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Pesticides can move from their initial point of release and distribution by a number of processes. In air and water (including air and water in soil) pesticides move only short distances by diffusion. To travel longer distances pesticides move by mass transfer, usually in moving water or through the air by wind currents. The tendency of a pesticide to move in air or water is determined by how much it is retained by the surfaces to which it was originally deposited. Pesticides may attach (sorb) to soil, vegetation, or other surfaces. The strength of the sorption often determines availability of the pesticide for mass transfer. Some persistent pesticides used many years ago that strongly adsorbed to soil particles can still be found today in lake and stream sediments. |
