ISO 5667-26:2022

INTERNATIONAL ISO
STANDARD 5667-26
First edition
2022-11
Water quality — Sampling —
Part 26:
Guidance on sampling for the
parameters of the oceanic carbon
dioxide system
Qualité de l’eau – Echantillonnage —
Partie 26: Lignes directrices pour l’échantillonnage d’eau de mer en
vue de l’analyse des formes du carbone
Reference number
© ISO 2022
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Apparatus . 3
5.1 General . 3
5.2 Drawing tube . 3
5.3 Sample container . 3
5.3.1 General . 3
5.3.2 Samples for f measurement . 4
CO2
5.3.3 Samples for C and A measurement . 4
T T
5.3.4 Samples for pH measurement . 4
5.4 Mercury dispenser . 4
6 Reagent: Mercuric chloride solution, HgCl . 4
7 Procedure .5
7.1 General . 5
7.2 Filling procedure . 5
7.2.1 Rinse the sample bottle . 5
7.2.2 Fill the sample bottle . 5
7.2.3 Adjust the headspace . 5
7.2.4 Prevent biological activity in the sample . 5
7.2.5 Close the bottle . 6
7.2.6 Secure the lid . 6
7.3 Sample storage . 6
7.4 Sample documentation . 6
8 Assurance and quality control . 7
Annex A (informative) Determination of the size of a headspace in the sample bottle .8
Bibliography .11
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 6,
Sampling (general methods).
A list of all parts in the ISO 5667 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
The ocean is currently absorbing about one quarter of the carbon dioxide that humans are emitting.
When carbon dioxide combines with seawater, chemical reactions occur that reduce the seawater pH,
hence the term ocean acidification. Acidification can affect many marine organisms, but especially
those that build their shells and skeletons from calcium carbonate. Over the past few years, several
high-profile reports have highlighted the urgent need to better understand the effects of changes in
carbonate chemistry on marine organisms and ecosystems. Research in this field was limited to a few
groups around the world until recently but the number of scientists involved in ocean acidification
research has been rapidly rising over the past few years. The reliable characterization and manipulation
of the carbonate system involves good analytical skills and measuring facilities and continuous
monitoring of seawater chemistry in the field and during experimentation. The predictive power of
field surveys and the robustness of results from experiments critically depend on proper sampling and
experimental protocols.
The oceanic carbonate system can be described by measuring at least two parameters of the following
four parameters, total dissolved inorganic carbon (C ), total alkalinity (A ), fugacity of carbon dioxide
T T
( f ) and pH in seawater. This document describes how to collect and preserve discrete seawater
CO2
samples, from a Niskin bottle or other water samplers, for the analysis of four measurable inorganic
carbon parameters including: C A f and pH, according to highest standard levels accepted by
T, T, CO2
global ocean carbon community.
NOTE This document is based on Reference [5].
v
INTERNATIONAL STANDARD ISO 5667-26:2022(E)
Water quality — Sampling —
Part 26:
Guidance on sampling for the parameters of the oceanic
carbon dioxide system
1 Scope
This document specifies how to collect discrete seawater samples, from a Niskin or other water sampler,
that are suitable for the analysis of the four measurable inorganic carbon parameters: total dissolved
inorganic carbon, total alkalinity, pH and CO fugacity.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5667-14, Water quality — Sampling — Part 14: Guidance on quality assurance and quality control of
environmental water sampling and handling
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
total alkalinity
A
T
number of moles of hydrogen ion equivalent to the excess of proton acceptors (bases
–4,5
formed from weak acids with a dissociation constant K ≤ 10 at 25 °C and zero ionic strength) over
–4,5
proton donors (acids with K > 10 ) in 1 kg of sample
Note 1 to entry: The formula to determine A is:
T
− −
−−2 −−2 3− −
   
           
A = HCOC+22OB+ ()OH + OH + HPOP+ O + SiOO()HN+[]HH+ S +…
T 33 4 44 3
4 3
               
+−
   
− HH− SO −[]HFFH−[]PO −…
4 34
   
F
+
Note 2 to entry: The brackets represent total concentrations of these constituents in solution, [H ] is the free
F
concentration of hydrogen ion and the ellipses stand for additional minor acid or base species that are either
unidentified or present in such small amounts that they can be safely neglected. In open ocean water, the
–
concentrations of NH and HS are typically so low that they can be neglected; they may, however, be significant
in anoxic environments.
3.2
total dissolved inorganic carbon
C
T
dissolved inorganic carbon content of sea water is defined as
* −−2
     
C = CO + HCOC+ O
T 23 3
     
–1
where the brackets represent total concentrations of these constituents in solution (in µmol kg ) and
[CO *] represents the total concentration of all unionized carbon dioxide, whether present as H CO or
2 2 3
as CO
3.3
fugacity
f
chemical potential of an individual component of a vapor phase
Note 1 to entry: The fugacity of carbon dioxide, f , is not the same as its partial pressure the product of mole
CO2
fraction and total pressure,xp. but rather takes account of the non-ideal nature of the gas phase. The fugacity
CO2
of gas such as CO can be determined from knowledge of its formula of state:
p
 
 
fx=−.p exp ()VRTp''dp
CO2CO2 CO2
∫
RT
 
 0 
where
x is the mole fraction of CO ;
CO2 2
p is the total pressure;
p' is the partial pressure of CO ;
V is the volume of CO ;
CO2 2
−1 −1
R is the molar gas constant which is 8.31446261815324 J K mol ;
T is the temperature in kelvin.
It should be noted that to apply the results of four meas
...