ISO/CD TS 22171.2

Soil quality — Determination of potential cation exchange capacity (CEC) and exchangeable cations buffered at pH 7, using a molar ammonium acetate solution

Qualité du sol — Détermination de la capacité d'échange cationique (CEC) potentielle et de la teneur en cations échangeables, à l'aide d'une solution molaire d'acétate d'ammonium tamponnée à pH 7

Kakovost tal - Določanje potencialne kationske izmenjalne kapacitete (CEC) in izmenljivih kationov z uporabo pufrske raztopine amonijevega acetata s pH 7

General Information

• Status: Not Published
• ICS: 13.080.10 - Chemical characteristics of soils
• Technical Committee: ISO/TC 190/SC 3 - Chemical and physical characterization
• Drafting Committee: ISO/TC 190/SC 3/WG 14 - Physical methods
• Current Stage: 3099 - CD approved for registration as DIS
• Completion Date: 13-Jul-2023
• Ref Project: oSIST ISO/DIS 22171:2023 - Soil quality - Determination of potential cation exchange capacity (CEC) and exchangeable cations buffered at pH 7, using a molar ammonium acetate solution

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST ISO/DIS 22171:2023
01-junij-2023
Kakovost tal - Določanje potencialne kationske izmenjalne kapacitete (CEC) in
izmenljivih kationov z uporabo pufrske raztopine amonijevega acetata s pH 7
Soil quality - Determination of potential cation exchange capacity (CEC) and
exchangeable cations buffered at pH 7, using a molar ammonium acetate solution

Qualité du sol - Détermination de la capacité d'échange cationique (CEC) potentielle et

de la teneur en cations échangeables, à l'aide d'une solution molaire d'acétate
d'ammonium tamponnée à pH 7
Ta slovenski standard je istoveten z: ISO/DIS 22171
ICS:
13.080.10 Kemijske značilnosti tal Chemical characteristics of
soils
oSIST ISO/DIS 22171:2023 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST ISO/DIS 22171:2023
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oSIST ISO/DIS 22171:2023
DRAFT INTERNATIONAL STANDARD
ISO/DIS 22171
ISO/TC 190/SC 3 Secretariat: DIN
Voting begins on: Voting terminates on:
2022-02-17 2022-05-12
Soil quality — Determination of potential cation exchange
capacity (CEC) and exchangeable cations buffered at pH 7,
using a molar ammonium acetate solution
ICS: 13.080.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
This document is circulated as received from the committee secretariat.
NOT BE REFERRED TO AS AN INTERNATIONAL
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ISO/DIS 22171:2022(E)
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PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022
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oSIST ISO/DIS 22171:2023
ISO/DIS 22171:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© 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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oSIST ISO/DIS 22171:2023
ISO/DIS 22171:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Reagents ........................................................................................................................................................................................................................ 1

6 Apparatus .................................................................................................................................................................................................................... 3

7 Laboratory samples ..........................................................................................................................................................................................4

8 Procedure ....................................................................................................................................................................................................................4

8.1 Test portion ............................................................................................................................................................................................... 4

8.2 Extraction step ....................................................................................................................................................................................... 4

8.3 Ammoniacal nitrogen assay by continuous flow spectrophotometry .................................................. 5

8.3.1 Apparatus set-up ................................................................................................................................................................ 5

8.3.2 Assays ........................................................................................................................................... ................................................ 5

8.4 Expression of results ......................................................................................................................................................................... 6

9 Test report .................................................................................................................................................................................................................. 6

Bibliography ................................................................................................................................................................................................................................ 7

iii
© ISO 2022 – All rights reserved
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oSIST ISO/DIS 22171:2023
ISO/DIS 22171:2022(E)
Foreword

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This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3,

Chemical and physical characterization.
© ISO 2022 – All rights reserved
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oSIST ISO/DIS 22171:2023
ISO/DIS 22171:2022(E)
Introduction

Cation exchange capacity (CEC) is an intrinsic property of soil defining the concentration of negatively

charged sites on soil colloids that can adsorb exchangeable cations. Cation exchange capacity can be

a good indicator of soil productivity and is useful for making recommendations of phosphorus (P),

potassium (K), and magnesium (Mg) if testing soils of different textures. Cation exchange capacity is

also used for regulatory purposes in monitoring land application of biosolids.

Cation exchange capacity is a measure of exchangeable bases and soil acidity at some specific soil pH.

The exchangeable bases and acidity neutralize negative charges arising from permanent charges due to

isomorphic substitution in clays, or pH-dependent charges from hydroxyl groups on clay and oxides or

carboxyl groups on soil organic matter. A common method for determining CEC uses 1 M ammonium

acetate at pH 7 (neutral NH OAc) and is a standard method used for soil surveys by the Natural Resource

Conservation Service (Burt, 2004; Hendershot et al., 2008; Sumner and Miller, 1996). An advantage of

CEC measured at a constant pH of 7 is elimination of CEC variability due to differences in soil pH. Thus,

comparisons of CEC can occur across varied soil types and lime applications. A disadvantage of the

neutral NH OAc method is that it may not provide a realistic depiction of the actual CEC at the natural

pH of the soil, particularly with soils having considerable pH-dependent charge and a soil pH that is

significantly different from 7. An unbuffered salt extract can be used to determine CEC at the natural

pH of soil, for example by using a hexamine chloride solution ISO 23470, see also Burt, 2004; Sumner

and Miller, 1996; Pansu and Gautheyrou, 2006.

The method described here determines potential cation exchange capacity (CEC) buffered at pH 7 and

exchangeable cations Ca, Mg, K, and Na. Molar ammonium acetate is added to soil to saturate exchange

sites with NH and release exchangeable cations in a leachate which are measured. The exchanged

NH is then released either with 1 M KCl or 1 M NaCl and measured to quantify the potential cation

exchange capacity at pH 7.

Ammonium acetate, due to its complexing effect, can contribute to the dissolution of part of soil

carbonates and other salts present in the soil. Calcium concentrations (or even magnesium) are thus

no longer limited to exchangeable quantities. Presence of other soluble salts such as gypsum, sodium

chloride or else would also inflate exchangeable cation quantities.
© ISO 2022 – All rights reserved
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oSIST ISO/DIS 22171:2023
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oSIST ISO/DIS 22171:2023
DRAFT INTERNATIONAL STANDARD ISO/DIS 22171:2022(E)
Soil quality — Determination of potential cation exchange
capacity (CEC) and exchangeable cations buffered at pH 7,
using a molar ammonium acetate solution
1 Scope
This International Standard s
...