Abstract:
Endosulfan has been applied to control numerous insects in a variety of food and non-food crops. Limited
information is available on dynamics of this pesticide in the soil. The objective of this research was to
determine the adsorption–desorption behavior of the alpha (a) and beta (b) endosulfan in a Vertisol from
the southeast region of Turkey, where cotton is the main crop in the large irrigated lowlands. The a and b
endosulfan were adsorbed considerably and Freundlich adsorption–desorption isotherms fitted the a and
b endosulfan data (R2 > 0.98). Freundlich adsorption coefficients (Kf) for the a endosulfan ranged between
21.63 and 16.33 while for the b endosulfan they were between 14.01 and 17.98 for the Ap and Bw2 horizons. The difference of Kf values of a and b endosulfan for two horizons were explained with the slight
difference in the amount of organic matter and clay, but considerable difference in Fe contents of the
two horizons. Alpha and b endosulfan Kfd values were 118.03 and 45.81 for the Ap and 48.08 and
68.71 for the Bw2 horizons. Higher adsorption and desorption behavior of the endosulfan isomers for
the same horizon was attributed to poor physical bonding between the endosulfan molecule and the surfaces of fundamental soil particles. This fact is thought to increase the effective use of endosulfan in agriculture with a possibility of its movement to the surface and groundwater in the Vertisol studied.
