大亚湾某沙质剖面海底地下水排泄及其携带营养盐的研究

发布时间：2018-10-18 19:24

【摘要】：滨海地区地下水和海水的相互作用的研究是阐明该区域的地下水流动和溶质运移规律、陆-海交界面通量交换机理和过程及其对海岸带生态系统和生物多样性的影响的关键。此外,地下水—海水相互作用为有关部门解决及防治滨海生态环境问题提供可靠的依据。本文以大亚湾巽寮湾海域某沙质海滩为研究对象,结合野外观测的地下水头、盐度及部分营养盐数据及室内外实验,利用数值模拟软件MARUN进行了潮滩中地下水—海水相互作用的二维数值模拟研究,模型中加入了营养盐衰减常数,考虑了营养盐在运移过程中的降解损失和营养盐的海水边界,定量评估了海底地下水排泄和地下淡水排泄量及其所携带的营养盐。野外观测数据和数值模拟结果表明,该研究区域营养盐含量和盐度表现出很强的负相关,即盐度高的地方,营养盐低,盐度低的地方营养盐高。具体而言,潮间带上部和下部表现为低盐度、高营养盐,而潮间带中部则为低营养盐、高盐度。由此判断该区域存在盐度晕(USP)、咸淡水混合带以及陆源淡水排泄通道(FDT)。该海域潮滩地下水中营养盐含量较高,无大型河流汇入,通过地下水向海域输入营养盐为该海域营养盐的最主要来源。数值模拟结果表明,在一个大小潮周期内,该研究剖面单位长度海岸线上海底地下水排泄量(SGD)为8.68m2/d,其中地下淡水排泄量(FSGD)为2.03 m2/d,占海底地下水排泄总量的23.4%;内陆地下水淡水(FSGD)携带的无机氮通量为18.67 g/(d·m),而海底地下水排泄(SGD)携带的无机氮通量为14.39 g/(d·m),最终进入海水中的无机氮为进入含水层无机氮的77.1%,约有23%在运移的过程中降解。在以往的研究中认为潮下带的海底地下水排泄是很小的,而数值模拟结果表明,本剖面潮下带存在一定量的海底地下水排泄,为1.84 m2/d,约为整个剖面海底地下水排泄的21.2%。
[Abstract]:The study of the interaction between groundwater and sea water in coastal area is the key to clarify the law of groundwater flow and solute transport, the flux exchange mechanism and process of land-sea interface and its influence on coastal ecosystem and biodiversity. In addition, the groundwater-seawater interaction provides a reliable basis for the relevant departments to solve and prevent coastal ecological environment problems. In this paper, a sandy beach in Shunliao Bay, Daya Bay, is taken as the research object, and the field observation data of groundwater head, salinity and some nutrients are combined with indoor and outdoor experiments. A two-dimensional numerical simulation study on the interaction between groundwater and seawater in tidal flat was carried out by using the numerical simulation software MARUN. The attenuation constant of nutrient salt was added to the model, and the degradation loss of nutrient salt and the seawater boundary of nutrient salt were considered in the model. The discharge of undersea groundwater and the discharge of underground fresh water and the nutrients they carry are quantitatively evaluated. The results of field observation and numerical simulation show that there is a strong negative correlation between the nutrient content and salinity in the study area, that is, where the salinity is high, where the nutrient is low, where the salinity is low, the nutrient content is high. Specifically, the upper and lower intertidal zone showed low salinity and high salinity, while the middle intertidal zone showed low salinity and high salinity. It is concluded that there are salt halo (USP), salt and fresh water mixed zone and continental freshwater discharge channel (FDT). In the region. The nutrient content in the groundwater of the tidal flat in this area is high and there are no large rivers flowing in. The main source of nutrient salt in the sea area is the input of nutrients from the groundwater to the sea area. The numerical simulation results show that, in a large or small tidal period, The (SGD) of groundwater discharge on the unit length coastline of the study section is 8.68 m2 / d, of which the (FSGD) of underground fresh water is 2.03 m2 / d, accounting for 23.4g / d of the total discharge of undersea groundwater, and the inorganic nitrogen flux of freshwater (FSGD) in inland groundwater is 18.67 g / (d m), and that in the sea is 18.67 g / (d m),. The flux of inorganic nitrogen carried by (SGD) in the bottom groundwater is 14.39 g / (d m), and the inorganic nitrogen that enters the seawater is 77.1% of the inorganic nitrogen in the aquifer. About 23% of the inorganic nitrogen is degraded in the process of transport. The results of numerical simulation show that there is a certain amount of undersea groundwater discharge in the subtidal zone of this section, which is 1.84 m2 / d, which is about 21.2g / d of that of the whole section.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P641;P734

【相似文献】