Preliminary Tests of a Laboratory Chamber Technique Intended to Simulate Pesticide Volatility in the Field

Pesticides volatilize into the atmosphere in measurable quantities and concentrations; however, reliable methods of trapping pesticide vapors are not readily available. Laboratory simulations of field pesticide volatilization can provide information from which inferences can be made regarding actual field-scale volatilization. The objective of this study was to evaluate a simple laboratory technique that can be used to simulate field volatilization of pesticide vapor, in this particular case metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] vapor. In addition, this study was also used to evaluate the trapping efficiency of XAD-8 sorbent resin for metolachlor. A custom-designed volatilization chamber consisting of a 1.5-L bell-shaped jar was fitted with a vacuum air check valve. The chamber was connected to an air sampling tube that was filled with a polymeric resin, XAD-8, to trap metolachlor vapor. The air sampling tube was connected to a computerized air sampling pump, which could be programmed to sample air from the chamber at a variety of different flow rates and sampling intervals. The volatilization chamber was used inside of a controlled environment chamber to measure metolachlor volatilization from a glass surface over a 24 h period. Total metolachlor recovery averaged 102%. Total metolachlor volatilized under the controlled conditions of this study averaged 84%. Metolachlor trapped by the XAD-8 sorbent averaged 65%. The chamber design performed satisfactorily and when used inside a controlled-environment chamber provides a means of evaluating the effects of various microclimate parameters that influence pesticide volatilization.