A Study on Preservation of Underwater Archaeological Relics

1992 Fiscal Year Final Research Report Summary

• Project/Area Number: 03451057
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: 考古学(含先史学)
• Research Institution: Syowa Women's University
• Principal Investigator: IINO Hisakazu Syowa Women's University, Fac. of Home Economics, Assistant Professor, 家政学部 (00146911)
• Co-Investigator(Kenkyū-buntansha): WATANABE Syuuichi Hokkaido University, Fac. of Fisheries, Assistant, 水産学部, 助手 (00167131) ; TKEDA Akiko Syowa Women's University, Fac. of Home Economics, Lecture, 家政学部・助教授, 講師 (50124326)
• Project Period (FY): 1991 – 1992
• Keywords: seabed deposition environment / temperature changes in seabed / chemical and microbiological investigation of seawater / dissolved oxygen and sulfate-reducer / metal corrosion in the sea / insect control method using copper net. / aerobic sea area / salt damage of archaeological relics

Research Abstract

Part of the present state of Kaiyo-maru preserved in the seabed has been revealed through two-year measurements of temperature changes in the seabed and chemical and microbiological investigation of the seawater.
The seawater temperature varied remarkably in the range of 4 to 22ﾟC over a period of a year. In addition, the seabed temperature temporarily showed rapid changes when the weather took a winter-type pressure pattern. This is attributed to the seawater exchange in Esashi Harbor, which was supposed to cause the outflow of particles in the harbor. This means that it is difficult to realize the insect control effect by producing a reductive environment with copper ions and sediment. The concentration of dissolved oxygen showed only seasonal changes, but not secular ones. Copper ions were observed in the sea-water immediately above the copper net, but not in the intermediate and surface water. This suggests that at present surrounding pollution is not a problem. The copper net was most severely worn at sites where the seawater struck hard, but there seems no fear of erosion by components in the sludge. Common bacteria were detected on the order of 10^2-10^3 in all samples. This area of the sea was thought to be aerobic, because the seabed is around 10m deep. This was supported by the absence of sulfate-reducers. The harbor was very turbid for a local one due to the sludge and microbes, which was thought to cause increasing corrosion. The above results lead to a conclusion that Kaiyo-maru should be early salvaged.
Especially iron ones, are most affected. These relics should be early retreated and stored in a well-equipped warehouse.