Processes > Reactive transport modelling

Isotopes output in PhreeqcRM

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GeeqC:
For the output of isotope ratios the following keywords seem to work:

SELECTED_OUTPUT
-isotopes R(13C)_CO2(aq) R(13C)_HCO3-

Of course, the delta value can be calculated as: Delta = (R - Rstd)/Rstd * 1000

But I wonder if this is necessary, since the database already contains Rstd and delta values may already have been calculated internally. Is there a keyword to directly select delta values as selected output?

dlparkhurst:
You should look at the results, and read the manual for the -isotopes option of SELECTED_OUTPUT.

You could also look at the Basic functions ISO and ISO_UNITS.

GeeqC:
The User manual says:
"The -isotopes identifier allows isotopic values in the units of the isotope standard to be written to the selected output file. The isotopic values are identified by the names of CALCULATE_VALUES Basic functions that have been identified in the ISOTOPE_RATIOS data block."

If these "isotopic values" are 'in the units of the standard', I suppose they are deltas?
But what confuses me is that they are labelled as 'I_R...' in the output.

dlparkhurst:
They are permit for 13C. You will have to deal with it.

GeeqC:
You mean:
delta13C = (R - Rstd)/Rstd * 1000  in permille? So, this is calculated internally in Phreeqc?

This is what I need.

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