Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Carrizosa, M. J. Articles by Cornejo, J. Search for Related Content GeoRef GeoRef Citation

INTERACTIONS OF TWO SULFONYLUREA HERBICIDES WITH ORGANOCLAYS

¹ USDA-ARS, Soil and Water Management Research Unit, 1991 Upper Buford Cir. Rm 439, St. Paul, MN 55108, USA
² Instituto de Recursos Naturales y Agrobiologia de Sevilla, CSIC, P.O. Box 1052, 41080 Sevilla, Spain

^* E-mail address of corresponding author: koskinen{at}umn.edu

The sorption of two sulfonylurea herbicides (SU), metsulfuron methyl and nicosulfuron, on pure clays and organoclays was investigated. Three clays (Arizona smectite, SAz-1, Wyoming smectite, SWy-2, and hectorite, SHCa-1), were treated with amounts of octadecylammonium (ODA) or dioctadecyldimethylammonium (DODMA) cations equal to ~50 and 100% of the clays’ cation exchange capacity (CEC). Sorption isotherms were fitted to the Freundlich equation. While no measurable sorption was found on the pure clays (K_f = 0), organoclays prepared using both primary and quaternary amines were effective as SU sorbents. The metsulfuron methyl K_f values ranged between 196 and 1498 µmol^1– kg^–1 L^1/n, and K_f values for nicosulfuron, which were lower than those of metsulfuron methyl, ranged from 35 to 198 µmol^1–1/n kg^–1 L^1/n. As shown by sorption coefficients, K_d and K_OC, SWy-2 treated with DODMA at ~100% of the CEC was the most effective sorbent for metsulfuron, K_d = 684 L kg^–1 and K_OC = 2138 L kg^–1. For nicosulfuron the most effective sorbent was SAz-1 with ODA at ~ 50% of the CEC (K_d = 147 L kg^–1 and K_OC = 1233 L kg^–1). In contrast to other weak-acid herbicides, such as phenoxy and picolinic acids, no clear relationships were found between sorption and layer charge, organic carbon content, and basal spacing of the organoclays for both sulfonylurea herbicides. Sorption of both herbicides on organoclays was assumed to involve hydrophobic and polar interactions for which the availability of interlayer room between organocations was a very important factor.

Key Words: Metsulfuron • Nicosulfuron • Organoclays • Sorption • Sulfonylureas