Factors That Affect Conductivity in Water

Electrical conductivity is the property of water to conduct electricity from an area of high electric field to an area of low electric field, by the help of dissolved ions that act as conductors. An ion is an atom that is freed from an element and carries either a positive charge or a negative charge. Although metals are far more effective conductors, water also has the ability to conduct electricity. There are several factors that affect the electrical conductivity of water, such as total dissolved solids (TDS, or concentration of salts in water), mineral purity and temperature of water.

TDS or Salinity of Water

• Saline water conducts electricity much more effectively and more readily than pure water. This is because the dissolved ions enhance salinity, as well as increase conductivity. Salts that usually cause salinity in aqueous medium are sulfates, carbonates, chlorides, potassium, sodium, calcium and magnesium. It is the electrical conductivity, which differentiates between the types of water (i.e. ground water, runoff water, water drained from agricultural fields and rainfall). Furthermore, various sub-factors, such as geology, soil, land use and flow of water (i.e. conductivity increases as water flow decreases) also affect the salinity of water, thus influencing electrical conductivity.

Mineral Purity

• The electrical conductivity of pure water is low, but it can be greatly increased by soluble impurities that will ionize the water (such as common salt). Pure water consists of one oxygen and two hydrogen atoms. The oxygen atoms share covalent bonding (i.e. a chemical bond formed between atoms by the sharing of electrons). Therefore, one oxygen atom can bond covalently with two hydrogen molecules (celled “dihydrogen”). Electricity travels easily and readily through materials having atoms that form an ionic bond (i.e. a chemical bond formed between oppositely charged species because of their mutual electrostatic attraction). Oxygen atoms in the water pull the electrons strongly, thereby developing a negative charge. On the other hand, dihydrogen forms a positive charge, thus resulting into negligible transfer of electric flow. If impurities (minerals) are added to the water, the ionic bonds conduct electricity and the electrolytic conductivity of water increases.

Temperature

• Electrical conductivity in water invariably increases with an increase in temperature. Warm water is less viscous and has greater electronic movement, thus allowing free flow of electric current. It is generally expressed as a relative change per degree Celsius, at a particular temperature. Small variation or difference in temperature reports a marked difference in conductivity, and therefore, readings are normally referenced to 25 degrees Celsius. Generally, conductivity increases by about 2 percent for every degree rise in temperature.