The measure of salt dissolved in water is called salinity.
Salinity quantifies the amount of dissolved salts present in a body of water. It's a crucial parameter in oceanography, limnology (the study of inland waters), and environmental science because it influences water density, osmotic pressure, and the distribution of aquatic life.
How Salinity is Measured
Salinity is typically expressed in:
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Parts per thousand (ppt): This represents the number of grams of salt dissolved in 1000 grams of water. For example, a salinity of 35 ppt means there are 35 grams of salt in every 1000 grams of water.
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Percentage (%): This represents the number of grams of salt dissolved in 100 grams of water. This is less common than ppt for scientific measurements.
Salinity Levels in Different Water Bodies
| Water Body | Salinity (ppt) |
|---|---|
| Freshwater (Rivers) | 0.5 or less |
| Brackish Water | 0.5 to 30 |
| Seawater (Oceans) | 30 to 50 |
| Saline Lakes (e.g., Dead Sea) | Greater than 50 |
Factors Affecting Salinity
Several factors influence the salinity of a water body:
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Evaporation: Higher evaporation rates increase salinity as water is removed, leaving the salts behind.
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Precipitation: Rainfall and snowfall dilute the water, decreasing salinity.
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River Runoff: Freshwater input from rivers lowers salinity near river mouths.
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Ice Formation: When seawater freezes, the salt is largely excluded, increasing the salinity of the remaining water.
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Melting Ice: Conversely, melting ice adds freshwater, reducing salinity.
Understanding salinity is vital for assessing water quality, studying marine ecosystems, and managing water resources.
