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Chloride and Salinity

What is chloride and salinity?
1. Chloride (Cl-) is one of the major inorganic anions, or negative ions, in saltwater and freshwater. It originates from the dissociation of salts, such as sodium chloride or calcium chloride, in water. Chlorides are binary compounds of chlorine. Chlorine chemically combines with a metal to from chloride.
2. Salinity is the total of all non-carbonate salts dissolved in water. This is comprised mosty by Cl- and Na+ ions. Seawater may have other ions, such as K+, Mg2+, or SO42-.

What factors influence the amount of chloride and salinity in your watershed?
1. When hydrochloric acid reacts with any metal in water, chloride is naturally formed.
2. Chloride is common in areas with limestone deposits, but is not found in most other soils, rocks, or minerals.
3. Water pollution may be the cause of chloride found in areas where it does not naturally occur. Some sources may be from rock salt (NaCl) runoff. Other sources may be from septic tank effluent, animal waste, water softener regeneration, chlorinated drinking water, and potash fertilizer (KCl).
4. Sources of chloride ions may come from the mixing of seawater with freshwater.
5. High salt concentrations may occur in arid regions of the United States when evaporated irrigation waters are returned to the rivers.

What is the optimal amount of chloride and salinity in a watershed?
1. A chloride range of 45-155 mg/L for a river is considered normal.
2. A chloride range of 35-125 mg/L for groundwater is considered normal.
3. When the chloride concentration is greater than 250-400 mg/L, the water will taste salty.
4. Seawater has a chloride concentration of about 19,400 mg/L.
5. Seawater has a salinity of 35,00 mg/L.
6. Brackish water has a chloride concentration between 500-5,000 mg/L.
7. Brackish water has a salinity of 1,000-10,000 mg/L.
8. Freshwater has a chloride concentration from1-250 mg/L.
9. Freshwater has a salinity concentration between 1-500 mg/L.

What factors are affected by the amount of chloride and salinity in a watershed?
1. Chloride contaminates rivers and groundwater and can make it unsuitable for humans to drink.
2. High levels of chloride can kill aquatic plants and animals.
3. The salt concentration of water affects the distribution of aquatic plants and animal species according to the amount of salinity they can tolerate. Saltwater organisms may survive in salinity levels up to 40,00 mg/L, yet many freshwater organisms cannot live in salinity levels above 1,000 mg/L.



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