CREATION OF DOMAINS FOR PESTICIDE SORPTION VIA K/CA-DEMIXING IN SMECTITES

Authors: LI, H - MICHIGAN STATE UNIVERSITY; TEPPEN, B - MICHIGAN STATE UNIVERSITY; JOHNSTON, C - PURDUE UNIVERSITY; Laird, David; BOYD, S - MICHIGAN STATE UNIVERSITY

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/6/2003
Publication Date: 11/6/2003
Citation: LI, H., TEPPEN, B.J., JOHNSTON, C.T., LAIRD, D.A., BOYD, S.A. CREATION OF DOMAINS FOR PESTICIDE SORPTION VIA K/CA-DEMIXING IN SMECTITES. ASA-CSSA-SSSA ANNUAL MEETING ABSTRACTS. 2003. CD-ROM. MADISON, WI.

Interpretive Summary:

Technical Abstract: Pesticide adsorption on soil minerals is often dramatically influenced by the exchangeable cations present. Among the common exchangeable cations in soils, K-saturated minerals frequently demonstrate the strongest sorption of pesticides. In the presence of multiple exchangeable cations in the system, we hypothesize that the magnitude of pesticide sorption to soil minerals is proportional to the fraction of clay interlayers saturated with K+ ions. To test this hypothesis, we measured sorption of three pesticides with different polarity (dichlobenil, monuron, and biphenyl) on a smectite (Swy-2) containing various populations of K+/Ca2+ on the exchange sites. The sorption of dichlobenil and monuron increased with the K+/Ca2+ ratios, but the latter to a much lesser extent. Nonpolar biphenyl displays the same sorption capacities on Ca- and K-Swy-2. X-ray diffraction patterns were also measured on these clays. The results indicate that at lower ratios of K+ to Ca2+, these exchangeable ions are randomly distributed in clay interlayers, and increasing K+ levels do not result in an increase in sorption of dichlobenil. At higher populations of K+ (vs. Ca2+), demixing occurs causing some clay interlayers or regions to become fully saturated by K+, accompanied with a greatly enhanced pesticide adsorption.