Author
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Laird, David |
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Submitted to: Bouyoucos Conference Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 3/9/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Water is the solvent of ecosystems on the earth's surface, and smectites are perhaps the most abundant class of clay minerals found in soils and surficial sediments throughout the world. Thus, understanding of chemical reactions between anthropogenic organic molecules and smectite surfaces in aqueous systems is crucial for understanding the fate of pesticides and other organic contaminants in natural environments. On a macroscopic scale, smectites are strongly hydrophilic; however, the hydrophobic/hydrophilic character of smectite surfaces varies dramatically on a molecular scale. An understanding of the nature of smectite surfaces provides a framework for understanding reactions between organic molecules and smectite surfaces. Strongly polar organic molecules, such as pyridine, are not sorbed on smectites from aqueous systems. Pyridine is not polar enough to be competitive with water for salvation of the inorganic cations but it is too polar (lacks a nonpolar moiety) to interact with the hydrophobic nanosites. By contrast, weakly polar molecules, such as atrazine and 3-butylpyridine, are sorbed on smectites from neutral aqueous systems. Sorption of weakly polar compounds varies from 0 to 100% depending on the surface charge density and percentage of tetrahedral charge. Nonpolar molecules, such as chlorpyrifos and phenanthrene, are strongly sorbed by smectites from aqueous systems. Sorption of nonpolar molecules, however, is not correlated with surface charge density or percentage of tetrahedral charge. |
