Application of Fenton reaction for nanomolar determination of hydrogen peroxide in seawater

Heterogeneity and potential aquatic toxicity of hydrogen peroxide concentrations in selected rivers across Japan

Hydrogen peroxide (H₂O₂) is a reactive oxygen species formed in natural water. It is reportedly toxic to aquatic organisms with a predicted no-effect concentration (PNEC) of about 380 nM. In this study, a countrywide investigation of H₂O₂ concentrations in selected rivers across Japan was conducted to identify rivers that pose toxicity concerns. Twelve rivers with a total catchment area of 13,646 km² were selected from different prefectures. Spatial and temporal variation studies showed that the H₂O₂ concentrations (avg. 320 nM, n = 111) varied by two orders of magnitude (range 21-2929 nM) across the rivers. The Yamato River in Osaka and Nara prefectures and the Kokubu River in Chiba Prefecture had the highest concentrations at 276-669 nM and 236-2929 nM, respectively. >75% of the data from the two rivers were either close to or exceeded the PNEC. Most of the results for the other rivers were less than the PNEC. There was a clear seasonal variation in the H₂O₂ concentrations, with the highest values obtained in summer because of high solar irradiation. The H₂O₂ concentration had the highest positive correlation (r = 0.61, p < 0.01, n = 111) with the product of dissolved organic carbon and solar radiation intensity, which suggests that these two factors in combination are important in determining the H₂O₂ concentrations in river water. It was also observed that bigger rivers had lower H₂O₂ concentration and vice-versa. This shows that the size of a river may influence its H₂O₂ concentration. This study is the first countrywide survey of H₂O₂ concentrations in different rivers and evaluation of their relationship with the PNEC. The data provide insight on the factors influencing the concentrations of H₂O₂ in river water.

Factors controlling the degradation of hydrogen peroxide in river water, and the role of riverbed sand

Diurnal changes of H₂O₂ in river water during mid-summer were investigated. H₂O₂ in river water increased with the increase in intensity of solar radiation in the morning, and reached a maximum at 14:00, although solar radiation reached a maximum around 12:00. In the afternoon, a gradual decrease in H₂O₂ was observed, and H₂O₂ reached a minimum just before sunrise. Degradation rate constants determined using unfiltered river water samples were 0.081-0.161 h^-1, corresponding to a half-life of 4.3-8.5 h. We simulated diurnal changes in H₂O₂ using a simple formation, accumulation, and degradation model for static water using formation and degradation rate constants. The results of the modeling suggested that in situ degradation rate constants in rivers could be faster than those determined for unfiltered river water samples. Experiments using river sand indicated that riverbed sand could play an important role in H₂O₂ decay in rivers. We discussed the decomposition process of H₂O₂ in rivers.

Sensing of hydrogen peroxide and glucose in human serum via quenching fluorescence of biomolecule-stabilized Au nanoclusters assisted by the Fenton reaction

Sensitive detection of H₂O₂ and glucose were realized by Fenton reaction assistant oxidation of Au NCs.