霞ケ浦底泥の物性および堆積特性に関する調査と検討

抄録

Mud sumples were collected from Lake Kasumigaura in July 1981. Grading curve, water content, specific gravity and iginition loss of the samples were measured. The vertical profiles and horizontal distributions of these parameterss are discussed. The distribution characteristics, especially those of the grading curves, changed distinctly at 0.3m deep. Mud samples less than 0.3m deep had larger mud particle diameters and higher ignition loss than those bellow 0.3m and showed regional differences. The region from Takahamairi Bay to the center of Lake Kasumigaura had the largest diameter, the highest water content and ignition loss and the lowest specific gravity. Distributions for cases more than 0.3m deep showed little regional differences. Apparently some big change occurred in the environment about Lake Kasumigaura at the time bottom sediments about 0.3m deep accumlated. Taking into consideration the vertical changes in water content of bottom sediments layer, we estimated that this sediment had accumlated about 65-85 years ago. It was found almost all the annual accumlation rates as determined by some researchers are basically in agreement with ours although there are some differences in their expressions.