CEN ISO/TS 21268-4:2009

SLOVENSKI STANDARD
01-februar-2010
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Soil quality - Leaching procedures for subsequent chemical and ecotoxicological testing
of soil and soil materials - Part 4: Influence of pH on leaching with initial acid/base
addition (ISO/TS 21268-4:2007)
Bodenbeschaffenheit - Eluierungsverfahren für die anschließende chemische und
ökotoxikologische Untersuchung von Boden und von Bodenmaterialien - Teil 4: Einfluss
des pH–Wertes unter vorheriger Säure/Base-Zugabe (ISO/TS 21268-4:2007)
Qualité du sol - Modes opératoires de lixiviation en vue d'essais chimiques et
écotoxicologiques ultérieurs des sols et matériaux du sol - Partie 4: Essai de
dépendance au pH avec ajout initial d'acide/base (ISO/TS 21268-4:2007)
Ta slovenski standard je istoveten z: CEN ISO/TS 21268-4:2009
ICS:
13.080.05 Preiskava tal na splošno Examination of soils in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN ISO/TS 21268-4
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
November 2009
ICS 13.080.05
English Version
Soil quality - Leaching procedures for subsequent chemical and
ecotoxicological testing of soil and soil materials - Part 4:
Influence of pH on leaching with initial acid/base addition
(ISO/TS 21268-4:2007)
Qualité du sol - Modes opératoires de lixiviation en vue Bodenbeschaffenheit - Eluierungsverfahren für die
d'essais chimiques et écotoxicologiques ultérieurs des sols
anschließende chemische und ökotoxikologische
et matériaux du sol - Partie 4: Essai de dépendance au pH Untersuchung von Boden und von Bodenmaterialien - Teil
avec ajout initial d'acide/base (ISO/TS 21268-4:2007) 4: Einfluss des pH-Wertes unter vorheriger Säure/Base-
Zugabe (ISO/TS 21268-4:2007)
This Technical Specification (CEN/TS) was approved by CEN on 8 September 2009 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
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Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

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© 2009 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 21268-4:2009: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
The text of ISO/TS 21268-4:2007 has been prepared by Technical Committee ISO/TC 190 “Soil quality” of the
International Organization for Standardization (ISO) and has been taken over as CEN ISO/TS 21268-4:2009
by Technical Committee CEN/TC 345 “Characterization of soils” the secretariat of which is held by NEN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO/TS 21268-4:2007 has been approved by CEN as a CEN ISO/TS 21268-4:2009 without any
modification.
TECHNICAL ISO/TS
SPECIFICATION 21268-4
First edition
2007-11-15
Soil quality — Leaching procedures
for subsequent chemical
and ecotoxicological testing of soil
and soil materials —
Part 4:
Influence of pH on leaching with initial
acid/base addition
Qualité du sol — Modes opératoires de lixiviation en vue d'essais
chimiques et écotoxicologiques ultérieurs des sols et matériaux du
sol —
Partie 4: Essai de dépendance au pH avec ajout initial d'acide/base

Reference number
ISO/TS 21268-4:2007(E)
©
ISO 2007
ISO/TS 21268-4:2007(E)
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ii © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Symbols and abbreviations . 3
5 Principle. 4
6 Apparatus . 4
7 Reagents. 6
8 Sample pretreatment . 6
8.1 Sample size . 6
8.2 Particle size reduction. 6
8.3 Determination of the dry matter content and of water content. 7
8.4 Preparation of test portion. 7
9 Procedure . 7
9.1 Contact time . 7
9.2 pH-range . 8
9.3 Leaching test. 8
9.3.1 General. 8
9.3.2 Preparation of leachant. 8
9.3.3 Leaching procedure. 9
9.4 Natural pH. 11
10 Eluate treatment, storage and analysis. 11
11 Analytical determination . 12
12 Blank test. 12
13 Calculation. 12
14 Test report . 13
15 Performance characteristics . 13
Annex A (informative) Example of a specific liquid-solid separation procedure for soil sample. 14
Annex B (informative) Operation and uses of the test: influence of pH on the leaching behaviour. 15
Annex C (informative) Preliminary determination of the acid/base consumption. 19
Bibliography . 23

ISO/TS 21268-4:2007(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of document:
⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 21268-4 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 7, Soil
and site assessment.
ISO/TS 21268 consists of the following parts, under the general title Soil quality — Leaching procedures for
subsequent chemical and ecotoxicological testing of soil and soil materials:
⎯ Part 1: Batch test using a liquid to solid ratio of 2 l/kg dry matter
⎯ Part 2: Batch test using a liquid to solid ratio of 10 l/kg dry matter
⎯ Part 3: Up-flow percolation test
⎯ Part 4: Influence of pH on leaching with initial acid/base addition
iv © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
Introduction
In various countries, tests have been developed to characterize and assess the constituents that can be
released from materials. The release of soluble constituents upon contact with water is regarded as a main
mechanism of release, resulting in a potential risk to the environment during the use or disposal of materials.
The intent of these tests is to identify the leaching properties of materials. The complexity of the leaching
process makes simplifications necessary.
Not all of the relevant aspects of leaching behaviour can be addressed in one standard.
Tests to characterize the behaviour of materials can generally be divided into three categories (see
References [1], [2] and [4]). The relationships between these tests are summarized below.
a) “Basic characterization” tests are used to obtain information on the short- and long-term leaching
behaviour and characteristic properties of materials. Liquid/solid (L/S) ratios, leachant composition,
factors controlling leachability, such as pH, redox potential, complexing capacity, role of dissolved organic
carbon (DOC), ageing of material and physical parameters, are addressed in these defined tests.
b) “Compliance” tests are used to determine whether the material complies with a specific behaviour or with
specific reference values. These tests focus on key variables and leaching behaviour previously identified
by basic characterization tests.
c) “On-site verification” tests are used as a rapid check to confirm that the material is the same as that which
has been subjected to the compliance test(s). On-site verification tests are not necessarily leaching tests.
The test procedure described in this method belongs to category a) “Basic characterization” tests.
NOTE Up to now, the test procedures described in this part of ISO/TS 21268 have not been validated.

TECHNICAL SPECIFICATION ISO/TS 21268-4:2007(E)

Soil quality — Leaching procedures for subsequent chemical
and ecotoxicological testing of soil and soil materials —
Part 4:
Influence of pH on leaching with initial acid/base addition
1 Scope
This part of ISO/TS 21268 specifies a test method to obtain information on the short- and long-term leaching
behaviour and characteristic properties of materials.
It applies to the determination of the influence of pH on the leachability of inorganic and organic constituents
from soil and soil material, and the ecotoxicological effects of eluates with respect to microorganisms, fauna
and flora. The test is not suitable for constituents that are volatile under ambient conditions. The equilibrium
condition, as defined in this part of ISO/TS 21268, is established by the addition of predetermined amounts of
acid or base to reach desired final pH values.
The test procedure specified in this part of ISO/TS 21268 produces eluates that are subsequently
characterized by physical, chemical and ecotoxicological standard methods.
For the purposes of ecotoxicological tests, the relevant pH range (see 9.2) will usually be pH 5 to 9.
NOTE 1 Volatile organic constituents include the low molecular weight components in mixtures such as mineral oil.
NOTE 2 It is not always possible to optimize test conditions simultaneously for inorganic and organic constituents and
optimum test conditions may also vary between different groups of organic constituents. Test requirements for organic
constituents are generally more stringent than those for inorganic constituents. The test conditions suitable for measuring
the release of organic constituents will generally also be applicable to inorganic constituents.
NOTE 3 For ecotoxicological testing, eluates representing the release of both inorganic and organic contaminants are
needed. In this document, ecotoxicological testing is meant to include genotoxicological testing.
This test cannot be used alone to determine the total leaching behaviour of a soil. More leaching tests are
needed for that extended goal. This part of ISO/TS 21268 does not address issues related to health and
safety. It only determines the leaching properties outlined in Clause 5.
2 Normative references
The following referenced documents are indispensable for the application 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 3696, Water for analytical laboratory use — Specification and test methods
ISO 5667-3, Water quality — Sampling — Part 3: Guidance on the preservation and handling of water
samples
ISO 7027, Water quality — Determination of turbidity
ISO/TS 21268-4:2007(E)
ISO 10381-1, Soil quality — Sampling — Part 1: Guidance on the design of sampling programmes
ISO 10381-2, Soil quality — Sampling — Part 2: Guidance on sampling techniques
ISO 10381-3, Soil quality — Sampling — Part 3: Guidance on safety
ISO 10381-4, Soil quality — Sampling — Part 4: Guidance on the procedure for investigation of natural, near-
natural and cultivated sites
ISO 10381-5, Soil quality — Sampling — Part 5: Guidance on the procedure for the investigation of urban and
industrial sites with regard to soil contamination
ISO 10523, Water quality — Determination of pH
ISO 11465, Soil quality — Determination of dry matter and water content on a mass basis — Gravimetric
method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
leaching test
test during which a soil or soil material is put into contact with a leachant under strictly defined conditions and
some constituents of the material are extracted
3.2
leachant
liquid used in a leaching test
3.3
eluate
solution obtained by a laboratory leaching test
3.4
single batch leaching test
leaching test in which a fixed amount of material is leached in one step with a fixed amount of leachant
3.5
liquid to solid ratio
L/S
ratio between the amount of liquid (L) and of solid (S) in the test
NOTE L/S is expressed in litres per kilogram (l/kg) of dry matter.
3.6
dry matter content
w
dm
ratio, expressed in percent, between the mass of the dry residue, determined in accordance with ISO 11465,
and the corresponding raw mass
3.7
water content
w
H O
ratio, expressed in percent, between the mass of water contained in the material as received and the
corresponding dry residue of the material.
NOTE The basis for the calculation of the moisture content is the mass of the dry residue in this part of
ISO/TS 21268, as specified in ISO 11465 (for the determination of the water content of soil).
2 © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
3.8
laboratory sample
sample or subsample(s) sent to or received by the laboratory
[IUPAC:1997]
3.9
test sample
sample, prepared from the laboratory sample, from which test portions are removed for testing or analysis
[IUPAC:1997]
3.10
test portion
amount or volume of the test sample taken for analysis, usually of known weight or volume
[IUPAC:1997]
3.11
soil material
excavated soil, dredged materials, manufactured soils, treated soil and fill materials
[ISO 15176:2002]
4 Symbols and abbreviations
ANC acid neutralization capacity
BNC base neutralization capacity
C is the concentration of the base (mol/l) (see 7.4)
B
DOC dissolved organic carbon
L/S liquid to solid ratio
m is the mass of the dried sample (kg)
D
m is the mass of non-dried sample (kg)
W
+
n is the base consumption for the particular pH (mol /kg OH dry matter)
B
t time at the start of the leaching test
V V volume of acid /base used in leachant
A, B
V volume of demineralized water used in leachant
d
V volume of prepared leachant
L
w dry matter content of the soil
dm
w water content
H O
ISO/TS 21268-4:2007(E)
5 Principle
Several separate test portions (up to eight) are leached at a fixed L/S ratio (L/S = 10 l/kg) with leachants
containing different preselected amounts of acid or base containing a low concentration (0,001 mol/l) of
calcium chloride in order to reach stationary pH values at the end of the extraction period (see 8.4). Each
leachant is added in three steps in the beginning of the test. In the full test eight final pH-values are required,
covering the range pH 4 to pH 12 (both included, i.e. the lowest value 4 and the highest value 12). The
amounts of acid or base needed to cover the pH range can be derived from the results of a preliminary
titration, from available experimental data on the material to be tested or from an arbitrary division of the
predetermined maximum consumption of acid and base. The tests are carried out at a fixed contact time at
the end of which an equilibrium condition can be assumed to be reached for most constituents in most soil
materials to be characterized. The equilibrium condition, as defined in this part of ISO/TS 21268, is verified at
the end of the extraction period.
The results are expressed in milligrams per litre (mg/l) of constituents for each final pH value. For each final
+
pH value, the quantity of acid that is added is also expressed in mol/kg H dry matter and the quantity of base
+
that is added is expressed as negative mol/kg H dry matter.
NOTE 1 This test can also be performed using continuous pH control. The results are generally consistent (see
Annex B).
NOTE 2 Other expressions of results are possible (including mg/kg of dry matter).
From the amount of acid and base used to reach a given end pH, the acid or base neutralization capacity
(ANC, BNC) of the soil or soil material can also be determined.
NOTE 3 The pH range covered by the test can be restricted to a pH range relevant for the specific material and the
considered problem (see 9.2).
NOTE 4 The leachant is made with 0,001 mol/l CaCl to minimize the mobilization of DOC caused by a too-low ionic
strength of the leachant. At the level of 0,001 mol/l CaCl the complexation of metals with chloride is considered to be
negligible.
The constituents in the eluate(s) are measured using methods developed for water analysis adapted to meet
criteria for analysis of eluates. The eluate may also be applied for subsequent ecotoxicity or genotoxicity
testing.
After the test, the leaching conditions (in terms of pH, electrical conductivity, DOC and, optionally, turbidity and
redox potential dictated by the material) are recorded.
NOTE 5 These parameters often control the leaching behaviour of soil materials and are therefore important for
checking the leaching test.
6 Apparatus
6.1 Borosilicate glass, of high purity in accordance with ISO 5667-3, with a nominal volume of 1 l, glass
bottles having caps of inert material, for example, PTFE (polytetrafluoroethylene). Rinsing is compulsory.
NOTE 1 If only inorganic parameters are analysed, alternative materials such as HDPE/PP bottles can be used, except
for unpreserved samples for mercury analysis.
NOTE 2 If Boron analyses are necessary, any plastics bottles may be used, e.g. PTFE (polytetrafluoroethylene).
The nominal volume of 1 l is selected in combination with the mass, m , of 60 g, in order to minimize head-
D
space. For m = 15 g and 30 g, bottle sizes of, respectively, 250 ml and 500 ml shall be used. In the case of
D
materials with low densities, a deviation from this requirement can be necessary while still attempting to
minimize headspace. This deviation should be reported.
4 © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
Glass of high quality is considered adequate for both inorganic and organic contaminants, particularly since
the pH range usually covered in soil testing does not reach the conditions (pH > 12 and pH < 4) where the
glass itself is attacked. For ecotoxicity testing, eluates with both inorganic and organic contaminants are
needed, which emphasizes the need to generate integrated eluates.
−1 −1 −1
6.2 End-over-end tumbler (5 min to 10 min ) or roller table, rotating at about 10 min .
Other shaking devices can be used, provided that they can be shown to provide equivalent results. These
agitation devices are specified for excessive abrasion leading to significant particle size reduction.
6.3 Filtration apparatus, either a vacuum filtration device (between 2,5 kPa to 4,0 kPa) or a high pressure
filtration apparatus (< 0,5 MPa). Cleaning is compulsory.
6.4 Pre-rinsed 0,45 µm membrane filters, for filtration (e.g. rinsed with 0,1 mol/l HNO as described in 7.2,
and water as described in 7.1).
1) 1)
The filters shall be glass fibre filters without organic glue or regenerated cellulose (S&S , RC 55 or
comparable quality). The filter material shall be compatible with the extractant solution to be tested.
NOTE If only inorganic contaminants are to be analysed, alternative filter materials can be selected, e.g. cellulose
acetate, PTFE.
6.5 Sieving equipment, with sieves of 2 mm nominal screen size.
NOTE Due to sieving, contamination of the sample can occur to an extent which affects the leaching of some
constituents of concern, e.g. chromium, nickel and molybdenum from stainless steel equipment or plasticizers from plastic
sieves.
6.6 Centrifuge, operating at 20 000 g to 30 000 g using centrifuge tubes of FEP (fluorinated ethylene
propylene) or tubes of an alternative material, which is inert with regard to both inorganic and organic
compounds and suitable for high-speed centrifugation.
Alternatively, if a high-speed centrifuge is not available, a centrifuge operating at 2 000 g to 2 500 g using
glass bottles may be used in combination with increased centrifugation time. Cooling shall be applied to
maintain the desired temperature.
6.7 Glass bottles, with screw cap and PTFE (polytetrafluoroethylene) inlay for centrifugation.
6.8 Device for measuring electrical conductivity.
6.9 pH meter, in accordance with ISO 10523.
6.10 Redox potential meter (optional).
6.11 Balance, with an accuracy of at least 0,1 g.
6.12 Sample splitter, for sub-sampling of laboratory samples (optional).
6.13 Turbidity meter, as specified in ISO 7027.
6.14 Crushing equipment, a jaw crusher.
NOTE Due to particle size reduction, contamination of the sample can occur to an extent which affects the leaching
of some constituents of concern, e.g. chromium, nickel and molybdenum from stainless steel equipment.

1) S&S and RC 55 are examples of suitable products available commercially. This information is given for the
convenience of users of this part of ISO/TS 21268 and does not constitute an endorsement by ISO of these products.
ISO/TS 21268-4:2007(E)
7 Reagents
Reagents used shall be of analytical grade purity.
7.1 Leachant, demineralized water, deionized water or water of equivalent purity (5 < pH < 7,5), with a
conductivity of < 0,5 mS/m in accordance with grade 3, specified in ISO 3696, made up to 0,001 mol/l CaCl .
If organic contaminants are considered, a blank test should be included to prove that no background
contamination exists in the leachate.
7.2 Rinsing solutions: nitric acid 0,1 mol/l (analytical grade) and/or organic solvent (acetone).
7.3 Nitric acid (pro-analysis), 0,1 mol/l to 5 mol/l.
7.4 Sodium hydroxide, NaOH, 0,1 mol/l to 5 mol/l.
8 Sample pretreatment
8.1 Sample size
Obtain a representative laboratory sample of at least 1 kg (dry matter) of the material. Use a sample splitter
(6.12) or apply coning and quartering to split the sample.
Sampling should be performed in accordance with the guide to the preparation of a sampling plan for soil
materials, as specified in ISO 10381-1 to ISO 10381-5, in order to obtain representative laboratory samples.
If the proportions in terms of L/S are maintained, larger volumes of eluate can be produced if needed for
ecotoxicity testing. Deviations to compensate for volume requirement shall be reported in the test report.
The size of the laboratory sample is dependent on the particle size distribution of the soil to be analysed (refer
to sampling standard). The prescribed sample size will generally be adequate. In specific cases, a smaller
sample size can be accepted (for instance, if for specific reasons, less material is available), provided that the
test can be carried out as specified in 8.2. The deviation shall be recorded in the test report.
8.2 Particle size reduction
The tests shall be carried out, preferably, on material as received. However, the test portion to be prepared
shall have at least 95 % (mass fraction) of grain size u 4 mm. If required, the laboratory sample shall be
sieved (6.5). Oversized natural material (e.g. stones, pebbles, twigs) in the sample shall be separated and
discarded. The mass and nature of the oversized material shall be recorded. If oversized material is not of
natural origin and exceeds 5 % (mass fraction), the entire oversized fraction shall be crushed with suitable
crushing equipment. On no account shall the material be finely ground. Irrespective of any necessary size
reduction, the separate fractions with the exception of the non-crushable material shall be mixed to constitute
the test sample. Only in the case that the laboratory sample cannot be crushed or sieved because of its
moisture content, the laboratory sample may be dried. The drying temperature shall not exceed 25 °C.
NOTE If national regulations specify other particle sizes, these can be applied.
Sieving and drying at 25 °C can still lead to loss of some volatile components (inorganic and organic). In this
case, particle size reduction and drying is best avoided, as it can alter the leaching characteristics.
6 © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
8.3 Determination of the dry matter content and of water content
The whole test sample, complying with the size criterion in 8.2, shall not be further dried. The moisture content
of the test sample shall be determined on a subsample at (105 ± 5) °C. It shall be taken into account when
adjusting the L/S ratio. The dry mass of the sample shall be determined at (105 ± 5) °C, in accordance with
ISO 11465, and the dry matter content calculated in accordance with Equation (1):
wm=⋅100 m (1)
dm D W
where
w is the dry matter content, in percent (%);
dm
m is the mass of the dried sample, in kilograms (kg);
D
m is the mass of non-dried sample, in kilograms (kg).
W
The water content (w in percent) is calculated in accordance with Equation (2):
H O
wm=⋅100 −mm (2)
( )
HO W D D
If volatile or unstable compounds are present in the soil sample, this gravimetric method cannot be used for
accurate determination of the water content (see ISO 11465).
If the soil sample is air-dried prior to testing, the dry matter content w of the air-dried sample shall be
dm,AD
determined as well.
8.4 Preparation of test portion
Prepare at least eight test portions by the use of a sample splitter or by coning and quartering. Based on
sample heterogeneity and eluate volume requirement for analysis, the test portion size shall be either
m = 15 g, 30 g or 60 g (with an accuracy of ± 1 g).
D
Calculate the non-dried mass of the test portion, m , to be used for the test, in accordance with Equation (3):
W
m
D
m=⋅100 (3)
W
w
dm
where
m is the dried mass of the test portion (g);
D
m is the non-dried mass of the test portion (g);
W
w is the dry matter content of the soil (%).
dm
9 Procedure
9.1 Contact time
The leaching procedure consists of three defined stages:
⎯ Period A (acid/base addition) from t to (t + 4 h) for acid/base additions in three steps;
0 0
⎯ Period B (equilibration period) from (t + 4 h) to (t + 44 h) equilibration period;
0 0
⎯ Period C (verification period) from (t + 44 h) to (t + 48 h) for verification of equilibrium condition.
0 0
ISO/TS 21268-4:2007(E)
Measure pH in the liquid after each of these periods. The total contact period (A + B + C) is 48 h.
9.2 pH-range
The full test shall cover the range pH 4 to pH 12 (both included, i.e. the lowest value W 4 and the highest
value u 12) with eight pH values tested, including the natural pH (without acid or base addition). The
maximum difference between two consecutive pH values shall not exceed 1,5 pH units.
To ensure that the appropriate pH values can be obtained in one run, additional bottles can be prepared of
which only the ones with the desired final pH values are retained for analysis.
The pH range covered by the test may be restricted to a pH range relevant to the specific material and the
considered problem. The pH range to be covered may depend on the specific properties of the soil material,
the available information on this material and the questions to be answered by performing the test. The
number of pH levels considered can be reduced, correspondingly, for example, for the purpose of
ecotoxicological tests; the relevant pH range will usually be pH 5 to 9.
9.3 Leaching test
9.3.1 General
The following procedure applies to each of the chosen pH values to be tested.
9.3.2 Preparation of leachant
+
Identify the acid or base consumption for reaching the relevant pH values as A (mol/kg H dry matter) or
–
B (mol/kg OH dry matter) and the total volume of leachant.
NOTE The acid or base consumption for the considered pH values can be derived from available information, from
the preliminary procedures in Annex B, or from information in Annex C.
Calculate the volume V of liquid to establish L/S = 10 ± 0,2 (l/kg) for the actual size of test portion m (see 8.4),

w
including the volume of acid or base, in accordance with Equation (4):
Vm=⋅10 (4)
D
where
V is the total volume of the added extractant solution, in millilitres (ml);
m is the dry mass of the test portion, in grams (g) (see 8.4);
D
10 is the factor, in litres per kilogram (l/kg).
NOTE In relation to the L/S-ratio, V in this equation is equivalent to “L” and m is equivalent to “S”.
D
Calculate the amount of leachant to be added to the actual size of test portion and compensate for the water
content in the test portion in accordance with Equation (5):
VV=−(1−)⋅m (5)
LD
w
dm
where
V is the total volume of the added extractant solution, in millilitres (ml);
m is the dry mass of the test portion, in grams (g) (see 8.4);
D
8 © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
w is the dry matter of the soil, in percent (%) (see 8.3);
dm
V is the volume of prepared leachant, in millilitres (ml).
L
Prepare the leachant from demineralized water (see 7.1) and acid or base (see 7.2 or 7.4) according to the
acid/base consumption for the relevant pH.
Prepare the acid-adjusted leachant in accordance with Equation (6) and Equation (7):
VV=+V (6)
Ld A
nm⋅
AD
V = (7)
A
C
A
where
V is the volume of prepared leachant, in millilitres (ml);
L
V is the volume of demineralized water used, in millilitres (ml);
d
V is the volume of acid needed, in millilitres (ml);
A
+
n is the acid consumption for the particular pH, in mol/kg H dry matter;
A
m is the dry mass of the test portion, in grams (g) (see 8.4);
D
C is the concentration of the acid, in moles per litre (mol/l) (see 7.2).
A
Prepare the base-adjusted leachant in accordance with Equations (8) and (9):
VV=+V (8)
Ld B
nm⋅
BD
V = (9)
B
C
B
where
V is the volume of prepared leachant, in millilitres (ml);
L
V is the volume of demineralized water used, in millilitres (ml);
d
V is the volume of base needed, in millilitres (ml);
B
–
n is the base consumption for the particular pH, in mol /kg OH dry matter;
B
m is the dry mass of the test portion, in grams (g) (see 8.4);
D
C is the concentration of the base, in moles per litre (mol/l) (see 7.4).
B
Split the volume V of leachant into three equal parts, V /3.
L L
9.3.3 Leaching procedure
Carry out the test at a temperature of (20 ± 5) °C.
Select the appropriate bottle size according to the test portion size. For m = 15 g, 30 g and 60 g, this means
D
bottle sizes of, respectively, 250 ml, 500 ml and 1 000 ml.
ISO/TS 21268-4:2007(E)
Clean the bottle before use by filling it with 1 mol/l nitric acid (see 7.3), leaving it for at least 24 h and then
rinsing it with demineralized water (see 7.1).
Place one of the test portions in the rinsed bottle.
Add the leachant volume, V /3, at three different times:
L
a) first fraction at t ;
b) second fraction at t + 30 min;
c) third fraction at t + 2 h.
Close the bottle and agitate the suspension (see 7.2) between each leachant addition. Measure and record
the pH before the addition of the second and third fractions, and, if deviations are observed from the expected
pH at that time, prepare additional bottles with modified acid/base additions.
Development of carbon dioxide should be taken into account when using acidic leachants. This may lead to
pressure build-up. When this is expected or observed, the pressure can be relieved by opening the bottle a
few times during the test. Main gas production will, however, take place in the first period of acid addition.
Continue to agitate after the last leachant addition until t = t + 48 h.
NOTE 1 For the high pH values (pH > 9 ), CO uptake can affect the leaching process. This can be reduced by
minimizing the contact time with the air during handling.
Measure and record the pH at t + 4 h, t + 44 h, t + 48 h. For the measurement of the pH, stop the agitation
0 0 0
and allow the mix to settle for 5 min. Measure the pH by inserting the clean electrode into the supernatant.
NOTE 2 The pH value at t + 4 h is used for checking that sufficient pH adjustment has been obtained by the acid or
base additions, respectively.
Since the pH is measured directly in the suspension, rinse the pH electrode thoroughly and dry softly before
and between uses in order not to contaminate the suspension.
The pH value measured before filtration at t + 48 h will be the one assigned to the analysis of the eluate.
NOTE 3 The pH is measured directly in the bottle at t + 48 h, since filtration can change pH in the eluate.
Report the pH deviation between t + 4 h and t + 44 h.
0 0
The deviation between pH at t + 44 h and pH at t + 48 h shall not exceed 0,3 pH units, which is the limit for
0 0
approaching an equilibrium condition. A special note shall be made in the report if this requirement is not met.
If too many experimental points deviate (more than three amongst eight), the conclusion is that this test is not
applicable to this material.
When the equilibrium condition is strictly compulsory for specific use, but is not fulfilled in the test, it is possible
to continue the test to a maximum of 7 d for all the eight experimental points (selected pH values) in order to
avoid association of results at 48 h with those at a longer leaching time. In this case, the pH deviation can be
limited to 0,3 pH units for the last 24 h (maximum between the sixth and seventh day). The experimental
point(s), which do not conform to these new conditions, will not be exploited and this fact will be mentioned in
the report. This specific procedure is not part of this document.
Allow the suspended solids to settle for (15 ± 5) min.
Transfer the supernatant to centrifuge tubes (6.7).
10 © ISO 2007 – All rights reserved

ISO/TS 21268-4:2007(E)
There are two options for solid-liquid separation.
1) Centrifuge the eluate for 30 min at 20 000 g to 30 000 g using a high-speed centrifuge (6.6).
2) Centrifuge the eluate for 5 h at 2 000 g to 2 500 g in glass bottles using a lower speed centrifuge (6.6).
Cooling shall be applied to maintain the temperature at (20 ± 5) °C (see 6.6).
NOTE 4 Based on Stoke's law, the results of both centrifugation methods are expected to be comparable.
Gentle breaking shall be applied in order to avoid resuspension. Deceleration time shall not exceed 20 min.
After centrifugation, the eluate shall be transferred immediately to an appropriate container
...