Abstract:In the Hiuchi-Nada area of the Seto Inland Sea, Japan, sedimentation rates were determined with the Pb-210 technique, and heavy metals in sediments were also analyzed. Sediments were collected in twelve short sediment cores and a long sediment core, using 1-m and 6-m gravity corers.The sedimentation rates vary from 0.14 to 0.31gcm -~yr -l, The highest sedimentation rate was observed in the central part of the area, while lower sedimentation rates were observed in the eastern part.In Hiuchi-Nada, a remarkable increase in copper and zinc contents is noticeable as early as the 1800's. Over the past 240 years a copper smelter at the south-western side of this area has been causing serious pollution of the sediment. Now, anthropogenic copper and zinc loads into the sediment are 123 and 376 tonyr -1 compared to natural copper and zinc loads of 82 and 401 ton yr -l, respectively. The highest level of copper and zinc pollution was observed in the 1960's, when the relative enrichments above background values (copper; 19 and zinc; 93mg kg -t) were 5.5 and 2.8, respectively.
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