Conductivity, Salinity, TDS
Conductivity is a measure of the water’s ability to conduct electricity
Salts and other inorganic chemicals form electrically charged particles called ions
Pure water is a poor conductor of electricity
Conductivity is a measure of the ionic strength of water
(cathode/anode)
Conductivity is usually reported as specific conductance – temperature compensated conductivity to 25 °C
Conductivity probes detect the AC resistance between two electrodes
Salinity is then calculated from this conductivity value
Salinity is the total concentration of all dissolved salts in water
The most common ions in sea water (chloride, sodium, magnesium, sulfate, calcium, potassium, bromine)
Total dissolved solids (TDS) combine the sum of all ion particles that are smaller than 2 microns
EPA recommends an upper limit of 500 mg/L TDS
Units of measure
Salinity – ppt
Conductivity – mS/cm & uS/cm
TDS – mg/L
INTERESTING FACT
The higher the dissolved salt concentration, the higher the density of water. This increase in density with salt levels is one of the driving forces behind ocean circulation
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