Chemical Parameters
Total Dissolved Solids
Definition
Ranges in Natural Water
Significance of Total Dissolved Solids
Significance to Fish and Aquatic Life
Electrical Conductivity
Definition
Range and Significance
Primary Cations and Anions
Calcium
Sources
Significance
Significance to Fish and Aquatic Life
Significance
Magnesium
Sources
Significance
Hardness
Sodium
Potassium
Carbonate and Bicarbonate
Sulfate
Chloride
Primary Nutrients and Eutrophication
Nitrogen
Phosphorus
Significance of the Primary Nutrients
The Concept of Eutrophication
pH
Alkalinity
Acidity
Interrelationships of Acidity and Alkalinity
Fluoride
Iron
Manganese
Aluminum
Toxic Constituents
Heavy Metals
Copper
Mercury
Nickel
Silver
Zinc
Non-Metals
Arsenic
Cyanide
Boron
Bromine
Iodine
Dissolved Gases
Dissolved Oxygen
Biological Oxygen Demand
Chemical Oxygen Demand
Total Organic Carbon
Carbon Dioxide
Pesticides
Oil
Water contains a variety of chemicals.
Practically all of the naturally occurring elements of the Earth’s crust could probably be found in natural waters. However, some of these substances would be expected to occur only in minute concentrations. In addition to the gaseous components, chemicals are found in varying quantities in natural waters include carbonates, chlorides, sulfates, phosphates and often nitrates. These anions occur in combination with cations such as calcium, sodium, potassium, magnesium and iron to form different ionizable salts.
As a result of availability and high solubility of carbon dioxide in water, carbonates are usually the most abundant salts in fresh waters. Both the quantitative and qualitative aspects of the chemical composition of natural waters are influenced to a high degree by the geochemistry of the watershed. And in the case of lakes, influenced by the form and geology of the basin with respect to inflow and outflow. In general, the inorganic composition of the water of an open lake (that is one with effluents) through which water moves is a reflection of the nature of the influent Waters. The inorganic composition of closed lakes (those lacking significant effluents) is greatly modified by precipitation and concentration of salts as determined by evaporation. Also, lakes near the ocean coast may receive substances from sea spray and moist ocean air.
Chemical Water Quality Parameters
The main differences between lake and stream chemical characteristics usually pertain to relative concentrations, composition, and longitudinal distribution of the substances. Seasonal variation in rainfall and surface runoff along with the geochemical nature of the drainage basin strongly influence the composition of waters of small streams. This combination imparts considerable individuality to streams even within a restricted area or region.Waters from large streams and rivers, on the other hand, typically exhibit general uniformity of composition, so much so that a quantitative expression of average content becomes meaningful. The mean composition, as percentage proportions of major cations of river water has been given as:
Calcium – 63.5%, Magnesium – 17.4%, Sodium – 15.7%, and Potassium – 3.4%.
Note: that the order of prominence here differs only slightly from that of the North American. In fact, the average composition of rivers is quite similar to that of open lakes, as might be expected.
Next Topics…
Total Dissolved Solids
Electrical Conductivity
Primary Cations and Anions
Primary Nutrients and Eutrophication
pH
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Toxic Constituents
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