Abstract
Monthly measurements (January - May, 2013) of reactive oxygen species (ROS), which include H2O2, NO and OH radicals in Kurose river of Higashi-Hiroshima, Japan were carried out. Water samples were collected at six different locations (upstream to downstream) of the river. H2O2 concentrations were analyzed via Fenton reaction. NO and .OH were measured using 4,5-diaminofluorescein-2 (DAF-2) and benzene as probes, respectively. Range of mean values showed that H2O2 concentrations were from 94-172 nM, while those of NO and .OH photoformation rates(x 10-10 Ms-1) were from 0.03?14.81 and 0.06?6.36, respectively. Lifetimes of NO and .OH were 0.11-0.49 s and 0.39-5.84 ?s, respectively. Steady-state concentrations of NO and .OH were 0.01?3.66 (x 10-10 M) and 0.52?27.46 (x 10-16 M), respectively. There was a strong correlation (r2 = 0.933) between NO photoformation rates and the [NO2-] present in the river, suggesting the anion as the major NO precursor; also, >70% of the photoformed .OH was contributed by the NO2-.
