Influence of conductivity on the generation of a radio frequency plasma surrounded by bubbles in water

A radio frequency plasma was generated and maintained in water over a wide range of water conductivities (0.2–7000 mS m−1). The conductivity of water was changed by adding NaCl to it. The size of the plasma increased with conductivity. Although the intensity of the OH(A–X) line monotonically decreased with increasing conductivity, the generation of hydrogen peroxide and the degradation of methylene blue suggested that the number of generated OH radicals decreased with increasing conductivity in the range 0.2–80 mS m−1 and increased in the range 80–7000 mS m−1. Ultraviolet irradiation was found to enhance the degradation of methylene blue not only in pure water but also in high-conductivity water (5000 mS m−1).