PARENT SESSION
Oral Session # 39: Limnology I: Ecosystems, Eutrophication, and Restoration.
Presiding: KL Cottingham
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 101.
The basic study on modeling variable fluid mud.
Tada, Kazufumi1, Hibino, Tadashi1, Murakami, Kazuo 2, Matsumoto, Hideo3, Tran, Kim Chi4, 1 Depertment of Social and Environmental Engineering, Higashi-Hiroshima, Hiroshima, Japan2 Institute for Marine Resources and Environment, Kure, Hiroshima, Japan3 Hiroshima port airport technical investigation office, Hiroshima, Hiroshima, Japan4 School of Policy Studies, Sanda, Hyogo, Japan
ABSTRACT- By the inflow load from Ota River and Seto Inland Sea, or by death and excretion of zooplankton, death of phytoplankton, nutrition salt, and organic matter sediment, a fluid mud layer (high turbidity layer) is formed near a submarine surface. The purpose of this research is to study the variable characteristics of fluid mud in Hiroshima Bay. Fluid mud is easily transported and deposited on stagnated ocean space. It is suspected that Kure Bay is the stagnated ocean space within Hiroshima Bay. Fluid mud thickness varied seasonally from 3 cm in May to a peak of 8 cm in September. The wet density of mud was lowest in September. The nutrition salt in mud is highest in September. The fluid mud changes state physically and chemically from July to September. In one month of continuous observations during the summer of 2002 in Kure Bay, the flow velocities were 0-3 cm/s, and turbidity measurements were 4-10 ppm at the seabed. Sedimentation flux increased with depth. Moreover, it was larger in September than August. In mud, insoluble Fe3+ reduces to Fe2+, and will begin to dissolve in water. The soluble Fe2+ reacts immediately with hydrogen sulfide, and FeS is generated, which is responsible for the black color of the mud. Fluid mud is characterized by the amount of sedimentation and horizontal inflow, and the chemical change in the mud.
Key words: seasonal variation, chemical change, fluid mud, sedimentation