Conductivity ranges between water bodies, but typically lakes and streams have a conductivity range between 0-200 µS/cm, while major rivers can have a conductance value up to 1000 µS/cm. Water that has a conductivity range of 1000-10,000 µS/cm indicates that it is saline.
Electrical conductivity (EC) refers to a solution’s ability to carry an electrical current, measured in microsiemens per centimeter (µS/cm).
Water can conduct electricity because of the ion concentration within the water, which comes from dissolved solids and inorganic materials like carbonate compounds, chlorides, and sulfides like sodium (salt). The conductivity range also depends on the ion’s potential to bind with water.
Why Are Conductivity Ranges Important In Water?
Conductivity ranges tell us a lot about the quality of water because it is a direct measurement of how many pollutants and contaminants are in the water and an indirect measurement of salinity.
Fish and other aquatic organisms that live in freshwater cannot tolerate large increases in salinity, therefore measuring the conductivity range is important to create stable environments.
Measuring conductance values can also indicate if water has become polluted from human factors such as agricultural and impervious surface runoff, septic leachate, and the use of road salts. However, it is important to mention that not all sources of water pollution are indicated by conductivity changes. For example, as oil doesn’t conduct electricity, oil spills would not be detected when measuring the conductivity in water.
Freshwater and seawater have typical ranges, yet, there is no set standard for the conductivity of water because of the effect surrounding environments have on electrical conductivity. Despite the lack of set standards, there are approximate conductivity ranges for water.
To determine conductivity ranges, a history of conductivity measurements is recorded to establish the range for each particular body of water. The conductivity ranges can then be used as a baseline against current measurements.
The typical conductance ranges are displayed below:
Freshwater has a low conductivity range due to the lack of salt ions present in the water, however, freshwater that flows through clay and limestone soils has a higher conductivity value because of the presence of materials that ionize when flushed into the water, hence the large range.
In estuaries, the conductivity range varies depending on freshwater and saltwater in and outflows. Saltwater has a greater conductance range than estuaries and rivers because of the high salt ion content (35 ppt; parts per thousand), therefore the conductivity of seawater is dependent on the salinity and also the temperature of the water.
Typically, the conductivity and salinity of seawater remain constant around the world, yet surface salinity is dependent on the amount of rainfall. This is why oceanographers measure the conductivity of seawater at different depths with a CTD (conductivity, turbidity, depth) measurement tool.
Implications Of Unusual Conductivity Ranges
Unusual conductivity ranges and salinity are often indications of water pollution. Naturally, low levels of salt are found in waterways, but often this increases from natural and human impacts. When salts increase in freshwater, it causes issues for aquatic ecosystems and complicates human uses due to poor water quality.
When conductivity ranges exceed the usual range, it is detrimental to aquatic life, which is why many species have adapted to fluctuations in salinity. Those that cannot migrate or adapt to conductivity changes will not survive.
Conductivity Ranges And Uses
As conductivity ranges determine how much electricity can pass through the water, different conductivity ranges have specific uses.
0-800 µS/cm: Drinking water supplies, irrigation, and all livestock.
800-2,500 µS/cm: Irrigation, all livestock, and sometimes drinking water (lower conductance ranges are preferred).
2,500-10,000 µS/cm: This conductance range is not recommended for drinking water supplies, but up to 3,000 µS/cm is still considered safe. It is used for irrigation up to 6,000 µS/cm on very salt tolerant crops. With regard to livestock, pigs can tolerate levels up to 6,000 µS/cm, but all other livestock can survive on levels up to 10,000 µS/cm.
>10,000 µS/cm: This range is not suitable for drinking water or irrigation. Only beef cattle can use water that has a conductance level lower than 17,000 µS/cm and adult sheep fed dry food can tolerate levels up to 23,000 µS/cm, all other livestock cannot utilize levels greater than 10,000 µS/cm. Conductance levels that exceed 10,000 µS/cm are therefore primarily used to flush toilet systems (up to 50,000 µS/cm) and in concrete production.
The conductivity probe is inserted into the water, and an electrical current flows between the two electrodes inside, reading the electrical current and providing the conductance value.
As mentioned, conductivity is typically measured in microsiemens per centimeter (µS/cm), however, it can also be measured as specific conductivity. Specific conductivity is a standardized measurement that shows the conductance level at 25℃ (77℉). For that reason, the temperature of the water is often measured alongside conductivity with a temperature probe.
Conductivity measurements are of paramount importance in water quality assessment, as high or low conductivity ranges are used to detect environmental changes and pollution.
Conductivity measures the ability of water to conduct electricity and is directly related to the number of ions present in the water. Typical water values vary depending on the type of water. Uncontaminated freshwater contains no salt ions and therefore has a low conductance range of 10-2,00 µS/cm. Saltwater contains salt ions, so the conductance range is much higher (55,000 µS/cm).
If you have any questions regarding the conductivity of water or what testing kits we have to offer, do not hesitate to contact our world-class team at Atlas Scientific.
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