LEACHING OF ATRAZINE AND SOME OF ITS METABOLITES IN UNDISTURBED FIELD LYSIMETERS OF 3 SOIL TYPES

The movement of C-14-atrazine was studied in lysimeters (10 x 70 cm) under field conditions in loamy clay, calcareous clay and a high clay soils. Ten months after atrazine treatment and with a cumulative rainfall of 502 mm, the leachates from the calcareous clay soil contained 3.3% of applied s-triazine radioactivity, while those from the loamy clay and high clay soils contained only 0.9% and 1.1%, respectively. The mobility of the s-triazine residues was not related to the distribution of organic carbon content with depth. The proportion of extractable residues in the upper levels of the lysimeters was lower for the calcareous clay soil, 19.2% compared to 30.0 and 28.6% in the loamy clay and high clay soils. The extractable residues increased with depth in the calcareous clay soil, 62.8% in the 54-60 cm layer, whereas it decreased in the loamy clay and high clay sails down to 16.3 and 17.6%, respectively. Atrazine was observed to a depth of 36 cm in the loamy clay and high clay soils, and to a depth of 54 cm in the calcareous clay soil. Diamino-atrazine was detected in some places while deethyl-atrazine and deisopropyl-atrazine were present over a large part of the soil profile, sometimes to depths greater than that of the parent molecule. The results suggest a greater mobility of the s-triazine residues in the calcareous clay soil.