胶州湾海底地下水排泄(SGD)的多学科多手段综合评价研究

Owing to the importance and significance in marine geochemistry, nearshore marine ecosystem, and quantifying the role played by groundwater in global hydrologic cycle, submarine groundwater discharge (SGD) has become the hot and difficult focus in the field of international hydrogeology. Despite this, most of the previous studies in SGD focused on the coastlines in developed countries, and did not couple the exchange in water quantity (mass of water) and water quality (mass of various chemicals in water) between seawater and groundwater for main reasons such as large scale of ocean flow and complicated ocean currents. In this project, Jiaozhou Bay, a semi-isolated bay with moderate scale, is chosen as our study area so that the whole seawater-groundwater system in the area can be conveniently and quantitatively modeled. The data and information obtained through multi-method (such as the seepage flux through the sea-land interface, the level/head, salinity, temperature, concentrations of environmental isotope tracers of radium and radon and various anions and cations of seawater and groundwater at selected monitoring locations, groundwater age, data or information of hydrogeological structure of regional-scale aquifers and various geological exploration), will be technically incorporated and integrated into a numerical model to couple the exchange in water quantity and quality between seawater and groundwater. The numerical model will be developed by ourselves via translating, compiling and linking of multi-disciplines including marine geochemistry, fluid mechanics of seawater and surface water, hydrogeology, groundwater dynamics, isotope geochemistry, applied and computational mathematics, and computer numerical simulation. On the basis of above work, we will quantify the temporal and spatial distribution of the total SGD and its freshwater component in the study area.

海底地下水排泄的研究在海洋地球化学、近岸海洋生态系统、地下水在全球水文循环中所起作用的定量评估等方面均具重要意义，是国际水文地质学界热点、难点和焦点之一。以往的研究均相对集中在发达国家的海岸线上，且由于海水流动区域广、洋流复杂等原因，未能耦合海水-地下水水量水质交换。本项目计划选定相对封闭、尺度适中的胶州湾海域，以整个海水-地下水系统为研究对象，将多手段测得的数据信息（如水陆界面渗流量，海水和地下水的水位或水头、盐度、温度、环境同位素示踪剂镭和氡以及各种阴阳离子浓度，地下水年龄，区域尺度含水层水文地质结构和各种地质勘探资料等），通过海洋地球化学，海水和地表水流体力学，水文地质学，地下水动力学，同位素地球化学，应用和计算数学等多学科解译综合到自己开发的一个数值模型中，耦合水陆界面上的水量水质交换，实现对该地区海底地下水排泄量及其淡水分量时空分布规律的定量评价。

本项目通过多学科手段综合评价了胶州湾海底地下水排泄量（SGD），通过定期观测潮间带和咸淡水混合区地下水动态、营养盐以及环境同位素镭和氡动态变化规律，评估了SGD及其淡水分量，评估了SGD对陆源物质向海输送的贡献，初步评价它们对沿海环境的影响，初步分析讨论了对海湾的富营养化作用。建立了针对研究区的海水-地下水相互作用综合数值模拟模型，正在进行数值模拟，初步掌握了当地典型剖面海底地下水排泄规律。在国际学术刊物发表标注本项目的SCI检索论文5篇。由本课题部分资助，举办了“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5人次，国内学术会议15人次。在开展项目期间的4年间，培养博士毕业生3名，硕士毕业生15名。.项目将利用结余经费进一步开展如下工作：结合实测数据，开展系统的数值模拟，掌握深层海水-地下水相互作用过程，综合深入评价它们对沿海环境的影响，深入讨论海湾的富营养化作用。搞清海底地下水排泄量季节性变化规律，预测研究区海底地下水排泄量的动态变化趋势，为类似该研究区的其它地区的SGD 研究提供借鉴。