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(W/EH049) Adsorption and degradation of atrazine on argentinian soil. Hang, Susana1,2, Nassetta, Mirtha2, Caņas, Irene2, Sereno, Roberto1, 1 2 ABSTRACT- In the last decade, in Argentina, a notable increment has been observed in the fitosanitarios use, -especially of herbicides,- associated to a descent in the price of these comodities and the surface increase sowed in non-tillage systems. Atrazine is a very effective, low cost herbicide, and in the agricultural campaign 1999-2000 it was the third herbicide sold. We worry about this new situation of the argentine agriculture, since we ignore the capacity of the argentine soils to resist this increment of products that are incorporated. A soil that has received atrazine for more than 10 years, and that is under systems of non-tillage was used. The soil samples were obtained of each one of the horizons, they were characterized by organic carbon, pH, cationic exchange capacity, clay, sand and silt content, cationic exchange. It was determined for each horizon the atrazine adsorption by means of isotherm of adsorption and the degradation rate by means of incubation under controlled conditions of humidity and temperature (80% of field capacity and 30 grade). It was determined that the highest adsorption was associated to the horizons with bigger organic carbon and clay content, and it fell in the subsoil horizons in an order of magnitude. The degradation rate was higher in the surface horizon and it fell in the underground. In the horizons of the underground a very limited degradation was detected in the first 15 days but later atrazine degradation started. This would indicate that in the surface microorganisms adapted to metabolize this compound exist, while in the underground there should take place an adaptation to the substratum so that the degradation process begins. Key words: Soils contamination, Atrazine, Degradation, Adsorption |
