Soil quality -- Guideline for the screening of soil polluted with toxic elements using soil magnetometry

This document specifies methods for the measurements of magnetic susceptibility of soils (κ) as an indicator of potential soil pollution/contamination with trace elements associated with technogenic magnetic particles (TMPs) and describes related procedures, protocols and guidelines to be applied as a screening geophysical method of determination of soil pollution with trace elements. The results of measurements are used for preparing the maps of magnetic susceptibility of soils in the area of interest. From these maps, the areas of elevated and high magnetic susceptibility indicating high trace element total pollution load are discriminated for further identification of pollutants by geochemical methods. This document is applicable to screening all TMPs-related anthropogenic emission sources including long-range transport of airborne elements, of which TMPs are carriers and indicators. Such emission sources comprise the majority of high-temperature industrial processes, where iron is present in any mineralogical form in raw materials, additives or fuels, is transformed into ferrimagnetic iron oxides (e.g. fossil solid and liquid fuels combustion, metallurgy, cement and ceramics industry, coke production, industrial waste landfills, land transport). This document is not applicable to screening anthropogenic emissions not associated with TMPs, e.g. organic pollutants or emissions from agricultural sources. NOTE 1 Copper, zinc and other non-ferrous metal ores also contain iron (in many sulfides) as this element is abundant in almost all environments. During smelting, the iron occurring in sulfides is transformed into ferrimagnetic oxides (TMPs). However, in such cases, the proportion of TMPs and related PTEs is usually less than at coal combustion or iron metallurgy, for example, and not all PTEs are physically associated and transported by TMPs. Non-airborne elements are deposited in the close proximity of the emission source, while TMPs can be used in these cases as indicators of airborne elements and of the spatial distribution of the total element deposition from a smelter in the area. In rare cases, some soils are developed on bedrock exhibiting geogenically high magnetism, which can cause false-positive results. This influence can, however, be easily indicated by measurements of magnetic susceptibility along soil profiles. This method is not applicable when the bedrock exhibits extremely high magnetic signals. NOTE 2 Such cases are rare.

Qualité du sol -- Lignes directrices pour le diagnostic de la pollution du sol par des éléments toxiques en utilisant la magnétométrie

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Status
Published
Publication Date
11-Dec-2019
Current Stage
6060 - International Standard published
Start Date
22-Nov-2019
Completion Date
12-Dec-2019
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ISO 21226:2019 - Soil quality -- Guideline for the screening of soil polluted with toxic elements using soil magnetometry
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INTERNATIONAL ISO
STANDARD 21226
First edition
2019-12
Soil quality — Guideline for the
screening of soil polluted with toxic
elements using soil magnetometry
Qualité du sol — Lignes directrices pour le criblage du sol pollué par
des éléments toxiques en utilisant la magnétométrie du sol
Reference number
ISO 21226:2019(E)
ISO 2019
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ISO 21226:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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

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Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO 21226:2019(E)
Contents Page

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

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

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

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

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

4 Symbols and abbreviated terms ........................................................................................................................................................... 3

5 Fundamentals .......................................................................................................................................................................................................... 3

5.1 Screening principle ............................................................................................................................................................................. 3

5.2 Screening work processes ............................................................................................................................................................. 4

5.3 Field measurements and works ............................................................................................................................................... 4

5.4 Laboratory measurements ........................................................................................................................................................... 4

5.5 Data mapping ........................................................................................................................................................................................... 4

5.6 Soil sampling for geochemical analysis ............................................................................................................................. 4

6 Apparatus ..................................................................................................................................................................................................................... 4

6.1 Field equipment ..................................................................................................................................................................................... 4

6.2 Laboratory equipment ..................................................................................................................................................................... 5

6.3 Data mapping ........................................................................................................................................................................................... 5

7 Procedures .................................................................................................................................................................................................................. 5

7.1 Measurement network ..................................................................................................................................................................... 5

7.2 Measurements of magnetic susceptibility at the topsoil surface ................................................................ 5

7.3 Measurements of vertical magnetic susceptibility distribution ................................................................... 6

7.3.1 General...................................................................................................................................................................................... 6

7.3.2 Topsoil core sampling .................................................................................................................................................. 6

7.3.3 Field measurements...................................................................................................................................................... 6

7.3.4 Laboratory measurements ...................................................................................................................................... 6

7.3.5 Topsoil magnetic profile analysis ...................................................................................................................... 6

7.4 Magnetic susceptibility mapping and data analysis ............................................................................................... 7

7.4.1 Data processing ................................................................................................................................................................. 7

7.4.2 Magnetic susceptibility surface mapping ................................................................................................... 7

7.4.3 Data analysis ........................................................................................................................................................................ 7

7.5 Soil sampling for geochemical analysis ............................................................................................................................. 7

8 Screening report ................................................................................................................................................................................................... 8

Annex A (informative) Relation between magnetic susceptibility and trace element

contamination of topsoil .............................................................................................................................................................................. 9

Annex B (informative) Measurement performance according to 7.1 and 7.2 .........................................................16

Annex C (informative) Example of a screening report to record measurement results

according to 9 ........................................................................................................................................................................................................18

Annex D (informative) Validation summary ..............................................................................................................................................22

Bibliography .............................................................................................................................................................................................................................26

© ISO 2019 – All rights reserved iii
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ISO 21226:2019(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

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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).

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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 the following

URL: www .iso .org/ iso/ foreword .html.

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

Chemical and physical characterization.

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.
iv © ISO 2019 – All rights reserved
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ISO 21226:2019(E)
Introduction

At the time of publishing this document, the mapping of soil pollution status is generally based on

geochemical methods that, despite development of new, more sophisticated and precise equipment,

have apparent disadvantages, among them uncertainty, as usually there is no satisfactory information

on the extent and range of pollution in the area. This results in the need of a large number of samples to

be collected, followed by expensive and time-consuming chemical analysis.

Among anthropogenic soil pollutants, trace elements [potentially toxic elements (PTEs)] are the most

problematic, widespread and persistent group that has accumulated in soil since the beginning of

industrial revolution, mostly due to dry and wet deposition of particulates originating from emissions

to the atmosphere. Due to the historical and persistent character of pollution, determination of soil

quality, sources, extent and range of pollution requires large-area dense environmental monitoring

network. In addition, identification of sources, pathways and extent of long-range transboundary

transport of airborne trace elements creates serious technical problems and uncertainties. This

has resulted in the development and broad application of soil magnetometry as easy-to-use, quick,

inexpensive but sensitive and reliable screening geophysical technique based on the measurements of

magnetic susceptibility in topsoil.

The method has not yet been standardized. For this purpose, a standard procedure, protocols and

guidelines for the using soil magnetometry as a screening method are developed primarily to support

the implementation of the two-stage optimized geophysical/geochemical method of measuring the

soil spatial anthropogenic pollution with airborne trace elements from the dry and wet deposition,

for further delineation of polluted soil areas to be adequately managed. The method provides data on

the volume-specific magnetic susceptibility, κ, which reflects cumulative anthropogenic pollution of

soil with trace elements, expressed as a PLI. The method is intended to serve as a screening and early

warning system to be applied at any scale, from local to large regional one, also for the investigation of

a long-range airborne element transport.

The application of this screening method alone does not allow determining the kind and concentrations

of specific trace elements in soils. To carry out a more precise survey of the anthropogenic soil pollution

with airborne trace elements, soil magnetometry as the screening geophysical “in situ” measurement

technique (the 1st stage) is to be integrated with the classical geochemical methods (the 2nd stage)

of the optimized procedure. Specifically, on the basis of geophysical methods used for screening, a

relevant dense geochemical monitoring network can be applied in the areas of diagnosed elevated risk,

thus reducing the number of samples and chemical analyses required.
© ISO 2019 – All rights reserved v
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INTERNATIONAL STANDARD ISO 21226:2019(E)
Soil quality — Guideline for the screening of soil polluted
with toxic elements using soil magnetometry
1 Scope

This document specifies methods for the measurements of magnetic susceptibility of soils (κ) as an

indicator of potential soil pollution/contamination with trace elements associated with technogenic

magnetic particles (TMPs) and describes related procedures, protocols and guidelines to be applied as

a screening geophysical method of determination of soil pollution with trace elements. The results of

measurements are used for preparing the maps of magnetic susceptibility of soils in the area of interest.

From these maps, the areas of elevated and high magnetic susceptibility indicating high trace element

total pollution load are discriminated for further identification of pollutants by geochemical methods.

This document is applicable to screening all TMPs-related anthropogenic emission sources including

long-range transport of airborne elements, of which TMPs are carriers and indicators. Such emission

sources comprise the majority of high-temperature industrial processes, where iron is present in any

mineralogical form in raw materials, additives or fuels, is transformed into ferrimagnetic iron oxides

(e.g. fossil solid and liquid fuels combustion, metallurgy, cement and ceramics industry, coke production,

industrial waste landfills, land transport). This document is not applicable to screening anthropogenic

emissions not associated with TMPs, e.g. organic pollutants or emissions from agricultural sources.

NOTE 1 Copper, zinc and other non-ferrous metal ores also contain iron (in many sulfides) as this element

is abundant in almost all environments. During smelting, the iron occurring in sulfides is transformed into

ferrimagnetic oxides (TMPs). However, in such cases, the proportion of TMPs and related PTEs is usually less than

at coal combustion or iron metallurgy, for example, and not all PTEs are physically associated and transported

by TMPs. Non-airborne elements are deposited in the close proximity of the emission source, while TMPs can

be used in these cases as indicators of airborne elements and of the spatial distribution of the total element

deposition from a smelter in the area.

In rare cases, some soils are developed on bedrock exhibiting geogenically high magnetism, which

can cause false-positive results. This influence can, however, be easily indicated by measurements of

magnetic susceptibility along soil profiles. This method is not applicable when the bedrock exhibits

extremely high magnetic signals.
NOTE 2 Such cases are rare.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
© ISO 2019 – All rights reserved 1
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ISO 21226:2019(E)
3.1
topsoil

upper part of a natural soil that is generally dark coloured and has a higher content of organic matter

and nutrients when compared to the (mineral) horizons below, excluding the humus layer

Note 1 to entry: For arable land, topsoil refers to the ploughed soil depth, while for grassland it is the soil layer

with high root content.
3.2
subsoil
natural soil material below the topsoil (3.1) and overlying the parent material

Note 1 to entry: All or much of the original rock structure has been obliterated by pedogenic processes.

3.3
technogenic magnetic particles

different mineral forms of iron oxides exhibiting magnetic properties that are components of

anthropogenic emissions from high-temperature technologic processes and are carriers of airborne

trace elements
3.4
soil magnetometry

geophysical survey technique used for mapping spatial variations in the magnetic properties [mostly

magnetic susceptibility (3.5)] of topsoil (3.1) and subsoil (3.2)
3.5
magnetic susceptibility

measure of the ability of a material to be magnetized expressed in SI magnetic units, which is

proportional to the concentration of technogenic magnetic particles (3.3) in topsoil (3.1), indicating

cumulative anthropogenic contamination of soil with trace elements
3.6
mass magnetic susceptibility

magnetic susceptibility (3.5) divided by density of sample material, measured in a laboratory when the

mass of measured sample is known
3.7
frequency dependence of magnetic susceptibility

parameter revealing presence of superparamagnetic particles, being the result of natural (pedogenic or

biogenic processes)
3.8
magnetic susceptibility mapping

development of 2D or 3D maps with the use of measured data of magnetic susceptibility (3.5) in the area

of interest correlated with pollution load index
3.9
pollution load index

dimensionless index showing cumulative anthropogenic pollution of soil with trace elements used to

validate results of magnetic susceptibility (3.5) screening
3.10
contamination factor
ratio of specific metal concentration in soil and its background value in soil
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ISO 21226:2019(E)
3.11
natural background concentration

concentration of a substance that is derived solely from natural sources (i.e. of geogenic origin)

commonly expressed in terms of average, a range of values or a natural background value

Note 1 to entry: For the practical purposes of this document, this is mean element concentration in subsoil

measured in soil cores collected from studied area.
3.12
soil core

core collected from an uppermost soil layer (min. 200 mm long and 35 mm in diameter)

3.13
boundary depth

depth in soil profile where magnetic susceptibility (3.5) stabilizes after decreasing from its maximum

value, indicating the transition from the polluted layer to unpolluted part of soil profile

4 Symbols and abbreviated terms
PTE potentially toxic trace element
TMP technogenic magnetic particle
C element concentration in a sample
C baseline value for an element e
Bl-e
CF contamination factor
PLI pollution load index
SITE
κ magnetic susceptibility
χ mass magnetic susceptibility
χ frequency dependence of magnetic susceptibility
5 Fundamentals
5.1 Screening principle

Magnetic iron oxides are components of industrial and urban dusts emitted to the atmosphere and

deposited on the soil surface. Anthropogenic emission sources of pollution containing technogenic

magnetic particles (TMPs) comprise metallurgy, combustion of fossil fuels, coke industry, cement and

ceramic industry, land transport, waste landfill sites and others.

Volume-specific magnetic susceptibility κ is directly proportional to the concentration of magnetic

particles within the sensor penetration area and reflects cumulative anthropogenic contamination

of soil with PTEs. High interdependence between the total historic dust dry and wet deposition, and

magnetic susceptibility has been well confirmed. Magnetic susceptibility can be measured quickly and

accurately in trace amounts as validated in Annex D. Magnetic susceptibility mapping of an area of

interest based on the measurements of magnetic susceptibility in topsoil (soil surface and uppermost

horizons), correlates with cumulative anthropogenic pollution with airborne trace elements expressed

as pollution load index (PLI). Annex A describes the relation between magnetic susceptibility and trace

element contamination taking place in topsoil.
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ISO 21226:2019(E)
5.2 Screening work processes

This screening method consists of two or three steps. All measurements may be performed either in

the field only (two-step procedure), or as field and laboratory works (three-step procedure):

— field measurements and works;
— laboratory measurements;
— data mapping.

The next step is related to the use of screening measurement data maps with delineated potentially

polluted areas for the targeted soil sampling within the proper geochemical analysis of soil

pollution status:
— soil sampling for geochemical analysis.
5.3 Field measurements and works
Field measurements and works to be carried out are as follows:
— surface measurements of magnetic susceptibility of topsoil;

— in situ measurements of magnetic susceptibility along soil profiles (optional);

— topsoil core sampling for laboratory measurements of magnetic susceptibility along soil profiles.

5.4 Laboratory measurements
Magnetic susceptibility is measured along soil profiles in a laboratory.
5.5 Data mapping
Data mapping to be completed are as follows:
— magnetic susceptibility mapping of the area;
— delineation of contaminated sites for further geochemical analysis.
5.6 Soil sampling for geochemical analysis

Soil sampling is necessary, in case geochemical analysis is additionally arranged. See 7.5.

6 Apparatus
The following equipment and devices are used.
6.1 Field equipment
6.1.1 Field magnetic susceptibility loop sensor.
6.1.2 GPS.
6.1.3 Datalogger coupled with GPS or laptop.
6.1.4 Topsoil core sampler.
6.1.5 Plastic tubes for the topsoil core sampler.
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ISO 21226:2019(E)
6.1.6 Hammer.
6.1.7 Field core magnetic susceptibility meter (optional).

6.1.8 Laptop coupled with a field core magnetic susceptibility meter (optional).

6.2 Laboratory equipment
6.2.1 Dual-frequency laboratory magnetic susceptibility sensor.
6.2.2 Laboratory core magnetic susceptibility meter.
6.3 Data mapping
6.3.1 Visualization, contouring and surface modelling software.

NOTE Software used for terrain modelling, bathymetric modelling, landscape visualization, surface

analysis, contour mapping, 3D/2D surface mapping, gridding and volumetrics.
7 Procedures
7.1 Measurement network

The main purpose of surface measurements of magnetic susceptibility is the determination of spatial

distribution of pollution with trace elements. Basic measurements of magnetic susceptibility (κ) in the

area of interest are performed in the field in a possibly regular network that is designed as discussed

in Annex B.2. The grid density is selected depending on the size of an area to be screened, and the

availability of preliminary information concerning possible sources and extent of anticipated pollution,

but no less than 1/7 to 1/10 of the surveyed area, at the distance ratio DR approximately 1:1 to 1:2

between basic measurement points.

In the areas of identified elevated magnetic susceptibility, additional measurements should be

performed close to about every third basic point, at the considerably smaller distance ratio DR

approximately 1:5 to 1:10.

Within delineated areas of magnetic susceptibility higher than the average for the area, dense

measurements should be carried out. The measurement points may be sited in irregular distances.

7.2 Measurements of magnetic susceptibility at the topsoil surface

Magnetic susceptibility (κ) at the topsoil surface is measured in the field with a portable hand magnetic

susceptibility loop sensor in network points. The geographic position of each measurement point is

recorded with GPS as is shown in the scheme in Annex B.1. Within about 2 m radius around the GPS

position, at least 11 measurements (odd number) of magnetic susceptibility shall be taken. The soil

surface shall be available for a sensor, thus a thick vegetation or litter in the measurement point should

be racked aside.
The time needed for a single measurement is approximately 1 s.

The measurement results can be downloaded from a datalogger coupled with GPS and are ready for

analysis. The downloaded table for a single measurement includes coordinates and measured values of

soil magnetic susceptibility.

NOTE Extraordinary high values of magnetic susceptibility (outliers) can be caused by the occasional

occurrence in topsoil layer of metallic artefacts. The possible impact of artefacts is eliminated by the rejection of

the highest and the lowest values from the measured set of results when calculating mean value for a single point.

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ISO 21226:2019(E)
7.3 Measurements of vertical magnetic susceptibility distribution
7.3.1 General

The main purpose of measurements of magnetic susceptibility (κ) along the topsoil profile is: (a)

determination of vertical distribution of anthropogenic pollution of the soil with trace elements that

could be caused by different accumulation in organic horizons or by vertical migration of TMPs; (b)

detection of possible influence of magnetic properties of a bedrock; (c) evaluation of the background

magnetic susceptibility values;

Measurements of magnetic susceptibility along the soil profiles can be performed in two ways:

— by taking topsoil cores in the field and sending to the laboratory for magnetic susceptibility analysis;

— by in situ measurement of magnetic topsoil profile (optional).

The choice of field or laboratory measurements depends on the convenience, the need of obtaining

instant information for further measurement performance and availability of equipment.

7.3.2 Topsoil core sampling

The topsoil core samples should be taken in the parts of the area showing the highest magnetic

susceptibility (κ). Additionally, for a reference at least one core sample from the area of the lowest, and

also of the moderate magnetic susceptibility shall be taken. The number of sampling points should be

specified individually with regard of representativeness.

Cores are taken in the field in plastic tubes with the use of soil core sampler hammered into the soil

layer. Plastic tubes, after checking the core status, shall be protected from core destabilization within

the tube by capping from both sides with neutral caps, marked and wrapped tightly into thin plastic foil

for the protection from moisture loss.
7.3.3 Field measurements

In situ measurements are more time-consuming, and slow down the measurement campaign; they

preferably need dry weather for convenient performance. These measurements should be carried out if

the results are required for a further proper design and conducting spatial field measurements.

The automatic “in situ” measurement of magnetic topsoil profile can be performed with the use of

a core magnetic susceptibility meter for field measurements along the soil profile to detect vertical

distribution of pollutants and horizons of pollutant accumulation. These data in the form of tables and

graphs presenting magnetic susceptibility values vs layer depth are available instantly at the laptop

coupled with the meter.

NOTE 1 A core magnetic susceptibility meter for automated in situ measurements is not indispensable

equipment. The same results can be obtained with the use of a laboratory analysis of core samples taken in the field.

NOTE 2 In case of in situ measurements, the diameter of core sampler is compatible with core magnetic

susceptibility meter.
7.3.4 Laboratory measurements

Soil cores taken in the field in plastic tubes with the use of soil core sampler are measured in a laboratory

using a laboratory magnetic susceptibility sensor.
7.3.5 Topsoil magnetic profile analysis
Topsoil magnetic susceptibility profiles are analysed to determine:
a) origin of elevated magnetic susceptibility (anthropogenic or natural);
6 © ISO 2019 – All rights reserved
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ISO 21226:2019(E)
NOTE In the case of an anthropogenic origin of elevated magnetic susceptibility.
b) vertical distribution of pollutants resulted from;
1) Anthropogenic accumulation in organic hori
...

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