As near as I can tell, it has been a month since the last
communication to the list on this proposal (for pH names). Is there
an appropriate next step to take at this point?
John
----------
Subject: Re: [CF-metadata] new standard name request for pH
Date: March 25, 2009 11:05:22 AM PDT
Per Roy's keen suggestion, here are some definitions for the 4 terms
for pH, provided by my scientific expert. A reference for those
interested is [1].
sea_water_pH_NBS_scale: the measure of acidity of sea water, defined as
the negative logarithm of the activity of dissolved hydrogen ions; it
can be measured or calculated; when measured, the scale is defined
according to standard solutions from the National Institute of Standards
and Technology (formerly NBS). This scale is acceptable for freshwater
pH measurements, but because of the large difference in ionic strength
between seawater and these buffers which significantly changes the
liquid
junction potentials, it is generally not recommended that seawater pH be
measured on this scale. [canonical units = moles/liter]
sea_water_pH_free_scale: the measure of acidity of sea water, defined as
the negative logarithm of the concentration of dissolved hydrogen ions
in a seawater medium; it can be measured or calculated; when measured
the scale is defined according to a series of buffers prepared in
artificial seawater. pH(free) = - log[H+](free). [canonical units =
moles/kg ].
sea_water_pH_total_scale: the measure of acidity of sea water, defined
as the negative logarithm of the concentration of dissolved hydrogen
ions plus bisulfate ions in a seawater medium; it can be measured or
calculated; when measured the scale is defined according to a series of
buffers prepared in artificial seawater containing bisulfate.
pH(total) = - log([H+](free) + [HSO4-]). [canonical units = moles/kg ].
sea_water_pH_seawater_scale: the measure of acidity of sea water,
defined as the negative logarithm of the concentration of dissolved
hydrogen ions plus bisulfate ions plus hydrogen fluoride in a seawater
medium; it can be measured or calculated; when measured the scale is
defined according to a series of buffers prepared in seawater
containing both sulfate and fluoride ions.
pH(sws) = - log([H+](free) + [HSO4-] + [HF]). [canonical units = moles/
kg ].
John
[1] Zeebe & Wolf-Gladrow (2001). CO2 in Seawater: Equilibrium, Kinetics,
Isotopes. Published by Elsevier as part of their oceanographic series.
On Mar 11, 2009, at 6:18 AM, Roy Lowry wrote:
> Hi John,
>
> How about a nice concise definition to store with the standard name?
>
> Might it also be useful to capture the expertise you have behind
> this proposal and create a full set of pH standard names, embracing
> the scales you mention (that are new to me) and the version widely
> used outside the carbonate system community based on moles of
> hydrogen ion per litre?
>
> Cheers, Roy.
>
>>>> John Graybeal <graybeal at mbari.org> 03/09/09 8:12 PM >>>
> In the ocean we are measuring pH, and I have not found a term for pH
> in the standard names. We therefore propose for our particular
> measurement
>
> sea_water_pH_total_scale
>
> Two notes: First, about the scale. The total_scale refers to one of
> the 3 scales with which pH is measured in sea water: total scale, sea
> water scale, and free scale (these all represent chemical activity,
> with units in moles/kg). Although many of these have the same units
> (moles/kg), the actual value will be different (in non-trivial ways)
> in the different scales. As the value in total_scale will not be
> immediately convertible to a value in free scale they are measurements
> with different meanings and can be easily confused. It was not
> obvious to me how this should be indicated other than by the standard
> name.
>
> Second, pH has the H capitalized, reflecting common usage. I couldn't
> see any rule against this but I wanted to point it out, just in case.
>
> John
>
> --------------
> John Graybeal -- 831-775-1956 -- Monterey Bay Aquarium Research
> Institute
>
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
>
> --
> This message (and any attachments) is for the recipient only. NERC
> is subject to the Freedom of Information Act 2000 and the contents
> of this email and any reply you make may be disclosed by NERC unless
> it is exempt from release under the Act. Any material supplied to
> NERC may be stored in an electronic records management system.
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
John
--------------
John Graybeal <mailto:graybeal at mbari.org> -- 831-775-1956
Monterey Bay Aquarium Research Institute
Marine Metadata Interoperability Project:
http://marinemetadata.org
Received on Mon Apr 27 2009 - 11:13:58 BST
