Chemical Characteristics in Coastwise Waters of Japan

Abstract

In order to provide reference data for an appropriate location of seawater utilization facilities as well as for environmental assessment, the authors conducted in the past 4 years investigations on the quality of seawater in the coastal regions of Japan and made the quality of water clear in each sea region, obtaining the following results:
(1) In the Pacific coasts in the Hokkaido and Tohoku districts which are under the influence of the Oyashio Current, chlorinity is about 18% and both nutrients contents and chlorophyll are relatively high, and transparency is low.
(2) In the bay regions, chlorinity is showing a very large seasonal fluctuation by the effect of land water. Also, in these sea regions, there is a marked trend of eutrophication, and COD is over 1 ppm, with very low transparency.
(3) In the Seto Inland Sea, there are regional differences in the quality of seawater, and the progress of eutrophication is seen in the center of the inland sea. Also, the seawater shows an open-sea character as it approaches the Bungo Channel.
(4) In the west coast of Kyushu under the influence of the Tsushima Current, chlorinity is about 19%0 and its seasonal fluctuation is small. This sea region is in a state of oligotrophication and contains low chlorophyll.
(5) In the west coast of the Japan Sea, chlorinity is high,i. e., about 19%0, and nutrient contents have a tendency of increasing in winter. Also, transparency is very high,i. e., 15 meters or more.