Role of Smectite Quasicrystal Dynamics in Adsorption of Dinitrophenol

347 Soil Sci. Soc. Am. J. 72:347-354 doi:10.2136/sssaj2007.0081 Received 22 Feb. 2007. *Corresponding author ([email protected]). © Soil Science Society of America 677 S. Segoe Rd. Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Organic matter and clay minerals are the two most important soil constituents in the sorption of pesticides and organic contaminants by soils. Previous studies have concluded that the mineral phase is the dominant sorbent for neutral organic compounds in soils when the clay/organic matter ratio is suffi ciently high (e.g., 10–30) (Karickhoff, 1984; Grundl and Small, 1993; Hassett et al., 1981), and that soil clays are especially important for sorption of polar organic compounds (Sheng et al., 2001). Among the various clay minerals, smectites are considered important in this regard due to their widespread occurrence (Allen and Hajek, 1989), high surface area (~800 m2 g−1), and reversible interlayer expansibility. Several studies have demonstrated that smectites have the potential to adsorb large amounts of various organic compounds, and that adsorption affi nity varies widely depending on the properties of the smectite, the saturating cations, and the sorbate (Jaynes and Boyd, 1990, 1991; Lee et al., 1990; Laird et al., 1992, 1994; Haderlein and Schwarzenbach, 1993; Haderlein et al., 1996; Boyd and Jaynes, 1994; Laird, 1996; Boyd et al., 2001; Sheng et al., 2002). The compound 2-methyl-4,6-dinitrophenol (4,6-dinitroo-cresol, or DNOC) has been widely used in agriculture and industry. Some former uses were as a contact herbicide, larvicide, or dormant spray insecticide especially for fruit trees, or on waste grounds to kill locusts and other insects. Recent uses are as an inhibitor of polymerization in styrene and vinyl and for insecticidal spraying (Hawley, 1981; USEPA, 1988). Insecticidal spraying has been the major source of DNOC that enters the environment (USEPA, 1988). Use of this compound has resulted in contamination of soils and shallow aquifers, Tanya R. Pereira Dep. of Crop and Soil Sciences Michigan State Univ. East Lansing, MI 48824-1325