Dissolved inorganic phosphorus in seawater takes several forms, with
phosphate (P043-) being only one of them. Furthermore, PO43- is not
even the most abundant form at normal seawater pH. Rather it is HPO42-
(hydrogen phosphate). Oceanographers do often refer to phosphate but
what they really taking about is total dissolved inorganic phosphorus
(the sum of all inorganic forms).
The seawater system for dissolved inorganic silicon is simpler because
we only need to consider two forms: silicic acid (Si(OH)4) and silicate
(SiO(OH)3-). The former is more abundant than the latter in seawater.
It is best then to refer to
- total dissolved inorganic phosphorus rather than phosphate and
- total dissolved inorganic silicon rather than silicate.
For more insight see the last figure in the OMIP-BGC protocols paper
in the CMIP6 special issue at
http://www.geosci-model-dev-discuss.net/gmd-2016-155/
Cheers,
Jim
On Fri, 24 Mar 2017, Lowry, Roy K. wrote:
Dear All,
If one makes the assumption that all the silicon and phosphorus atoms not
associated with organic ligands are
in a single chemical form associated with oxygen in solution then what Martin
says is correct. In my
experience I have never known anybody challenge this assumption and I cannot
think of any other anions
incorporating P and Si. Consequently, I would agree that whilst there is a
theoretical semantic difference
between the members of each Standard Name pair I would agree that this could be
ignored and they could be
considered synonyms.
Note, this only holds true as these are MOLE concentrations. The MASS
concentration of inorganic phosphorus
is very different from the MASS concentration of phosphate as the oxygen atoms
have mass.
If the decision is taken to take action on this then I would recommend that the
'inorganic_silicon' and
'inorganic_phosphorus' names be than ones to be converted to aliases. This is
based on common terminology
usage in the oceanographic community.
Cheers, Roy.
Please note that I partially retired on 01/11/2015. I am now only working 7.5
hours a week and can only
guarantee e-mail response on Wednesdays, my day in the office. All vocabulary
queries should be sent to
[email protected]. Please also use this e-mail if your requirement is urgent.
_____________________________________________________________________________________________________________
From: CF-metadata <[email protected]> on behalf of
[email protected]
<[email protected]>
Sent: 24 March 2017 08:48
To: [email protected]
Subject: [CF-metadata] Silicate vs. dissolved inorganic silicon
Hello Alison, others,
the standard name list includes both
(1) mole_concentration_of_dissolved_inorganic_silicon_in_sea_water and (2)
mole_concentration_of_silicate_in_sea_water
The definition of the first says that "dissolved inorganic silicon" means
silicate ions in solution. Both
have units of "mol m-3". It looks to me as though they are describing the same
thing. If this is true, should
one be demoted to the alias of the other? If they are different, what is the
difference?
The same question applies to
mole_concentration_of_dissolved_inorganic_phosphorus_in_sea_water and
mole_concentration_of_phosphate_in_sea_water.
regards,
Martin
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