Revista Brasileira de Milho e Sorgo (Apr 2005)
SORPTION, DESORPTION, AND LEACHING POTENTIAL OF ATRAZINE IN BRAZILIAN SOILS
Abstract
Atrazine was applied on soil samples for sorption and desorption determination and leaching potential in different soils. After 24 hours shaking, the soil samples were centrifuged, the supernatant filtered and then analyzed by HPLC. Desorption periods were established by substituting the removed supernatant volume in each CaCl2 solution (0,01 M), tube shaking for 24 hours, and centrifuging. The procedure was repeated three times every 24, 48, and 72 hours, the supernatant was filtered, and analyzed by HPLC. Atrazine sorption, described by Freundlich isotherm, was calculated by differences between applied concentrations and those measured by the HPLC. Desorption percentages after 24, 48, and 72 h were calculated by the difference among the sorbed quantities and those measured in the HPLC. Pearson correlation was set up to determine the correlation between kf, kfoc, desorption, and the main soil properties, and the GUS coefficient was used to estimate the leaching potential. The low atrazine kf values suggest that this herbicide is of low sorption in these soils. For the LVd-a profile a significant and positive correlation between sorption and organic carbon content was established in the individual analyses. The kfoc values varied from 70,37 to 201,47, in surface samples of the studied soils. They presented a significant correlation with the organic carbon content detected only when the LVd-a soil profile was analyzed. The leaching potential showed that atrazine may be classified as a leaching herbicide in all analyzed soils. Up to 72 hours after application, the desorption was weaker than the sorption. Desorption is greater in deeper LVd-a soil layers, in which organic carbon contents are lower.
