Volatilization of Alachlor from Polymeric Formulations

Pesticides may be dispersed throughout the environment by several means, including groundwater contamination, surface water contamination, and volatilization with subsequent atmospheric transport and deposition. In earlier research primarily directed at reducing the potential for groundwater contamination, a number of herbicides were microencapsulated within several different polymers. These polymeric formulations were evaluated for efficacy in the greenhouse. In the studies described in this paper, three polymeric alachlor formulations that were the most effective in the greenhouse were evaluated in laboratory volatility studies using pure alachlor and a commercial formulation (Lasso 4EC) for comparison purposes. In a given experiment, technical alachlor, Lasso 4EC, and two polymeric formulations were applied to soil and evaluated in a contained system under 53% humidity with a fixed flow rate. Evolved alachlor was collected in ethylene glycol, recovered with C18 solid phase extraction cartridges, and analyzed by reverse-phase high-performance thin-layer chromatography with densitometry. Duration of the studies ranged from 32 to 39 days. In studies in which all formulations were uniformly incorporated in the soil, total alachlor volatilization from the polymeric microcapsules was consistently lower than that from the alachlor and Lasso 4EC formulations. In studies in which the polymeric formulations were sprinkled on the surface of the soil, microcapsules prepared with the polymer cellulose acetate butyrate released the smallest quantity of volatilized alachlor.