1. Guideline
Ambient Air Quality Monitoring Network
Recommendations and Rules
Content
Chap. 1 - Introduction
 Guidelines for the Operation of the Air Quality Monitoring System
 Concept of the Air Quality Monitoring Network
Chap. 2 - Measurement Strategy
 Measurement Principles and Measurement Methods
 Planning of ambient air quality measurements - General rules
 Planning of ambient air quality measurements – Rules for planning
investigations of traffic related air pollutants in key pollution areas
 Measurement Strategies for the Determination of Air Quality Characteristics in
the Vicinity of Stationary Emission Sources
 Handling of Measurement Uncertainty
 Siting of Air Quality Monitoring Stations
Chap. 3 - Operation of the Monitoring Network
 Measurement Procedures for the Determination of Particulate Matter
Concentration and Gaseous Components
 Monitoring network service
 Performing of Maintenance/Maintenance Plans
 Calibration of NO/NOx Analysers/Calibration Form
 Calibration of SO2 Analysers/Calibration Form
 Calibration of Ozone Analysers/Calibration Form
 Calibration of CO Analysers/Calibration Form
 Calibration of BTX Analysers/Calibration Form
 Performing Repairs on Analysers/Repairs-Log
 Change of Container Sites
 Change of Measurement Location of Monitoring Vehicle (in German language)
1

2. Chap. 4 - Calibration Laboratory
 Calibration Laboratory
 Receiving inspection, basic calibration, linearity test and type approval test for
suitability evaluation of measurement devices
 Certification of test gases
 Certification of test gas cylinders
 Gravimetric Determination of PM10 Concentration by means of the High-
Volume-Sampler DIGITEL DHA-80
 Gravimetric Determination of PM2.5 Concentration by means of the High-
Volume-Sampler DIGITEL DHA-80 (in German language)
 Filter Handling (Cellulose Nitrate, Quartz Fibre) during the Determination of
PM10 Concentration by means of DIGITEL DHA 80
 Filter Preparation and Storage (Cellulose Nitrate, Quartz Fibre) for the
Determination of PM10 Concentration by means of DIGITEL DHA 80
 Balance Manual for the Verification of the Electronic Analytical Balance MC
210 P
 Pipette Manual for the Verification of a Piston-Driven Air Displacement Pipette
by means of an Analytical Balance
 Calibration of the Reference Standard, Organisation and Deadlines
 Determination of Uncertainty of Measurement for the Pollutant Nitrogen
Dioxide (NO2) while employing a NO/NOx Chemiluminescence-Monitor
Chap. 5 - Network Data Centre
 Recommendations on data validation in air quality monitoring networks
 Recommendations on the calculation of aggregated data and statistical
parameters
 Automatic validation of air quality data
 Information of the public on air quality
 Control and release of air quality data / Forms daily/monthly/yearly validation
 Reports, statements, publications
 Handling of external requests on air quality data
2

3. Chap. 6 - Analytical Laboratory Air Quality
 Inductive coupled mass spectroscopy (VARIAN ICP-MS 820)
 Measurement of elements in dust and deposition dust
 HPLC system Merck
 Measurement of polycyclic aromatic hydrocarbons (PAH) in fine dust
 Ion chromatograph Metrohm
 Measurement of anions and cations in ambient air probes
 Measurement of deposition dust and heavy metals content
 Sampling of deposition dust
 Digestion of dust and deposition dust for ICP-MS analysis
Chap. 7 – Air Quality Measurements by Passive Sampling
 Air Quality Monitoring by Passive Sampling
 The search for hot spots via passive sampler with respect to average NO2
exposure in an urban area
 Evaluation of average benzene concentration by the use of passive samplers
for the assessment of air quality according to EU Directive 2008/50/EC
 Methods for measurement of Nitrogen Dioxide concentration in Ambient Air via
Passive Sampler - Measurement method based on Saltzman Reaction
 Determination of Benzene in ambient air via Passive Sampler
3

4. Guidelines for the Operation of the
Air Quality Monitoring System
Content
1. Introduction ............................................................................................................ 5
2. Legal Framework ................................................................................................... 5
3. Tasks and Objectives of Air Quality Monitoring ............................................... 6
4. Quality Assurance ................................................................................................. 6
5. Organizational Foundations of the Guidelines ................................................. 7
6. Structure of the Guidelines for a Monitoring Network ..................................... 7
4

5. 1. Introduction
The following guidelines were drawn up within the framework of the following
twinning-project:
Strengthening Administrative
Capacities for Implementation
of Air Quality Management
SR 07 IB EN 01
They describe the proposal of the twinning-experts with regard to the operation of the
network for air quality monitoring. They consist of recommendations, rules, standard
operation procedures (SOP) and should be used as a guidance for the operation of
air quality monitoring networks.
2. Legal Framework
The guidelines refer to the monitoring of air pollutants in the ambient air. The main
legal foundation in this regard in Europe are the CAFE-Directive 2008/50/EC and the
4th Daughter Directive 2004/107/EC of the Commission of the European Community,
which set limit values and guide values for each air pollutant. The European
directives with their mandatory implementation in the member states have led to
significant development on the legislative level but also to important technical and
analytical progress. The following criteria are to be mentioned as main focus:
 Significantly severer limit values by implementation of the effect-oriented
standards of the World Health Organisation WHO
 Extensive measures plans and action plans for the improvement of air quality
 Extensive information of the public
 Significantly higher demands with regard to the quality of air quality data and
to the quality management systems of the monitoring networks (Data Quality
Objectives of the EU Directives)
5

6. 3. Tasks and Objectives of Air Quality Monitoring
The air quality monitoring tasks may be basically divided in:
 Area-oriented measurements: determination of the overall exposure to air
pollutants in different areas and its influence upon the population living there,
upon the vegetation and upon assets.
 Local-oriented measurements: determination of specific exposure to air
pollutants in places with unusually high emissions and the sometimes limit-
value-exceeding levels of air pollutants deriving from it. (e.g. highly frequented
urban canyons)
 Facility-oriented measurements: determination of specific pollution produced
by air pollutants from one or more industrial emitters.
The specific objectives of air quality monitoring according to EU Directives are the
following:
 To verify whether the limit values and guide values set in the EU Directives are
being observed.
 The analysis of reasons for high air pollution.
 To control the effectiveness of the measures taken for air quality improvement.
 To verify Dispersion Modelling for pollutants in the ambient air.
 To determine temporal trends with regard to air pollutant levels.
 To investigate long range transport of air pollutants.
4. Quality Assurance
As a rule, the metrological air quality verification is regulated by state provisions,
which mainly rely on European Directives, and takes place according to state-
acknowledged standards and guidelines. Reference to this will be made in some
instances in the present guidelines. The quality assurance measures for the
investigation of air quality refer to the following levels of action:
 Specifications with regard to the monitoring strategy i.e. definition of task,
choice of monitoring location, monitoring period, etc.
 The use of verified monitoring equipment, the use of reference and
equivalence procedures.
6

7.  Proof of calibration procedure traceability to National Standards.
 Confirmation of professional competence through accreditation of laboratories
and monitoring networks by an accreditation body with European recognition
 Quality control of monitoring stations and networks by means of national and
international interlaboratory tests, audits and quality management systems
The guidelines provide valuable support for many of these points, in order to reach
quality targets and to be able to provide the European Commission with reliable data
on air quality.
5. Organizational Foundations of the Guidelines
The guidelines mainly refer to European EN standards and Directives, that will not be
detailed here, but that will be referred to in particular cases. There will also be
reference to the operating instructions of the individual devices of the monitoring
network.
In the SOPs the operation of regional monitoring networks will be taken as a basis.
The national level will only be referred to. This means that neither the function of the
National Data Centre (for the provision of EoI requirements) nor that of the National
Reference Laboratory will be described.
6. Structure of the Guidelines for a Monitoring Network
The guidelines comprise all important tasks which belong to the operation of air
quality monitoring networks according to the EU Directives for air quality:
 Guidelines for the measurement strategy of air quality
 Regulations for the operation of the monitoring network
 Regulations for the work of the calibration laboratory
 Regulations for the network data centre with regard to data collection, the
database for measured values, the data validation steps and several aspects
on reporting.
 Guidelines for important tasks of the analytical laboratory air quality
7

8.  Guidance for air quality measurements by passive sampling
The steps in the quality assurance process are comprised in the guidelines for
operation and maintenance of the stations, as well as in the European standards they
have been based upon.
The guidelines can be divided as follows:
 Structure of the air quality monitoring system
 Guidelines measurement strategy
 Guidelines concerning the operation tasks of the monitoring network
 Guidelines concerning the tasks of the calibration laboratory
 Guidelines concerning the tasks of the network data centre
 Guidelines concerning the tasks of the analytical laboratory air quality
 Guidelines concerning air quality measurements by passive sampling
A complete list of all documents included in this Guideline ―Ambient Air Quality
Monitoring Network‖ is given in the content.
Concept of the Air Quality Monitoring Network
Content
1. Structure of the Air Quality Monitoring Network ............................................ 9
2. Tasks description of the monitoring fields ................................................... 10
3. Quality Management in Air Quality Monitoring ............................................. 13
3.1 Traceability of air quality data ..................................................................... 14
3.2 Linearity test ............................................................................................... 14
3.3 Receiving inspection .................................................................................. 14
3.4 Type approval test for suitability evaluation on site .................................... 16
3.5 Reference standards for physical measures .............................................. 16
3.6 Gravimetric analysis ................................................................................... 16
8

9. 1. Structure of the Air Quality Monitoring Network
Flow Chart of Assumptive Structures
National
National National Data Modelling .........
Level
Reference Centre: EU-
Laboratory Reporting,
national
information
Regional
Level
Monitoring Network
1/0/1*
* = No. Acad./Eng./Techn.
Monitoring network Calibration lab and Monitoring network centre
service analytical lab
1/1/4 1/3/3 1/1/1
Maintenance Test gases bottles Data control and
Test gases release
Repairs Transfer standards Validation
Gravimetric Calculation of
Calibration analysis statistical parameters
Evaluation of Data Analysis and
measurement Assessment
devices Reporting
Balance manual Data dissemination
Information of the
public
Local
Level
Station operation:
Fault-clearance service
Maintenance work
Security aspects
Information of the population
9

10. 2. Tasks description of the monitoring fields
Regional Level:
The monitoring network is headed by a scientist/academic, to whom an assistant is
assigned.
The monitoring network service is led by an academic and also comprises one
engineer and 4 technicians. Their tasks are the following:
Task description:
Academic Managing, monitoring strategy, personnel management and budget
Engineer Start-up verifications
Adaptation of new devices to the monitoring network
Training of technicians
Procurement (devices, spare and consumable material)
Location planning and arrangement
Responsible for transfer standards and their verification in the
calibration lab
Control of completed calibrations
Technician Maintenance and repairs
Calibrations
According to qualification divided into maintenance technician and
repair technician.
The Laboratory belonging to the monitoring network is composed of the two units:
- Calibration lab
- Analytical lab for inorganic and organic air pollutants
The laboratory is led by an academic. He has three subordinate engineers with the
following assignments:
- Calibration lab (reference equipment for SO2, NO, NO2, O3, CO, benzene,
particles; gravimetric analysis PM10 and PM2,5; transfer standards;
calibrations and linearity verifications for new and repaired equipment
- Analytical lab for inorganic air pollutant components: Pb, Cd, Ni, As, Hg and
other heavy metals; inorganic components in dust and deposit.
- Analytical lab for organic air pollutant components: BTX, PAH,
Benzo(a)Pyrene, rust; if necessary: Furan, Dioxin
Task description:
Calibration lab engineer Chemistry, physics, electronics
Engineer Analytical lab/inorg. Focus on inorg. chemistry, AAS, ICP/MS
Engineer analytical lab/org. Focus on org. chemistry, GC, HPLC
General: quality management, determination of measurement uncertainty, procedure
development, participation in interlaboratory tests, laboratory comparisons.
10

11. The monitoring network centre is headed by an academic and also comprises one
engineer and a technician. Their tasks are the following:
Task description:
Academic Management of the data centre
Planning/further development of database and data communication
Further development of data validation procedures
Reporting
Engineer Administration of network of monitoring network
Data validation
Data assessment
Preparation work for reporting
Data dissemination according to requirements (EU-requirements,
requests from municipalities, research, media)
Technician Computer maintenance, data transfers, database, support with data
validation, assessment, reporting
11

12. Local Level:
On this level, the „air quality‖ unit takes on the tasks of caring for the monitoring
network in the monitoring department. This unit is led by an engineer, who mainly
organizes the support for stations and takes on the data assessment on local level as
well as information of the local public. He is accompanied by 1-2 technicians who are
responsible for fault clearance, maintenance work and the overall operation of the
stations. The number of necessary employees depends on the number of the
attended stations; as indicative number one technician can be calculated for every
three stations.
Task description:
Engineer Organization of monitoring station
Data assessment/ collaboration in Clear Air Plans and action
plans
Information of the local public, municipalities, businesses, media,
schools, action groups, etc.
Support of monitoring network service in special investigations
(e.g. in the framework of approval procedures, road planning,
specific land-use areas, industrial parks, regional planning
procedures)
Special programmes for the determination of PM-10 pollution
Technician Maintenance: exchange of all consumable material
Repairs: exchange of worn out pieces (Pumps, membranes,
magnet valves).
First fault diagnosis until the decision is taken, whether the
devices needs to be exchanged.
Support with Public Relations
The tasks of the regional and local levels need to be defined very accurately.
Experience has shown that otherwise responsibility in case of malfunctions is
critically.
12

13. 3. Quality Management in Air Quality Monitoring
It is stringent to establish a Quality Management System (QMS) for the air quality
monitoring. This system must comply with EU regulations and must be implemented
at the same time with the installation of the air quality monitoring networks.
For each air quality monitoring network, the QMS is vital, because very important
decisions regarding air quality monitoring, legislation against emission source
operators depend totally or partially on the measurement data. Not only are incorrect
data and false information useless, but they can lead to wrong decisions and
endanger human health. The QMS should comprise the following elements:
 Selection of measurement locations
 Selection of measurement devices used
 Calibration of measurement devices (monitors)
 Maintenance of monitors and monitoring stations
 Management of measurement data
 Validation of measurement data
A good data quality and a high data capture rate are essential in an air quality
monitoring network in order to reach the Data Quality Objectives (DQO) of the EU
Directives. In order to ensure that the data are sufficiently accurate, reliable and
comparable to other monitoring networks, the measures for quality management
have to be consistently used in the entire network.
The QM-System has the following fundamental objectives:
 The measurement data of the network must be representative for existing air
pollutions in the monitored (urban) area.
 The measurement must be accurate, precise and traceable.
 The measurement data must be comparable and reproducible: the results of a
geographically extended area must be consistent and comparable to
international standards.
 The measurement results over the entire period of the monitoring network
operation must be consistent (consistent over time).
The basics for the measurement are the primary and secondary standards, which are
usually cared for by the National Reference Laboratory (NRL). Additionally, there are
the necessary absolute or traceable metrological standards, for which the National
Metrological Institute is responsible (temperature, pressure, flow rate, weight, etc).
The necessary requirements for the achievement of uniformity are:
 The used measurement methods must be known (known performance) and
their scope must be defined.
 Each calibration must be traceable by means of an uninterrupted string to
international standards.
 The measurements must be performed within a documented QMS.
Because of the importance of these general requirements for the measurements in
an air quality monitoring network, the main tasks of the regional calibration
laboratories (RCL) are described in more detail in the next pages.
13

14. 3.1 Traceability of air quality data
The regional calibration labs (RCL) have many diverse tasks. One of the main tasks
is the supply of traceable transfer standards for the calibration of measurement
devices in the monitoring networks.
Traceable means, that these transfer standards are connected to
national/international standards by an uninterrupted chain of comparison
measurements with known measurement uncertainty.
National standards shall be kept by the National Reference Laboratory (NRL) and
shall be linked to international standards by means of international comparison
measurements.
The laboratory reference standards used in the calibration labs as a basis for
calibration have to be certified by the NRL by means of comparison measurements
with the national standards. The uncertainty of the certified test gas concentration
shall always be indicated in this process.
Both test gases in test gas bottles and test gas generators can be used as laboratory
reference standards. The stability of the laboratory reference standards used must be
monitored constantly by the Reference Calibration Labs by means of appropriate
measures (e.g. cross-checks with a second standard or independent procedures).
The calibration labs perform comparison measurements of the transfer standards
with the laboratory reference standards and determine their uncertainty. To this
purpose, reference measurement devices are used, which have been previously
calibrated with the laboratory reference standards. Then, the transfer standards are
deployed in the monitoring stations for the calibration of measurement devices. Thus,
the traceability of air quality data to national standards is guaranteed.
Additional to reference standards, the RCL‘s also have other standards at their
disposal (laboratory work standards), which can be used, for example for the daily
zero/span control of the reference measurement devices and for the linearity test of
measurement devices.
3.2 Linearity test
The linearity of measurement devices is to be tested regularly, yearly or every three
years, according to test results. Also, after repairs or basic maintenance works on
measurement devices, a new linearity test shall be necessary.
With newly procured measurement devices the linearity test shall take place in the
RCL before its installation in a monitoring station.
3.3 Receiving inspection
The EN ISO/IEC 17025 „General requirements for the competence of testing and
calibration laboratories― requires that newly acquired measurement devices are
tested for the observance of technical specifications and for compliance with the
requirements of that particular measurement procedure. These receiving inspections
shall take place in the RCL.
The receiving inspection for new measurement devices comprises a formal part, in
which the completeness of delivery is checked and a practical part, in which data
transfer, device parameterisation and the compliance with special performance
14

15. characteristics are checked. The basic calibration and the first linearity test shall also
take place in the framework of the receiving inspection. Only if the measurement
device fulfils all requirements it may be cleared for measurement use.
The results of the inspection and the approval of measurement devices are to be
documented.
The following scheme shall again make clear the tasks described above:
National Standards
(NRL)
measurements
comparison
certification
calibration measurement
Laboratory Reference
Reference Analyser Transfer Standards
Standards
certification
zero/span
check
basic calibration
Laboratory Working
Standards
calibration
Lack of Fit check
initial checks
Analyser
15

16. 3.4 Type approval test for suitability evaluation on site
The European standards for the measurement procedures for SO 2, NO/NO2, O3 and
CO require that before use a measurement device be tested for its suitability to fulfil
the requirements of EU Directives regarding data quality even in the specific
conditions of the envisaged measurement site. For this, the measurement uncertainty
of the measurement device is calculated taking into consideration the results of the
type approval test and the specific conditions of the measurement site and then
compared with the requirements regarding measurement uncertainty of the EU
Directives.
The task of performing the type approval test for suitability evaluation shall be fulfilled
in the RCL‘s. A close collaboration between calibration lab, monitoring network
service and monitoring network centre shall be necessary in order to determine the
starting values required for the calculation of measurement uncertainty.
All calculations shall be documented
3.5 Reference standards for physical measures
In the monitoring network service volume flows, from PM10 samplers for instance, as
well as pressure and temperature sensors have to be verified regularly.
The balances used for the gravimetric determination of PM10 shall be calibrated
regularly with reference weights.
The RCL‘s must have at their disposal calibration reference measurement devices
and certified reference weights for the measures volume flow, pressure, temperature
and mass and must organise and ensure their regular recalibration or metrological
verification by the NMI.
These reference measurement devices shall be used in order to calibrate the
measurement devices used for the tests in the stations and the balances.
3.6 Gravimetric analysis
The RCL‘s are responsible for the gravimetric determination of PM10 and PM2,5. For
this, they have air conditioned balance rooms for filter conditioning and weighting.
The course of action and the requirements for the gravimetric determination of PM10
and PM2,5 are described in the corresponding European standards (EN 12341 and
EN 14907).
16

17. Measurement Principles and Measurement Methods
Content
Measurement Principles and Measurement Methods .............................................. 17
1. Discontinuous methods .......................................................................................... 18
2. Continuous Measurements ..................................................................................... 18
2.1 Suitability Tests .................................................................................................... 19
2.2 Description of Continuous Ambient Air Measurement Equipment ........................ 19
2.3 Measurement Principles ....................................................................................... 19
2.3.1 Conductometry ............................................................................................... 19
2.3.2 Chemiluminescence Measurement................................................................. 20
2.3.3 UV Fluorescence Measurement ..................................................................... 20
2.3.4 Measurement of UV Absorption ...................................................................... 21
2.3.5 Flame lonisation Measurement ....................................................................... 21
2.3.6 Optical Long-Path Monitoring (Path-Integrating Measurement) ...................... 22
2.3.7 Automated Gas Chromatography ................................................................... 22
2.3.8 Measurement with Beta-Ray Absorption ........................................................ 23
17

18. Measurement methods for ambient air quality measurement are usually divided into
- discontinuous methods and
- continuous methods.
1. Discontinuous methods
Discontinuous methods are mostly manual methods for which sampling on site and
analysis in the laboratory are two separate steps. Continuous methods typically
involve automatic equipment at a fixed site to carry out both sampling and analysis.
However, these distinctions do not quite take account of the great variety of air
quality measurement methods. "Discontinuous" measurements can be carried out
with automatic equipment at the sampling site as well as in the laboratory. The
employment of automatic sampling equipment - e.g. with several, independently and
subsequently controllable absorption receptacles - allows continuous and
uninterrupted measurements. Analyses can be carried out with an automatic
apparatus in the laboratory.
One specific example is the measurement of dust deposition. This is in principle a
discontinuous, manual measurement method, but because of the length of the
exposition time of one month without breaks for a single measurement, it is termed
semi-continuous.
Continuous measurements have the advantage of providing temporarily unbroken air
monitoring. They are predestined for stationary employment, but it is also possible to
fit them in mobile monitoring laboratories. Since higher temporal than spatial variation
is to be expected for air pollution in city areas with widely distributed pollutants - such
as SO2 -, continuous measurements provide advantages for air quality monitoring.
For the implementation of Smog Regulations continuous measurements are
indispensable. Expenditure for automatic continuous measurements is high: the
measurement equipment is quite expensive and highly qualified personnel is needed
for its operation. Therefore, equipment for continuous ambient air quality
measurements has been developed so far only for a limited number of substances.
Discontinuous, manual ambient air quality measurement methods are most useful for
random sampling, and for covering many measuring sites in an examination area.
Often, the measurements apparatus can be employed for the detection of several
different substances. Finally, this working area covers the measurement of all those
substances for which no automatic equipment is available.
2. Continuous Measurements
Continuous ambient air quality measurements are carried out mainly for the
implementation of government regulations in particular of the European Community.
The German law specifies that listings of suitable measurement equipment for
continuous measurements shall be published by the Federal Minister for the
Environment, Nature Protection and Nuclear Safety (BMU) following consultation with
the responsible authorities of the individual Federal States. These publications shall
be made in the Joint Ministerial Gazette.
18

19. 2.1 Suitability Tests
The publication of suitable equipment for continuous ambient air quality
measurement by the BMU requires the successful completion of a suitability test. An
examination schedule for suitability tests, which has been designed by experts of
official Federal and local government institutions and has been approved.
A suitability test is normally carried out following a request by the measurement
equipment manufacturer to one of the institutes named above. On completion of the
suitability test, which is carried out at the manufacturer's expense, the institute
provides a test report to the Federal Environmental Agency (UBA). If their
assessment is positive, publication follows as mentioned above in the Joint
Ministerial Gazette by the Federal Minister for the Environment, Nature Protection
and Nuclear Safety (BMU).
2.2 Description of Continuous Ambient Air Measurement Equipment
Detailed descriptions of quite a number of continuously operating ambient air quality
measurement devices can be found in Guidelines by the Commission on Air Pollution
Prevention in the Association of German Engineers (VDI/DIN). These Guidelines
describe continuously operating measurement devices for the measurement of
sulphur dioxide, nitrogen oxide, carbon monoxide, ozone, sum of organic compounds
and suspended particulate matter.
2.3 Measurement Principles
Suitability-tested, continuously operating ambient air quality measurement devices
are available for the following air polluting substances:
- sulphur dioxide,
- nitrogen oxides,
- carbon monoxide,
- ozone,
- total gaseous organic compounds,
- benzene,
- toluene, ethyl benzene, xylene and
- suspended particulate matter, PM10, PM2.5.
The measurement principles employed by these instruments are briefly described in
the following. In most cases they correspond to the methods used for continuous
emission measurements so that the descriptions have partly been borrowed from the
Emission Manual.
2.3.1 Conductometry
In the conductometric measurement principle the sample gas is introduced into a
suitable liquid reagent and the change of the conductivity is measured after
completion of the reaction between the liquid and the gas. Objects of measuring are
mainly sulphur dioxide and carbon monoxide.
In continuous conductometry the sample gas and the reagent liquid are continuously
delivered into the reaction cell. As the conductivity is dependent on the ratio of
sample gas to the liquid volumetric flow, suitable means must be provided to ensure
19

20. that the flow of both streams is kept constant. The influence of temperature on the
conductivity must be compensated.
2.3.2 Chemiluminescence Measurement
Some chemical gas reactions produce a characteristic radiation, the so-called
Chemiluminescence. The intensity of this Chemiluminescence is proportional to the
mass flow rate of the sample gas under constant reaction conditions, if the auxiliary
gas necessary to produce the reaction is present in excess.
The Chemiluminescence emitted during the oxidation of nitrogen oxide molecules
with ozone is used in the determination of NO concentration: NO + O3 —¥ NO2 + O2
+ hv.
Chemiluminescence measurements take place in a reaction chamber. Air which has
first passed through an ozone generator flows into this chamber. The partial
conversion of the oxygen in the air to ozone is accomplished by electrical discharges
or by UV irradiation. A constant flow sample gas enters the reaction chamber via
another entrance nozzle and is mixed with the ozone rich air. An ozone filter is fitted
in the outlet of the reaction chamber to prevent pollution of the environment. The
chemiluminescence, after being optically filtered, is measured with a photomultiplier.
A thermostatically temperature controlled reaction chamber operating at a constant
internal pressure is absolutely necessary to obtain a stable measurements.
For the determination of the nitrogen dioxide concentration, the sample gas is first
passed through a thermocatalytic converter which reduces NO2 to NO before the
analysis is performed.
This method is also used to measure ammonia in ambient air. For this purpose, NH3
is transformed into NO, and the amount of NH3 in the sampling air is determined by
measuring the difference to the previous amount of NO.
The principle of chemiluminescence is also employed for ozone in ambient air quality
measurements (Table 7). Here also the reaction of O3 and NO (in excess) described
above is used for continuous measurements.
2.3.3 UV Fluorescence Measurement
The sample air passes through a beam of light from a UV lamp (e.g. Zn-hollow
cathode lamp). As a result the molecules of the gas to be measured are activated
into a fluorescence radiation which is led into a photomultiplier as a receiver and can
be measured after amplification. An interference filter placed before the receiver
filters out the specific fluorescence radiation of the gas to be measured. The
fluorescence intensity is a function of the concentration of the gas to be measured
and the light energy of the UV light source.
The method is employed as an ambient air quality measuring technique for the
continuous measurement of sulphur dioxide. It also enables the measurement of
hydrogen sulphide. Before the measurement H2S is oxidized to SO2.
Measurement by Non-Dispersive Infrared Absorption and Gas Filter Correlation
All heteroatomic molecules like CO, CO2, SO2 and NO possess a typical
characteristic absorption spectrum in the infrared range. In ambient air quality
measurement, the principle of infrared absorption is employed exclusively for the
measurement of carbon monoxide (CO) and carbon dioxide (CO2), because the
20

21. radiation absorption of these gases is high enough even in low concentrations in
atmospheric air.
The non-dispersive infrared absorption methods (NDIR) dispense with the spectral
refraction and obtain the desired selectivity by the use of a sample of the measuring
component stored in the instrument itself. Depending on the method of storing the
sample, the non-dispersive infrared absorption method (NDIR) and the gas filter
correlation method (GFC) are distinguished.
The NDIR method uses the light receiver for storage. The radiation transformed in
the gas filled receiver chambers and modulated by a revolving chopper wheel
produces periodic pressure variations in the receiver chambers. These are sensed,
either by a membrane capacitor, or in a micro flow detector which senses the
pressure equalizing flow between each of two receiver chambers, and converted into
electrical signals.
The gas filter correlation (GFC) method uses a gas filled chamber fixed to a filter
wheel. This filter chamber and either an opening or a N2 gas filled filter are
alternately and periodically brought into the light path.
2.3.4 Measurement of UV Absorption
UV absorption measurement is employed for continuous measurements of ozone in
ambient air. The measurement is based on the absorption of ultraviolet light by
ozone, which has a maximum wavelength of 254 nm.
The sample air is passed into a measurement cell, which is placed between the UV
radiation source and the radiation receiver (i.e. a photomultiplier). The air is passed
into the cell by means of a magnetic valve alternating between direct flow and flow
through a catalytic converter, which quantitatively reduces ozone to oxygen. The
radiation intensity measured in ozone free air is stored and subtracted from the
intensity measured in the air containing ozone.
2.3.5 Flame lonisation Measurement
Organic carbon compounds are relatively easily ionizable in a hydrogen flame. In an
ionization chamber the ion cloud thus produced is extracted by applying an electric
field via electrodes and generates an electric current. This current is, to a large
degree, approximately proportional to the mass flow rate of organic bound carbon
atoms. There is, however, a certain dependence on the structural bond of the C
atoms of the particular molecule.
The flame ionization detector consists of a combustion chamber. Pure hydrogen,
which can be taken from a pressurized gas cylinder or produced in an electrolytic
hydrogen generator unit, flows through a nozzle into the combustion chamber.
Combustion air from the atmosphere is admitted via an annular slit around the
nozzle. After electrical ignition, a steady hydrogen flame produces a very small ion
density (zero value) in the absence of organic carbon compounds in the sample gas.
The electrodes necessary to extract the ion cloud are arranged near the flame. The
combustion nozzle itself can be used as one of the electrodes. With a sufficiently high
electric potential difference, all the charge carriers will find their way on to the
electrodes, i.e., the saturation current is flowing. This is raised to the desired signal
amplitude by a sensitive direct depends on the material of the combustion nozzle and
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22. the detector geometry. For continuous measurements the temperature and the mass
flow rate of the sample gas must be kept constant.
For ambient air quality measurements, the determination of the sum of gaseous
organic compounds is current amplifier, and at the same time, the zero value is
compensated. The absolute measuring sensitivity performed after the separation of
methane, which is always contained in samples but hygienically negligible. The
separation can be obtained by placing before the FID either a short separation
column or a cooled storage column or by catalytic burning of hydrocarbons, taking
advantage of the fact that they have a larger mass than methane.
2.3.6 Optical Long-Path Monitoring (Path-Integrating Measurement)
Optical long-path monitoring techniques for air quality monitoring have already been
used for years for various measuring tasks, particularly for the registration of
emission rates and for air-chemical as well as meteorological research. The following
optical techniques for gas long-path monitoring are designated and described:
- Lidar
- Derivative Spectroscopy
- Differential Optical Absorption Spectroscopy (DOAS)
- FTIR-Spectroscopy (Fourier-Transformation-Infra-Red)
- Correlation Spectroscopy.
Optical long-path monitoring does not include sampling by suction of air. This
measures the radiation absorption which occurs when a defined beam passes
through an air distance of the gas to be analysed.
Long-path monitoring is usually closer to emission measurements than to ambient air
quality measurements. The pollution concentrations close to emission sources is
often measured. Detection limits and interferences caused by fog, dust and other
substances limit the use of long-path monitoring for ambient air quality
measurements.
The optical long-path monitoring technique (DOAS) is based on the absorption of UV
light or visible light by the gas to be measured on a length up to several kilometers
between a light emitter and a receiver system. It proved efficient for ambient air
quality measurement as for instance by the suitability test of an instrument for
measurement of sulphur dioxide. Instruments for measuring nitrogen oxide, ozone
and benzene are currently undergoing suitability tests.
2.3.7 Automated Gas Chromatography
The principle of gas chromatography is also used in new suitability tested devices for
continuous-automatically measurement of aromatic hydrocarbons (benzene, toluene,
xylene, ethyl benzene) in ambient air. Minimum requirements and examination for
devices measuring automatically for individual measurements of benzene in air with
enriched sampling and subsequent gas-chromatographical separation are described
in the DIN-norm 33963-2.
Particularly the measurement of benzene as an air-hygienically critical component of
motor vehicles' exhausts is a priority of air quality supervision today.
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23. 2.3.8 Measurement with Beta-Ray Absorption
In dust measurement with beta-ray absorption systems, the sample air is sucked
through a filter tape which is getting moved stepwise. The dust quantity precipitated
on the filter tape is measured by the gradual attenuation of the beta-ray radiation that
is passing through the dust laden filter.
A synthetically manufactured radioactive probe of suitable activity (e.g. carbon 14 or
krypton 85 isotopes) is used as the radiation source and a Geiger-Müller counter or
an ionisation chamber employed for the detection. To compensate for the gradual
reduction in radioactivity over a period of time and the variation of the radiation
weakening due to the filter material, measurements of the absorption are taken
before and after, or before and during dust filtration and the measured values
compared with each other. During the absorption measurement, while dust sampling,
the accumulated particle mass is measured and indicated. Generally, the double-
beam compensation method is employed in devices of this kind. This facilitates a
real-time measurement of dust on the filter.
Planning of ambient air quality measurements
General rules
Contents
1 Problem analysis
1.1 Content of the task description
1.2 Analysis of background information
1.3 Assessment of the results of the measurements
1.4 Measurement parameters, measurement area and measurement period
1.5 Requirements on the results
2 Organization
2.1 Project management
2.2 Personnel planning
2.3 Scheduling
2.4 Subcontracts
3 Measurement techniques
3.1 Time resolution of the measurements
3.2 Performance characteristics
3.3 Standardization of the measuring procedure
3.4 Infrastructure for using measurement techniques
3.5 Data recording and documentation of the measurements
4 Measurement strategy
4.1 Measurement locations
4.2 Measurement times
4.3 Sampling period
4.4 Duration of the measurement program
4.5 Supplementary measurements
5 Evaluation
5.1 Producing measured values
5.2 Evaluation algorithms
5.3 Measurement uncertainty
5.4 Uncertainty of the result
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24. 6 Quality assurance
7 Reports
1 Problem analysis
The intention of the requirements described here is for the planning of ambient air
quality measurements to be completed so as to enable a given task description to be
processed with sufficient conclusiveness and with an acceptable outlay. This should
ensure that the results gained from the measurements will meet the requirements
stipulated in terms of the data being representative and with regard to the
measurement uncertainty.
This is an aid to everyone involved in the planning, performance or evaluation of
ambient air quality measurements. Basic knowledge in the following fields is useful:
- assessment of air pollution and its effects,
- chemistry of air,
- measurement techniques in the field of trace analysis,
- meteorology,
- statistics,
- quality assurance.
The aim of problem analysis is to differentiate the investigation task so that appropriate and
unambiguous technical stipulations can be defined for carrying out the investigations. In order
to do so, the following must be analyzed:
- what objective is to be achieved,
- what background information concerning the problem is available,
- how the results of the measurements are to be assessed,
- which air quality characteristics, which measurement area and which
measurement period are to be studied.
1.1 Content of the task description
A specific task description is required in order to plan the measurements. The task is
considered to be described with sufficient clarity if it allows stipulations to be made
concerning the following points:
- air pollutants to be investigated,
- assessment standards to be applied,
- measurement techniques, including sampling,
- measurement area and density of measuring sites or measurement locations,
- duration of an individual measurement, frequency and period of measurement,
- quality assurance,
- evaluation and report.
1.2 Analysis of background information
The problem analysis phase includes gathering information which will allow
classification of the task. Before a measurement task is formulated, a model concept
is usually developed to determine a causal relationship between the occurrence of air
pollution at a location or within an area under consideration and its possible effects
on a group of objects to be protected or an individual from such a group. The extent
to which a planned investigation using techniques to measure the respective air
pollution in the atmosphere can help to answer the question raised will depend,
among other things, on how realistic this model concept is. It can be used to analyze
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25. how the problems presumably caused by air pollution in the area in question can be
described adequately and how they can be investigated using measurements and
whether an investigation task requires further detailing.
Starting points for the analysis are matters concerning measurement data available,
sources which contribute to the occurrence of air pollution within the measurement
area, and effects on the objects to be protected.
Analysis of measurement data available
If results of surveys on air pollution carried out within the measurement area are
available, they may provide important information for the planning of further
measurements. If the measurement area contains one or more permanent measuring
stations, these should be taken into account when planning the measurements. The
measurements recorded by these permanent measuring stations may be included in
the evaluation. The same applies to any meteorological data available.
Analysis of the sources
To determine the air pollution occurring within the measurement area, it may be
necessary to carry out an analysis of the sources present within the measurement
area and its vicinity and of the emissions from such sources. This requires expert
knowledge in plant and process engineering. In this context, it may also be helpful to
analyze any emission survey charts which may be available. Generally the following
types of sources are distinguished:
- industrial facilities,
- small industry and house fires,
- traffic,
- natural sources.
Any sources of emissions with a low outlet or stack height are extremely significant
for the occurrence of near-ground air pollution within a measurement area. Sources
with higher stacks contribute to a lesser extent to the occurrence of near-ground air
pollution near to the source owing to the greater dilution of the emissions on their
dispersion paths. In many cases, dispersion calculations can be applied to estimate
the anticipated proportions from known sources in the air pollution within the
measurement area. Provisions covering such calculations are laid down in pertinent
guidelines and procedures. The result of these analyses should be a register of types
of air pollution anticipated. Information on the sources or types of sources causing
the pollution should be included in the register.
Effects of air pollution
When planning the measurements, it is also useful to know what effects may be
caused by air pollution on objects to be protected and what hazards may be involved.
The following outline will show how important this is. A precondition for the effect of
air pollution on an object to be protected is firstly the contact of the object with the air
pollutants. Such a contact can take place either directly by direct exposure or
indirectly (however, the indirect effect of trace substances relevant to the climate, for
example, will not be examined here). In the case of man as the object to be
protected, there is direct contact, e.g. by inhalation and additionally through
unprotected skin, as well as indirect contact which is mainly through the food chain.
In contrast to indirect contact over which man has a certain amount of control by
suitable preventive measures (control and selection of food), it is generally very
difficult to apply acceptable measures to prevent direct exposure when the substance
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26. has already escaped into the atmosphere. Since effects are usually determined by
the mass of a substance absorbed, the duration of exposure and the pattern of
exposure over time, the differences mentioned may be significant when stipulating
the measurement strategy to assess the impact of a pollution situation. Additionally,
in the case of direct exposure, consideration should be given to the fact that the
different pollutants can have different effects on the objects to be protected. For
instance, acute effects may occur due to the effect of high concentrations of
particular substances (e.g. irritant gases such as ozone, sulfur dioxide or nitrogen
dioxide), and chronic effects may occur due to an accumulation of possibly extremely
low concentrations of various substances (e.g. heavy metals such as lead or
cadmium). As far as measurements are concerned, the carcinogenic substances
(e.g. benzene, benzo(a)pyrene or asbestos) shall be treated in the same way as the
cumulative substances. Such aspects should therefore also be taken into account
when stipulating measurement strategies.
1.3 Assessment of the results of the measurements
International and national assessment standards are derived from the information
gained concerning interrelations between exposure and observed effects. For
instance, assessment standards are included in national environmental legislation
with the associated Regulations and Administrative Orders and in corresponding
Executive Orders. The assessment standards include, for example, action values,
threshold values, test values and recommended values. The applicable assessment
standards form the basis to derive air quality characteristics which are to be
determined within the framework of the measurements.
1.4 Measurands, measurement area and measurement period
The problem analysis shall include verifying whether the measurands to be collected,
the measurement area and the measurement period have been stipulated in an
unambiguous and targeted manner. In doing so, any appropriate environmental
provisions shall be observed. In this context, it should now be clear what
supplementary information (e.g. results from preliminary investigations) is required to
carry out the investigation task.
1.5 Requirements on the results
During the detailing of the task description, stipulations shall be made with regard to
the air quality characteristics (characteristic values) to be determined, the
requirement on the measurement uncertainty, and the requirement on how
representative the measurements are to be in terms of area and time.
It is important to stipulate these boundary conditions since they have a major
influence on the outlay required for the measurements. Reference shall be made to
pertinent standards and guidelines if these can be applied to specify the above
requirements.
2 Organization
2.1 Project management
The person appointed as project manager shall have the knowledge and practical
experience required for planning and carrying out ambient air quality measurements.
A suitably qualified deputy project manager shall also be appointed. Verification of
their qualification may be provided.
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27. 2.2 Personnel planning
Planning of the personnel resources required to carry out the measurements shall
depend on the measurement task set. The personnel shall have relevant experience
with the measuring procedures used. Measurement technicians and their assistants
shall have acquired their knowledge through practical work in the field of air quality
measurements. A technical qualification and knowledge of electronics and computers
are an advantage.
2.3 Scheduling
Planning and organizing the schedule to carry out the measurements will depend on
the measurement strategy and the measurement procedures. The time sequence
shall be documented. In the case of measurements based on random samples,
alternative dates shall be planned for the event of any measurement gaps.
2.4 Subcontracts
Subcontracts should only be awarded for precisely defined tasks. The qualification of
the subcontractors to carry out the task shall be verified by provision of documented
evidence (e.g. quality assurance manual. Any subcontractors participating in a
measurement contract shall be specified in the measurement plan.
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28. 3 Measurement techniques
With regard to the measuring procedures to be used, stipulations shall be laid down
concerning sampling, analytical determination and data production. The measuring
procedures will be selected in accordance with the measurement task. The results of
the measurements must meet the requirements set. When selecting the
measurement techniques, the following points shall be examined in particular:
- Will the required temporal differentiation be achieved using the measuring
procedure?
- Are the performance characteristics of the procedure sufficient with regard to
the task description?
- Is a standardized measuring procedure required for the measurement task?
- Can the infrastructure necessary for the measurements be provided?
- Is the measuring procedure sufficiently documented?
Continuous measurements comprise uninterrupted recording of air pollution
throughout the measurement period (apart from interruptions for calibration,
servicing, etc.). If automatically recording measuring instruments are used, sampling,
analytical determination and data production can be carried out in situ. In these
cases, the data is recorded using line recorders and/or data-recording computers and
memories. Any non-recording measuring instruments are usually used for
supplementary procedures, and the measurements need to be evaluated in the
laboratory at specific intervals.
Discontinuous measurements provide individual, non-connected measurement data
(measurements of random samples). Therefore they do not provide full information
throughout the measurement period. The number and times of measurements of
random samples shall be selected to correspond to the measurement strategy
stipulated and to meet the requirements set for the results of the measurements. For
many measurement tasks, it is customary to stipulate the number and temporal
distribution of measurements of random samples giving due regard to the statistical
uncertainties involved.
Semi-continuous measurements exist, according to the above definition, if the results
of discontinuous measurements do not differ by more than 5% from the results of the
theoretically correct, continuous measurements over the reference period. In the
case of different air pollutants, the requirements may vary greatly and will be
dependent on the respective time constant with which the concentrations may rapidly
change. Measurements will be semi-continuous in cases where a discontinuous
measuring procedure is used to carry out measurements which as far as possible are
continuous over the relevant period.
With the aid of automatic measurement techniques (robots), it is now possible to
convert some discontinuous measuring procedures into semi-continuous procedures
at an acceptable effort, e.g. by automatic exchange of the sampling medium
(accumulation material) and subsequent on-the-spot evaluation (e.g. benzene). For
this purpose, a particular time cycle can be specified for the individual measurements
up to continuous recording.
3.1 Time resolution of the measurements
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29. The time resolution of the measurements shall be in accordance with the air quality
characteristics to be determined. For continuously recording measuring instruments,
the time periods can be divided up on a broadly variable basis. These will not provide
genuinely instantaneous values. The shortest possible integration time will depend
on the measurement arrangement, the response time of the instruments, the
sampling cycle, etc. In the case of measurements taken by non-continuously
recording instruments, the time resolution will be determined primarily by the type
and duration of sampling required to achieve given performance characteristics of the
procedure, above all in this case, the detection limit.
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30. 3.2 Performance characteristics
The requirements for the performance characteristics of the measuring procedure to
be used (e.g. detection limit, confidence range, cross-sensitivity) shall be based on
the assessment standards and on the level of the concentrations or deposits
anticipated. The detection limit of the measuring procedure should in any case be
less than 10 % of the assessment standard. This must be ensured with acceptable
outlay in terms of quality control and documented in a reproducible manner. The
frequency and scope of calibration required shall be stipulated in the measurement
plan. The reference materials, reference measuring procedures and test gases to be
used shall be specified. The performance characteristics specified for standardized
measuring procedures in guidelines and standards and in suitability test reports for
measuring instruments can be used as a guide when selecting the measuring
procedure. The analytical function of the measuring procedure used shall be verified
at regular intervals. When using non-standardized measuring procedures, the
performance characteristics shall be redetermined whenever the operating
instructions are amended. The performance characteristics shall be recorded
accurately and attached to the reports of the results.
3.3 Standardization of the measuring procedure
To guarantee uniform practices in the monitoring of ambient air quality throughout the
Federal Republic of Germany, stipulations relating to measuring procedures and
measuring instruments are set out in general Administrative Orders. Standardized
measuring procedures are listed in the 4th Administrative Order on Air Pollution
Control. Continuously operating measuring instruments shall meet minimum
requirements and this shall be verified in comprehensive suitability tests at an
approved test institute. The performance characteristics and possible applications
shall be documented in the test report. Lists of approved measuring instruments will
be published in the Joint Ministerial Gazette by the relevant ministry in agreement
with the supreme state authorities responsible for air pollution control.
Wherever there are appropriate guidelines or standards, only standardized
measuring procedures should be applied. The documentation shall include the name,
origin and number of the guideline or standard.
If no standardized measuring procedures are available, the measuring procedure
used shall be documented in a comparable manner. Methods and operating
instructions shall be prepared giving sufficient detail to ensure that the sequence of
the investigation can be retraced precisely at any time. The performance
characteristics shall be redetermined whenever the operating instructions are
amended. The operating instructions shall be numbered and kept in the archives.
3.4 Infrastructure for using measurement techniques
For the measurement techniques to be employed, a specific infrastructure must be
available or be able to be provided with acceptable outlay. In this context, the
following aspects shall be examined:
- Is there a guaranteed energy supply to meet requirements (e.g. secure against
being switched off or against power failure if supplied by a third party)?
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31. - Are the measuring procedures affected by the weather (temperature, humidity,
sunlight, frost), and is there a suitable measurement location available e.g. air-
conditioned measuring room or vehicle, if required?
- Are the measuring instruments sufficiently insensitive to vibrations, for
instance during transportation? (This applies particularly to use in measuring
vehicles.)
- In the case of measuring instruments operating unsupervised, can outside
manipulation be ruled out?
- In the event of measuring instruments breaking down, are spare parts or
replacement instruments available at short notice to reduce interruptions?
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32. These points of infrastructure shall be taken into account when selecting the
measurement techniques.
3.5 Data recording and documentation of the measured values
All raw data required for the evaluation and traceability of the measurements shall be
documented and stored. Before the measurements begin, suitable measurement
report sheets and, for laboratory evaluations, sample record forms shall be prepared.
The way in which the measurement data is to be recorded shall be described in the
measurement plan. Wherever possible, the data should be recorded using electronic
data processing facilities. The main factor is to achieve guaranteed and traceable
data storage. The storage periods shall be stipulated.
The measurement data shall be validated by an independent internal control body.
The validated measurement data shall be identified as such and stored in such a way
that they can only be amended using control codes. Details relating to any
calibrations carried out as well as servicing work, instrument inspections, any
malfunctions, etc. shall likewise be documented. Furthermore, the data evaluation
techniques and the algorithms of statistical methods shall be documented and stored
in such a way that the evaluation can be retraced at any time.
4 Measurement strategy
When using measurements to investigate air pollution, the "air pollution object"
measured generally has both a temporal and a spatial structure. The measurement
strategy to be stipulated should be a realistic reflection of the temporal and spatial
conditions occurring on the object measured during the measurement period within
the measurement area. The temporal and spatial distribution of the measurements to
be carried out, i.e. the measurement strategy, determine the quality or
"representativeness" of this reflection. This means that the representative nature of
an investigation of the air quality is not an absolute, but is a measure of the quality of
the reflection, by the temporal/spatial random sample collected, of the conditions
which have occurred on the "air pollution object" measured. This is also greatly
influenced by the measurement outlay.
Continuous measurements can be carried out, for example, to achieve a nearly
uninterrupted reflection of the temporal structures of the air pollution investigated at
the measurement locations. This means that the investigation will be highly
representative in terms of time. In contrast, complete recording of the spatial
distribution of the types of air pollution under consideration within a large
measurement area is nearly impossible. Investigations of air pollution using
measurements in large measurement areas will therefore be of the random sample
type, at least in terms of area. The representativeness of the results of random
sample investigations is generally limited and may be described by the survey-related
proportion of the uncertainty of the result.
When planning the measurements, the question is raised as to how these sample-
related uncertainties in the investigation of air pollution can be controlled. The
temporal and spatial density of the measurements and the existing temporal and
spatial structures of the object measured are all deciding factors. For this reason, the
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33. spatial arrangement of the measuring points, the temporal distribution of sampling,
the duration of individual measurements and the duration of the measurement
program shall be stipulated in detail. On the one hand, it will then be possible for the
timing of the measurement program to range from many time periods up to
continuous registration of the measurands. However, this is only possible for some
selected types of air pollution and, for reasons of outlay, usually only at comparatively
few measurement locations, consequently with little spatial resolution. On the other
hand, it will generally only be possible to achieve high spatial resolution at the cost of
less temporal resolution. Between these two extremes, stipulations will have to be
made which result from
the task description and the available means. Air quality measurements will generally
only provide random samples of the population. The reliability with which an
investigation object can be characterized based on a random sample investigation
depends on how well it is represented, i.e. reflected, by the random samples. An
important task of planning the measurements therefore consists in organizing the
investigations in such a way that the random samples collected are representative of
the investigation object, and that it will be possible to assess the effects in question, if
necessary by comparison with relevant assessment standards. The measurands
must be suitable to determine the air quality characteristics required to achieve the
objective.
4.1 Measurement locations
Random selection of measurement locations
A simple and reliable method of carrying out a random spatial selection consists in
arranging the measurement locations in a square grid. This ensures that the
measurement locations are independent of the basic infrastructure patterns within the
measurement area, provided that these do not exhibit the same regularity as the
measurement grid selected, and this can easily be checked. Measurement locations
stipulated in this way form a representative random sample of the points covered by
the measurement area.
The grid width selected will expediently limit the achievable spatial resolution of the
measurement grid produced. Thus, with a measurement grid having a grid width of
1 km, it is not possible to carry out systematic recording of spatial structures of the air
quality characteristics investigated if they have an extent of less than 1 km; if
appropriate, shorter distances between the measurement locations should be
selected.
Stratification of measurement locations
The population of possible measurement locations within the area to be investigated
is divided into similarity strata. The elements of each stratum have common
characteristics which differentiate them from the elements of the other strata. An
example of a suitable stratification is similarity with regard to the structures of use.
Targeted selection of measurement locations
Once conclusive and traceable data has been obtained, from which the anticipated
spatial structures of the air quality characteristics investigated within the
measurement area can be derived, a targeted selection of measurement locations
can be made, for example at the location where the highest values of stipulated air
quality characteristics are expected. Documents prepared in a traceable manner shall
be kept to demonstrate how the selection of the measurement location was made.
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34. 4.2 Measurement times
Continuous recording
Continuous recording of air quality characteristics is absolutely essential if
information is required concerning temporarily elevated concentration values, such as
is the case in warning systems. In extended measuring grids, this type of recording
may prove to be expedient for other reasons, for example reducing the personnel
required by having unsupervised operation of automatic analyzers or collectors.
Deposit values are usually determined on the basis of continuous recording. If this
type of recording is not necessary for technical reasons, preference should be given
to one of the following selection procedures.
Random selection of measuring times
An equally distributed random selection of the measuring times, i.e. the starting times
for sampling, from a given measurement period allows representative random
samples to be chosen from the temporal distribution of the air quality characteristics
investigated, irrespective of whether these are half-hourly, hourly or daily mean
values. A precondition, however, is that the individual measurements within the
random sample are independent of one another in a statistical sense. This can be
achieved, for example, by collecting no more
than one sample in any sampling period of up to 8 hours per day. With a sampling
period of 24 hours, this can be achieved by not collecting samples on consecutive
days. There are relevant regulations which give stipulations relating to sampling
frequency for ambient air quality measurements.
Stratification of measuring times
Air quality characteristics often have typical time dependencies, for example daily
cycles, weekly cycles or annual cycles. Conclusive and verifiable information on such
temporal regularities can be utilized to limit the time requirement for the
measurements and thus to make them more cost-effective. For instance, if the
population to be investigated covers a temporal distribution over one year,
information on the annual cycle can be utilized to determine annual characteristic
values by extrapolation from shorter measurement periods, provided that the error
bands associated with this type of extrapolation are acceptable. If dependencies of
the air quality characteristics in question relating to the time of day result in elevated
values during specific hours of the day, sampling carried out exclusively during these
times will lead to overestimates of the characteristic values in relation to the whole
day. If such overestimates can be tolerated, it is acceptable to restrict the measuring
times to these particular hours of the day.
Knowing the times of the day when the maximum air pollution impact occurs may
also be useful for specific determination of the maximum values of the air pollution
impact. In this way, if guide values are not exceeded, for example, it can be deduced
with a high degree of certainty that the values at the measurement location have not
been exceeded, even under unfavourable conditions.
Targeted selection of measuring times
If the proportions from a known source in the concentrations of specified air
pollutants are to be recorded at a few specifically selected measurement locations, it
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35. is advisable likewise to target the selection of the measuring times, for example as a
function of the emission characteristics of the source and the wind direction. It is
especially advisable to make a targeted selection of measuring times if the
measurements relate to effects which can be predicted to occur at specific times.
This is frequently the case when investigating complaints. For instance, if the
proportion of air pollution from a specific source at a given location is to be
investigated, measuring times should be selected, on the one hand, at which an
impact on the measurement location is anticipated owing to the activity of the source
and the prevailing wind direction and, on the other hand, measuring times at which
an impact due to the identified source can be ruled out. By comparing the results of
the two categories, the contribution from the source in question at the measurement
location can be estimated. In this case, the determination and consideration of the
wind direction is thus helpful in selecting the measuring times.
4.3 Sampling period
The sampling period depends on the assessment standard and the measurement
procedure. For discontinuous measurements, it is usually between half an hour and
72 hours. Longer sampling times are also permissible if the assessment standard
and the measurement procedure make allowance for this.
4.4 Duration of the measurement program
The duration of the measurement program is to be specified in the measurement
plan. In many cases, the duration of a measurement program can be deduced from
the air quality characteristics in question. If, for example, annual characteristic values,
such as the annual mean value or the 98-percentile, are to be determined, the
measurement period should always cover 12 months. Deviations from this period are
permissible in exceptional circumstances.
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36. If information is available concerning seasonal differences in the impact caused by
the types of air pollutants in question, this information can be used for some task
descriptions to arrange for the measurements to be taken only in the six-month
period with the higher air pollution impact. Shortening the measurement period to 6
months is also acceptable if the air pollutant investigated has not been shown to
have an annual cycle. The characteristic values derived for a six-month period are
then used as estimated values for the annual characteristic values required.
If the investigation relates, for example, to the frequency with which the ozone
concentrations at a measurement location exceed the threshold value of 180 μg/m3,
the measurements can be limited to the summer half-year since such concentrations
are not experienced in the winter half-year.
For measurements taken for orientation purposes, the measurement period may be
reduced down to one month, provided that extrapolations known to be reliable can be
carried out to estimate the annual characteristic values required.
4.5 Supplementary measurements
It will often be necessary to carry out supplementary measurements to achieve the
measurement target. These may include meteorological parameters if such
information cannot be acquired from other sources. Other important parameters may
also be details of traffic structure, such as type of vehicle, vehicle density or traffic.
5 Evaluation
The rules of calculus used when evaluating the measurement data are generally
required,
- to obtain measured values from the measured signals,
- to determine the air quality characteristics in question from the measured
values, and
- to estimate measurement uncertainties.
More thorough statistical evaluations, e.g. for causal analysis or the planning of
preventive measures, can be based on the above.
5.1 Producing measured values
In order to ensure that the measurement process is reproducible, the analytical
functions used, their parameters and the associated standard deviations and
covariances must be documented and included in the measurement report.
5.2 Evaluation algorithms
Mathematical algorithms are usually needed to determine the air quality
characteristics required from the measured values. To ensure that the evaluations
are reproducible, the evaluation algorithms used must be documented and included
in the measurement report in a reproducible form. It is also advisable to refer to
standardized evaluation procedures wherever possible.
Detection limit
For the purpose of the evaluation, stipulations shall be made as to how measured
values below the detection limit are to be treated. These measured values can be
taken into account, for example, using half the value of the detection limit.
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37. Measurement gaps
The proportion of measurement gaps shall be specified and reasons given in the
evaluation. It may be necessary to agree a maximum permissible proportion of
measurement gaps. If gaps in the measurement data can be filled by calculation, the
calculation method used shall be specified. The substituted measured values shall be
identified as such.
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38. Outliers
The treatment of outliers shall be specified and reasons given. The measured values
determined as outliers shall be identified as such.
5.3 Measurement uncertainty
During planning the measurements stipulations must also be made stating how the
measurement uncertainty in the data collected is to be quantified and documented.
This complies with the requirement of producing data of a known quality. The
measurement uncertainty inherent in the measurement process can be characterized
by specifying a standard deviation or variance in accordance with the
recommendations of the international publication "Guide to the expression of
uncertainty in measurement". In the simplest case, the model function used will be
the analytical function. Using the methods of uncertainty propagation described in the
international guideline, an equation can be derived for the variance of the measured
values inherent in the measurement process. To do so, the variances and possibly
also the covariances of the parameters of the analytical function describing the
influencing factors must be known. The temporal and spatial structures of the
measured object have no influence on the measurement uncertainty since they have
to be assigned to the measured object and are thus part of the investigation. If it is
impossible to specify a suitable model function which realistically describes the
measurement process taking the dominant influencing factors into account, the
precision and accuracy of the measured values can be quantified in accordance with
the International Standard ISO 5725. Departing from the concept of the international
guideline, the ISO 5725 series of standards does specify the precision of a measured
value, but not its trueness as a variance or standard deviation; this is given as a bias.
5.4 Uncertainty of the result
It should be examined separately during planning the measurements whether the
uncertainty of the results (air quality characteristics) is to be determined in addition to
the measurement uncertainty. It may be necessary to stipulate what procedure is to
be applied and what additional measurement or calculation outlay this will entail.
The uncertainty of the results (air quality characteristics) of an investigation of air
quality based on random samples will be influenced not only by the measurement
techniques used, but also by the selection of measuring times and measurement
locations, i.e. by the measurement strategy selected. The question of how the
measurement strategy will influence the uncertainty of the result is raised whenever
conclusions are to be drawn from a limited quantity of air quality measurement data
collected to give the frequency distribution (population) of the states of the measured
object which occurred during the measurement period and within the measurement
area. The air quality characteristics to be specified as results, such as mean value or
98-percentile are functions of the measurement data collected as random samples
and as such are estimates of the corresponding characteristic values of the
frequency distribution investigated which are subject to statistical uncertainties.
Additional measurement and calculation outlay is generally required to examine the
influence of a selected measurement strategy on the uncertainty of derived air quality
characteristics, and planning this outlay requires specific knowledge of statistical
investigation planning. It is therefore advisable, wherever possible, to use
investigation examples and to apply these to investigations using the same
measurement strategy if necessary. However, such cases must assume that the
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39. measurement uncertainty inherent in the measurement techniques is known. If it is
only a case of ensuring that the influence of the measurement strategy on the air
quality characteristics determined is comparable, a requirement for equal temporal
and spatial density of the survey to be carried out is sufficient.
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40. 6 Quality assurance
The measurement plan should contain quality assurance (QA) statements. The
measurement plan should clearly describe the type and scope of the QA measures to
be applied. In particular, the details should include the calibration tests and
comparison measurements to be carried out. The relevant reference standards or
reference procedures shall be specified. If appropriate descriptions are available
elsewhere, for example in the quality manual of the measurement institute, reference
can be made to such documents. The details given must be sufficient to enable the
intended QA measures to be verified as corresponding to the agreements or
requirements.
7 Reports
It is important to stipulate during the planning stage how the measurements to be
carried out are to be evaluated, documented and stored. If requested by the client, an
agreement should be reached concerning the type and scope of reports.
The measurement report should as a minimum contain details of the following points:
- Task description
- Measurement methods
- Measurement strategy
- Results
- Measurement uncertainties.
Planning of ambient air quality measurements – Rules for planning
investigations of traffic related air pollutants in key pollution areas
Content
1 Introduction
2 Problem analysis
2.1 General
2.2 Classification of the objective
2.3 Analysis of background information
2.4 Use and assessment of the measurement results
3 Organization
3.1 Project management
3.2 Personnel planning
3.3 Scheduling
3.4 Subcontracting
4 Measurement techniques
4.1 Typical measurement and sampling methods
4.2 Determining the measurement uncertainty of non-standardized
measurement methods
5 Measurement strategy
5.1 General planning sequence
5.2 Preliminary measurements
5.3 Monitoring measurements
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41. 6 Evaluation
6.1 Production of measured values
6.2 Evaluation algorithms
6.3 Measurement uncertainty
6.4 Uncertainty of the result
7 Quality assurance
8 Reporting
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42. 1 Introduction
Air pollution measurements are carried out to answer specific questions regarding specified
air quality characteristics in a given area or at specified locations. A leading role is generally
played by questions as to the effect of air pollutants on protected objects. The object of
measurement planning is to analyze submitted objectives and from this to derive
requirements of the organization, the measurement method, the measurement strategy, the
assessment, the quality assurance and reporting.
The report details the requirements with respect to studying traffic-related air pollution at key
points where pollution occurs. The considerations reproduce fundamental knowledge to be
taken into account in the planning of traffic-related studies. This is intended to enable
planning of air pollution measurements in such a manner that any question asked can be
answered with sufficient meaningfulness and with reasonable expenditure. This is intended
to result in the fact that the measurement results obtained can be assessed with respect to
their representative nature and measurement uncertainty.
Traffic-related air pollutants play an important role in urban areas in particular in the vicinity
of very busy roads. Vehicle occupants as well as passers by and residents are exposed to
these air pollutants. To answer the question as to whether such air pollutants can lead to
harmful effects on humans, not only is the concentration of the air pollutant of importance,
but also the residence time of humans in the vicinity of the road traffic. When possible routes
of pollution for residents are being studied, in addition to the outdoor air, indoor air pollution
may also need to be taken into account. The report is relevant to all those involved with the
planning, performance or assessment of studies of traffic-related air pollution. The contents
can serve clients and contractors equally as a reference base, for example for formulating
specifications and articles and conditions for performing studies or air quality. For the
measurement planning fundamental knowledge in the following areas is helpful:
- Assessment of air pollutants and effects
- Atmospheric chemistry
- Methodology in the trace analysis area
- Meteorology
- Statistics
- Quality assurance
2 Problem analysis
2.1 General
In problem analysis, the investigation task shall be specified to the extent that an economical
solution for the measurement method and equipment resources and for the measurement
strategy can be given. For this purpose it is necessary to analyze:
- what objective is to be achieved,
- how much prior knowledge exists at the object to be studied,
- how the results of the measurement are to be assessed or utilized.
During problem analysis it can be helpful to classify the task description as a standard case
for which provisions or recommendations exist to carry it out. Measurement planning in the
study of traffic-related air pollutants at key pollution sites may be limited essentially to the
following standard cases:
- preliminary measurements
- monitoring measurements
If the task description should not be adequately specified, it should be made more precise in
a discussion with the client.
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43. 2.2 Classification of the objective
2.2.1 Preliminary measurements
Preliminary measurements are measurements of air pollutants which, with the lowest
possible use of resources and within a narrow time frame, give indications as to whether and
at which measuring sites in a selected area, harmful environmental effects on humans are
caused by road traffic. Therefore, preliminary measurements generally have the character of
spot checks. They can be used for:
 providing first indications of the level of expected concentrations of air pollutants at
selected measurement sites
 verifying with respect to analytical methodology the selection of measurement sites for
carrying out monitoring in a selected area
 verifying decisions on the necessity of monitoring.
Preliminary measurements of traffic-related air pollutants are generally differentiated from
monitoring measurements by a lower equipment requirement, a generally simpler and more
mobile measurement method and a narrow time restriction. Preliminary measurements are
therefore generally considerably less costly than monitoring measurements. Under certain
circumstances, preliminary measurements can replace monitoring measurements.
The results of preliminary measurements are also suitable for checking simple theoretical
modelling treatments, since these are frequently burdened with relatively high uncertainties.
This report does not deal with questions of modelling traffic-related air pollution and possible
uses of the model. Preliminary measurements can also be used to obtain initial indications of
the level of pollution at places where it is not possible to obtain a description by modelling.
2.2.2 Monitoring measurements
Monitoring measurements serve to monitor compliance or exceedance of predetermined
environmental assessment standards. The associated measurement resources make careful
planning of such measurements necessary. Monitoring measurements are generally carried
out with greater frequency and over a longer period than preliminary measurements. They
are carried out at measuring sites at which there are sufficient indications of the occurrence
of harmful environmental effects due to air pollution and at which humans receive not only
short-term exposure. Therefore, the selection of measuring sites for monitoring
measurements is of great importance.
In some circumstances, carefully carried-out preliminary measurements, depending on the
question, can lead to the result that the available information is sufficient for an evaluation
and monitoring measurements are thus no longer necessary.
2.3 Analysis of background information
Planning of measurements of traffic-related air pollution can make significant usage of the
analysis of existing information on the object under study. The points below shall be taken
into account in analysis of background information.
a) Traffic-related air pollutants
Numerous citations may be found in the specialist literature on the effects of air pollutants on
humans. More detailed studies should be left open to experts.
In addition, it should be noted whether the objects measured are primary or secondary air
pollutants, since the latter are only formed by reactions in the atmosphere and only permit
restricted conclusions to be made on the originating sources. This includes, for example,
ozone, which is formed, depending on the particular meteorological conditions, by reactions
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44. of hydrocarbons and nitrogen oxides which shall be assigned to motor vehicle traffic as
primary air pollutants.
b) Selection of the measuring sites
Frequently, the client will select the measuring sites. In other cases, the information below
can be valuable:
 Road geometry
 Height and density of buildings
 Building use
 Traffic frequency and composition
 Prevailing wind direction
 Background pollution
This information about the source and the local circumstances and about the meteorological
conditions is also useful for assessing the results and measurements to be derived
therefrom.
c) Level of the expected air pollutant concentrations
During analysis of the background information a check shall be made as to whether
information is available on the level of the expected air pollutant concentrations from
measurements or modelling. This knowledge should act in supporting the decision of the
type of measurement strategy to be employed.
2.4 Use and assessment of the measurement results
When studies of traffic-related air pollutants are being planned, later use of the results
obtained shall also be taken into account, since differing uses may result in different
requirements with regard to the quality of the results. Appropriate quality requirements shall
be agreed between client and contractor when the order is placed. Topics of relevance here
are:
- the use of type-approved measuring instruments in a calibrated state by an accredited
test laboratory
- determination of the measurement uncertainty of the measured values
- determination of uncertainties of the result
Specific requirements shall be agreed in individual cases.
The measures which are proposed by the contractor to meet the quality requirements will
also effect the resultant costs of a measurement program. This shall be taken into account
when different quotes are being compared. Without a reliable statement on the measurement
uncertainty, the measurement values produced are ultimately not comparable and thus
cannot be assessed either. At the same time, a statement of this type is a precondition for
uncertainties of the result being able to be determined.
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