[A-HW22] Hydrological Cycle and Water Environment

[AHW22-18] Investigating trends of hydrogen peroxide in Ohta and Kurose rivers and rainwater in Hiroshima prefecture, Japan

*Waqar Azeem Jadoon¹, Ryuta UEKI², Kazuhiko TAKEDA¹, Hiroshi SAKUGAWA¹ (1.Graduate School of Biosphere Science, Hiroshima University, Japan, 2.School of Integrated Arts and Sciences, Hiroshima University, Japan)

Keywords:Hydrogen peroxide, River water, Rainwater, Hiroshima prefecture

Hydrogen peroxide (H₂O₂) plays a significant role in advanced oxidation process to remove the pollutants from water systems. However, its excess concentration in water has been proven detrimental for many of aquatic life forms under laboratory conditions. For this purpose we determined H₂O₂ distribution in river water (Ohta River: six sites = OR2–OR7 and Kurose River: KR1–KR3, Saijo A, Saijo B, Shitami A and Shitami B) and precipitation (rain and snow at Hiroshima University Higashihiroshima campus) from Hiroshima prefecture, Japan. In both rivers, H₂O₂ concentrations varied spatially with it’s increasing concentrations from upstream (sites: KR1 and KR2; OR2 and OR3) to mid/downstream (K3; OR6 and OR7). The H₂O₂ concentrations ranged between 67–175 nM and 21–195 nM in Ohta and Kurose rivers, respectively. The H₂O₂ ranged from 1.91 μM to 4.23 μM in rainwater and was 0.61 μM in snow samples. The H₂O₂ concentrations at mid/downstream sites in both rivers could be related with anthropogenic activities. For example at two branches of Kurose River (Shitami A and Shitami B) elevated H₂O₂ may be the result of untreated domestic wastewater discharge and agricultural runoff in these streams. Additionally, rainfall also increased the H₂O₂ levels at Shitami A and Shitami B, when measured one hour after rainfall started. In Kurose River higher levels of H₂O₂ were recorded during October compared with H₂O₂ values reported for December month. The H₂O₂ concentrations correlated well with the water temperature (r²=0.66; p < 0.001, n=14) and fairly with solar radiation (r²=0.41; p < 0.05, n=14) in Kurose River. This study suggested that these two parameters are important in determining the H₂O₂ levels in Kurose River. However, in Ohta River and rainwater, no significant correlation of H₂O₂ with water temperature, solar radiation and dissolved carbon was observed, which could be due to scarcity of available data.