Skip to main content
ARS Home » Research » Publications at this Location » Publication #169226
Title: CO-SORPTION OF ATRAZINE AND A LAURYL POLYOXYETHYLENE OXIDE NONIONIC SURFACTANT ON SMECTITE

Author
item CHAPPELL, MARK - IOWA STATE UNIVERSITY
item Laird, David
item THOMPSON, M - IOWA STATE UNIVERSITY
item EVANGELOU, V - DECEASED

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2005
Publication Date: 12/1/2005
Citation: Chappell, M.A., Laird, D.A., Thompson, M.L., Evangelou, V.P. 2005. Co-sorption of atrazine and a lauryl polyoxyethylene oxide nonionic surfactant on smectite. Journal of Agricultural and Food Chemistry. 53(26):10127-10133.

Interpretive Summary: In the U.S., large quantities of pesticides are used annually to control weeds, insects, and various pathogens in production agriculture. Public concern over the presence of detectable levels of many pesticides in surface and ground water has prompted a considerable amount of research into processes that control the fate of pesticides once they enter the soil. Most of these studies have been conducted using the pure, chemical form of the pesticide. In practice, however, the pure form of the chemical is almost never applied to agricultural fields; rather, the pesticide is applied as part of a formulation. Pesticide formulations contain several ingredients in addition to the pesticide. Nonionic surfactants (compounds that behave like soap) are one of the most common ingredients in pesticide formulations. We discovered that when atrazine (a common herbicide) is mixed with low and moderate amounts of a non-ionic surfactant, that the surfactant inhibits adsorption of the atrazine by clay minerals. However, when atrazine is mixed with high levels of the non-ionic surfactant, the surfactant may enhance adsorption of atrazine on the clay. This research demonstrates that the other ingredients present in pesticide formulations may have a large influence on the fate of pesticides in soils and consequently the risk of pesticide contamination of surface and groundwater. This research will help scientists to more accurately predict the fate of pesticides in the environment and will help policy makers to develop more effective regulations governing pesticide use.

Technical Abstract: Commercial atrazine formulations commonly contain nonionic surfactants that serve as solubilizing and wetting agents for enhancing the efficacy of the weakly polar pesticide. Numerous sorption studies have investigated the fate of atrazine in soil, yet most of these studies utilized "neat" atrazine solutions without considering the effect of formulation components. In this study, we investigated the influence of the nonionic surfactant, Brij 35, on the sorption of atrazine. Atrazine sorption isotherms were constructed by adding atrazine-Brij 35 emulsions to suspensions of Panther Creek (PC) bentonite and equilibrating for 24 hours. In general, atrazine sorption was inhibited by Brij 35 additions from 50 to 2100 mg L-1. However, atrazine sorption was enhanced as Brij 35 concentration increased from 2100 to 6300 mg L-1. For concentrations at or below 2100 mg L-1, Brij 35 was apparently filling the clay interlayers and competing with atrazine for sorption sites. By contrast, at 6300 mg L-1, the interlayers were completely filled with Brij 35 and excess Brij 35 accumulated on the external surfaces of the clay as surface micelles. The surface micelles provided an ideal environment for retaining atrazine. The potential for MeOH, a co-solvent in this system, to enhance Brij 35-surface micellization and promote atrazine partitioning is discussed.