pHnbs2sws {seacarb}

Converts pH from NBS to SWS scale

Description

Converts pH on NBS scale to pH on SWS scale pCO2. The NBS-to-SWS conversion is done with the total activity coefficient fH (combined activity coeff for H+, HSO4-, and HF) from Takahashi et al. (1982) based on data from Culberson and Pytkowicz (1973). The approach is old and full of uncertainty. Newer approaches are more complicated (Pitzer equations) and big uncertainties remain (Marion et al., 2011; Pilson, 2013).

Usage

pHnbs2sws(pHNBS, S=35, T=25)

Arguments

pHNBS

pH on NBS scale

S

Salinity on the practical salinity scale, default is 35

T

Temperature in degrees Celsius, default is 25oC

Details

The pHSWS is computed from pHNBS using the total activity coefficient and relying on the following basic chemistry equation: ah = fH * hsws, where ah is the activity of hydrogen ion, fH is the total activity coefficient, and hsws = [H+] + [HSO4-] + [HF]. In other words, hsws is the hydrogen ion concentration on the seawater scale.

The two pH scales are defined as pHNBS = -log10(ah) and pHSWS = -log10(hsws).

Value

pHSWS

pH on SWS scale

Author(s)

James Orr [e-mail]

References

Culberson, C.H., & Pytkowicz, R.M. (1973). Ionization of water in seawater. Marine Chemistry, 1(4), 309-316.

Marion G.M., Millero F.J., Camoes M.F., Spitzer P., Feistel R., Chen C.T.A. 2011. pH of seawater. Marine Chemistry 126 89-96.

Pilson M.E.Q. (2013) An introduction to the chemistry of the sea, 2 edn. Cambridge, UK: Cambridge University Press.

Takahashi T., Williams R.T., and Ros D.L. (1982) Carbonate chemistry. GEOSECS Pacific Expedition, Volume 3, Hydrographic Data 1973-1974, 77-83.

See Also

fH and pHsws2nbs

Examples

## Convert pHNBS to pHSWS
   pHNBS = 8.0                          # pH on the NBS scale
   pHSWS = pHnbs2sws(pHNBS, T=25, S=35) # pH on the SWS scale
   print(pHSWS)
## Check value: the result should be 7.853336