ISO 5667-26:2022

Water quality — Sampling — Part 26: Guidance on sampling for the parameters of the oceanic carbon dioxide system

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 CO2 fugacity.

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

General Information

• Status: Published
• Publication Date: 02-Nov-2022
• ICS: 13.060.45 - Examination of water in general
• Technical Committee: ISO/TC 147/SC 6 - Sampling (general methods)
• Drafting Committee: ISO/TC 147/SC 6/WG 15 - Sampling for oceanic carbon dioxide in sea water
• Current Stage: 6060 - International Standard published
• Start Date: 03-Nov-2022
• Due Date: 26-Jul-2022
• Completion Date: 03-Nov-2022

Standards Content (Sample)

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 5667-26:2022(E)
© ISO 2022
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ISO 5667-26:2022(E)
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© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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© ISO 2022 – All rights reserved
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ISO 5667-26:2022(E)
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
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ISO 5667-26:2022(E)
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

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

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

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

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

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO 2022 – All rights reserved
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ISO 5667-26:2022(E)
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].
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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

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:
− −
−−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
   

Note 2 to entry: The brackets represent total concentrations of these constituents in solution, [H ] is the free

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.
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ISO 5667-26:2022(E)
3.2
total dissolved inorganic carbon
dissolved inorganic carbon content of sea water is defined as
* −−2
     
C = CO + HCOC+ O
T 23 3
     

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
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:
 
 
fx=−..p exp ()VRTp''dp
CO2CO2 CO2
 
 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 measurable inorganic carbon parameters to calculate carbonate

chemistry of seawater, the in-situ temperature, pressure, salinity as well as phosphate and silicate concentration

of the seawater may need to be measured.
3.4
total hydrogen ion concentration
total hydrogen ion concentration of sea water is defined as:
   
HH= ()1+SK/
   
   
≈ HH+ SO
   
where
[H ] is the free concentration of hydrogen ion in sea water;
− 2−
S is the total sulfate concentration ([HSO ]+[SO ]);
T 4 4
K is the acid dissociation constant for HSO
S 4
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ISO 5667-26:2022(E)
3.5
negative of the base 10 logarithm of the hydrogen ion concentration:
 
pH=−logH
 
 
where H is the hydrogen ion concentration, expressed in expressed in mol kg-soln
 
4 Principle

For the analysis of A , C , pH and f in seawater, samples are collected in clean glass containers in a

T T CO2
manner designed to minimize gas exchange with the atmosphere.

NOTE CO exchange affects the various carbon parameters to differing degrees ranging from the very

sensitive CO fugacity, f , to alkalinity which is not affected by gas exchange.
2 CO2

If the sample is treated with a mercuric chloride solution to prevent biological activity, this occurs

prior to the container being closed to prevent exchange of carbon dioxide or water vapour with the

atmosphere.
5 Apparatus
5.1 General

The sample containers are somewhat different depending on which parameter is being collected, but

the basic concept is similar for the four possible inorganic carbon samples. In general, a flexible plastic

drawing tube, a clean glass sample container with stoppers, a container and dispenser for the mercuric

chloride solution (if it is being used) and a sampling log to record when and where each of the samples

were collected.
5.2 Drawing tube
® 1)

Tygon tubing is normally used to transfer the sample from the Niskin water sampler to the sample

container (5.3); however, if dissolved organic carbon samples are being collected from the same Niskins,

then it may be necessary to use silicone tubing to prevent contamination from the Tygon . The drawing

tube can be pre-treated by soaking in clean seawater for at least one day. This minimizes the amount of

bubble formation in the tube when drawing a sample.
5.3 Sample container
5.3.1 General

Sample containers depends on the parameter being measured, volume of sample required for analysis,

length of anticipated storage and collection method. Important considerations in bottle choice include

[1]

volume, leaching of bottle material, gas permeability, opening size, neck size, and sealing . Ideally,

sample containers should be prepared by cleaning in a 1 M HCl bath for approximately 24 h, followed by

rinsing for approximately 24 h in Milli-Q water (18,2 MΩ cm resistivity). However, care shall be taken

to remove all residual acid during rinsing. Then, containars should be wrapped in aluminium foil and

placed in a 450 °C muffle furnace for 4 h to remove organic carbon.

1) Tygon tubing is an example of a suitable product available commercially. This information is given for the

convenience of users of this document and does not constitute an endorsement by ISO of this product.

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ISO 5667-26:2022(E)
5.3.2 Samples for f measurement
CO2
Typically, the f samples are analysed directly fr
...