Retention Characteristics of Acetochlor in Soils Collected from Different Depths in Relation to Soil Properties (Žitný ostrov area, SW Slovakia)

Determination of the sorption-desorption of herbicides within soil profile is one of the first steps in predicting their leaching potential. Batch experiments were performed to evaluate the influence of soil properties on acetochlor retention. Soil samples were taken from horizons A, B, and C of three soil types representative of the Zitny ostrov area. The sorption and desorption isotherms were fitted to the Freundlich equation. The Freundlich sorption coefficient (Kfs) values ranged from 0.71 to 6.58 mg(1–1/n).l(1/n)/kg and were correlated positively with soil organic carbon, humic and fulvic acid carbons, amorphous aluminum oxides, and negatively with soil pH. The Freundlich desorption coefficient (Kfd) values were greater than those for sorption, showing that not all acetochlor sorbed was desorbed after four washing steps. The percentage of acetochlor desorbed ranged from 7.80 to 54.5% with decreased desorption from soil horizons B and C. The higher sorption capacity of surficial soil horizons in the three soils may be a limiting factor for penetration of acetochlor through soil profiles into groundwater.