Abstract
The Database, namely “the Second Sediment Survey Database” in this paper is constructed as a continuation database of the sediment survey by the Japan Environment Agency, and the monitoring/surveying original data published by research centers and administrative organs in Japan are summarized in this database. Its period is eleven years from 1984 to 1994. It is able to refer to the data, which is in the first period for 14 years from 1970 to 1983, from the Second Database. The monitoring items are more than 225, and numbers of sediment samples in the second database are 9,594 in rivers, 713 in lakes and reservoirs, 7,199 in sea areas, respectively.
Monitoring condition, actual distribution, and trends of sediment pollution that data are modified in each prefecture and in time series for 25 years from 1970 to 1994, are discussed with the statistical analysis. Results are as follows: The mean concentrations of sediment for 25 years are 15.7mg·g-1 as COD, 2.4μg·g-1 as Cd, 41.9μg·g-1 as Pb, 10.8μg·g-1 as As, 1.82μg·g-1 as total-Hg and 0.74μg·g-1 as PCB. The mean values in 1994 are 15.3mg·g-1 as COD, 0.59μg·g-1 as Cd, 33.3μg·g-1 as Pb, 7.1μg·g-1 as As, 0.44μg·g-1 as total-Hg and 0.056μg·g-1 as PCB. Thus it is able to consider that the sediment concentration of COD is almost unchanged during in recent 25 years, and other items are gradually decreasing. In addition, the COD contaminant in sediment is noticed the dispersion phenomena of pollution as the remaining concentration in urban area, and as the increasing concentration in local area.
