湄洲湾峰尾围垦工程施工期间海水悬浮泥沙输移扩散的数值模拟

Numerical simulation of the transport diffusion of suspended matter during the construction of Fengwei reclamation project at Meizhou Bay

围填海工程施工过程导致海域悬浮物迅速增加,影响周围海洋生态系统,研究围填海工程悬浮泥沙的输移扩散规律对于区域生态环境质量及工程建设的综合生态影响评价具有重要的参考意义.针对湄洲湾峰尾围垦工程施工期悬浮泥沙可能造成的生态影响,对爆破挤淤(5.17 t/s)和抛石挤淤(1.39 kg/s)的悬沙源强进行了分析计算.在工程海区平面二维潮流场数学模型的基础上,采用二维对流扩散数学模型对施工范围内的模型网格点(40 m×40 m)进行了逐点计算,数值模拟结果表明,悬浮泥沙扩散范围和形态主要受潮流控制,工程施工联合影响下悬沙质量浓度大于10mg/dm3的全潮最大影响包络面积为5.848 km2,施工9 h后悬沙影响基本消失,为工程施工期环境管理提供了参考依据.施工悬浮泥沙的扩散整体表现为总悬沙质量浓度在离工程区较近的范围内较大,而距离越远质量浓度越接近自然状态的本底含沙量.施工悬浮泥沙对浮游生物、游泳生物和底栖生物等均会产生一定的影响,但随着施工结束而消失,不会对海洋生态产生长期的不利影响.

Suspended matter in the sea increases rapidly as a result of the reclamation project during the construction period, which in turn influences the marine ecosystem. Therefore, the study on the transport diffusion of suspended matter in reclamation projects provides an important reference for regional environmental quality assessment and comprehensive ecological impact assessment. To investigate the possible ecological impact of suspended matter produeed during the construction of the Fengwei reclamation project in Meizhou Bay,this study analyzes the suspended matter emission caused by explosion and compaction （5.17 t/s） and riprap silt extrusion （1.39kg/s）,respectively. Based on the 2-dimensional tide current modal of the project area,the study analyzes each mesh point （40 m × 40 m） in the construction area using the 2-dimensional suspended load modal. The numerical simulation shows that the scope and pattern of suspended matter diffusion are affected by the current. The suspended matter in density of more than 10 mg/dm3 , cause by the construction, can reach a maximum envelop area of 5. 848 km2. That the impact mostly disappears in 9 h after the construction can be taken as reference for the environmental management of the construction. The diffusion of suspended matter during the construction period manifests that near the construction site the total suspended matter concentration is relatively high and with increasing distance the concentration gradually become closer to the background concentration. Suspended matter produced in the construction period can, to some extent,influence the plankton, nekton and benthos. But this impact will disappear after the end of construction with no long-term negative impact on the marine ecological system.