Why are my ion concentrations larger in the aqueous phase column than in the total column?
A user reported that the ion concentration in a report are larger in the aqueous phase column than in the total column. Why is that?
The problem here is perception. The results are correct but it is sometimes difficult to mix and match concentration units. The Total column is for all phases while the Aqueous is just for the water-rich phase.
Let’s look at an example and specifically the species Sr2+ ion (because it is near the top of the report):
It does appear that the total value of 337 mg/L is less than the amount in the aqueous phase of 366 mg/L. However the “L” is different in each column. To make this clearer let’s switch units sets to a mass basis instead of concentration basis. See How to change units
You can see that the mass values are identical. What is different is the total volume. This is in a different section of the report:
(note I had to change units here too).
You can see that the total value is slightly larger than the aqueous value so the mg/L calculations are going to be different. So for Sr2+ ion in the total column the value is:
For the aqueous column it is much the same except for a different volume:
It is important to keep the values consistent.