Browsing by Author "Taira, Hatsuo"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Photochemical activity of seawater contaminated with red soil in the northern part of Okinawa
    (2003-08) Hamdun, Asha; Okada, Kazunori; Fujimura, Hiroyuki; Arakaki, T.; Taira, Hatsuo
    Hydroxyl radical (. OH) as a most reactive oxidant, posses an oxidizing power to control the lifetime of many synthetic and natural organic compounds in natural waters. Northern part of Okinawa Main Island is experiencing high soil erosion rate, particularly by acidic reddish soil that contains about 3.3- 5.3% of Fe. Past work has shown that low pH and high iron concentration favour OH fo
  • Thumbnail Image
    Item
    Simultaneous Measurement of Hydrogen Peroxide and Fe Species (Fe(II) and Fe(tot)) in Okinawa Island Seawater: Impacts of Red Soil Pollution
    (2005-05) Arakaki, T.; Fujimura, Hiroyuki; Hamdun, Asha; Okada, Kouichirou; Kondo, Hiroaki; Oomori, Tamotsu; Tanahara, Akira; Taira, Hatsuo
    The northern part of Okinawa Island suffers from red soil pollution—runoff of red soil into coastal seawater—which damages coastal ecosystems and scenery. To elucidate the impacts of red soil pollution on the oxidizing power of seawater, hydrogen peroxide (HOOH) and iron species including Fe(II) and total iron (Fe(tot), defined as the sum of Fe(II) and Fe(III)) were measured simultaneously in seawater from Taira Bay (red-soil-polluted sea) and Sesoko Island (unpolluted sea), off the northern part of Okinawa Island, Japan. We performed simultaneous measurements of HOOH and Fe(II) because the reaction between HOOH and Fe(II) forms hydroxyl radical (•OH), the most potent environmental oxidant. Gas-phase HOOH concentrations were also measured to better understand the sources of HOOH in seawater. Both HOOH and Fe(II) in seawater showed a clear diurnal variation, i.e. higher in the daytime and lower at night, while Fe(tot) concentrations were relatively constant throughout the sampling period. Fe(II) and Fe(tot) concentrations were approximately 58% and 19% higher in red-soil-polluted seawater than in unpolluted seawater. Gas-phase HOOH and seawater HOOH concentrations were comparable at both sampling sites, ranging from 1.4 to 5.4 ppbv in air and 30 to 160 nM in seawater. Since Fe(II) concentrations were higher in red-soil-polluted seawater while concentrations of HOOH were similar, •OH would form faster in red-soil-polluted seawater than in unpolluted seawater. Since the major scavenger of •OH, Br−, is expected to have similar concentrations at both sites, red-soil-polluted seawater is expected to have higher steady-state •OH concentrations.