For most dissolved oxygen testing, it is not necessary to compensate for salinity. However, when measuring dissolved oxygen concentration in highly saline water (>1 part per thousand salinity), the calibration value entered into the software for air-saturated water (from standard tables) should be adjusted. To determine the adjusted value, use the formula:

DO(salt) = DO – (k*S)

Where:
– DO(salt) is the dissolved oxygen concentration (in mg/L) of air-saturated salt water.
– DO is the dissolved oxygen concentration (in mg/L) of air-saturated distilled water as determined from standard tables (found in the sensor’s user manual).
– S is the salinity value (in parts per thousand) of the sample.
– k is a constant. The value of k varies according to the sample temperature, and can be determined from the table below.

Salinity correction constant values