Good understanding of the different phases of involved plasma-chemistry is essential for the development of non thermal plasma technologies for pollution control. These techniques are often based on the production of radicals from dissociation parent gases that, in turn, decompose the toxic compounds. Our research concerns OH radical production in a high pulse voltage triggered dielectric barrier discharge (DBD). OH (A2+ - X2 (0,0)) emission in argon-water vapor gas mixtures has been studied. Particular attention has been paid to the influence of water vapor partial pressure on the lifetime and intensity of emitted fluorescence in order to develop a pulse DBD UV light source for spectroscopic investigation. This UV probe allowed to perform OH(X2) time resolved average absolute density measurements in other DBD discharges based on resonant absorption spectroscopy. This diagnostic has been validated in argon and air water vapor mixtures. Temporal behavior of OH(X2) density radicals after a pulse discharge has been studied in argon and air with and without 500 ppm of TCE. This simple and inexpensive tool, compare to more sophisticated laser absorption or LIF measurements, for plasma investigation is very useful to characterize the OH radical potential for pollutant oxidation.