BrianH

Brian - Thanks for your continue assistance. I am just really struggling to get these numbers right. But they are critical in marine work! I still cannot get any manipulation of the numbers to work. I did suppress ALL carbonate and bicarbonate complexes with any other cations. Obviously I left HCO3- and CO3-- unsuppressed. I then tried 1950umol/kg HCO3- (total DIC) and 1795umol/kg HCO3- free (and these did not return the right values where I was expecting to find them... which was really disturbing.). I also printed out the logK values, but these seem to be just the value at temperature with no correction for ionic strength, so this is not much use. (I.e., -6.36 and 10.34 for k1 and k2). For T = 25, S = 35, Alk = 2150, DIC = 1950, you should get HCO3- = 1785, CO32- = 148, CO2(aq) = 17 (ish) and pH = 7.87. I suppressed all carbonate and bicarbonate ion pairs, and get numbers that dont seem to make sense - .e.g, DIC adds up to 2020 with Alk at 1935? (At pH 7.88, we are still closer to the CO3-- side of the system...) I *think* the Ks are not adjusting properly... but how can i tell? GSS_seawater_Test.sp8

Thanks Brian, this is super helpful. However, in comparing my GWB output to 'standard' calculators of seawater alkalinity (e.g., 'CO2calc"), I still find offsets. I'll send a GWB example tomorrow, but you can try using a temp of 25°C, a salinity of 35 PSU (Cl- = 546; Na+ = 469; Mg++ = 53; SO4-- = 28; Ca++ = 10.3; K+ = 10.2 all in mmol/kg), then set HCO3- = 1795 umol/kg and pH = 7.80. The results should give Total Alkalinity = 2125; Tot DIC = 1950; HCO3- = 1795 (i.e., as set 'free'); CO3-- = 135; CO2(aq) = 20 (all in umol/kg). I find that GWB comes 'close' but seems to be 10, 20% (more?) off. This is a real problem with CO3--, especially. Do you find similar? (Note, this is very simple system, assumed total oxic, and with no redox chemistry.) Is there any way to have GWB output the actual Kds it uses for any given reaction? I'd be especailly interested to see what values of k1, k2 and kH GWB is using for the carbonate system at these conditions... Thanks a million!

Hi gang. I am all new to GWB, and so these may be dumb questions. But here you go: Ocean chemistry is largely a function of carbonate chemistry. I am really struggling to get GWB to give me numbers that look like those I hand calculate for carbonate chemistry. Technically, one should only need two numbers from the following variable to calculate the carbonate system: alkalinity, pH, Total inorganic Carbon (TotC), pCO2 (or other spps. of carbonate). I am struggling to figure out how to set any two of these in GWB. I have tried setting HCO3- as a basis (so one variable is established...to 2 mmol/kg for example), and pH (to 8.1 for example). But the resultant alkalinity is nonsensical. And GWB also alters the [HCO3-]... which it should, considering it is using the HCO3- variable as TotC (I think...?) Also - is there any way to hardwire the SpecE8 output files to give alkalinity (or carboante alkalinity) in other units (mole equivalents, for example)? Someone else asked about this, but I was baffled by the answer. Thanks for any help to get going. I'm sure once I figure out the logic, I will have fewer problems! - Brian