 and increases significantly at higher pH. Temperature effects on the desorption rate are also significant, and an activation energy of around 90 kJ/mol was calculated from experimental data. This relatively large value suggests that phosphate desorption is a surface controlled process. (Acknowledgments:  This work is partially supported by FUNDACION ANTORCHAS and CONICET)