Studies on the Occurrence of Hypoxic Water in the Interior Parts of the Ariake Sea and its Preventive Measures

利用DoPa通信系统2005-2007年夏季每小时测得的离海底30 cm高度的溶解氧浓度（DO）、流速(V)、盐度(S)和水温(T)数据，阐明了有明海西部内陆缺氧水体的实际情况。同时，通过在该海域设置的纵向和横向测量线，掌握了沙塔的低氧水的发生与密度垂直结构的关系，表明密度斜斜总是在低氧水爆发时形成，并且在密度斜斜附近垂直扩散系数迅速下降。此外，底层DO的消耗率在很大程度上取决于底层悬浮有机杂交物的数量。另一方面，利用双层箱模型对34年的DO数据分析结果表明，夏季随着密度分层参数的大幅升高，垂直扩散系数迅速下降，消耗率大幅增加。夏季缺氧水的出现是由于随着密度斜斜的形成，海水柱表层向底层DO的垂直扩散通量大于底层DO的消耗量。实验还表明，在海底设置特殊形状的三角块可以有效地防止研究海域缺氧水的发生

The actual conditions of hypoxic water which occurred in the western interior parts of the Ariake Sea were clarified based on the data of dissolved oxygen concentration (DO), velocity (V), salinity (S) and water temperature (T) at the 30 cm height from the sea-bottom measured hourly in summer of 2005-2007 using two multi-items measures with DoPa communication system. The relationships between the occurrence of hypoxic water and vertical structure of density calculated from Sand Talong the measurement lines in longitudinal and lateral directions set in this sea area were also grasped, and it was shown that the density pycnocline were always formed at the time of the outbreaks of hypoxic water and the vertical diffusion coefficient decreased rapidly near the density pycnocline. Moreover the consumption rates of DO in the bottom layer depended largely on the amount of suspended organic mutter there. On the other hand, the analysis results of DO data during 34 years by a two-layer box model indicated that the vertical diffusion coefficients decreased rapidly, and on the contrary, the consumption rate increased largely as the density stratification parameter rose greatly in summer. The occurrence of hypoxic water in summer was due to the fact that with the formation of the density pycnocline, the vertical diffusion flux of DO from the surface layer to the bottom one in the sea-water column became more than the consumption of DO in the bottom layer. It was also presented experimentally that the installation of a triangle block with special shape on the sea-bottom was effective for prevention of the occurrence of hypoxic water in the study sea area