You are here:
MODELING THE INTERACTION OF AGROCHEMICALS WITH ENVIRONMENTAL SURFACES
Sawunyama, P. AND G W. Bailey. MODELING THE INTERACTION OF AGROCHEMICALS WITH ENVIRONMENTAL SURFACES. Presented at 219th American Chemical Society National Meeting, San Francisco, CA, March 26-30, 2000.
The interactions between agrochemicals and organo-mineral surfaces were studied using molecular mechanical conformational calculations and molecular dynamics simulations. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), 2,4-D (1, 2-dichlorophenoxyacetic acid), and DDT (2,2-bis-(4-chlorophenyl)-1,1,1-trichloroethane) were selected as representative agrochemicals. Model natural organic compounds comprised an oxidized softwood lignin chain (I) generated from eight guaiacyl-propane units connected by b-O-4 bonds, a non-bonded inclusion lignin-carbohydrate complex in which a carbohydrate chain (II) was placed inside the broad helix (I), and b-cyclodextrin. A metal oxide, rutile TiO2, was chosen as the model mineral surface. The electrostatic interactions and hydrogen bonds were accounted for with atomic charges. The results show that the organic coating does not decrease sorption energies although the organic contaminants show a strong tendency to associate with the pristine mineral surface. The proposed binding mechanisms between the agrochemical and the natural organic, the agrochemical and the mineral surfaces and the agrochemical and the organo-mineral aggregate will be discussed.