CC区深海采矿羽流扩散的数值模拟研究  

Modelling of sediment plumes generated by deep-sea mining in CCZ

作　　者：旷芳芳 张俊鹏 靖春生 郭小钢 王翠 KUANG Fangfang;ZHANG Junpeng;JING Chunsheng;GUO Xiaogang;WANG Cui(Third Institute of Oceanography,MNR,Xiamen 361005,China)

机构地区：[1]自然资源部第三海洋研究所,福建厦门361005

出　　处：《应用海洋学学报》2024年第3期462-472,共11页Journal of Applied Oceanography

基　　金：国家重点研发课题(2022YFC2803901,2022YFC2804001)。

摘　　要：深海采矿可能带来深海矿区生物栖息地退化或生物多样性丧失等潜在风险,评估和预测深海采矿可能导致的环境影响成为国际社会普遍关注的问题。其中,预测采矿羽流的扩散程度是深海采矿环境影响评价的重要内容。本研究研发了适用于东太平洋克拉里昂-克利珀顿区(CC区)中国大洋协会多金属结核合同区深海模拟需求的高分辨率水动力数值模型,对商业采矿规模情景下的采矿羽流的源强进行了测算,以及开展了羽流扩散的数值模拟研究。结果表明:采矿尾水在大洋协会合同区底层排放,排放深度距底6 m、排放量63 kg/s、连续采矿1个月、采矿面积5.35 km^(2)、平均流速大小约5 cm/s的情景下,再沉积厚度最大值约4.3 mm,再沉积厚度大于1 mm和大于0.1 mm的范围分别为9.4 km^(2)和63 km^(2);在采矿作业结束后有约60%的颗粒物仍悬浮在水体中,然而因为被海水稀释,悬浮物浓度值非常低,均小于0.01 mg/L;沉降速率的敏感性实验表明,沉降速率从0.08 mm/s增加至0.30 mm/s时,再沉积厚度增加,最大值约12.9 mm,再沉积厚度大于1 mm和大于0.1 mm的范围分别为16.5 km^(2)和98 km^(2),水体中的悬浮物也相应减少,采矿作业结束后80%的颗粒物沉降到了海床上。Deep-sea mining may bring potential risks such as degradation of biological habitats or loss of biodiversity in deep-sea mining areas.Thus,assessing and predicting the potential environmental impacts of deep-sea mining has become a common concern by the international communities.Among them,predicting the extent of sediment plume is an important element in the environmental impact assessment of deep-sea mining.We developed a high-resolution hydrodynamic numerical model applicable to the deep-sea simulation needs of the COMRA polymetallic nodule contract area in the CCZ,where the source term of the sediment plume under a commercial mining scale scenario was measured and a numerical modeling pilot study of the plume dispersion carried out.The study showed that when the mining tailwater was discharged at the bottom of the COMRA contract area with a discharge depth of 6 m from the bottom and a discharge rate of 63 kg/s in one month of continuous mining in a mining area of 5.35 km^(2) and an average flow velocity about 5 cm/s,the maximum redeposition thickness reached about 4.3 mm and the ranges of redeposition thickness in between 1 mm and 0.1 mm were 9.4 km^(2) and 63 km^(2),respectively.Because of the dilution by seawater,the suspended sediment concentration were very low and all less than 0.01 mg/L.Sensiti-vity experiments show that the redeposition thickness increased as the settling velocity increased from 0.08 mm/s to 0.30 mm/s,with a maximum value of approximately 12.9 mm,the area of redeposition thicknesses higher than 1 mm and 0.1 mm are 16.5 km^(2) and 98 km^(2),respectively,and particle in the water column are reduced with 80%of the particle settling to the seabed at the end of the mining operation.

关 键 词：海洋环境科学 深海采矿 羽流 数值模型 克拉里昂-克利珀顿区 

分 类 号：P76[天文地球—海洋科学]