The primary sources of salinity in groundwater include the dissolution of salts, evaporation from shallow groundwater, a combination of both, and connate water.
Here's a breakdown of these key contributors:
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Dissolution of Salts: This is a significant source, accounting for approximately 26% of the total area affected by saline groundwater. As groundwater flows through geological formations containing soluble salts (like halite, gypsum, etc.), it dissolves these minerals, increasing the salinity.
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Evaporation from Shallow Groundwater: In areas with shallow water tables and arid or semi-arid climates, evaporation can concentrate salts in the remaining groundwater. This process accounts for about 20% of the area with saline groundwater.
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Combination of Evaporation and Dissolution: In some regions, both evaporation and dissolution processes contribute significantly to groundwater salinity, representing about 13% of the total area.
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Connate Water: Connate water, or fossil water, is water trapped within sedimentary rocks during their formation. This water often has high salinity due to long-term interaction with the surrounding rock matrix. It contributes to groundwater salinity in approximately 14% of the total area.
In summary, the salinity of groundwater arises from natural processes involving the dissolution of minerals, concentration through evaporation, and the presence of ancient, highly saline waters.
