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

利用2005-2007年夏季DoPa通信系统的2个多项目测量数据，对有明海西部内陆水域溶解氧浓度（DO）、流速（V）、盐度（S）和30 cm水深水温（T）进行逐时测量，分析了有明海西部内陆水域缺氧的实际情况。掌握了该海域纵向和横向测线上由沙塔计算的密度垂直结构与缺氧水出现的关系，发现缺氧水出现时总是形成密度跃层，在密度跃层附近垂直扩散系数迅速减小。底层溶解氧的消耗速率在很大程度上取决于底层悬浮有机物的数量。利用双层箱模式对34 a来的溶解氧资料进行分析，结果表明，夏季随着密度分层参数的增大，溶解氧的垂直扩散系数迅速减小，而溶解氧的消耗率则显著增大。夏季低氧水体的出现是由于密度跃层的形成，海水柱中DO由表层向底层的垂直扩散通量大于底层溶解氧的消耗。实验还表明，在研究海域海底安装特殊形状的三角形挡块，可以有效地防止缺氧水的发生

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