Factors controlling mechanisms of groundwater salinization and hydrogeochemical processes in the Quaternary aquifer of the Eastern Nile Delta, Egypt
Factors controlling mechanisms of groundwater salinization and hydrogeochemical processes in the Quaternary aquifer of the Eastern Nile Delta, Egypt
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DOI：
10.1007/s12665-012-1744-6
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发表时间：
2012
影响因子：
2.8
通讯作者：
M. A. Ahmed;S. A. Abdel Samie;H. Badawy
中科院分区：
文献类型：
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作者：
M. A. Ahmed;S. A. Abdel Samie;H. Badawy
本研究结合水中保守溶解离子和环境同位素的解释，研究了控制埃及东尼罗河三角洲地下水盐化和水文地球化学过程的主要因素和机制。对研究区61个水样进行了水文地球化学和同位素研究。地下水的总溶解固体 (TDS) 含量沿着流道从南边 (410 mg/L) 到北边 (14,784 mg/L) 变化很大，这意味着地下水严重恶化和盐化。根据 TDS 和离子比，地下水样品分为三组。在低盐度组中，水化学很大程度上受到阳离子交换、矿物质溶解/沉淀、人为污染物以及与地表水混合的影响。而在高盐度组中，水化学会受到盐水入侵、反向阳离子交换和蒸发的影响。使用离子增量和饱和指数方法成功区分了源自咸水源、反向离子交换和矿物溶解的化学成分。 δ18O-δ2H 关系绘制在典型的蒸发线上，表明补给水在渗透之前可能会蒸发。同位素证据得出的结论是，地下水是在不同气候条件下补给的枯竭大气水和最近渗透的富集地表水和过量灌溉水混合形成的。 δ18O 数据与氯化物浓度相结合，为过去地质时期海洋起源蒸发岩沉积物的溶解对北部地区地下水盐度的影响提供了确凿的证据。此外， 14 C活性和Cl-浓度之间的关系证实了这一假设。
In this study, combining interpretations of conservative dissolved ions and environmental isotopes in water were used to investigate the main factors and mechanisms controlling groundwater salinization and hydrogeochemical processes in the Eastern Nile Delta, Egypt. Hydrogeochemical and isotopic study has been carried out for 61 water samples from the study area. Total dissolved solid (TDS) contents of groundwater are highly variable rising along flowpath from the south (410 mg/L) to the north (14,784 mg/L), implying significant deterioration and salinization of groundwater. Based on TDS and ionic ratios, groundwater samples were classified into three groups. In low-saline groups, water chemistry is greatly influenced by cation exchange, mineral dissolution/precipitation, anthropogenic pollutants and mixing with surface water. Whilst, in high-saline groups, water chemistry is affected by salt-water intrusion, reverse cation exchange and evaporation. The chemical constituents originating from saline water sources, reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta and saturation index approaches. The δ18O–δ2H relationship plots on a typical evaporation line, suggesting potential evaporation of the recharging water prior to infiltration. Isotope evidence concludes that the groundwater have been considerably formed by mixing between depleted meteoric water recharged under different climatic conditions and recently infiltrating enriched surface water and excess of irrigation water. The δ18O data in conjunction with chloride concentrations provide firm evidence for impact of dissolution of marine-origin evaporite deposits, during past geologic periods, on groundwater salinity in the northern region. Moreover, the relation between14C activities and Cl−concentration confirms this hypothesis.