镭同位素评估莱州湾等地海底地下水排泄（SGD）

发布时间：2018-03-31 15:21

本文选题：海底地下水排泄　切入点：地下淡水　出处：《中国地质大学(北京)》2015年博士论文

【摘要】：海底地下水排泄(SGD)是近岸、滩涂和河口区典型而重要的海水—地下水相互作用过程。由于受陆地和海洋双重驱动力作用,它包括来自内陆的陆源淡水(SFGD)和海水循环量(RSGD)两部分。作为全球水循环的重要组成部分,海底地下水排泄是海洋中水和各种化学物质的重要来源之一,同时也是各种污染物从陆地向海洋输送的一个重要而隐蔽的通道,对近岸海洋环境有着重要影响和作用。作为渤海三大海湾之一的莱州湾,其半封闭性性质使其与外海的交换能力较差,海湾环境因受人类活动而不断恶化。对此,地下水的贡献可能相比地表水更为重要。而大尺度的海底地下水排泄的评估,在渤海海域除了几个重要河口做过相关研究外,其他地区还是一片空白。本研究以天然镭同位素示踪为主要研究方法,在构建镭同位素质量平衡模型、水盐质量平衡模型基础上,评估莱州湾海底地下水、地下淡水排泄及海湾中水体混合过程。根据上述物理模型,计算得出莱州湾海水水体的刷新时间为36.6+5.3天,利用获得的水体刷新时间,耦合水、盐和镭同位素质量平衡模型,估算出2012年8月莱州湾海底地下淡水排泄量(SFGD)为4.12×107 m3/d～6.36×107 m3/d,海底地下水排泄量(SGD)为5.32×108 m3/d～6.20×108 m3/d。SFGD和SGD分别是2012年黄河年平均入海径流量的0.57～0.88倍和7.35～8.57倍。研究还发现,2012年8月黄河流入莱州湾的径流量不到其总入海径流量的14%。对于水体混合过程,本研究根据短半衰期的224Ra在湾口断面的活度分布,利用一维224Ra扩散模型计算了湾口表层和中层水体水平涡动扩散系数。2012年8月表层水体和中层水体的水平涡动扩散系数分别为253.1×106 m2/d和56.5×106 m2/d。此外,本文也利用224Ra质量平衡模型估计了SGD,结果为4.2×108 m3/d。在渤海湾北部,利用纳潮量法计算了近岸20 km区域内水体刷新时间,其结果为11.5天,然后利用226Ra质量平衡模型评估了该区域的SGD。226Ra收支平衡表明,约99%的226Ra来源于SGD,从而得到该研究区域的SGD为4.83×107 m3/d。以上评估结果对莱州湾乃至渤海的水环境和资源的可持续管理具有重要指导意义。
[Abstract]:Seafloor groundwater discharge (SGD) is a typical and important seawater groundwater interaction process in coastal, tidal flat and estuary areas. As an important component of the global water cycle, undersea groundwater discharge is one of the important sources of water and various chemicals in the ocean, It is also an important and hidden channel for the transport of pollutants from land to sea, which has an important effect on the coastal marine environment. Laizhou Bay, one of the three major bays in the Bohai Sea, Its semi-closed nature makes it less capable of exchanging with the open sea, and the Gulf environment is deteriorating as a result of human activities. The contribution of groundwater may therefore be more important than that of surface water, and the assessment of the discharge of groundwater on a large scale, In the Bohai Sea area, except for several important estuaries, there is still a blank in other areas. In this study, the natural radium isotope tracer is used as the main research method, and a radium isotope mass balance model is constructed. On the basis of water and salt mass balance model, the mixing process of groundwater, underground fresh water discharge and water body in Laizhou Bay was evaluated. According to the above physical model, the refresh time of seawater in Laizhou Bay was calculated to be 36.6 5.3 days. Using the obtained water refresh time, coupled water, salt and radium isotopic mass balance model, In August 2012, it was estimated that the subsea freshwater discharge of Laizhou Bay was 4.12 脳 10 ~ 7 m3/d~6.36 脳 10 ~ 7 m ~ (3 / d), and the groundwater discharge was 5.32 脳 10 ~ 8 m3/d~6.20 脳 10 ~ (8) m3/d.SFGD and SGD was 0.57 ~ 0.88 times and 7.35 ~ 8.57 times of the average annual runoff of the Yellow River in 2012, respectively. The study also found that in August 2012, the annual runoff of the Yellow River entered the sea was 0.57 ~ 0.88 times and 7.35 ~ 8.57 times respectively. The flow of the Yellow River into the Laizhou Bay is less than 14% of its total runoff into the sea. In this study, the activity distribution of 224Ra with short half-life at the mouth of the bay was studied. Using one-dimensional 224Ra diffusion model, the horizontal eddy diffusion coefficients of surface and middle water bodies were calculated. In August 2012, the horizontal eddy diffusion coefficients of surface water and middle water were 253.1 脳 106m2 / d and 56.5 脳 106m2 / d, respectively, and the diffusion coefficients of horizontal eddies were 253.1 脳 106m2 / d and 56.5 脳 106m2 / d, respectively. In this paper, the 224Ra mass balance model is also used to estimate the 224Ra, the result is 4.2 脳 10 ~ 8 m ~ 3 / d. In the northern Bohai Bay, the water refresh time in the coastal area of 20 km is calculated by using the tidal absorption method, and the result is 11.5 days. Then the 226Ra mass balance model is used to evaluate the SGD.226Ra balance in the region. About 99% of 226Ra came from SGDs, and the SGD of the study area was 4.83 脳 107m3 / d. The above evaluation results are of great significance for the sustainable management of water environment and resources in Laizhou Bay and Bohai Sea.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：X55

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