Submitted to: International Humic Substances Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/2/1996
Publication Date: N/A
Technical Abstract: Organic matter content is the major factor controlling herbicide sorption in soil/water systems. Complexation with soluble humic and fulvic acids may have a marked effect on the apparent solubility and mobility of slightly-soluble herbicides. Humic acids from different sources displayed widely different complexation affinities, possibly due to variations in chemical structure of the acids. The lower molecular weight fulvic acids have been neglected in previous studies, probably because of problems with dialysis tubing molecular weight cut-off and adsorption. An equilibrium dialysis method was considered to be the most quantitative method for determining extent of interaction. Extensive comparisons were required to select dialysis membranes of appropriate type and pore size. Highly purified and characterized fulvic acids were used to give a better description of the complexation. Napropamide interacted with 14 fulvic acids from different sources of soil and water showed the influence of the nature of fulvic acids on complexation. Fulvic acids appeared to form much weaker complexes with napropamide than humic acids. Our data show that complexation of herbicides with soluble fulvic acids was strongly influenced by the properties of both herbicide and fulvic acids. The equilibrium dialysis method can effectively assess such complexation. The method can be further developed as a tool for herbicide sorption.