渤海和胶州湾海底地下水排泄及其环境效应研究

Submarine groundwater discharge (SGD) has become the hot issue in the frontier of international hydrogeology since it is closely related to the nearshore ecological environment and submarine freshwater resources. The study on SGD in China falls far behind those in Europe, America and other developed countries. This project intends to select Bohai Sea and Jiaozhou Bay, two semi-closed seas with remarkably different scales, and their surrounding coasts as the research objects. The conventional, multidisciplinary methods will be used to make various field and laboratory sampling and measurements during spring and fall, including observations of the hydraulic head, salinity and temperature of sea water and groundwater, the concentrations of environmental isotopes radium and radon (as tracers), of common anions and cations, of the contaminants such as nutrients and heavy metals, etc. At the same time, field observation experiments and corresponding physical model experiments in laboratory of the key processes of SGD study will be carried out, such as "vertical hydraulic gradient method" tests, "stand-pipe falling-head method" tests, systematic observations of groundwater dynamic at typical profiles, measurements of the seawater flow velocity and discharge by the ADCP method at the cross-sections of Jiaozhou Bay mouth and Bohai Sea mouth. Then mass balance models and numerical simulation models will be set up for describing the movement and transport processes in aquifers and seawater of various chemicals including water and salt, radium and radon, and contaminants such as nutrients and heavy metal, coupling the complex boundary conditions on sea-land interface in the sense of mass exchanges between seawater and aquifer. The total submarine groundwater discharge and the corresponding freshwater component will be evaluated by the means of multidisciplinary comprehensive methods. Scientific advices for ecological environmental protection and rational utilization of water resources will be put forward based on the quantitative assessments of environmental effects of SGD, and of the transports and reactions of contaminants.

海底地下水排泄(SGD)同近岸海陆生态环境和海底淡水资源密切相关，是国际水文地质学前沿热点问题。我国对SGD的研究远远落后于美欧发达国家。本项目拟选择渤海和胶州湾两个尺度迥异的半封闭性海域及其周边海岸为研究对象，利用常规多学科方法在春秋两季测定海水和地下水的水头、盐度、温度、镭氡环境同位素示踪剂、常见阴阳离子、营养盐和重金属的浓度等，同时开展“垂向水力坡度法”、“竖管降水头法”、典型剖面地下水动态系统观测、湾口断面海水流速流量的ADCP法测定等野外观测实验，以及关键环节的室内物理模型实验。然后建立包括营养盐和重金属等污染物、水盐镭氡等化学物质在含水层和海水运移过程中的质量平衡模型和数值模型，耦合海-陆界面上物质交换的复杂边界条件，通过多学科手段综合评估当地海底地下水排泄总量、淡水分量，结合污染物迁移转化规律，定量评估其环境效应，为生态环境保护和水资源合理利用提出科学建议。

海底地下水排泄（SGD）是全球水文循环的重要组成部分，对近岸海洋生态环境具有重要影响。本项目选取渤海和胶州湾两个尺度迥异的半封闭海域为研究对象，以环境同位素作为示踪剂，通过考虑海水再循环引起的镭、氡等同位素的损失，改进了国际同行通用的传统镭氡质量平衡模型，在此基础上，耦合水、盐、镭氡、氘氧等质量平衡模型，同时开展“垂向水力坡度法”、典型剖面地下水动态监测及湾口断面ADCP走航测速等野外观测实验，采用多学科多手段准确评估小尺度的胶州湾和大尺度渤海海域海底地下水排泄总量及其淡水分量。结合地下水及近岸孔隙水污染物质浓度，定量评估了SGD输入的陆源物质通量。初步探讨了SGD对营养盐和重金属等元素的地球化学循环的影响，分析了SGD对海岸带生态环境的潜在影响。建立了海水-地下水相互作用综合数值模拟模型，探讨了潮汐引起的河口盐度周期性变化对浅层含水层地下水流、盐分和氮素运移的影响。发表标注本项目的SCI论文22篇，（其中包括国际知名学术期刊WRR，GCA，JGR，JoHydro，STOTEN, EP，ADWR等），中文核心期刊论文1篇。这些成果为海岸带生态环境保护提供了基础科学数据和依据。由本项目资助，举办了两次“Ra & Rn同位素应用专题研讨会”。项目组成员参加国际学术会议18人次，国内学术会议27人次。在项目开展的5年间，培养博士后1名，博士研究生7名、硕士研究生25名。.项目将利用结余经费进一步开展如下工作：建立描述渤海和胶州湾典型剖面地下水污染物运移反应的数值模型，耦合海-陆界面上各个关键化学物质通量交换的非线性复杂边界条件，对整个海水-地下水系统的水动态和水化学变化过程等进行数值模拟，为其他类似研究区SGD的研究提供有益借鉴。