Determination of the volatility of pesticides from soil and plant surfaces

Since 1992 data on the volatilization potential of pesticides out of soil and from plant surfaces are required for registration of pesticides in Germany. The method described here was developed to perform measurements as volatilization chamber tests in a wind tunnel in compliance with the respective German guideline (BBA guideline part 1V/6-1 from 1990). The following standard parameters are applied: air temperature 20 degC, relative air humidity approximately 50%, air velocity > 1.0 m/s. Volatilization is determined from a test area of 0.4 - 0.6 m2. The test substance is applied as commercial product or as formulated radio-labelled compound. Radio-labelling is recommended for pesticides with low application rates. A part of the total air stream of the wind tunnel is sucked through polyurethane foam filters (approximately 2.5%). After extraction the amount of pesticide trapped is analysed. The volume stream of both, main air stream and partial air stream, are measured by appropriate devices. Test duration is 24 hours with four sampling intervals (0 - 1 hours, 1 - 3 hours, 3 - 6 hours, and 6 - 24 hours). The amount of pesticide volatilized is calculated in relation to the initial application dose and is expressed as volatilization rate in percent. The threshold value of the BBA-guideline for further testing is a volatilization rate of 20%. Volatilization rates in this range are reproducible within + - 1 % absolute