Comparison of chemical effects of UV radiation from spark discharge in air and a low-pressure mercury lamp

The chemical effects of UV radiation from atmospheric-pressure spark discharge and a DBK-9 low-pressure mercury lamp in distilled water and aqueous solutions of hydrogen peroxide and tryptophan have been studied. Reactive species generated in water by the both radiation sources are HO2· radicals, acid residue ions NO2− and NO3−, and ammonium ions. The yield of HO2· radicals has appeared to be the same for both sources, (1.1–1.2) × 10−6 mol L−1 s−1. This is confirmed by measurements of the degradation kinetics of tryptophan, which can be destroyed by HO2· radicals. The pH of water monotonically decreases with time during the spark discharge treatment. In the case of the mercury lamp, the pH varies insignificantly because of the competition of NH4+ alkali ions with the acid residues. UV radiation plays the major role in the decomposition of hydrogen peroxide.