School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India.
J Contam Hydrol. 2023 May;256:104197. doi: 10.1016/j.jconhyd.2023.104197. Epub 2023 May 6.
Seawater intrusion has become a common problem in coastal and island aquifers with the rise in climate change that greatly affects the majority of developing countries. The island hydrology is very complex and associated with a unique set of environmental characteristics with the dynamic interaction of groundwater, surface water, and seawater. Further, Sea level rise, erratic rainfall, and over-extraction of groundwater triggered salt-water intrusion. A study on seawater intrusion and the effect of limestone caves on groundwater was carried out in middle Andaman using a combination of ionic ratios of major ions. A total of 24 samples and a reference sample from the sea were collected and analysed using ICP, spectrophotometer, and flame photometer. A combination of 10 ionic ratios Cl/HCO, Ca/(HCO + SO), (Ca + Mg)/Cl, Ca/Mg, Ca/Na, Cl/(SO + HCO), Ca/SO, K/Cl, Mg/Cl, and SO/Cl was used to assess the dissolution of limestone minerals and the level of saltwater intrusion into groundwater. The geospatial method was used to extract and combine all the hydrogeochemical parameters and ionic ratios in the GIS platform. Durov plot was used for the interpretation of groundwater chemistry and the identification of natural processes controlling the hydrogeochemistry of the area. The dominance of Ca-HCO and Na-HCO was confirmed in 48% and 24% of the sample respectively. The equiline graph of chloride with other major ions showed the enrichment of alkali and alkaline earth metal salt in groundwater. Schoeller's diagram depicted the dominance of Cl, Ca, and the sum of CO and HCO in seawater near Mayabunder. The lower concentration of Na with respect to Cl (64%) and Ca (100%) showed the presence of a reverse ion exchange process. Further, the correlation matrix showed a strong relationship between Cl, K, Ca, and Na. The analysis of X-ray diffraction of the rock samples confirmed the presence of limestones such as Aragonite, Calcite, Chlorite, Chromite, Dolomite, Magnetite, and Pyrite in the study area. The integration of ionic ratios showed moderately affected and slightly affected saline regions in 44% and 54% of the region respectively. Finally, the role of tectonic activities and active lineaments connected to the sea was found to play a major role in the intrusion of seawater where interconnected faults created an opening for surface water to recharge groundwater leading to the deep aquifer.
海水入侵已成为气候变化背景下沿海和岛屿含水层的一个常见问题，这对大多数发展中国家产生了重大影响。岛屿水文学非常复杂，与地下水、地表水和海水的动态相互作用有关。此外，海平面上升、降雨不稳定和地下水过度开采引发了海水入侵。在安达曼中部，使用主要离子的离子比组合对海水入侵和石灰岩洞穴对地下水的影响进行了研究。共采集并分析了 24 个样本和一个来自海洋的参考样本，使用 ICP、分光光度计和火焰光度计。使用 10 种离子比 Cl/HCO3、Ca/(HCO3+SO4)、(Ca+Mg)/Cl、Ca/Mg、Ca/Na、Cl/(SO4+HCO3)、Ca/SO4、K/Cl、Mg/Cl 和 SO4/Cl 的组合来评估石灰岩矿物的溶解程度以及海水入侵地下水的程度。地理空间方法用于提取和结合 GIS 平台中的所有水文地球化学参数和离子比。杜罗夫图用于解释地下水化学并确定控制该地区水文地球化学的自然过程。在 48%和 24%的样本中分别证实了 Ca-HCO3 和 Na-HCO3 的优势。氯与其他主要离子的等直线图显示了地下水中碱性和碱性土金属盐的富集。Schoeller 图描绘了靠近梅阿班德的海水中 Cl、Ca 和 CO 和 HCO3 总和的优势。与 Cl（64%）和 Ca（100%）相比，Na 的浓度较低表明存在反向离子交换过程。此外，相关矩阵显示 Cl、K、Ca 和 Na 之间存在很强的关系。岩石样本的 X 射线衍射分析证实了研究区存在霰石、方解石、绿泥石、铬铁矿、白云石、磁铁矿和黄铁矿等石灰岩。离子比的综合分析表明，在 44%和 54%的区域内，受海水入侵影响的区域分别为中度影响和轻度影响。最后，发现构造活动和与海相连的活动线性构造在海水入侵中发挥了重要作用，因为相互连接的断层为地表水补给地下水创造了一个开口，导致深部含水层。
