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.