SEASONAL DYNAMICS OF ATRAZINE IN 3 SOILS UNDER OUTDOOR CONDITIONS

The fate of C-14 labelled atrazine was followed in the first centimeters of soil throughout one year in a microlysimeter experiment under outdoor conditions. Leaching of atrazine reached 40 to 60 % and depends on the soil type and soil structure. As a whole, the pool of reversibly adsorbed residues decreased with time from 100 to less than 5 %, according to the rainfall distribution. Hydroxyatrazine was the main degradation product of atrazine and was preferentially adsorbed rather than leached in the three soils studied. Bound atrazine residues were formed from the first 45 days and their amount increased in the order : pelosol < brown soil < rendzina according to the soil organic matter content. These residues were involved in partial degradation processes after 180 days.