CEN/TR 18076:2024
(Main)Ambient air - Equivalence of automatic measurements of elemental carbon (EC) and organic carbon (OC) in PM
Ambient air - Equivalence of automatic measurements of elemental carbon (EC) and organic carbon (OC) in PM
This document provides definitions of the quantities measured by various candidate methods, their basic principles, and their advantages and disadvantages.
Currently no traceable primary reference materials are available for EC and OC analyses. This document provides guidance to test the equivalence between candidate methods and EN 16909 for EC and/or OC determination(s), based on EN 16450.
Außenluft - Äquivalenz von automatischen Messungen von elementarem Kohlenstoff (EC) und organischem Kohlenstoff (OC) in PM
In diesem Dokument werden Definitionen der Messgrößen durch verschiedene infrage kommende Verfahren, ihre Grundlagen und ihre Vor- und Nachteile angegeben.
Derzeit sind für EC- und OC-Analysen keine rückführbaren primären Referenzmaterialien verfügbar. Dieses Dokument bietet eine Anleitung zur Prüfung der Gleichwertigkeit zwischen infrage kommenden Verfahren und EN 16909 für EC- und/oder OC Bestimmungen auf Grundlage von EN 16450.
Air ambient - Équivalence des mesurages automatiques du carbone élémentaire (EC) et du carbone organique (OC) dans la matière particulaire
Le présent document fournit les définitions des grandeurs mesurées par différentes méthodes candidates, leurs principes de base ainsi que leurs avantages et leurs inconvénients.
À l’heure actuelle, on ne dispose d’aucun matériau de référence primaire traçable pour l’analyse du carbone élémentaire et du carbone organique. Le présent document fournit des recommandations pour vérifier l’équivalence existant entre les méthodes candidates et l’EN 16909 pour le dosage du carbone élémentaire et/ou du carbone organique, en s’appuyant sur l’EN 16450.
Zunanji zrak - Ekvivalentnost avtomatskih meritev elementarnega ogljika (EC) in organskega ogljika (OC) v delcih PM
Ta dokument podaja definicije količin, izmerjenih z različnimi možnimi metodami, ter njihova osnovna načela, prednosti in slabosti.
Sledljiv osnovni referenčni material za analize elementarnega ogljika (EC) in organskega ogljika (OC) trenutno ni na voljo. Ta dokument
podaja smernice za preskušanje ekvivalentnosti med možnimi metodami in standardom EN 16909 za določanje elementarnega in/ali organskega ogljika
na podlagi standarda EN 16450.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2024
Zunanji zrak - Ekvivalentnost avtomatskih meritev elementarnega ogljika (EC) in
organskega ogljika (OC) v delcih PM
Ambient air - Equivalence of automatic measurements of elemental carbon (EC) and
organic carbon (OC) in PM
Außenluft - Äquivalenz von automatischen Messungen von elementarem Kohlenstoff
(EC) und organischem Kohlenstoff (OC) in PM
Air ambiant - Equivalence des systèmes automatisés de mesurage du carbone
élémentaire et du carbone organique
Ta slovenski standard je istoveten z: CEN/TR 18076:2024
ICS:
13.040.20 Kakovost okoljskega zraka Ambient atmospheres
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEN/TR 18076
TECHNICAL REPORT
RAPPORT TECHNIQUE
June 2024
TECHNISCHER REPORT
ICS 13.040.20
English Version
Ambient air - Equivalence of automatic measurements of
elemental carbon (EC) and organic carbon (OC) in PM
Air ambient - Équivalence des mesurages Außenluft - Äquivalenz von automatischen Messungen
automatiques du carbone élémentaire (EC) et du von elementarem Kohlenstoff (EC) und organischem
carbone organique (OC) dans la matière particulaire Kohlenstoff (OC) in PM
This Technical Report was approved by CEN on 10 June 2024. It has been drawn up by the Technical Committee CEN/TC 264.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 18076:2024 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 6
5 Potential automatic candidate methods . 6
5.1 Online thermal analyses . 6
5.2 OC and EC determination . 6
5.3 TC determination . 7
5.4 Photoacoustic spectrometry [11]. 7
5.5 Photo-Thermal Interferometry [13] . 8
5.6 Extinction minus scattering . 8
5.7 Filter-based absorption photometry . 8
5.8 Laser-induced incandescence spectrometry [12] . 9
5.9 Filter-based absorption photometry with high temperature heated inlet . 9
5.10 Online Aerosol Mass Spectroscopy . 10
6 Discussion . 10
7 Uncertainties . 11
7.1 General. 11
7.2 EC . 11
7.3 OC . 12
8 Suggestions for testing the equivalency of candidate methods with EN 16909 . 12
8.1 General. 12
8.2 Sampling . 13
8.3 Type testing . 13
8.4 Field operation and QA/QC . 14
Bibliography . 15
European foreword
This document (CEN/TR 18076:2024) has been prepared by Technical Committee CEN/TC 264 “Air
quality”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
Introduction
The Directive on ambient air quality and cleaner air for Europe [1] requires the chemical speciation of
the sub-2,5 µm size fraction of suspended particulate matter (PM ) in ambient air, as described in
2,5
Annex IV. For air quality to be assessed on a consistent basis across the European Union, Member States
are required to employ standard measurement techniques and procedures. The aim of the European
Standard EN 16909 is to present guidance on the measurement procedures to be followed when
monitoring elemental carbon (EC) and organic carbon (OC) by collecting PM on filters, and
2,5
subsequently performing thermal-optical analyses.
Although EC and OC are only defined in an operational way, measurements according to EN 16909 are
reproducible and EC and OC as defined by the standard are commonly applicable variables. But the
measurement is time consuming, and automated online measurements of EC and OC is not part of
EN 16909. Substitution of OC and EC thermal-optical analyses as described in EN 16909 by automatic
methods would be useful, if the equivalence of candidate methods with the standard EN 16909 can be
demonstrated.
1 Scope
This document provides definitions of the quantities measured by various candidate methods, their basic
principles, and their advantages and disadvantages.
Currently no traceable primary reference materials are available for EC and OC analyses. This document
provides guidance to test the equivalence between candidate methods and EN 16909 for EC and/or OC
determination(s), based on EN 16450.
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.
EN 16909:2017, Ambient air — Measurement of elemental carbon (EC) and organic carbon (OC) collected
on filters
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 16909:2017 and the following
apply.
3.1
notional limit value
limit values for EC and OC estimated from WHO Guideline recommendation for PM 24 h average limit
2,5
value (15 µg/m ) [2] and the average concentration of EC and OC observed in Europe at such level of
PM concentration
2,5
3.2
Black Carbon
BC
carbonaceous component of particulate matter that absorbs light in all wavelengths of solar radiation
present in the troposphere, i.e. 280 nm to 2500 nm
3.3
Equivalent Black Carbon
EBC
black carbon, derived from optical absorption methods (unit: µg/m ), calculated as the ratio of the
measured aerosol light absorption coefficient to an a priori defined Mass Absorption Cross section (MAC)
parameter
3.4
Mass Absorption Cross section
MAC
characteristic value for light absorbing atmospheric aerosol, providing the particle absorption cross
section normalized by the mass of particles causing the observed light absorption (unit m /g) [3]
3.5
refractory Black Carbon
rBC
black carbon, derived from incandescence methods (unit: µg/m ), that address the thermal stability of
the carbonaceous matter [4]
Note 1 to entry: These incandescence methods need specifying means of calibration, conversion factor from
thermal radiation to carbon mass, and the size-cut of rBC particles.
4 Symbols and abbreviations
For the purposes of this document, the abbreviations and acronyms given in EN 16909:2017 and the
following apply.
AMS Automatic measurement system
BC Black carbon
DQO Data quality objectives
EBC Equivalent black carbon
MAC Mass absorption cross section
NDIR non-dispersive infrared detector
OAMS Online aerosol mass spectrometer
PTI Photo-Thermal Interferometry
rBC Refractory black carbon
RM Reference method
5 Potential automatic candidate methods
5.1 Online thermal analyses
Online carbon thermal analysis is based on the analysis of particulate matter collected on a filter located
in the analyser. PM is collected at ambient temperature. The filter is subsequently heated up, and
collected carbonaceous matter evolves from the filter by volatilisation and/or oxidation. Gaseous carbon
compounds can be quantified using various detectors. PM collection and analysis can be performed
automatically in sequence for several days.
5.2 OC and EC determination
Besides the standard method described in EN 16909, many other methods for the determination of the
organic and elemental carbon content of PM samples deposited on filters have been described. The
principle of these methods is similar to that of the standard method (EN 16909), namely that EC is more
refractory than OC.
In particular, OC and EC can be measured automatically and semi-continuously with instruments where
PM collection and OC and EC analyses are performed sequentially. Carbonaceous compounds are oxidized
and detected as CO by e.g. a NDIR. Some instruments can combine the measurement of OC and EC with
measurements of EBC. The thermal protocol described in EN 16909 and light transmittance-based
correction of charring can be applied [5]. The main difference with the standard method (EN 16909) is
that PM sampling is shorter (usually 1 h to 3 h) and the filter is located inside the analyser downstream
of a denuder. Hundreds of sampling/analysis sequences can be performed with a single filter.
Other types of thermal analyses have been used to determine OC and EC in PM samples deposited on
filters. Some methods do not include any optical correction for charring of organic substances. Others
only use oxygen containing carrier gas. Both types of methods distinguish OC from EC from the
temperature at which they evolve. Some of these methods have been implemented in automatic analytical
devices [6].
There is no fundamental reason why OC and EC as determined by automatic analysers would differ from
OC and EC as determined according to EN 16909 as long as the same thermal protocol is used, except for
sampling artefacts. Indeed, different studies of positive and negative sampling artefacts have shown that
the magnitude depends on the use of denuder, sampling face velocity, sampling duration, filter substrate,
pre-firing of filters, ambient temperature and aerosol mixture [7, 8 and 9]. Online thermal analysers can
be equipped with denuders which minimize OC positive sampling artefacts [6].
Pros
The advantage of this method (as compared to other candidate methods) is that it measures OC and EC
mass.
Cons
The disadvantage is that it is semi-continuous only (no sampling during analysis) and time resolution
cannot be less than ½ h.
5.3 TC determination
Online total carbon analysers collect carbonaceous aerosols on a filter which subsequently is heated
rapidly, ≤ 2 min, to a high temperature, ≥ 800°C, under an oxidizing atmosphere. The carbonaceous
aerosol is converted to CO which is quantified by a detector, e.g. NDIR. The TC measurements can be
associated with estimates of OC and EC by parallel, internal or external, optical measurements. Online
thermal TC analysers can be equipped with denuders to minimize OC positive sampling artefacts [10].
Pros
Simplicity (low demand on consumables).
Cons
No determination of EC and OC. Time resolution cannot be less than 20 min.
5.4 Photoacoustic spectrometry [11]
Air is drawn in the instrument, where pulsed light is absorbed by light absorbing particles resulting in an
increase of the particles’ temperature. Particle temperature increase is typically less than 1K for typical
aerosol size and laser power used. Heat transfers by conduction from the particle to the surrounding air,
expanding the air, and creating a pressure disturbance or soundwave. The volumetric expansion of the
heated particle is negligible compared to that of the surrounding air. The conversion of light absorption
into sound is known as the photoacoustic effect. A microphone is used to detect the soundwave
amplitude. Aerosol light absorption can be quantitatively determined by use of a calibrated laser power
meter and a microphone, as long as all the heat exits the particle to the surrounding air during the acoustic
cycle [12]. Quantitative measurement of aerosol absorption is obtained for commercial photoacoustic
instruments using NO gas standards for calibration, for monochromatic light in the range of about
500 nm to 1000 nm.
Pros
The photoacoustic technique is based on first physical principles, does not suffer from matrix effects and
is independent of particle size.
Cons
The NO gas calibration cannot be extended to short wavelengths due to dissociation of NO . In urban
2 2
environments high variability of NO and other absorbing gases can cause interferences. In order to
eliminate these interferences a second particle free channel can be used in parallel.
5.5 Photo-Thermal Interferometry [13]
At its most fundamental level, the PTI technique measures the optical pathlength change that one arm (or
light path) of an interferometer (referred to as the “probe” arm) experiences relative to the other arm of
the interferometer (called the “reference”). When the two arms are recombined at a beam-splitter an
interference pattern is created. If the optical pathlength in one arm of the interferometer changes, a
commensurate shift in the interference pattern will take place. For the specific application of this
technique for measuring aerosol light absorption, the optical pathlength change is induced when the
dissipation of the spectrally absorbed energy creates a temperature gradient. This localized heating
creates an air refractive index gradient surrounding the particle (or molecule) causing the probe arm of
the interferometer to take a slightly shorter optical pathlength relative to the unperturbed reference arm.
Pros
This method directly measures the aerosol absorption coefficient, avoiding filter interaction artefacts,
and remains unaffected by particle size or relative humidity.
Cons
Further evaluation is needed for a full assessment.
5.6 Extinction minus scattering
The Extinction Minus Scattering method is a differential technique to determine aerosol particle light
absorption by subtracting the aerosol particle light scattering from the aerosol particle light extinction.
Scattering is measured by an integrating nephelometer whereas extinction is measured by a separate
extinction cell, or by a single instrument combining an integrating nephelometer and an extinction cell
[14]. The calibration of the integrating nephelometer is performed using gases with known scattering
coefficients, while the calibration of the extinction cell can be based on the calibration of the integrating
nephelometer by using purely scattering (i.e. non-absorbing) particles.
Pros
The overall method is based on basic optical properties and is traceable to SI units.
Cons
The EMS method suffers from a high detection limit and a large uncertainty when aerosol particle light
absorption is small, and therefore extinction and scattering coefficients differ by a few percent only.
5.7 Filter-based absorption photometry
Aerosol absorption photometers measure the change in optical attenuation of a filter as aerosol is
deposited on this filter over time. Measurements are sensitive to all species adsorbing and scattering light
at the instrument wavelength(s) usually ranging between 370 nm and 950 nm, including graphite, some
aromatic and phenolic compounds, also some sulphides and oxides of heavy metals ([15], [16], [17], [18],
[19] and [20]). Light attenuation is measured at one or several wavelengths. Attenuation is converted to
atmospheric absorbance using manufacturer defined factors taking into account the set-up geometry and
flow rate, the multiple light scattering within the filter, the filter loading effect, and (optionally) the
aerosol scattering.
Filter-based absorption photometer measurements are affected by the nonlinear filter loading effect,
which can be corrected either by post-processing algorithms or, as in case with one absorption
photometer type, by real-time double spot measurements. Scattering particles and multi scattering by
the filter matrix also contribute to the optical attenuation of the PM deposited on the filter material.
Methods were developed to reduce the error in absorption determination due to aerosol scattering and
multiple scattering by the fibre matrix. Most are empirical corrections to be applied a posteriori to the
raw measurement data. However, one of the absorption photometer types measures light transmission
and back scattering at various angles [21]. The aerosol optical absorption coefficient is then calculated
by a radiative transfer model.
Pros
The measurement itself is simple and can be carried out automatically. Continuous measurements are
possible so that diel variations can be measured.
Cons
EBC mass concentrations that are provided by aerosol optical absorption photometers are estimated by
simply assuming the EBC mass absorption cross-section. In practice, the aerosol mass absorption cross-
section is highly variable in time and space due to i. a. factors related to the aerosol mixing state (internal
vs. external mixture of absorbing and non-absorbing species), the particle size distribution and the
contribution to light absorption by non-refractory carbonaceous matter.
5.8 Laser-induced incandescence spectrometry [12]
The method currently most used for atmospheric measurements of rBC combines the measurements of
the single particle incandescence and scattered light. Particle incandescence can be observed when
absorbed light heats the particle at such a temperature that it begins to incandesce. High temperature
particles emit radiation that can be used to derive the mass of the absorbing particles. At sufficient laser
energy, particles are heated to their vaporization temperature (or boiling point). Elastic scattering and
laser-induced incandescence are measured by various detectors at different wavelengths. Laser-induced
incandescence measurements in a broad and a narrow wavelength band are used to determine each
particle’s mass and boiling point: The peak intensity of the incandescence is proportional to the refractory
mass of the incandescent particle and the ratio of broad- to narrow-band incandescence can provide
information about its chemical composition. This makes it possible to discriminate BC from other
refractory materials [22]. Light scattering measurements lead to an estimate of each particle size before
volatilisation.
Pros
Laser-induced incandescence informs about the particle composition and can distinguish BC from other
light absorbing species. It is a powerful technique for providing valuable information on the state of
mixing of BC and non-refractory components. Results are obtained for individual particles of the aerosol
size range analysed.
Cons
The aerosol size range detected does not cover the full range of the fine
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...