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このケーススタデイは, 折戸湾(貯木場)と清水港が駿河湾(太平洋)の汚染を防止するための緩衝域として重要な役割を果たしていることを示す. 折戸湾は清水港の奥部にあって防波堤で開口部が狭い閉鎖域であり, 長い間貯木場として使用されてきた. 調査から河川から排出された懸濁物質は重金属などの種々の汚染物質を保持し, 湾底に堆積していることが判明した. 湾底は嫌気性条件となり, 硫化水素が発生し硫化物が生成している. 調査結果からは, 折戸湾堆積物の重金属含有量は高く, 清水港湾口へ向かってその量は減少する. 清水港口では重金属濃度は海底堆積物のバックグランド値に一致する., This case study shows that Orido Bay (wood pool) and Shimizu Port play an important role as buffer areas in preventing diffusion of pollutants to Suruga Bay (the Pacific Ocean). Orido Bay is located within the inner part of Shimizu Port and has a very narrow mouth with breakwaters. The suspended solids from the rivers that retain various pollutants, such as heavy metals, are settled on the bottom of the bay. Anaerobic conditions developed there promote production of hydrogen sulfide and subsequent sulfides with metals. The results show that the metal concentrations are relatively high in the sediments from Orido Bay and that they decrease with distance from the bay toward the outside of Shimizu Port. Near the entrance of the port, the concentrations of metals in sediments are in accordance with their background values.