河口湾海水淡化工程浓海水入海扩散与生态环境影响预测——以山东半岛丁字湾为例

Prediction of Diffusion of Concentrated Seawater into the Sea and Evaluation of Ecological and Environmental Impacts of Seawater Desalination Project in Estuary ——A Case Study of Shandong Peninsula Dingzi Bay

中文关键词:  海水淡化  浓海水入海  数值模拟  丁字湾

英文关键词:desalination  concentrated seawater discharges  numerical simulation  Dingzi Bay

中文摘要:

      以山东半岛丁字湾为例，综合国内外相关研究及标准，采用三维数值模拟方法对浓海水入海后丁字湾盐度时空分布、变化机理进行了预测，讨论分析了浓海水入海对河口湾生态环境的影响。研究结果显示，（1） 浓海水入海后导致注入海域盐度升高或降低，盐降主要是因为排放时的浓海水盐度低于注入海域背景盐度，但不同季节、潮型、潮时、水层和位置的盐升程度、盐升历时、盐度日变幅变化及平面分布差别很大。冬季盐升程度大于秋季，冬季大部分区域盐升小于3 PSU，秋季绝大部分区域盐升小于2 PSU，冬季和秋季半月潮平均盐升分别为 0.41 PSU和 0.36 PSU；浓海水注入丁字湾后，冬季半月潮 2 PSU以上盐升历时较大，3、4、5PSU盐升大于120 h累计历时分布格局均呈围绕排水口的椭圆形区域，秋季盐升历时较冬季显著为小。（2） 冬季在排放口周围20 m范围内形成锥形高盐度水体，入海高盐水下伏于低盐背景海水之下并与周边海水之间形成环状盐度锋；秋季排放口周围15 m范围内形成杯形的低盐度水体，入海低盐水上覆于高盐度背景海水之上与周边海水之间形成环状盐度锋。（3） 浓海水注入海后河口湾盐度变化主要受河口盐度锋、取淡导致的湾内外海水置换和海湾水交换能力等影响。一个半月潮期间内，湾内冬季和秋季平均盐升约为0.85 PSU和1.05 PSU。（4）3 PSU盐升可作为海洋生态系统能够忍受盐升的上限临界值，在此幅度以下盐升对生态系统影响较小。

英文摘要:

      Taking Dingzi Bay in the Shandong Peninsula as an example, this paper predicted the spatial and temporal distribution of salinity in Dingzi Bay after the entry of concentrated seawater into the sea by three-dimensional numerical simulation, followed by a discussion on the impacts of the entry of concentrated seawater into the sea on the ecological environment of Dingzi Bay. The results of the study showed that: (1) The salinity of the injected area increases or decreases after the entry of concentrated seawater into the sea. The salinity drop is mainly because the salinity of the concentrated seawater at the time of discharge is lower than the background salinity of the injected waters. However, the degree and duration of salinity rise, as well as the daily variation of salinity and the planar distribution of salinity in different seasons, tidal patterns, tidal times, water layers and locations vary greatly. The degree of salt rise is greater in winter than in fall, with most areas in winter having a salt rise of less than 3 psu, and the vast majority of areas in fall having a salt rise of less than 2 psu. The average salt rises of the semimonthly tides in winter and fall are 0.41 psu and 0.36 psu, respectively; After the injection of dense seawater into Dingzhi Bay, the salt rise episodes above 2 psu of semi-monthly tides were larger in winter, and the distribution pattern of the cumulative episodes of 3, 4, and 5 psu of salt rise greater than 120 h were in the form of an elliptical area around the outfall. In contrast, the salt rise episodes in fall were significantly smaller than those in winter. (2) In winter, a conical high-salinity body of water is formed 20 meters around the drainage outlet, with the high-saline water in a wedge shape underneath the upper low-saline water, and an annular salinity front is formed between the high saline seawater and the surrounding seawater; and in fall, a cup-shaped low saline body of water is formed 15 meters around the drainage outlet, with the lower high saline seawater in a wedge shape underneath the upper low saline concentrated seawater, and an annular salinity front is formed between the low saline body of water and the surrounding seawater. (3) Factors affecting the salinity change of concentrated seawater into the sea include estuarine salinity fronts, replacement of seawater in and out of the bay as a result of desalination, and the exchange capacity of water in the bay. The average winter and fall salt rise in the Bay was approximately 0.85 psu and 1.05 psu during the one-and-a-half-month tidal period. (4) Salt rise of 3psu can be taken as the upper critical value for marine ecosystems to be able to tolerate salt rise, and the impact of salt rise on ecosystems below this magnitude is small.