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Title: CO-SORPTION OF ATRAZINE AND THE NONIONIC SURFACTANT BRIJ 35 ON SMECTITES

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

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/4/2004
Publication Date: 11/4/2004
Citation: Chappell, M.A., Laird, D.A., Thompson, M.L., Evangelou, V.P. 2004. Co-sorption of atrazine and the nonionic surfactant Brij 35 on smectites [CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. Madison, WI.

Interpretive Summary:

Technical Abstract: The herbicide atrazine is commercially available in a number of different formulations. One of the main components in these formulations is nonionic polyoxyethylene oxide (PEO) alcohols (CnEOm, where C = alkyl group, EO = OCH2CH2, n = number of linear alkyl groups, and m = number of EO groups), which serve as solubilizing agents for concentrating atrazine, and as wetting agents to promote the pesticide's distribution in soil. This study investigates the influence of the PEO surfactant Brij 35 (C12EO23) on atrazine sorption by soil. Samples of three smectitic soils were rehydrated in either 10 mM CaCl2 or 20 mM KCl for 24 h. Aliquots of atrazine-Brij 35 emulsions were added and the suspensions were equilibrated for another 24 h. Atrazine sorption was evaluated in the presence of 0, 50, 200, and 2100 mg L-1 Brij 35. In general, the surfactant inhibited atrazine sorption, but in some cases, high additions of Brij 35 (2100 mg L-1) enhanced atrazine sorption. In separate experiments, sorption of atrazine originating from the commercial formulation, Aatrex 4L, was tested. Some of the sorption isotherms appeared curved upward, suggesting cooperative sorption. The nonionic surfactant in Aatrex 4L was identified as Brij 30 (C12EO4), a shorter, less hydrophilic polymer than Brij 35. We hypothesized that micelles of Brij 30, formed on the surface, were responsible for cooperative atrazine sorption.