EN 15852:2010
(Main)Ambient air quality - Standard method for the determination of total gaseous mercury
Ambient air quality - Standard method for the determination of total gaseous mercury
This European Standard specifies a standard method for determining total gaseous mercury (TGM) in ambient air using cold vapour atomic absorption spectrometry (CVAAS), or cold vapour atomic fluorescence spectrometry (CVAFS).
This European Standard is applicable to background sites that are in accordance with the requirements of Directive 2004/107/EC and to urban and industrial sites.
The performance characteristics of the method have been determined in comparative field validation tests carried out at four European locations: two background and two industrial sites. The method was tested for two months at each site over a period of twelve months using automated equipment currently used in Europe for determination of TGM in ambient air.
The working range of the method covers the range of ambient air concentrations from those found at background sites, typically less than 2 ng/m3, up to those found at industrial sites where higher concentrations are expected. A maximum daily average up to 300 ng/m3 was measured during the field trials.
Results are reported as the average mass of TGM per volume of air at 293,15 K and 101,325 kPa, measured over a specified time period, in nanograms per cubic metre.
Außenluftbeschaffenheit - Standardisiertes Verfahren zur Bestimmung des gesamten gasförmigen Quecksilbers
Die vorliegende Europäische Norm beschreibt ein standardisiertes Verfahren zur Bestimmung des gesamten
gasförmigen Quecksilbers (TGM) in der Außenluft mit der Kaltdampf-Atomabsorptionsspektrometrie (CVAAS)
oder der Kaltdampf-Atomfluoreszenzspektrometrie (CVAFS).
Diese Europäische Norm ist anwendbar auf Hintergrundstationen, die den Anforderungen der Richtlinie
2004/107/EG entsprechen, und auf Stadtgebiete sowie Gebiete mit Industrieeinfluss.
Die Verfahrenskenngrößen wurden mit vergleichenden Feldversuchen zur Validierung bestimmt, die an vier
europäischen Standorten durchgeführt wurden: zwei Hintergrundstationen und zwei Industriestandorte. Das
Verfahren wurde an jedem Standort für zwei Monate über einen Zeitraum von 12 Monaten mit automatisierten
Geräten geprüft, die derzeit in Europa zur TGM-Bestimmung in der Außenluft angewendet werden.
Der Messbereich des Verfahrens umfasst Außenluftkonzentrationen von kleiner 2 ng/m3, wie sie üblicherweise
an Hintergrundstationen anzutreffen sind, bis hin zu höheren Konzentrationen, wie sie in Gebieten mit
Industrieeinfluss erwartet werden. Bei den Feldversuchen wurde ein maximaler Tagesmittelwert von bis zu
300 ng/m3 gemessen.
Die Ergebnisse sind in ng/m3 als Mittelwert der über einen festgelegten Zeitraum bei 293 K und 101,325 kPa
bestimmten Masse an TGM je Luftvolumen angegeben.
Qualité de l'air ambiant - Méthode normalisée pour la détermination du mercure gazeux total
La présente Norme européenne spécifie une méthode normalisée pour la détermination du mercure gazeux
total (TGM) dans l’air ambiant par spectrométrie d’absorption atomique de vapeur froide (SAAVF) ou
spectrométrie de fluorescence atomique de vapeur froide (SFAVF).
La présente Norme européenne s’applique aux sites de fond conformes aux exigences de la
Directive 2004/107/CE et aux sites urbains et industriels.
Les caractéristiques de performance de la méthode ont été déterminées par des essais comparatifs de
validation sur le terrain réalisés sur quatre sites en Europe : deux sites de fond et deux sites industriels. La
méthode a été vérifiée pendant deux mois sur chaque site sur une période de douze mois à l’aide
d’équipements automatisés couramment utilisés en Europe pour la détermination du TGM dans l’air ambiant.
L’étendue de mesure de la méthode couvre la plage des concentrations dans l’air ambiant allant de celles
observées sur les sites de prélèvement de fond, généralement inférieures à 2 ng/m3, à celles observées sur
les sites industriels où des concentrations plus élevées sont attendues. Une moyenne journalière maximale
jusqu’à 300 ng/m3 a été mesurée au cours des essais sur le terrain.
Les résultats sont exprimés en masse moyenne de TGM par volume d’air à 293,15 K et 101,325 kPa,
mesurée sur une période de temps spécifiée, en nanogrammes par mètre cube (ng/m3).
Kakovost zunanjega zraka - Standardna metoda za določevanje celotnega živega srebra v plinasti fazi
Ta evropski standard določa standardno metodo za določevanje celotnega živega srebra v plinasti fazi (TGM) v zunanjem zraku z atomsko absorbcijsko spektrometrijo hladnih par (CVAAS) ali atomsko fluorescenčno spektrometrijo hladnih par (CVAFS). Ta evropski standard velja za zaledna območja, ki so v skladu z zahtevani Direktive 2004/107/ES, ter za urbana in industrijska območja. Značilnosti delovanja metode so bile določene s primerjalnimi validacijskimi preskusi na terenu, opravljenimi na štirih evropskih lokacijah: dve zaledni in dve industrijski območji. Metoda se je preskušala dva meseca v obdobju dvanajstih mesecev na vsakem območju z avtomatsko opremo, ki se trenutno uporablja v Evropi za določevanje TGM v zunanjem zraku. Delovni razpon te metode zajema razpon koncentracij zunanjega zraka od tistih, ki se nahajajo na zalednih območjih, običajno manjših od 2 ng/m3, do tistih, ki se nahajajo na industrijskih območjih, kjer so pričakovane višje koncentracije. Med preskusi na terenu je bilo izmerjeno maksimalno dnevno povprečje do 300 ng/m3. Rezultati so prikazani kot povprečna masa TGM na volumen zraka pri 293,15 K in 101,325 kPa, merjena v določenem roku v nanogramih na kubični meter.
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Außenluftbeschaffenheit - Standardisiertes Verfahren zur Bestimmung des gesamten gasförmigen QuecksilbersQualité de l'air ambiant - Méthode normalisée pour la détermination du mercure gazeux totalAmbient air quality - Standard method for the determination of total gaseous mercury13.040.20Kakovost okoljskega zrakaAmbient atmospheresICS:Ta slovenski standard je istoveten z:EN 15852:2010SIST EN 15852:2010en,fr,de01-november-2010SIST EN 15852:2010SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 15852
June 2010 ICS 13.040.20 English Version
Ambient air quality - Standard method for the determination of total gaseous mercury
Qualité de l'air ambiant - Méthode normalisée pour la détermination du mercure gazeux total
Außenluftbeschaffenheit - Standardisiertes Verfahren zur Bestimmung des gesamten gasförmigen Quecksilbers This European Standard was approved by CEN on 5 May 2010.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions.
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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 15852:2010: ESIST EN 15852:2010
Sampling sites . 26Annex B (informative)
Manual method TGM . 27Annex C (informative)
Summary of field validation tests . 29Annex D (informative)
Characteristics of the mercury vapour source . 34Annex E (informative)
Calibration . 37Annex F (informative)
Assessment against target uncertainty by an individual laboratory . 38Annex G (informative)
Relationship between this European Standard and the Essential Requirements of EU Directives . 44Bibliography . 45 SIST EN 15852:2010
This European Standard specifies a standard method for determining total gaseous mercury (TGM) in ambient air using cold vapour atomic absorption spectrometry (CVAAS), or cold vapour atomic fluorescence spectrometry (CVAFS).
This European Standard is applicable to background sites that are in accordance with the requirements of Directive 2004/107/EC and to urban and industrial sites.
The performance characteristics of the method have been determined in comparative field validation tests carried out at four European locations: two background and two industrial sites. The method was tested for two months at each site over a period of twelve months using automated equipment currently used in Europe for determination of TGM in ambient air.
The working range of the method covers the range of ambient air concentrations from those found at background sites, typically less than 2 ng/m3, up to those found at industrial sites where higher concentrations are expected. A maximum daily average up to 300 ng/m3 was measured during the field trials.
Results are reported as the average mass of TGM per volume of air at 293,15 K and 101,325 kPa, measured over a specified time period, in nanograms per cubic metre. 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.
ENV 13005, Guide to the expression of uncertainty in measurement CR 14377, Air quality
Approach to uncertainty estimation for ambient air reference measurement methods EN ISO 20988, Air quality
Guidelines for estimating measurement uncertainty (ISO 20988:2007) ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results
Part 2: Basic method for the determination of the trueness of a standard measurement method ISO 8573-1:2010, Compressed air
Part 1: Contaminants and purity classes 3 Terms and definitions For the purposes of this document, the following terms and definitions apply.
3.1 ambient air outdoor air in the troposphere, excluding workplace air
3.2 calibration operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication SIST EN 15852:2010
NOTE 3 Often, the first step alone in the above definition is perceived as being calibration [ISO/IEC Guide 99:2007 (VIM)]. 3.3
combined standard measurement uncertainty standard measurement uncertainty that is obtained using the individual standard measurement uncertainties associated with the input quantities in a measurement model
NOTE In case of correlations of input quantities in a measurement model, covariances should also be taken into account when calculating the combined standard measurement uncertainty [ISO/IEC Guide 99:2007 (VIM)]. 3.4 coverage factor number larger than one by which a combined standard measurement uncertainty is multiplied to obtain an expanded measurement uncertainty
NOTE A coverage factor is usually symbolized k [ISO/IEC Guide 99:2007 (VIM)]. 3.5 detection limit measured quantity value for which the probability of falsely claiming the absence of a component in a material is β, given a probability . of falsely claiming its presence NOTE IUPAC recommends default values for . and β equal to 0,05.
3.6 expanded standard measurement uncertainty product of a combined standard measurement uncertainty and a factor larger than the number one NOTE 1 The factor depends upon the type of probability distribution of the output quantity in a measurement model and on the selected coverage probability. NOTE 2 The term "factor" in this definition refers to a coverage factor. NOTE 3 Expanded measurement uncertainty is termed "overall uncertainty" in paragraph 5 of Recommendation INC-1 (1980) (see the GUM) and simply "uncertainty" in IEC documents [ISO/IEC Guide 99:2007 (VIM)]. NOTE 4 For the purpose of this document the expanded uncertainty is the combined standard uncertainty multiplied by a coverage factor k = 2 resulting in an interval with a level of confidence of 95 %. 3.7 measurement repeatability measurement precision under a set of repeatability conditions of measurement
[ISO/IEC Guide 99:2007 (VIM)] 3.8 measurement reproducibility measurement precision under reproducibility conditions of measurement
NOTE Relevant statistical terms are given in ISO 5725-1:1994 and ISO 5725-2:1994 [ISO/IEC Guide 99:2007 (VIM)]. SIST EN 15852:2010
NOTE 2 Measurement times during the field trial campaign ranged from 30 s to 30 min.
3.10 measurement uncertainty non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used NOTE 1 Measurement uncertainty includes components arising from systematic effects, such as components associated with corrections and the assigned quantity values of measurement standards, as well as the definitional uncertainty. Sometimes estimated systematic effects are not corrected for but, instead, associated measurement uncertainty components are incorporated. NOTE 2 The parameter may be, for example, a standard deviation called standard measurement uncertainty (or a specified multiple of it), or the half-width of an interval, having a stated coverage probability [ISO/IEC Guide 99:2007 (VIM)]. 3.11 method detection limit lowest amount of an analyte that is detectable using the method, as determined by sampling and analysis of zero gas 3.12 monitoring period time period over which monitoring is intended to take place, defined in terms of the time and date of the start and end of the period 3.13 monitoring station (for mercury) enclosure located in the field in which an analyser has been installed to monitor TGM concentrations
3.14 monitoring time length of time over which monitoring is intended to take place NOTE For example: an instrument measured TGM using a measurement time of 15 min, over a sampling time of 30 days (producing 2 880 data points). The monitoring period was from 0001 h on 1 April 2008 to 0001 h on 1 May 2008. 3.15 reference conditions ambient temperature of 293,15 K and pressure of 101,325 kPa
3.16 repeatability condition of measurement
condition of measurement, out of a set of conditions that includes the same measurement procedure, same operators, same measuring system, same operating conditions and same location, and replicate measurements on the same or similar objects over a short period of time NOTE 1 A condition of measurement is a repeatability condition only with respect to a specified set of repeatability conditions. SIST EN 15852:2010
measurement uncertainty expressed as a standard deviation [ISO/IEC Guide 99:2007 (VIM)] 3.20 total gaseous mercury
TGM elemental mercury vapour (Hg0) and reactive gaseous mercury, i.e. water-soluble mercury species with sufficiently high vapour pressure to exist in the gas phase
[Directive 2004/107/EC] NOTE This definition is taken in this standard to include all gaseous mercury species.
3.21 zero gas gas free from mercury, interfering compounds and particles
NOTE 1 Free from mercury means containing a concentration less than the method detection limit. NOTE 2 Zero gas is used in conjunction to calibration of automatic mercury instruments. It may consist of pure nitrogen or synthetic air from a gas cylinder. Purified air from the surrounding can also be used (see instructions in user manuals). 4 Symbols and abbreviated terms
For the purposes of this document, the following symbols and abbreviated terms apply.
4.1 Symbols A
is a constant with numerical value - 8,134 46; AHg
is the atomic weight of mercury, 0,20059; .
for a given detection limit the probability of a false positive identification occurring; B
is a constant with numerical value 3 240,87;
ß
for a given detection limit the probability of a false negative identification occurring;
is the mass concentration; amb
is the mercury concentration in a certain air volume V (T, P);
d,i
is the daily mass concentration value on day d from instrument i; Hg
is the theoretical mass concentration of mercury vapour samples that can be collected from the
mercury vapour source using a syringe;
Hg, sou is the mercury concentration in the source; Hg, syr
is the mercury concentration in the syringe; MDL
is the method detection limit; ref
is the mass concentration of TGM in reference air at 293,15 K and 101,325 kPa; sam
is the mercury concentration related to a certain air temp (Tsam) and pressure (Psam); γ
is the mean mass concentration over all N days and across all M instruments; d
is the mean mass concentration on day d across all M instruments; D
is a constant with numerical value 3 216 522;
/
is the estimated statistical uncertainty associated with the mercury vapour equation used; /d,i
is the deviation of instrument i from the mean mass concentration on day d; iδ
is the mean deviation of instrument i from the mean mass concentration over all N days; k
is the coverage factor; sam
is the sampling efficiency; mair
is the mass of air under reference conditions; mtrap
is the mass of mercury found on the gold trap;
M
is the number of parallel samplers used in a field trial;
Mair
is the molecular weight of air, 0,029 kg/mol;
n
is the number of measurements; N
is the duration of the field trial in days; PHg
is the vapour pressure of mercury; Pref
is the reference pressure, 101,325 kPa; Psam
is the actual pressure of the sampled air; qv,ave
is the average volume flow rate of ambient air through the trap during the monitoring period;
r2
is the correlation coefficient; SIST EN 15852:2010
is the flow calibration coefficient,
rsyr
is the volume calibration coefficient;
R
is the ideal gas constant, 8,314 J/K·mol; Rcal
is the instrumental response produced after the injection of a volume of mercury saturated gas; R i
is the instrumental response generated from measurement i; R sam
is the instrumental response following analysis of the sample;
R
is the average of n (n)10≥repeat measurements of iR; 0R
is the instrumental response generated upon the injection of a zero volume of mercury saturated gas; 0R
is the average of n (10≥n) repeat measurements of i0,R; i0,R
is the instrumental response generated upon introduction of zero gas from measurement i; 1i
is the standard deviation of the deviation of instrument i over all N days; 1R
is the relative standard deviation of a set of n measurements; t is the sampling time;
Tsam
is the actual temperature of the sampled air; Tsou is the temperature of mercury source; Tsyr is the temperature of syringe; Tref
is the reference temperature, 293,15 K;
uc ()
is the relative combined standard uncertainty in the TGM concentration in ambient air;
uc,i () is the relative combined standard uncertainty from instrument i;
ui, vol is the uncertainty in the sampled volume for instrument i; ur ()
is the relative random contribution to the uncertainty; ur, i () is the random contribution to the relative combined uncertainty from instrument i; us ()
is the relative non-random contribution to the uncertainty; us, i () is the non-random contribution to the relative combined uncertainty from instrument i; U is the expanded uncertainty;
Vamb
is the volume of ambient air sampled onto the trap;
V (T,P) is a certain air volume;
Vsam(T,P) is the corresponding air volume at the actual temperature Tsam and pressure Psam; SIST EN 15852:2010
0,cal=tV& is the measured sensitivity of the instrument at time t=0;
ttV=,cal& is the measured sensitivity of the instrument at time t;
calV&∆ is the drift in the sensitivity of the measuring system, over a time, t; VHg
is the volume of mercury saturated gas from within the mercury vapour source; Vref
is the reference air volume; x is the mass of mercury; y
is the measurement result; Y is the measurand. 4.2 Abbreviations CVAAS Cold Vapour Atomic Absorption Spectrometry CVAFS Cold Vapour Atomic Fluorescence Spectrometry EMEP Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air pollutants in Europe (European Monitoring and Evaluation Programme) FEP Fluorinated ethylene propylene IUPAC International Union of Pure and Applied Chemistry MFC Mass flow controller MFM Mass flow meter ng Nanogram; 10-9 g PTFE
Polytetrafluoroethylene TGM Total Gaseous Mercury Zeeman AAS Zeeman Atomic Absorption Spectrometry 5
Principle The methods described in this standard are automated methods that involve either:
adsorption of TGM from a measured air volume on a gold trap, followed by thermal desorption of total mercury from the gold trap and determination as gaseous elemental mercury by CVAAS or CVAFS; or direct continuous measurement of elemental mercury by Zeeman AAS. SIST EN 15852:2010
6.1 Siting criteria The siting requirements for TGM measurements are given in Annex A. 6.2 Method requirements The method for the measurement of total gaseous mercury concentrations in ambient air shall be an automated method based on Atomic Absorption Spectrometry or Atomic Fluorescence Spectrometry, as specified in Annex V.III of Directive 2004/107/EC. 6.3 Method detection limit The detection limit of the gold trap analysis method (expressed in nanograms of mercury) shall not exceed 10 % of the lower limit of the working range of the mercury expected to be collected during any measurement period. This will depend on the measurement time and the sampling flow rate. The detection limit of the Zeeman AAS method (expressed in nanograms per cubic metre) shall not exceed 10 % of the lower working range.
6.4
Field operation and quality control
After the installation at the monitoring station, the analyser shall be tested to ensure that it is working correctly.
It is essential that the expanded uncertainty of measurements in the field does not exceed the 50 % according to Directive 2004/107/EC. Requirements and recommendations for quality assurance and quality control are given for the measurements in the field (see Clause 11).
7 Reagents
7.1 Argon, of purity greater than 99,999 %, suitable for use as a carrier gas for CVAAS and CVAFS. 7.2 Nitrogen, of purity greater than 99,999 %, suitable for use as a carrier gas for CVAAS and CVAFS. 7.3 Air, of class 3.3.3 purity or better according to ISO 8573-1:2010. 7.4 Elemental mercury, of purity 99,999 9 %, for preparation of gaseous mercury vapour standard. WARNING — Mercury is toxic by skin absorption and inhalation of vapour. Use suitable personal protective equipment (including gloves, face shield or safety glasses, etc.) and minimize exposure by using a fume hood.
7.5 Water, resistivity greater or equal to 18 M·cm at 298 K. The ultrapure water used in this method is for cleaning purposes only. 7.6 Hydrochloric acid (HCl), concentrated, density ~ 1,18 g/ml, mass fraction 36 % to 38 %. The concentration of mercury shall be less than 0,002 mg/l. WARNING — Concentrated hydrochloric acid is corrosive and hydrochloric acid is an irritant. Avoid contact with the skin and eyes, or inhalation of the vapour. Use suitable personal protective equipment (including gloves, face shield or safety glasses, etc.) when working with hydrochloric acid. SIST EN 15852:2010
7.7 Hydrochloric acid, diluted 1:49 with ultrapure water for cleaning of filter housings, glass manifolds and sampling components.
Add approximately 700 ml of water (7.5) to a 1 000 ml volumetric flask. Carefully add 20 ml of concentrated hydrochloric acid (7.6) to the flask and swirl to mix. Allow to cool, dilute to the mark with water, stopper and mix thoroughly.
8 Apparatus 8.1 Sampling equipment 8.1.1 Polytetrafluoroethylene (PTFE) filters, pore size 0,2 µm, mounted in a suitable fluorinated ethylene propylene (FEP) or PTFE housing, for installation in the sampling line to remove particles from the sampled air. 8.1.2 Sampling line, FEP or PTFE, as short as possible to avoid losses of mercury vapour. Condensation of water vapour shall be avoided from the inlet to the analyser. Connectors between the filter housing and mercury analyser shall be of a suitable material (e.g. FEP or PTFE) to avoid losses of mercury vapour.
8.2 Analytical instrumentation 8.2.1 Mercury analyser based on amalgamation and CVAAS or CVAFS. A mercury analyser consisting of a gold amalgamation system coupled to an atomic fluorescence or atomic absorption spectrometer.
8.2.2 Mercury analyser based on Zeeman AAS. A mercury analyser with Zeeman background correction. 8.2.3 Mass flow controller and mass flow meter. To measure and control the mass flowrate of air sampled through the gold trap or mercury analyser.
The flow rates of the mass flow controller (MFC) and mass flow meter (MFM) shall be traceable to (inter)nationally accepted standards.
NOTE
Direct measurements of the mercury concentration with Zeeman AAS do not depend on the air flow rate, however it is highly desirable to have a steady controlled flow at a measured temperature and pressure. The flow rates of the MFC and MFM shall be checked using a flow meter traceable to (inter)nationally accepted standards. This shall be performed during installation and commissioning and thereafter periodically. The accuracy of the MFC or MFM shall be within ± 5 %. If appropriate, record the atmospheric temperature and pressure at which the calibration of the MFC and MFM was checked.
8.3 Calibration equipment Known amounts of mercury vapour for instrument calibration are generated using a vessel containing a small volume of elemental mercury. This allows a saturated vapour of mercury to develop within the air in the vessel, which is in equilibrium with the atmosphere via a capillary tube. The temperature of the liquid mercury SIST EN 15852:2010
Calibration vessels are commercially available from several vendors. Please refer to manuals for more details. NOTE 2
The calibration vessel should be at atmospheric pressure by use of a capillary vent. This should be capped when the vessel is not in use. 9 Sampling considerations
9.1 Inlet location The siting requirements for TGM measurements are shown in Annex A. The monitoring of TGM requires a container or room equipped with climate control to keep the room at a stable temperature, usually around 20 °C. The sampling inlet shall be between 1,5 m (the breathing zone) and 4 m above the ground.
NOTE
It may be necessary to position the sampling inlet higher (up to 8 m) in some circumstances.
The sampling inlet shall not be positioned in the immediate vicinity of sources in order to avoid unrepresentative sampling. Local meteorological conditions, such as prevailing wind direction and formation of stagnant air pockets, shall also be considered.
The air flow around the sampling inlet shall be unrestricted. Obstructions to the air flow from buildings, trees and other obstacles shall be avoided. 9.2 Sampling inlet and sampling line
The sampling inlet may be made from borosilicate glass, quartz, FEP or PTFE. The inlet can be made fairly simple, but it shall be well-supported and constructed so that rain or snow cannot enter into the sampling system. Suitable inlets are commercially available. Two possible inlet designs are shown in Figure 1. If the inlet only serves one instrument, the sampling line shall be connected via a dust filter directly to the instrument.
a) The air enters into a funnel made of borosilicate glass that is directly connected to the sampling line (borosilicate glass, FEP or PTFE tubing). The funnel and the sampling line can be supported by an outer tube, made from a plastic material or metal with a suitable coating.
b) Inlet and sampling line consisting of borosilicate or quartz glass. This design can require a protecting frame (not shown) which is usually made from plastic or coated metal. Figure 1 — Sampling inlet for TGM SIST EN 15852:2010
Key 1 inlet 2 connection to instrument 3 drain Figure 2 — Manifold made from borosilicate or quartz glass The manifold is connected to the sampling inlet.
NOTE The residence time of the intake system depends on its dimensions and on the total flow rate. The residence time should be as short as possible. The residence time can be optimised by altering the support flow or the inner diameter of the sampling line. However, too high flow rates may create a pressure drop. Many instruments use mass flow regulators to regulate the sample flow rate and therefore are not very sensitive to the pressure. But for other instruments a pressure drop in the inlet system may be critical. Hence, the inlet and sampling line system need to be dimensioned considering the requirements at each individual instrument and sampling line. 9.3 Measurement time The required measurement time depends on the ambient concentration. Relative uncertainty is likely to increase as measurement time decreases. The measurement time shall be long enough to collect enough mercury to satisfy the quality control and uncertainty requirements of this European Standard. However, the measurement time shall not be so long that degradation of gold traps or sample breakthrough occurs. SIST EN 15852:2010
10.1 Calibration with AFS/AAS 10.1.1 Install and commission the mercury measurement system according to the manufacturer's instructions.
10.1.2 Place a small quantity of mercury carefully inside the calibration vessel. Allow the headspace to become saturated with mercury vapour. The saturated concentration is related to the temperature of the vessel. 10.1.3 Calibrate the instrument using injections of known volumes of air saturated with mercury vapour and a gas-tight syringe with an adequate volume. For verification, perform a "calibration robustness check" at least every two weeks and recalibrate, if necessary (see 11.1).
Following maintenance or any substantial changes to the instrumentation, a calibration shall be performed. The calibration vessel shall be thermally insulated (see Annex D). It is advisable to thermostatically control the calibration vessel. During calibration, measure the temperature of the calibration vessel using a temperature sensor calibrated to national or international standards with a valid calibration. The temperature sensor shall have a minimum resolution of ± 0,1 °C.
NOTE 1
More information on the calibration process may be found in [8]. NOTE 2
It may also be necessary to measure the temperature of the monitoring station enclosure during calibration using a temperature sensor calibrated to national or international standards with a valid calibration (see Annex D). The temperature sensor in the monitoring station enclosure should have a minimum resolution of ± 0,5 °C. Use a gas-tight syringe traceable to national or international standards with a valid calibration. Gas-tight syringes shall be pre-conditioned with mercury vapour to minimize losses of mercury. Refer to user manuals for more details. This procedure is outlined below for systems with amalgamation: a) Calculate the concentration of mercury in the syringe using the following formula:
)TB A(syrHgsou10TD/+−×= Tsyr ≥ Tsou (1) where
Hg
is the theoretical mass concentration of mercury vapour samples that can be collected from the mercury vapour source using a syringe in nanograms per millilitre;
Tsyr
is the temperature of the syringe in kelvins; Tsou
is the temperature of the mercury source in kelvins; A
is a constant with numerical value - 8,134 46; B
is a constant equal to 3 240,87;
D
is a constant equal to 3 216 523;
is a factor associated with the mercury vapour equation used which is taken to be equal to 1,0. Withdraw a known volume of the saturated mercury vapour using a gas-tight syringe of adequate volume, inject into the instrument and initiate the measurement sequence. b) Calculate the mass of mercury injected into the instrument from the injection volume and the concentration of mercury vapour using Equation (1). c) Repeat the above procedure using different injection volumes to cover a suitable range of masses of mercury and generate a calibration line. Further guidance is given in Annex E.
NOTE 3 Equation (1) is only valid when Tsyr is greater or equal to Tsou. Thermostatting the mercury vapour source at temperatures lower than room temperature will decrease the mercury vapour concentration and allow collection of smaller amounts of mercury. Equation (1) is based on the equilibrium vapour pressure of mercury [2]. More information on Equation (1) is found in Annex D. NOTE 4 The choice of an equation for calculating the vapour pressure of mercury is still a point of discussion. Equation (1) stems from a validation programme and is equal to that suggested in Ebdon et al. [3]. However, other equations to describe the vapour pressure of mercury are also available [4]. 10.1.4 Calculate the concentration of mercury in nanograms per cubic metre using the calibration function (see Clause 12).
10.2 Calibration with Zeeman AAS 10.2.1 Install and commission the mercury measurement system according to the manufacturer’s instructions.
Zeeman AAS is calibrated using cells containing mercury saturated vapour at known temperature. For verification, perform a "calibration robustness check" at least every three months, or more often if required by the guidelines of the laboratory practice. The calibration robustness check can be done the same way as the CVAAS/CVAAF calibration robustness check (see 11.1). 10.2.2 Make a measurement of the mercury mass concentration in zero gas to ensure that an acceptably low blank is found. This is particularly important after performing a calibration to ensure that the system has not become contaminated (see 11.2).
10.2.3 Activate the automated measurement sequence.
10.2.4 Calculate the concentration of mercury in nanograms per cubic metre using the calibration function (see Clause 12).
11 Quality control
11.1
Calibration robustness check
To verify the calibration, a known mass of mercury shall be measured every two weeks according to Clause 10. If the sensitivity (response per nanogram of mercury) of the instrument has changed by more than 10 % it is necessary to recalibrate.
NOTE
For CVAAS and CVAFS it is important to consider the artificial nature of the calibration procedure and how this might affect the accuracy of measurements. Ideally an equal or greater mass of mercury should be injected during calibration as is collected during sampling. The majority of sample results reported should fall towards the centre of the calibration range where the uncertainty associated with predicted concentrations is at its minimum. The uncertainty associated with extrapolated results or results generated from the lowest portion of the calibration line will have a much SIST EN 15852:2010
11.2
Zero gas check A zero gas check shall be performed at least every two weeks. This test shall involve the introduction of a known volume of zero gas through the sampling manifold and into the instrument and then performing an analysis. This check shall be performed using the same sampling and measurement conditions as the sample measurements.
The zero gas reading shall be a maximum of 10 % of the lower working range.
Appropriate steps shall be made to reduce the zero gas readings if this criterion is not met.
11.3
Degradation of gold traps The accuracy of measurements will be affected when gold trap degradation occurs. Gold traps shall be replaced or cleaned according to the manufacturers' guidelines. Measurements using gold traps which have shown some degradation will be accepted, provided that inclusion of the data does not increase the expanded uncertainty of the measurements above the 50 % data quality objective, as specified in Directive 2004/107/EC. NOTE 1 The uptake efficiency of new gold traps is close to 100 %, but may change with time probably due to poisoning from certain atmospheric constituents. Low uptake efficiency leads to underestimation of the actual TGM concentration. Unfortunately this phenomenon is not always revealed in terms of low response from mercury gas standards. The reason seems to be that the uptake efficiency depends on concentration. During standard injections (i.e. adding small samples of saturated mercury vapour) the gold traps are for a short moment exposed to very high mercury concentrations.
NOTE 2 Each instrumental provider uses their own gold traps and their individual characteristics may vary. No general rules regarding maintenance and replacement of gold traps are therefore given. But the performance of each instrument should carefully be observed following the recommendations given in the user manual.
11.4
Proficiency testing scheme
If laboratories carry out measurement of TGM on a regular basis, it is recommended that they participate in a relevant proficiency testing scheme at regular intervals.
11.5
Accreditation Laboratories using this European Standard shall demonstrate that they are working in accordance with the requirements of European quality systems. One of the ways of demonstrating compliance with these requirements is through formal accreditation by an accreditation body falling under the Multi-Lateral Agreement of the European Co-operation for Accreditation.
11.6
Measurement uncertainty Measurement uncertainties shall be calculated for each time averaged value to be reported. These shall be calculated according to Clause 13. 12
Calculation of results 12.1
General Following sampling, the mean of the data will be taken over any given time period. Unless the purpose of sampling is to examine acute high concentration events over short timescales, it is recommended that data be averaged over time periods not shorter than 24 h.
Calculation of TGM concentrations to reference conditions
From the ideal
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