热带地理

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非均质条件下珠江口潮汐湿地地下水流动特征

黄品怡1(), 唐常源1,2(), 禤映雪2, 江涛1, 曹英杰2   

  1. 1.中山大学,地理科学与规划学院,广州 510275
    2.中山大学,环境科学与工程学院,广州 510275
  • 收稿日期:2021-08-02 修回日期:2021-09-16 出版日期:2022-04-01
  • 通讯作者: 唐常源 E-mail:huangpy5@mail2.sysu.edu.cn;tangchy3@mail.sysu.edu.cn
  • 作者简介:黄品怡(1995—),女,广东兴宁人,硕士,研究方向为流域水循环与水化学,(E-mail)huangpy5@mail2.sysu.edu.cn
  • 基金资助:
    国家自然科学基金委员会面上项目(41877470);国家自然科学基金(42077154);广东省基础与应用基础研究基金区域联合基金青年基金项目(2021A1515110372)

Characteristics of Groundwater Flow in Tidal Wetland in Pearl River Estuary under Heterogeneous Conditions

Pinyi Huang1(), Changyuan Tang1,2(), Yingxue Xuan2, Tao Jiang1, Yingjie Cao2   

  1. 1.School of Geography and Planning, Sun Yat-Sen University, Guangzhou 510275, China
    2.School of Environment Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China
  • Received:2021-08-02 Revised:2021-09-16 Online:2022-04-01
  • Contact: Changyuan Tang E-mail:huangpy5@mail2.sysu.edu.cn;tangchy3@mail.sysu.edu.cn

摘要:

开展非均质条件下潮汐湿地中地下水流动特征研究,成为深入揭示潮汐湿地水循环及物质循环过程的重要前提。以广州南沙区的河畔潮汐湿地为对象,基于放射性氡同位素示踪技术考察含水层非均质情况下地下水的流动特征。结果表明:1)研究区介质干容重、介质孔隙度和介质氡释放(Ern)呈现空间异质性,介质氡释放是导致介质氡平衡能力([Rn]gw)呈现显著空间异质性(2 210.15~7 700.33 Bq/m3)的主要因素。2)非均质条件下地下水流动呈现显著的分区特征,根据氡的比活度可以划分为快速流动区和滞留区。其中快速流动区地下水氡比活度较小,观测期内平均值为1 522.39 Bq/m3,地下水呈现由陆向海近似“U”型的流动模式。滞留区地下水氡比活度显著增大,观测期内平均值为3 858.40 Bq/m3,地下水受潮汐作用而滞留更久。滞留区地下水流动状态受潮高差影响,潮高差越大,潮汐对湿地地下水的整体驱动力越大,滞留区地下水渗出相对容易,反之滞留区地下水渗出较难。由此可见,潮汐湿地含水层介质的空间异质性是影响地下水流动特征的关键因素。

关键词: 潮汐湿地, 空间异质性, 地下水动态, 222Rn, 珠江口

Abstract:

Groundwater flow in tidal wetlands is an important part of coastal estuarine hydrological cycle. The results of previous studies were based on the condition that the aquifer was homogeneous. Moreover, the understanding of groundwater circulation in tidal wetlands under heterogeneous aquifer medium is still insufficient. To explore the characteristics of groundwater flow in tidal wetlands under heterogeneous conditions and reveal the groundwater circulation process of wetlands, this study used a typical estuarine tidal wetland in Nansha District of Guangzhou as the research object. After analyzing the characteristics of the heterogeneous aquifer medium in the wetland, the groundwater flow characteristics under the heterogeneous aquifer were investigated using the radioactive radon isotope tracer technique. The results showed that the dry bulk density, porosity, radon release, and radon equilibrium capacity of the studied medium exhibited spatial heterogeneity. The dry bulk density of the medium varied from 0.39 to 1.44 g/cm3 and increased gradually from land to river and shallow to deep. The overall porosity of the medium varied from 0.42 to 0.78 without evident regularity. The main factor affecting the spatial distribution characteristics of the equilibrium capacity of the medium radon was its release. The former varied from 2210.15 to 7700.33 Bq/m3 and had a good positive correlation with the latter (R2=0.69). Under the condition of heterogeneous aquifer, the analysis of the total head of groundwater in the tidal wetland during ebb tide showed that the groundwater flowed from shallow to deep and land to river in the aquifer far from the tidal river. However, in the wetland aquifer close to the tidal river, the state of the groundwater flow changed and showed a trend from deep to shallow. According to the spatial distribution characteristics of radon specific activity, groundwater flow in tidal wetlands was divided into fast-flowing and retention zones. The radon-specific activity of the groundwater in the fast-flowing area was relatively low, with an average of 1522.39 Bq/m3 during the observation period. The groundwater showed an approximately U-shaped flow mode from land to river. The radon specific activity of groundwater in the retention area increased substantially, with an average of 3858.40 Bq/m3 during the observation period. In addition, the state of the groundwater flow in the retention area was affected by the difference in the tidal height. The larger the difference between the tidal heights, the greater the driving force of the tide on wetland groundwater; the seepage of groundwater in the retention area was relatively easy, and vice versa. Based on the actual heterogeneity of the aquifer, this study measured and analyzed the characteristics of groundwater flow in tidal wetlands, which is an important step relative to previous research on homogeneous conditions. It is of great importance to ascertain the groundwater flow in tidal wetlands under actual conditions. In the future, we can further clarify the influence mechanism of the heterogeneity of different media on the characteristics of groundwater flow in tidal wetlands, quantify the groundwater circulation process, and provide constructive suggestions for production activities and sustainable development.

Key words: tidal wetlands, spatial heterogeneity, groundwater dynamic, 222Rn, Pearl River Estuary

中图分类号: 

  • P641.2