Tropical Hydrogeology and Environmental Engineering, Institute of Applied Geosciences, Technical University Darmstadt, Germany.
Remote Sensing of Water Systems, Department of Geography, University of Zurich, Switzerland.
Sci Total Environ. 2020 Apr 15;713:136668. doi: 10.1016/j.scitotenv.2020.136668. Epub 2020 Jan 15.
Increasing water salinity in coastal areas is a concern for the coastal environment. Increased salinity is affecting water quality, freshwater availability, and water-related ecosystems in the southwest coastal region of the Bengal Delta. The study used a synergies and robust approach to assess the possible factors for increasing water salinity in an embanked coastal island in the southwest Bengal Delta. The hydrochemical analysis revealed that surface and groundwater are enriching with Na and Cl concentration, also controlling by seawater through the ion exchange mechanism (Ca and Mg replacing by Na, and Cl), mixing stage of water solution (freshwater-saltwater), and anthropogenic salt contamination by human activities (e.g., saltwater shrimp cultivation and excessive irrigation). Piper diagram showed that river water is occupying at the mixing stage of solution, where pond and groundwater are occupying at seawater (saline) zone. The water quality index showed that surface water is not fresh anymore and unsuitable for drinking purposes. The isotope analyses exposed the presence of strong precipitation variance in the study area. Cluster observation analysis showed a strong correlation between Na, Cl, and TDS (similarity is 97% to 99%). The remote sensing application illustrated that high salinity zones are in the northern part, and groundwater salinity is higher (7.5 to 8 ppt) in the northern part of polder 32. The salinity of both groundwater and surface water showed a positive correlation with land surface temperature and potential evapotranspiration. The study exposed four responding factors for increasing groundwater salinity in this region, which are - regional surface geological settings, hydrological settings, hydraulic head gradient, and human activities. A conceptual model illustrated the presence of lateral recharge of saltwater from the surrounding tidal rivers to the groundwater.
沿海地区的水盐度增加是沿海环境的一个关注点。在孟加拉三角洲西南沿海地区，水盐度的增加正在影响水质、淡水资源的供应以及与水有关的生态系统。本研究采用协同作用和稳健的方法来评估在孟加拉三角洲西南沿海地区的一个堤坝状沿海岛屿上增加水盐度的可能因素。水化学分析表明，地表水和地下水的 Na 和 Cl 浓度增加，这也是通过离子交换机制（Ca 和 Mg 被 Na 和 Cl 取代）、水溶液的混合阶段（淡水-咸水）以及人类活动（如咸水虾养殖和过度灌溉）导致的海水污染控制的。Piper 图表明河水处于溶液的混合阶段，而池塘和地下水处于海水（咸水）区。水质指数表明地表水不再新鲜，不适合饮用。同位素分析揭示了研究区域存在强烈的降水变化。聚类观测分析表明 Na、Cl 和 TDS 之间存在很强的相关性（相似性为 97%至 99%）。遥感应用表明，高盐度区位于北部，而 32 号圩区北部的地下水盐度更高（7.5 至 8 ppt）。地表水和地下水的盐分与地表温度和潜在蒸散量呈正相关。研究揭示了该地区增加地下盐水盐度的四个响应因素，包括区域地表地质环境、水文环境、水力头梯度和人类活动。一个概念模型说明了周围潮汐河流向地下水侧向补给盐水的存在。
