Free radical induced oxidation/reduction mechanisms of the hazardous water contaminant thiacloprid have been unravelled using pulse radiolysis techniques involving transient spectral analysis and redox titration experiments. The (OH)-O-center dot-induced oxidation of thiacloprid proceeds with appreciable rate, the reaction rate constant has been determined to be k(OH) = 4.8 x 10(9) mol(-1) Ls(-1). The (OH)-O-center dot attack leaves behind a rather complex free radical system consisting of similar to 9% alpha-aminoalkyl radicals, similar to 31% aminyl + aminium nitrogen centred radicals, nitrogen centred radical, similar to 46% radicals at the sulfur and similar to 14% hydroxycyclohexadienyl radical of the pyridyl moiety. Since similar to 86% of radicals are formed on the key cyanoiminothiazolidine pharmacophore, (OH)-O-center dot is anticipated to be an appropriate candidate for inactivation of this biologically active pollutant. The one-electron reduction exerted by e(aq)(-) occurs at a diffusion controlled rate. As a result of the eaq- attack pyridinyl radical forms that takes part in subsequent protonation and dechlorination processes. The course of events is anticipated to lead to the destruction of another important part of the molecule in respect to insecticidal activity. (C) 2017 Elsevier B.V. All rights reserved.