Vernier Software and Technology
Vernier Software & Technology
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How do I compensate for salinity when measuring dissolved oxygen?

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

Temp (°C) Constant, k
1 0.08796
2 0.08485
3 0.08184
4 0.07911
5 0.07646
6 0.07391
7 0.07135
8 0.06916
9 0.06697
10 0.06478
11 0.06286
12 0.06104
13 0.05931
14 0.05757
15 0.05602
16 0.05456
17 0.05328
18 0.05201
19 0.05073
20 0.04964
21 0.04854
22 0.04754
23 0.04662
24 0.0458
25 0.04498
26 0.04425
27 0.04361
28 0.04296
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