Researchers Study Pesticide Pathways into the Atmosphere (25x surface runoff!)

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http://www.ars.usda.gov/is/pr/2011/110712.htm

Researchers Study Pesticide Pathways into the Atmosphere

By Ann Perry
July 12, 2011

When soil moisture levels increase, pesticide losses to the atmosphere through volatilization also rise. In one long-term field study, U.S. Department of Agriculture (USDA) scientists found that herbicide volatilization consistently resulted in herbicide losses that exceed losses from field runoff.

Agricultural Research Service (ARS) soil scientist Timothy Gish and ARS micrometeorologist John Prueger led the investigation, which looked at the field dynamics of atrazine and metolachlor, two herbicides commonly used in corn production. Both herbicides are known to contaminate surface and ground water, which was primarily thought to occur through surface runoff.

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Many experts believed that volatilization was not a contributing factor to water contamination because atrazine and metolachlor had a low vapor pressure. However, the monitoring of both herbicide volatilization and surface runoff at the field-scale over multiple years had never been done.

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Most surprising was that throughout the study, herbicide volatilization losses were significantly larger than surface runoff. When averaged over the two herbicides, loss by volatilization was about 25 times larger than losses from surface runoff.

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See also: http://www.ars.usda.gov/is/AR/2011/jul11/emissions0711.htm