title: Atrazine sorption and fate in a Ultisol from humid tropical Brazil.
abstract: This study combined laboratory based microcosm systems as well as field experiments to evaluate the mobility of atrazine on a Ultisol under humid tropical conditions in Brazil. Results from sorption experiments fit to the Freundlich isotherm model [K(f) 0.99 mg kg(-1)/(mg l(-1))(1/n)], and indicate a low sorption capacity for atrazine in this soil and consequently large potential for movement by leaching and runoff. Microcosm systems using (14)C-atrazine to trace the fate of the applied herbicide, showed that 0.33% of the atrazine was volatilized, 0.25% mineralized and 6.89% was recorded in the leachate. After 60 d in the microcosms, 75% of the (14)C remained in the upper 5 cm soil layer indicating atrazine or its metabolites remained close to the soil surface. In field experiments, after 60 d, only 5% of the atrazine applied was recovered in the upper soil layers. In the field experiments atrazine was detected at a depth of 50 cm indicating leaching. Simulating tropical rain in field experiments resulted in 2.1% loss of atrazine in runoff of which 0.5% was adsorbed onto transported soil particles and 1.6% was in solution. Atrazine runoff was greatest two days after herbicide application and decreased 10 fold after 15 d. The use of atrazine on Ultisols, in the humid tropics, constitutes a threat to water quality, causing surface water and ground water pollution.
authors.affiliation: Instituto de Microbiologia, Universidade Federal do Rio de Janeiro - CCS Bloco I, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil. fabioverissimobr@yahoo.com.br
authors.forename: F V
authors.initials: FV
authors.lastname: Correia
authors.forename: A
authors.initials: A
authors.lastname: Macrae
authors.forename: L R G
authors.initials: LR
authors.lastname: Guilherme
authors.forename: T
authors.initials: T
authors.lastname: Langenbach
mesh_terms: D000327:Adsorption; D001280:Atrazine / Q000032:analysis / Q000737:chemistry*; D001938:Brazil; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D006813:Humidity; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D014872:Water Movements
chemical_list: D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D001280:Atrazine