The composition and photochemical properties of the Fe(III)-Pyr complexes in the aqueous solution was studied in this work. Fe(III) was complexed by Pyr in the ratio of 1:3. The photochemical processes occurred in the Fe(Ill)-Pyr system was studied in detail. Fe(II) was the main intermediate product. DMPO was used as scavenger to determine the active radicals, such as (OH)-O-center dot, CO3 center dot-, CO2 center dot-, H-center dot, and RCO2 center dot by ESR. Photodegradation of atrazine induced by the photolysis of Fe(III)-Pyr was studied and the reaction kinetics fitted the first order reaction. Parameters such as pH, the initial concentrations of Fe(III), pyruvate (Pyr) and atrazine were all investigated. Photoproducts were detected by the LC-MS and the photodegradation scheme was proposed. (OH)-O-center dot radical was the main pathway of atrazine degradation. (C) 2009 Elsevier B.V. All rights reserved.