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

Diurnal changes of HO in river water during mid-summer were investigated. HO 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 HO was observed, and HO reached a minimum just before sunrise. Degradation rate constants determined using unfiltered river water samples were 0.081-0.161 h, corresponding to a half-life of 4.3-8.5 h. We simulated diurnal changes in HO 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 HO decay in rivers. We discussed the decomposition process of HO in rivers.