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Title: Impact of Surface Soil Moisture of Pesticide Volatilization Fluxes

item Gish, Timothy
item Prueger, John
item Kustas, William - Bill
item Daughtry, Craig
item McKee, Lynn
item Russ, Andrew - Andy
item Hatfield, Jerry

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/21/2007
Publication Date: 7/21/2007
Citation: Gish, T.J., Prueger, J.H., Kustas, W.P., Daughtry, C.S., McKee, L.G., Russ, A.L., Hatfield, J.L. 2007. Impact of surface soil moisture of pesticide volatilization fluxes [abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. 2007 CDROM.

Interpretive Summary:

Technical Abstract: Volatilization of pesticides can detrimentally affect the environment by contaminating soil and surface waters many kilometers from where the pesticides were applied and intended. To improve quantifying the effect of soil moisture and meteorological interactions on pesticides volatization, metolachlor vapor concentrations were continuously measured at two locations for 120 hours after application using polyurethane foam plugs for two consecutive years. A flux gradient technique was used to measure volatilized concentration profiles combined with turbulent fluxes of momentum, heat and water vapor (eddy covariance) to estimate a pesticide flux diffusivity, thus allowing a vapor flux to be calculated. The two locations were 90 m apart having similar soil texture properties and under identical crop management and climate, but differ in surface soil moisture conditions. One location receives supplemental water from subsurface flow pathways as confirmed with ground-penetrating radar and extensive soil moisture monitoring. Although peak metoachlor volatization losses for each year occurred during the first 24 hours aftern application, the wetter location had metolachlor vapor losses that were almost twice that of the drier location. Cumulative vapor losses for 2004 show that the wetter location lost 32,108 pg metolachlor m-2 compared to 18,717 pg m-2 fpr the drier location. During 2005, the wetter location volatized 15,194 pg metolachor m-2 compared to 7,246 pg m-2 for the drier location. These results indicate that surface soil moisture is a critical factor influencing pesticides volatilization and will need to be characterized if pesticide volatilization fluxes are to be accurately quantified and eventually modeled.