Submitted to: IUPAC Congress
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2005
Publication Date: August 12, 2005
Citation: McConnell, L.L. 2005. Volatilization and deposition of pollutants from agricultural ecosystems. 40th IUPAC Congress, August 12-19, 2005, Beijing, China. p. 5.
For non-fumigant pesticides, volatilization is a loss process that is often ignored in environmental fate studies. In some cases, a fraction of applied active ingredient can be emitted to the atmosphere. During application, losses are influenced primarily by the application equipment, wind speed, and formulation. These immediate losses are often referred to as pesticide drift and may represent a significant mass of pesticide movement over a relatively short distance (10-100 m) with spray droplets. After application, pesticide volatilization continues, generally with the largest fluxes occurring within the first 24-48 hours, followed by an exponential decline over the next 4-5 days. It is the post-application period where a large number of factors come into play that may influence the flux rate to the atmosphere. The vapor pressure and aqueous solubility of the pesticide are overriding factors that govern the potential for volatile loss. The ratio of the vapor pressure to the aqueous solubility of a chemical is described as its Henry's Law Constant (HLC). Chemicals with high HLC values have a greater potential for volatile loss. Meteorological conditions such as temperature, wind speed, relative humidity, and precipitation are constantly changing and strongly influence the mass flux rate. Soil conditions are also critical in governing pesticide volatilization; e.g., moist soils with low organic carbon content have a lower capacity to retain pesticide residues, thereby enhancing volatile loss.