Can someone help me to convert pH values measured in a microalgae culture in CO2 concentrations. I suspect that there is not a direct relation but someone has an idea about how to obtain this concentration value.
Thank you in advance
pH and CO2 are connected, but you need to know the alkalinity to be able to calculate (rather estimate) the dissolved CO2 from the pH.
pH and CO2 are connected, but you need to know the alkalinity to be able to calculate (rather estimate) the dissolved CO2 from the pH.
Hi Lazaro,
It is exactly as Henrik mentions here above, but it would take you (quite) some time to figger out the mathematics of the basic equations to estimate CO2 from pH and alkalinity.
Therefore look at:
Mathematics of the total alkalinity–pH equation – pathway to robust and universal solution algorithms:the SolveSAPHE package v1.0.1 from G. Munhoven D́epartment of Astrophysics, Ǵeophysics and Oćeanography, Universit́é de Liège, 4000 Liège, Belgium
Correspondence to: G. Munhoven ([email protected])
Guy elaborated the whole set of equations and came to a set of equations which always give a solution for CO2 concentration in function of pH and alkalinity.
I added Guy's paper for your convenience.
Have fun,
Frank
There are free spreadsheets available at the websites below that calculate the corrosion rate steel in an environment that contains CO2. A portion of each of these spreadsheets is the calculation of pH as a function of temperature, CO2 partial pressure and alkalinity/bicarbonate concentration. You could trial and error the CO2 levels to find your pH to reverse the process and get your answer. In the case of the NORSOK spreadsheet, make certain that you select the "formation water" option to avoid calculations that only apply to pure water with no dissolved salts. Finally, both of these spreadsheets require you to run either as an Excel add-in or macro. Either of these situations usually requires you to enable an Excel feature that is usually turned off for security purposes.
http://www.corrosioncenter.ohiou.edu/software/freecorp/
https://www.standard.no/en/sectors/energi-og-klima/petroleum/norsok-standard-categories/m-material/m-5061/
As mentioned above, you need the alkalinity (or the total dissolved inorganic carbon) to get to CO2 from pH.
Once you have alkalinity (or DIC) other good tools for CO2 / carbonate calculations include CO2sys (excel: available at http://cdiac.esd.ornl.gov/oceans/co2rprt.html).
The r-project also has a very nice library called seacarb (http://www.obs-vlfr.fr/~gattuso/seacarb.php). Good luck.
If pH is below about 8.5 you can estimate that the alkalinity is approximately equal to the hydrogen carbonate concentration: Log[HCO3-]=LogKH+LogPco2+LogKs1+pH.
At 20 °C LogKH= -1.41 and LogKs1 = -6.38.
Yes, you can using the spreadsheet version of CO2SYS to calculate the pCO2 of water from temperature, salinity, pH and total alkalinity
Yah sir, i have used that software to find the conversion sir. thank you so much!!!!
Henrik Rasmus Andersen I am dealing with this as well and want to use your equation for pH below 8.5. Just to be sure, the [HCO3-] is in which unit, µmol/l or mg/l?
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