SEASONAL DYNAMICS OF ATRAZINE IN 3 SOILS UNDER OUTDOOR CONDITIONS

The fate of C-14 labelled atrazine was followed in the first centimete rs of soil throughout one year in a microlysimeter experiment under ou tdoor conditions. Leaching of atrazine reached 40 to 60 % and depends on the soil type and soil structure. As a whole, the pool of reversibl y adsorbed residues decreased with time from 100 to less than 5 %, acc ording to the rainfall distribution. Hydroxyatrazine was the main degr adation product of atrazine and was preferentially adsorbed rather tha n leached in the three soils studied. Bound atrazine residues were for med from the first 45 days and their amount increased in the order : p elosol < brown soil < rendzina according to the soil organic matter co ntent. These residues were involved in partial degradation processes a fter 180 days.