Mobility of atrazine from alginate-bentonite controlled release formulations in layered soil

The mobility of atrazine 16-chloro-N-2-ethyl-N-4-isopropyl-1.3,5-triazine-2 .4-diamine] from alginate-bentonite-based controlled release (CR) formulati ons was investigated by using soil columns. Two CR formulations based on so dium alginate(14.0 g kg(-1)), atrazine (6.0 g kg(-1)), natural or acid-trea ted bentonite (50 g kg(-1)). and water (924 g kg(-1)) were compared to tech nical grade product and commercial liquid (CL) formulation (Gesaprim 500FW) . All herbicide treatments were applied to duplicate layered bed systems si mulating the typical arrangement under a plastic greenhouse, which is compo sed of sand (10 cm), peat (2 cm), amended soil (20 cm) and native soil (20 cm). The columns were leached with 39 cm (1500 ml) and 156 cm (6000 ml) of 0.02 M CaCl2 solution to evaluate the effect of water volume applied on her bicide movement. When 39 cm of 0.02 M CaCl2 solution was applied, there nia s no presence of herbicide in the leachate for the alginate-bentonite CR tr eatments. However, 0.11% and 0.14% of atrazine appeared in the leachate whe n the treatment was carried out with technical grade and CL formulations, r espectively, When 156 cm of 0.02 M CaCl2 solution was applied, the use of t he alginate-acid treated bentonite CR formulation retards and reduces the p resence of atrazine in the leachate as compared to technical product. Analy sis of the soil columns show ed the highest atrazine concentration in the p eat layer. Alginate-bentonite CR formulations might be an efficient system for reducing atrazine leaching in layered soil and thus, it could reduce th e risks of pollution of groundwater. (C) 2001 Elsevier Science Ltd. All rig hts reserved.