Author(s): Tadaharu Ishikawa; Tomuyuki Suzuki; Kazuhiro Osaku; Katsuhide Yokoyama
Linked Author(s):
Keywords: Tone river estuary; Fine sediment suspension; Oxygen demand
Abstract: A series of field measurements were conducted in order to investigate the suspension of fine bed sediment and its oxygen consumption in the Tone River Estuary where anaerobic condition sometimes appears in a salt wedge after the construction of the Estuary Dam for the purpose of prevention of seawater from going up. Turbidity monitoring at a station and transect survey of turbidity and salinity shows that high turbidity appears near the nose of the salt wedge in the first half of rising tides but that the sediment entrainment takes place in a comparatively short time (one hour or so) and the sediments diffuse in the salt wedge for several hours. Laboratory experiment was conducted to estimate the relation of the oxygen demand of suspended solids (SSOD) with turbidity level. From the test results, SSOD in the practical condition of the Tone River Estuary was estimated, where the typical conditions of salt wedge thickness and turbidity maximum were assumed from observation in the above mentioned field experiment. The result show that SSOD is less than ten percent of oxygen consumption in the estuary, and it is concluded that SSOD is not a very important factor for the onset of hypoxia in the estuary.
Year: 2004