Detection of pesticide residues on individual particles

An aerosol time-of-flight mass spectrometer (ATOFMS) is used to analyze the size and composition of individual particles containing pesticides. Pesticide residues are found in the atmosphere as a result of spray drift, volatilization, and suspension of coated soils. The ability of the ATOFMS to identify the presence of these contaminants on individual particles is assessed for particles created from pure solutions of several commonly used pesticides, as well as pesticides mixed with an organic matrix, and coated on soils. The common names of the pesticides studied are 2,4-D, atrazine, chlorpyrifos, malathion, permethrin, and propoxur. Analysis of the mass spectra produced by single- and two-step laser desorption/ionization of pesticide-containing particles allows for identification of peaks that can be used for detection of pesticide residues in the ambient aerosol. The identified marker peaks are used to approximate detection limits for the pesticides applied to soils, which are on the order of a fraction of a monolayer for individual particles. Results suggest that this technique may be useful for studying the real-time partitioning and distribution of pesticides in the atmosphere immediately following application in agricultural regions.