BINDING OF A HERBICIDE TO WATER-SOLUBLE SOIL HUMIC SUBSTANCES

Dissolved organic matter (DOM) can act as a sorbent for organic chemicals in soils and natural waters. Therefore, distribution of an environmental chemical in soil is determined by a three compartment system of bulk soil matrix, water, and colloidal or dissolved organic matter. In the present study we demonstrate the binding of a new herbicide to DOM. Ultrafiltration techniques allowed the separation of two dissolved fractions of the free herbicide and the herbicide bound to DOM. Ion composition and pH exert a decisive influence on the sorption processes. An effective sorption isotherm is calculated, which takes into account the sorption onto DOM. Implications of the results on the movement of the herbicide in soils are discussed.