Adsorption of Imazaquin and Imazethapyr on Soils, Sediments, and Selected Adsorbents

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Abstract
Adsorption of imazaquin and imazethapyr on soils, sediments, clays, and ion exchange resins was studied. Multivariate regression analysis of Freundlich K values and soil and sediment properties yielded a model for imazaquin adsorption which included soil pH, organic carbon, and clay as significant independent variables. Clay content and pH were significant independent variables for the imazethapyr adsorption model. Adsorption of imazaquin and imazethapyr was greater at pH below 6 than at a higher pH. Adsorption of both herbicides on Ca- and H/Al-kaolinite and Ca-montmorillonite was low, but increased on H/Al-montmorillonite. The results of adsorption studies with ion exchange resins indicated that binding of protonated herbicide at low pH could be due to physical forces, hydrogen bonding, or cationic binding. At soil pH levels above the pKa's of imazaquin and imazethapyr, ionic bonding of herbicide anions with positively charged soil components could also occur.