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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #321497
Title: Multi-year measurements of field-scale metolachlor volatilization

Author
item Prueger, John
item Alfieri, Joseph
item Gish, Timothy
item Kustas, William - Bill
item Daughtry, Craig
item Hatfield, Jerry
item McKee, Lynn

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2017
Publication Date: 2/2/2017
Citation: Prueger, J.H., Alfieri, J.G., Gish, T.J., Kustas, W.P., Daughtry, C.S., Hatfield, J.L., McKee, L.G. 2017. Multi-year measurements of field-scale metolachlor volatilization. Water, Air, and Soil Pollution. 228. Article 84. https://doi.org/10.1007/s11270-017-3258-z.
DOI: https://doi.org/10.1007/s11270-017-3258-z

Interpretive Summary: Pesticide volatilization is a process where pesticides move from a liquid phase on soil or vegetation surfaces to a chemical gas phase that is then released to the atmosphere. The amount of pesticides applied annually in US farming operations is well over 100 million tons and yet the amount of pesticide volatilization to the atmosphere is not well known. In this study we measured concentrations of two commonly used herbicides (metolachlor and atrazine) for corn and soybean production for 13 consecutive years. Using meteorological measured parameters measured at the same time we computed the volatilization losses across all 13 years. Our results showedthat volatilization losses were significantly greater than previously believed. Our results also confirmed that volatilization losses for metolachlor and atrazine were greater than losses from leaching and runoff. Additionally the volatilization losses were closely correlated to the amount of soil water content which varies across years as a function of local meteorological conditions. This information is of value to pesticide compaies and regulatory agencies in improving their understanding of volatilization losses.

Technical Abstract: Volatilization is a critical pathway for herbicide loss from agricultural fields, and subsequently deposited downwind from the edge of the field. To better understand the volatilization process, field-scale turbulent volatilization fluxes of metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide) and atrazine (6-chloro-N-ethyl-N’-(1-methylethyl)-1,3,5-triazine-2,4-diamine) were quantified for 13 consecutive years using a combination of herbicide concentration profiles and eddy diffusivities derived from turbulent fluxes of heat and water vapor. Site location, type of herbicides, and agricultural management practices remained unchanged during this study in order to evaluate the effect of soil moisture on volatilization of metolachlor and atrazine. Twenty gravimetric surface soil moisture samples (0-5 cm) were collected immediately after herbicide application and then at 0430 h each morning to determine the impact of surface moisture on herbicide volatilization. Five days after application, cumulative herbicide volatilization ranged from 5% to 63% of that applied for metolachlor and from 2 to 11% of that applied for atrazine. For both atrazine and metolachlor, volatilization remained an important loss process more than 5 days after application, if the soil surface was moist. Conversely, if the soil surface was dry, negligible volatilization occurred beyond 5 days. Furthermore, the total amount of metolachlor volatilized into the atmosphere increased exponentially with surface soil water content during application (r2 = 0.78). However, volatilization of atrazine and initial surface soil moisture showed more variation over the different years due to the lower volatility of atrazine compared to metolachlor. Atrazine and metolachlor volatility were found to a large extent to be governed by surface soil moisture.