A multi-surface approach to organic chemical binding: The role of mineral phases in polar and charged pesticide sorption

Samenvatting

The mobility and availability of pesticides in soils is controlled by their sorption to soil constituents. However, for organic molecules, this process is poorly understood and only described by simplistic predictive models. In this thesis, a multi-surface approach is applied to three model pesticides – glyphosate, imidacloprid, and fomesafen – to investigate their sorption to the separate soil constituents of metal (hydr)oxides, clay minerals and soil organic matter. For glyphosate, metal (hydr)oxides are the main adsorbates in soil. A surface complexation model was derived for glyphosate binding to the two metal (hydr)oxides, goethite and ferrihydrite, including competition from soil organic matter and phosphate. For imidacloprid, clay minerals and soil organic matter were identified as important adsorbates, where hydrogen bonding appears to be the main mechanisms. For fomesafen, electrostatics strongly impact adsorption, where the mutual interaction between soil organic matter and metal (hydr)oxides are important factors in this process.