Application of chemical dosimetry to hydroxyl radical measurement during underwater discharge

The pulsed streamer discharge was generated in the liquid by using point-to-sphere electrode geometry. In this study, the OH radicals were measured indirectly by a chemical dosimetry. Terephthalic acid (TA) was used as an OH radical scavenger and fluorescence of the resulted 2-hydroxyterephthalic acid (HTA) was measured. Instead of the use of conventional fluorescence spectrophotometer, a novel fluorescence observing system by using a light-emitting diode (LED) as a light source and a simplified spectrometer as a detector was developed. As a result, the fluorescence intensity increased with time elapsed during the discharge process. The production rate of OH radicals in the liquid was estimated to be of the order of 10 M s to 10 M s under the present experimental conditions. As an advantage of terephthalate dosimetry, it was found that the discharge system in the small reactor used in our experiment was a useful means for in-situ evaluating formation of OH radicals in an underwater discharge.