Aged Desorption of 14C-Ethametsulfuron Methyl In Five Soils.

Use of aged sorption inputs is gaining acceptance of agrochemicals in the risk assessment. The objective of this study was to determine aged desorption of herbicide 14C-ethametsulfuron methyl from five agricultural soils. Radiolablled test material was applied into five soils individually and the soils were incubated under laboratory aerobic conditions at 20 ? 2?C for up to 120 days. Soil samples were collected at different intervals. At each sampling interval, a single sample for each incubation group was removed and the soil extracted as follows. A desorption step was performed first by adding 25 mL of 0.01 M CaCl2 solution. Extraction was facilitated by shaking on a wrist-action shaker for ca. 24 hours followed by centrifugation (ca. 3400 rpm; ca. 15 min) and decanting of the extract. The desorption coefficient, Kd_des, of 14C-ethametsulfuron methyl was calculated for each soil and label at each sampling interval using the amount of test substance extracted in CaCl2 and the soil concentration. The desorption coefficient results at zero time and Day 64 were determined for each soil type and were compared within this presentation. The results demonstrate that the desorption of 14C-ethametsulfuron methyl increased over time, with an increase in Kd_des of 5.5 to 38.4 times, with subsequently decreased soil mobility.