title: Characterization of the atrazine sorption process on Andisol and Ultisol volcanic ash-derived soils: kinetic parameters and the contribution of humic fractions.
abstract: Atrazine sorption was studied in six Andisol and Ultisol soils. Humic and fulvic acids and humin contributions were established. Sorption on soils was well described by the Freundlich model. Kf values ranged from 2.2-15.6 μg(1-1/n)mL(1/n)g⁻¹. The relevance of humic acid and humin was deduced from isotherm and kinetics experiments. KOC values varied between 221 and 679 mLg⁻¹ for these fractions. Fulvic acid presented low binding capacity. Sorption was controlled by instantaneous equilibrium followed by a time-dependent phase. The Elovich equation, intraparticle diffusion model, and a two-site nonequilibrium model allowed us to conclude that (i) there are two rate-limited phases in Andisols related to intrasorbent diffusion in organic matter and retarded intraparticle diffusion in the organo-mineral complex and that (ii) there is one rate-limited phase in Ultisols attributed to the mineral composition. The lower organic matter content of Ultisols and the slower sorption rate and mechanisms involved must be considered to assess the leaching behavior of atrazine.
authors.affiliation: Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone Pohlhammer 1007, Casilla 233, Santiago, Chile. mbaez@ciq.uchile.cl
authors.forename: María E
authors.initials: ME
authors.lastname: Báez
authors.forename: Edwar
authors.initials: E
authors.lastname: Fuentes
authors.forename: Jeannette
authors.initials: J
authors.lastname: Espinoza
mesh_terms: D000327:Adsorption; D001280:Atrazine / Q000032:analysis / Q000737:chemistry*; D004058:Diffusion; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D007700:Kinetics; D008956:Models, Chemical; D010573:Pesticide Residues / Q000032:analysis / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry; D012995:Solubility; D018707:Volcanic Eruptions / Q000032:analysis*
chemical_list: D006540:Herbicides; D006812:Humic Substances; D010573:Pesticide Residues; D012987:Soil; D012989:Soil Pollutants; D001280:Atrazine