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JRC- AQUILA Position Paper

Assessment on siting criteria, classification and representativeness of air quality monitoring stations

Structure of document

1. Introduction ................................................................................................................. 3

2. Scope ........................................................................................................................... 3

3. Provisions on siting of monitoring stations in current legislation and their

shortcomings ..................................................................................................................... 4

4. Guidance for the Implementing Decision on AQ Reporting (2011/850/EU) .......... 13

5. Proposed recommandations for the Review of Air Quality Legislation ............... 15

6. Suggestions for amendments to the AQD 2008/50/EC and 2004/107/EC ............. 18

4. Proposed guidance for the implementation of current legislation by Member

States ................................................................................................................................ 24

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This assessment was carried out by JRC in collaboration with the working group on “Siting criteria,

classification and representativeness of air quality monitoring stations” (SCREAM), composed of the

following experts:

AQUILA members

Jutta Geiger (D)

Laure Malherbe (F)

Francois Mathe (F)

Matthew Ross-Jones (S)

Karin Sjoberg (S)

Wolfgang Spangl (AT)

Brian Stacey (UK)

European Environment Agency

Alberto González Ortiz

Frank de Leeuw (ETC/ACM)

Joint Research Centre – IES

Annette Borowiak

Stefano Galmarini (FAIRMODE)

Michel Gerboles

Emile de Saeger

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1. Introduction

A lot of efforts are being dedicated by AQUILA to quality assurance and data quality of air pollution

measurements, with continually increasing requirements for ensuring that measurements are

carried out in comparable ways within the EU. Whilst an increasing amount of information is

becoming available on data quality related to the measurement method and equipment, its

calibration and maintenance, there is very little information available on whether stations providing

these measurements are located in the most relevant locations. In order for the air quality

assessments to be truly comparable, it is equally important that monitoring stations across the EU

are located in a consistent manner.

The need for harmonizing the implementation of the legislation with regards to where monitoring

sites are located is particularly felt in the light of the infringement proceedings within the EU for

Member States that exceed the Directives’ limit values. It is essential that assessment across the EU

is harmonized to ensure that compliance with limit values is being evaluated in a fair and consistent

way for all Member States, and thus that infringement actions are consistent and proportionate.

2. Scope

This documents summarizes discussions and considerations related to

siting criteria for AQ monitoring sites

classification of AQ monitoring sites

representativeness of AQ monitoring sites

as key requisites of AQ assessment, and provides input to

1. the Guidance to the Implementing Decision for Reporting1 (which is drafted at present by

the Commission)

2. the review of the AQ legislation (i.e. AQD 2008/50/EC and 4th DD 2004/107/EC2)

3. the implementation of current AQ legislation (which may concern additional guidance documents)

1 Commission Implementing Decision of 12 December 2011 laying down rules for Directives 2004/107/EC and

2008/50/EC of the European Parliament and of the Council as regards the reciprocal exchange of information and

reporting on ambient air quality (Decision 2011/850/EU) 2 AQD 2008/50/EC: Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008

on ambient air quality and cleaner air for Europe; 4th

DD 2004/107/EC: Directive 2004/107/EC of the European

Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic

aromatic hydrocarbons in ambient air

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The assessment was carried out by a group of national experts with a long standing experience in

the field of air quality assessment and amongst others active in AQUILA, FAIRMODE, the Time

Extension Notification assessments, the EU Ambient Air Quality Expert Group, the Implementing

Decision Pilot Group.

The leading principles of the assessment were guided by the need to harmonize current practices

amongst EU Member States and to simplify, clarify and streamline current legislation as far as

possible, without lowering the ambition level of current legislation.

The analysis of shortcomings in the current air quality legislation and suggested modifications were

based on technical and scientifical considerations only. However, the group of experts is aware that

the suggested modifications may impact on policy aspects for which this group has no

competences. Nor was it the objective of this group to evaluate in detail the impact of the

suggested changes in terms of resources. It should also be noted that, even if the group of experts

generally agreed on the recognition of shortcomings, the suggested modifications represent the

view of a majority of the experts, but do not necessarily reflect the opinions of each individual

expert. The considerations developed in this document are therefore meant to be submitted to the

Competent Authorities in the Member States and to the Commission as a basis for discussion for

the revision of the Air Quality policy.

3. Provisions on siting of monitoring stations in current legislation and

their shortcomings

3.1. Siting criteria

The siting criteria for AQ monitoring sites laid down in AQ legislation are basic provisions which aim

to ensure harmonized AQ assessment throughout the EU and provide comparable assessment data.

Macro-scale siting criteria provide minimum requirements on the types of locations where

measurements to assess AQ have to be performed. Micro-scale siting criteria shall ensure free air

flow around the sampling inlet – as a basic requirement for ensuring measurement representative

for a defined area – and provide minimum requirements for sampling near major roads.

Provisions of current legislation

The current legislative provisions regarding siting criteria are set out in Annexes III and VIII of the

Air Quality Directive (AQD, 2008/50/EC) and Annex III of the 4th DD (2004/107/EC). In the AQD

(2008/50/EC), Section A of Annex III provides some general criteria for ambient air quality

assessment. Section B provides macro-scale siting criteria for sampling points, which define how

sampling points shall be located in order to assess ambient air quality for compliance checking with

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the air quality standards (i.e. in areas with the highest concentrations to which the population is

exposed, and in other areas which are representative of the exposure of the general population for

the protection of human health or which are targeted at the protection of vegetation and natural

ecosystems). Macro-scale scale criteria also provide a basis for establishing the spatial

representitivty of monitoring sites, so that they are representative of similar locations not only in

their immediate vicinity. Section C provides micro-scale siting criteria, which provide detailed

guidelines for how sampling points shall be placed in relation to roads, buildings and other

obstacles within the areas identified through the application of the macro-scale criteria. Section D

requires that Member States shall fully document the site selection procedures through

photographs of the surrounding area and detailed maps. It also states that sites shall be reviewed

at regular intervals with repeated documentation.

Separate macro-scale and micro-scale criteria for ozone are included in Annex VIII of the AQD.

Siting criteria for the measurement of heavy metals and PAHs are laid down in Annex III, sections I

to III, of the 4th DD (2004/107/EC), largely corresponding to Annex III of the AQD (therefore the

following discussion commonly refers to Annex III of the AQD, but addresses also Annex III (I-III) of

the 4th DD).

In addition to the provisions in Annex III, Article 7 (4) of AQD is relevant, as it states that the

Commission shall monitor Member States’ application of the criteria for selecting sampling points,

in order to facilitate the harmonized application of these criteria throughout the EU.

The recent Commission Implementing Decision (2011/850/EU) on reporting of air quality

information and data is also relevant to siting criteria, since it provides the requirements according

to which Member States shall report information on the assessment regimes (Article 7 & Annex II,

Section C) and assessment methods (Article 9 & Annex II, Section D) applied within their territories.

It should also be noted that this Implementing Decision replaces Decision 97/101/EC (EoI) which

has been used by some Member States concerning meta data for their AQ monitoring sites.

Shortcomings

In consideration of the purpose of the provisions on siting criteria, the macro-scale siting criteria

are essential as they define the primary objectives regarding the siting of monitoring stations.

These provisions are generally well defined, especially those on micro-scale criteria. It is, however,

the implementation of these criteria by Member States that requires much more attention, in

particular where the assessment is directed at the protection of human health. This is due to

shortcomings in both the text and the implementation of certain provisions in the legislation. These

shortcomings are discussed below (points 1 to 6). No shortcoming has been identified so far

regarding siting criteria related to the protection of vegetation and natural ecosystems.

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1. Information on Member States’ site selection procedure at the classification stage is required

as part of the documentation procedure in Section D of Annex III. Information on siting is also

provided in both the current reporting obligations (EoI decision) and future reporting regimes

for air quality data & information (2011/850/EU). This information, however, covers the micro-

scale siting criteria (e.g. height of inlet above ground, distance of inlet from kerb, proximity of

nearby buildings, etc.) more in detail than the macro-scale ones (e.g. information on

representativeness where available). From this information on micro-scale criteria it is possible

to assess whether a monitoring station is placed appropriately within the chosen area. There is

however, no specific requirement to document or report the reasons for locating a monitoring

site at the chosen location (for example, in a particular street or background location).

Information such as photographs, maps and traffic volumes, provide an indication of

compliance with macro-scale siting criteria, but do not enable it to be assessed with any degree

of certainty. It is thus simply assumed that traffic and industrial sites represent areas where the

highest concentrations occur and that background sites are representative of the exposure of

the general population. This issue is compounded by the fact that there is currently no

requirement for reporting the documentation required in Section D of Annex III, meaning that

this information is not exchanged at the EU level.

Considering the importance of consistency in the application of macro-scale siting criteria in

ensuring the harmonization of air quality assessment across the EU, it is important that these

issues are tackled. Member States should be required to document their approach to

compliance assessment under the Directive. This should include evidence that their overall

approach provides adequate information on both the areas of maximum relevant exposure and

the exposure of the general population within a zone. Where supplementary assessment is

applied in zones, Member States should describe how these are used in combination with

other approaches to provide adequate information on the spatial distribution of the ambient

air quality.

2. It is unclear to what extent Article 7 (4) of the AQ Directive has been implemented. The

provision set out in this article requires the Commission to monitor Member States’ application

of the criteria for selecting sampling points. There is currently no defined system through

which the Commission implements this provision, and analyses of the limited information on

siting that is available through reporting are also lacking. A full and transparent implementation

of this provision is required.

3. One issue that needs specific attention is the siting of urban background monitoring stations.

While the siting of urban background locations is usually not crucial for compliance assessment

(the traffic or industrial hot-spot locations are usually the critical ones), it provides very

important information for exposure analyses of the “general urban population” and is very

relevant with regard to public health aspects. Difficulties are however experienced when trying

to compare results from urban background stations, due to the fact that areas with a very wide

range of characteristics can fall into the current classification of urban background, and no

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information is provided on the representativeness of stations. Urban background locations may

cover different pollution levels within an urban area. Urban background stations can, for

example, be placed in city centres, which are often heavily influenced by traffic, and may

represent “worst-case urban background”. Other urban background stations may be located in

parks and locations likely to be more representative of general city-wide exposure. It is also

possible to place urban background stations in suburban areas, in an attempt to monitor

exposure in areas less dominated by traffic. The urban background may be influenced by traffic

emissions in very different degrees across Europe, depending on the regional background

concentrations, urban topography, urban density, structure of the urban road network, traffic

density and fleet composition. In order to make better use of the information provided by

urban background stations, and improve comparability between different urban areas, more

accurate and detailed meta-information on monitoring sites would be beneficial It should be

noted that the new reporting Decision 2011/850/EU will be asking for this information and the

improvements made in legislation should be acknowledged.

4. With respect to AQD, Annex III.B.1(a) point 2, it is considered that the main purpose of all

background stations (urban, suburban, rural, etc.) is to provide information on the general

exposure of the population (but also vegetation and ecosystems) within a given area. This is in

line with the definition of “urban background locations” provided in Article 2 (23) of the

directive. This aim is however, not emphasised in the current supporting documentation (e.g.

Guidance on Assessment under the EU Air Quality Directives

http://ec.europa.eu/environment/air/pdf/guidanceunderairquality.pdf). This needs to be

rectified and consistency in the different definitions and descriptions provided in the

legislation and supporting documentation needs to be ensured. Rural and urban background

stations are also essential for the spatial source apportionment, to discriminate regional,

urban and local contributions.ontributions.

5. Micro-scale siting criteria are provided in Section C in Annex III. An appropriate degree of

flexibility in the micro-scale criteria should be given considering practical issues as well as

compatibility with macro-scale criteria. It is however essential that any deviation from the

prescribed micro-scale criteria have to be fully documented and justified by Member States.

(For example, in the cases where rooftop monitoring stations are used as urban background

stations).

6. The current guidance relating to air quality assessment in accordance with the air quality

directives lacks detail with regard to how monitoring sites should be located and how networks

should be designed in order to avoid some of the issues discussed above. Practical guidance,

with good practice examples, should be developed on the process that should be followed for

identifying appropriate monitoring locations, designing effective monitoring networks and

keeping these under review. This guidance should focus on methods for the identification of

locations with maximum relevant exposure (i.e. traffic or industrial sites), since these are most

relevant for compliance checking. Focus is further needed with regard to identifying

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appropriate background locations, representative for the exposure of the general population.

The terms “general public” and “exposure of the general population” are rather ambiguous and

open to many different interpretations. This highlights the need for clearer guidance. The

development of effective methods for defining station representativeness is also essential in

order to be able to assess the representativeness of background stations and allows accurate

comparisons to be made between the results from different sites.

3.2. Classification of monitoring stations

“Classification” of AQ monitoring sites is a prerequisite for any interpretation of AQ data. It is required for

1) Macro-scale siting criteria 2) Reporting of assessment meta-data (2011/850/EU) 3) Assessment of representativeness, assessment of exposure, model evaluation, source

apportionment, etc.

“Traditional” classification schemes, covered by the old Exchange of Information Decision and the Implementing Decision for Reporting (2011/850/EU), refer to two different spatial scales:

1. “Type of area” (“urban”, “suburban”, “rural”) refers to the environment on a scale of several kilometers

2. “Type of station” (“traffic”, “industrial”, “background”) refers to the impact (or absence) of near-by emissions (and is pollutant-specific in 2011/850/EU).

Additional “classifications” of monitoring sites refer e.g. to dispersion conditions on various spatial

scales.

Any classification has to deal with the problem that for uniform application across Europe well-

defined quantifiable parameters and clear thresholds between classes based on such parameters

are required.

The characteristics of what is considered as “urban background” may vary widely across Europe,

depending e.g. on the density of built-up areas, with high densities both of resident population and

traffic in “old” city centers, e.g. in typical Mediterranean cities (where population lives, works and

moves close to traffic), compared to lower population and emission densities in suburban areas and

“newer” cities, e.g. in northern Europe, characterized by far-sighted spatial planning and good

public transport. Harmonized criteria for “urban background” should be addressed in order to

ensure improved comparability between monitoring stations across the EU.

In principle, diverse classification schemes may be implemented, depending on the context in

which they will be used. One approach may be based on the human activities and associated

emissions which dominate in the area surrounding a given monitoring station, such as traffic or

industry (or their absence). This approach is especially interesting from a policy perspective, given

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that it allows assessing the impact of emissions on measured concentrations and evaluating the

effectiveness of measures targeting the specific human (economic) activities.

The current classification scheme used in AirBase is based on two indicators on different scales:

“type of area”, and “type of station”. This scheme is advantageous given that it is interesting both

for modeling and for policy-oriented studies. The resulting categories combine the “type of area”

(“classification of the area” in Decision 2011/850/EU) (“rural”, “suburban”, “urban”) with the “type

of station” (“Classification of the Station in relation to predominant emission sources relevant for

the measurement configuration for each pollutant” in 2011/850/EU) (“background”, “traffic”,

“industrial”), as already described in the Exchange of Information (EoI). The criteria and definitions

on station classification included in the EoI and the Guidance to the Implementing Decision for

Reporting is very useful to characterize in depth the different types of stations in air quality

networks, given that it allows to define the type of area and station. Meta-data requirements in

AirBase also comprise micro-siting criteria such as type of street (e.g., wide or narrow, for traffic

sites) and the station representativeness (categories like e.g., <1 km up to >50 km in EoI). However,

when implementing the criteria and definitions provided in the EoI and the Guidance to the

Implementing Decision for Reporting, there are a number of major issues which must be taken into

account:

1. “Background levels” are defined in the EoI as areas where the levels of a given pollutant are

not dominated by the impact of near-by emissions. Concentrations measured at background

stations are assumed to be representative of a wider area. The size of the area may vary when

applied to regional/rural, suburban or urban areas. The siting criteria laid down in the AQD,

Annex III.B.1(a) point 2, referring to “exposure of the general population”, are commonly related to

“background” , but it is acknowledged that strictly speaking both terms are not necessarily

equivalent.

2. Apart from background sites there are those locations where the levels of pollutants are

dominated by specific near-by sources (usually defined as “industrial” or “traffic”) and know as

“hotspots“. Hot-spot areas are also relevant for exposure, however of a minor fraction of

population. According to the European Air Quality Directives limit values have to be met in

both background and hotspot sites.

3. A further characterization for traffic sites in terms of local dispersion conditions (“wide street”,

“narrow street”, “canyon street”, “highway” and others) is applicable to urban areas and

suburban areas. It is recommended to provide a better definition for the terms “wide street”,

“narrow street”, “canyon street” and “highway”.

4. In addition to this classification, it is recommended to develop or refine other classification

schemes. Additional classification schemes can make use of AQ data (e.g. the methodology

developed by Joly and Peuch, 2012) in combination with (meta)data describing the station

surroundings (e.g. land cover types, population density, emission density within a certain

radius around the station; climatological or meteorological data). It is recommended that the

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EEA – as air quality data centre- incorporates to the air quality database other data containing

the supplementary information.

3.3. Spatial representativeness of monitoring stations

The AQD requires assessment of air quality throughout the European territory. Since air quality assessment is mainly based on monitoring at distinct locations, it is necessary to extend this point information to spatial information. The assessment of the representative area of a monitoring station allows extending information observed at one point – the monitoring site – to the “area of representativeness” (or “representative area”3).

Information about the representative area of monitoring stations is in particular required for the following tasks:

1) design of monitoring networks 2) exposure assessment 3) assessing model peformances

Representativeness of monitoring sites is closely related to the site classification “Type of area” and “Classification of the Station in relation to predominant emission sources relevant for the measurement configuration for each pollutant” in the Implementing Decision for Reporting. This Decision requires (not mandatory) an estimate of the representative area of a monitoring site (GIS information).

So far, a definition of the spatial representativeness of monitoring stations is still missing in the AQ legislation and there is a need to develop tools for its quantitative assessment.

A proposal for definition and criteria of representativeness has been developed in 2007 by the Austrian Umweltbundesamt in the study “Representativeness and classification of air quality monitoring stations” (http://www.umweltbundesamt.at/aktuell/publikationen/publikationssuche/publikationsdetail/?pub_id=1684) (cited as UMWELTBUNDESAMT 2007) as contractor of the European Commission.

According to this proposal, the representative area of a monitoring site is defined by

1. concentrations within a given range

2. similar reasons for this concentration.

The additional criterion for “similar reasons” is necessary because the same (or similar) concentrations can be caused by quite different combinations of sources, including secondary formation and long-range transport, and the influence of different dispersion conditions. For

3 The concept of representativeness applies theoretically to any point (location), not only to locations where a

monitoring site provides information about pollutant concentrations. Since at any point a concentration exists (even if it is presently not known), a “representative area” is linked to any location.

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example, it is not useful to assume an industrial and a traffic site with the same pollution as representative for each other; examples for locations with similar PM10 levels, but totally different dispersion conditions are London, the Hungarian plane and alpine valleys.

The “concentration range” is to be assessed by metrics related to annual air quality standards for NO2, PM10 and O3. The proposed parameters are:

NO2: annual mean;

PM10: 90.4 percentile of daily mean values4, and annual mean;

Ozone: 93.2 percentile of daily maximum 8 hour mean values5.

Representativeness is assumed to be stable over time periods of at least one year (i.e. not related to shorter time periods); representative areas may change slightly from year to year and to a larger extent over periods of several years due to changing emissions.

The range of concentrations for representativeness is – quite deliberately – proposed as 10 % of the total concentration range observed throughout Europe (based on data for 2002 to 2004 in UMWELTBUNDESAMT (2007); these concentrations did not change much over the recent years). This gives a concentration range of ±5 µg/m³ for NO2 (annual mean), ±8 µg/m³ for PM10 (P90.4), ±5 µg/m³ for PM10 (annual mean) and ±9 µg/m³ for Ozone (P93.2).

“Similar reasons” cover criteria for:

1. emissions

2. dispersion conditions

3. a maximum transport distance.

Emissions are assessed by quantifying the contribution from road traffic and industrial emissions6.

Dispersion conditions are assessed on the local, regional, and large scale. The local scale differentiates between street canyons, partly built-up areas (including forested areas), and open terrain. On a regional scale, different topographic features like valleys, basins, slopes and elevated mountainous areas are considered. On the large scale, topographic and climatic regions are identified – e.g. northern Alps, southern Alps, Po Valley, Hungarian Plane, German medium mountainous areas, north-west European planes, Bohemian mountains – to which representative areas of certain monitoring stations are limited.

To confine the spatial influence of emissions, the area of representativeness is limited to a surrounding of 100 km. This is roughly the average transport distance of air masses over 12 hours in central Europe, and corresponds to the time scale of atmospheric (trans)formation of NO2, secondary PM and Ozone. This transport distance over 12 hours is, of course, larger in oceanic

4 corresponding to the limit value definition of max. 35 days exceeding 50 µg/m³ per year.

5 corresponding to the definition of the target value for the protection of human health.

6 The sector “domestic heating”, also covered by the method proposed by Umweltbundesamt, is considered not very

useful.

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climate and smaller in Mediterranean or continental climate. This approach corresponds to the method applied by Henne and Solberg (see below).

To restrict representative areas to a maximum radius of about 100 km (as a first approach) is proposed because – based on all other criteria – a site in Hamburg may otherwise be representative for Brussels (or vice versa), which seems not reasonable.

The information to assess the representative area of a monitoring station can most easily be obtained where air quality modeling is applied on an appropriate spatial scale.

If model results are not available, emission inventories at an appropriate spatial resolution (in optimum case resolving the major road network) and (qualitative) information about the dispersion situation are necessary. In this case, quantitative criteria for “similar emissions” have to be applied.

In UMWELTBUNDESAMT (2007) the impact of road traffic emissions is assessed by the parameter “(emission per length and time unit)/(square root of the distance to kerb)”, which is a good approximation of modeled concentrations.

The impact of industrial emissions is assessed by expert estimate.

Temporary measurement campaigns, possibly supplemented by spatial information accounting for pollution sources, can be used to assess representativeness, but the results are related to the “spatial resolution” of the measurement network. An appropriate spatial and temporal sampling design has to be defined.

Other methodologies are being developed by Member States to assess the representativeness of their monitoring sites. References to some existing studies are provided below.

In addition, this issue will be further discussed in the framework of the collaboration between AQUILA and FAIRMODE. The concept of area of representativeness could further be worked out within the FAIRMODE modelling and monitoring work package that is currently being drafted as one of the aspects of the harmonization of modelling and monitoring activities in close collaboration with AQUILA.

References

Studies on representativeness of AQ monitoring sites, using aggregated Corine Landcover information as a parameter to describe the contribution of sector-specific emissions, have been published for Flanders:

- S. JANSSEN ET AL. (2008): Spatial interpolation of air pollution measurements using CORINE Landcover data. Atmospheric Environment, Vol. 42, Issue 20, pages 4884-4903.

- S. JANSSEN ET AL. (2011): Land use to characterize spatial representativeness of air quality monitoring stations and its relevance for model validation. Atmospheric Environment, Vol. 59, Issue 1, pages 492-500

- W. LEFEBVRE ET AL. (2010): Making high resolution air quality maps for Flanders, Belgium. Flemish Institute for Technological Research (VITO), Department of Environmental Modelling.

This approach gives comparable results as the method described in UMWELTBUNDESAMT (2007), apart from the impact of topography (which plays a minor role in Belgium).

Representativeness based on the transport of air masses during a certain time period is investigated for large-scale background sites by:

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- S. Henne, S. Solberg et al. (2009): Report on supersite representativeness and representativeness assessment method. GEOmon Project no. 036677.

This approach represents the basis of delimiting a representative area to about 100 km radius in Central Europe in UMWELTBUNDESAMT (2007).

Assessment of spatial representativeness based on sampling surveys is presented in Beauchamp et al. (2011) and Bobbia et al. (2008). The proposed approach makes it possible to take account of additional information describing emission sources (e.g. emission inventory, population density, land cover). Examples are provided for NO2 annual mean concentrations in urban areas.

- M. BEAUCHAMP ET AL. (2011). Spatial representativeness of an air quality monitoring station. Application to NO2 in urban areas. Spatial Data Methods for Environmental and Ecological Processes, 2nd Edition, Foggia and Gargano, Italy, 1-2 September 2011. http://aisberg.unibg.it/bitstream/10446/25284/1/54.pdf.

- M. BOBBIA ET AL. (2008). Représentativité spatiale d’une station de mesure de la pollution atmosphérique (Spatial representativeness of an air pollution measurement). Pollution Atmosphérique, n°197, 63-75.

4. Guidance for the Implementing Decision on AQ Reporting

(2011/850/EU)

The Guidance for the Implementing Decision for Reporting is presently being drafted by the Commission, with assistance from the Member States via the Ambient Air Quality Expert Group.

The tables providing the required datasets for the elements listed in Annex II will be included as soon as the “IPR Pilot Group” has finalined the schemata. In addition to these tables, guidance has to be drafted for several elements, including those related to classification of monitoring sites, representativeness, and documentation of siting in Annex II (D) (ii) Fixed measurement information.

These elements are listed below, giving their number in Annex II of the Implementing Decision.

(D) (ii) (16) Spatial representativeness of monitoring stations & (D) (ii) (17) Evaluation of representativeness

This information is to be provided “where available”.

It is proposed that the definition of spatial representativeness, as described in chapter 3.3, would

be included in the Guidance and that further guidelines for its application be developed.

The “spatial representativeness” of monitoring stations has to be provided in GIS information

(shape file), the “evaluation of representativeness” as a web-link to a report. However, there is

currently no agreed method available for defining the station representativeness. In order to

ensure that Member States provide this information in a consistent manner, it is recommended

that a working group is established in order to draft guidance on station representativeness. This

can be incorporated in the guidance for decision 2011/850/EU as soon as it is available.

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(D) (ii) (22) Classification of the Station in relation to predominant emission sources relevant for the measurement configuration for each pollutant

“Classification of the Station in relation to predominant emission sources relevant for the measurement configuration for each pollutant” corresponds to the element “Type of station” in the EoI meta-data (where it was, however, not pollutant specific) with the entries “traffic”, “industrial”, “background”.

The station classification provided in the EoI, which is included the current version of the guidance

document under preparation for decision 2011/850/EU, needs to be refined and precised. As

discussed in chapter 3, there is a need for consistency in the definitions and descriptions of

different types of monitoring stations. In order to improve this consistency and provide additional

informative guidance, the following guidance is proposed for the station classification.

The station classification required by Annex 2 (D) (ii) (22) of decision 2011/850/EU proposes one of the following station types:

traffic.

industrial

background

The following criteria can be used to identify the correct station type for a given station and a given pollutant.

Traffic Located in close proximity to a single major road.

Industrial Located in close proximity to a single industrial source or industrial area.

A wide range of industrial sources can be considered here, including

thermal power generation

district heating plants

refineries

waste incineration/treatment plants, dump sites

mining, including gravel, oil, natural gas

airports

ports

Background Any location with is neither to be classified as “traffic” or “industrial”.

Located such that its pollution levels are representative of the average

exposure of the general population (or vegetation and natural

ecosystems) within the type of area under assessment. The pollution

level should not be dominated by a single source type (e.g. traffic),

unless that source type is typical within the area under assessment. The

station should usually be representative of a wider area of at least

several square kilometers

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Annex II (C) Proposal for additional information on the assessment strategy

In order to encourage and facilitate the reporting of the documentation of site selection according

to Annex III section D of the Air Quality Directive and even to provide information on the design of

monitoring networks and choice of monitoring locations, it is suggested that a voluntary element is

provided within the reporting system for 2011/850/EU, via which Member States can provide

assessment strategies for each zone/agglomeration. This element would later become mandatory

should a requirement to report this information be included in the next directive.

It is proposed to include this element in Annex II, section (C), and should be named

“Documentation of monitoring site selection and network design”. This element should be provided

as a web-link to a report documenting the site selection and network design.

5. Proposed recommandations for the Review of Air Quality Legislation

5.1. Siting criteria

In order to improve the harmonization of air quality assessment across the EU, a number of

modifications or amendments in the directive are proposed relating to siting criteria. As discussed

in chapter 3, more information is needed with regard to how Member States are applying the

macro-scale siting criteria. Information on how monitoring stations comply with these criteria is

crucial on a number of levels. It is vital when comparing results from different stations and when

assessing compliance with the limit and target values in order to protect human health and the

environment. It also has a key role to play in creating a level-playing field for air quality assessment

within the EU, ensuring that compliance with limit values is being evaluated in a fair and consistent

manner for all Member States, and thus that infringement actions are consistent and

proportionate.

Documentation of assessment strategy

In order to provide the required information on the application of siting criteria, it is proposed to

extend the requirements of present Annex III (D) with a requirement for Member States to provide

an assessment strategy for all zones and agglomerations. This strategy should provide

documentation of the site-selection procedures and information that supports the monitoring

network design Where complementary methods (modelling, indicative measurement) are used,

assessment strategies should include details of these methods, along with information on how the

criteria for using supplementary information (provided in Article 7 (3)) are met. A requirement for

these strategies to be updated as necessary (i.e. due to changes in the network, monitoring

locations, etc.) and regularly reviewed, at least every 5 years, is also considered to be appropriate.

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The requirement laid down in Annex III, D of the AQ directive, however, requires merely that

Member States document and review site selection with photographs and maps. A revised

formulation for Section D of Annex III, taking into account the proposals above, is proposed in

chapter 6.

In order to utilise the extra information that would be provided by these assessment strategies, it is

proposed that a system be developed by which the Commission shall receive and evaluate Member

States’ strategies. This could be done via the IPR users´ requirements. This would enable the

Commission to identify issues and take appropriate actions to improve harmonization of air quality

assessment across the EU. The current directive contains a similar requirement in Article 7 (4),

which requires the Commission to monitor the application of the criteria for selecting sampling

points. However, the extent to which this provision is being implemented is currently unclear. It is

therefore proposed that this article shall be complemented with requirements for the Commission

to communicate the procedures by which this monitoring will take place and to make available the

results of any analyses/evaluations that are carried out as a result of this monitoring.

In order to aid the Commission in these monitoring procedures and also to enhance transparency, it

is suggested that assessment strategies be included in the requirements for transmission of

information and reporting set out in Article 27. Also this is linked to the IPR users’ requirements.

The proposals set out above may be considered to be extra burdens for both Member States and

the Commission. They are however considered to be well motivated, providing a range of benefits,

crucial in order to improve harmonization. Greater transparency would be provided by the

increased information on the implementation of assessment provisions. The Commission will be

better enabled to identify problems with assessment strategies and to take appropriate actions,

thereby enhancing the effectiveness of air quality assessment and ensuring improved health and

environmental protection. The accountability of infringement action would also be ensured since

Member States are provided with a level-playing field. Finally, guidance on air quality assessment

could be improved, since a range of good and bad practice examples would be gathered with

regard to assessment strategy design.

As discussed in chapter 3, the micro-scale siting criteria should provide an appropriate level of

flexibility, to ensure that they do not come into conflict with the macro-scale siting criteria. In order

to reduce the potential for such circumstances to arise, slight amendments are required to the

micro-scale criteria provided in Section C of Annex III.

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5.2. Minimum number of sites per zone

Annex V.A of the AQD lays down basic criteria for the minimum required number of monitoring

sites per zone per pollutant, depending on pollution level and population of the zone, and criteria

for their distribution between traffic and background locations.

These provisions represent, however, minimum numbers of monitoring sites, which can turn out to

be insufficient to achieve comprehensive information about air quality in zones with quite

heterogeneous emission distribution or complex terrain with different types of dispersion

conditions.

Therefore the following modifications are proposed:

1. In zones with complex topography, complex emission or population distribution, Member

States should be strongly encouraged to undertake supplemental assessments or modeling to

determine whether further monitoring is required.

2. The minimum number of PM monitoring sites in populated areas, as the sum of PM10 and

PM2.5 sites, laid down in Annex V.A.1 – together with footnote 2 – causes some problems for a

harmonized implementation. We recommend replacing the table in Annex V.A.1 by the

following one with additional columns for PM10 and PM2.5.

Population of agglomeration or zone (thousands)

Max conc above UAT Max conc between UAT and LAT

Pollutants except PM

Total PM

Min PM10

Min PM2.5

Pollutants except PM

Total PM

Min PM10

Min PM2.5

0-249 1 2 1 1 1 1 - -

250-499 2 3 1 1 1 2 1 1

500-749 2 3 1 1 1 2 1 1

750-999 3 4 2 2 1 2 1 1

1 000-1 499 4 6 2 2 2 3 1 1

1 500-1 999 5 7 3 3 2 3 1 1

2 000-2 749 6 8 3 3 3 4 2 2

2 750-3 749 7 10 4 4 3 4 2 2

3 750- 4 749 8 11 4 4 3 6 2 2

4 750-5 999 9 13 5 5 4 6 2 2

6 000+ 10 15 5 5 4 7 3 3

The minimum requirement on the total number of PM sampling points (Total PM) and the minimum requirements

provided for each pollutant individually (Min PM10 and Min PM2.5) should be verified together.

This proposal might however be reconsidered in the light of the new health evidence and the

discussion on whether the directive should focus on PM10 or PM2.5 and at background or hotspot

locations.

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6. Suggestions for amendments to the AQD 2008/50/EC and

2004/107/EC

6.1. Definition of “background”

Article 2

Definitions

For the purposes of this Directive: ….. 23. “urban background locations “ shall mean places where levels are representative of the average exposure of the population within the type of area under assessment;

6.2. Reporting of monitoring network design by MSs

Article 7

Sampling points

1. The location of sampling points for the measurement of sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM10, PM2,5), lead, benzene and carbon monoxide in ambient air shall be determined using the criteria listed in Annex III. 2. In each zone or agglomeration where fixed measurements are the sole source of information for assessing air quality, the number of sampling points for each relevant pollutant shall not be less than the minimum number of sampling points specified in Section A of Annex V. 3. For zones and agglomerations within which information from fixed measurement sampling points is supplemented by information from modelling and/or indicative measurement, the total number of sampling points specified in Section A of Annex V may be reduced by up to 50 %, provided that the following conditions are met: (a) the supplementary methods provide sufficient information for the assessment of air quality with regard to limit values or alert thresholds, as well as adequate information for the public; (b) the number of sampling points to be installed and the spatial resolution of other techniques are sufficient for the concentration of the relevant pollutant to be established in accordance with the data quality objectives specified in Section A of Annex I and enable assessment results to meet the criteria specified in Section B of Annex I. The results of modelling and/or indicative measurement shall be taken into account for the assessment of air quality with respect to the limit values. 4. The application in Member States of the criteria for selecting sampling points shall be monitored by the Commission so as to facilitate the harmonized application of those criteria throughout the European Union. The Commission shall communicate the procedures by which this shall take place and make publically available the results of these evaluations.

Article 27

Transmission of information and reporting

1. Member States shall ensure that information on ambient air quality is made available to the Commission within the required timescale as determined by the implementing measures referred to in

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Article 28(2). 2. In any event, for the specific purpose of assessing compliance with the limit values and critical levels and the attainment of target values, such information shall be made available to the Commission no later than nine months after the end of each year and shall include:

(a) the changes made in that year to the list and delimitation of zones and agglomerations established under Article 4; (b) the assessment strategies for all zones and agglomerations, as required in Section D of Annex III. These assessment strategies shall be made available at least every 5 years to coincide with their review; (c) the list of zones and agglomerations in which the levels of one or more pollutants are higher than the limit values plus the margin of tolerance where applicable or higher than target values or critical levels; and for these zones and agglomerations: (i) levels assessed and, if relevant, the dates and periods when such levels were observed; (ii) if appropriate, an assessment on contributions from natural sources and from re-suspension of particulates following winter-sanding or -salting of roads to the levels assessed, as declared to the Commission under Articles 20 and 21. 3. Paragraphs 1 and 2 shall apply to information collected as from the beginning of the second calendar year after the entry into force of the implementing measures referred to in Article 28(2).

6.3. Modifications of Annex III

The proposed modifications to Annex III of Dir. 2008/50/EC include

clarifications to macro-scale and micro-scale siting criteria

merging with siting criteria for Ozone (Annex VIII)

merging with siting citeria from the 4th DD.

Proposed amendments to the current version of Annex III are given in red hereafter.

ANNEX III

Assessment of ambient air quality and location of sampling points for the measurement of sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter (PM10 and

PM2,5), lead, arsenic, cadmium, nickel and B(a)P in PM10, Ozone, benzene and carbon monoxide in ambient air

A. General

Ambient air quality shall be assessed in all zones and agglomerations in accordance with the

following criteria:

1. Ambient air quality shall be assessed at all locations except those listed in paragraph 2, in accordance with the criteria established by Sections B and C for the location of sampling points for fixed measurement. The principles established by Sections B and C shall also apply in so far as they are relevant in identifying the specific locations in which concentration of the relevant pollutants are established where ambient air quality is assessed by indicative measurement or modelling.

2. Compliance with the limit values directed at the protection of human health shall not be assessed at

the following locations:

(a) any locations situated within areas where members of the public do not have access and there is no

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fixed habitation;

(b) in accordance with Article 2(1), on factory premises or at industrial installations to which all

relevant provisions concerning health and safety at work apply;

(c) on the carriageway of roads; and on the central reservations of roads except where there is

normally pedestrian access to the central reservation.

B. Macro scale siting of sampling points

1. Protection of human health

(a) Sampling points directed at the protection of human health shall be sited in such a way as to provide data on the following:

— the areas within zones and agglomerations where the highest concentrations occur to which the population is likely to be directly or indirectly exposed for a period which is significant in relation to the averaging period of the limit value(s),

— levels in other areas background areas within the zones and agglomerations which are representative of the exposure of the general population,

(b) Sampling points shall in general be sited in such a way as to avoid measuring very small micro-environments in their immediate vicinity, which means that a sampling point must be sited in such a way that the air sampled is representative of air quality for a street segment no less than 100 m length at traffic-orientated sites and at least 250 m × 250 m at industrial sites, where feasible;

(c) Urban background locations shall be located so that their pollution level is influenced by the integrated contribution from all sources upwind of the station. The pollution level should not be dominated by a single source unless such a situation is typical for a larger urban area. Those sampling points shall, as a general rule, be representative for several square kilometres;

(d) Where the objective is to assess rural background levels, the sampling point shall not be influenced by agglomera- tions or industrial sites in its vicinity, i.e. sites closer than five kilometres;

(e)Where contributions from industrial sources are to be assessed, at least one sampling point shall be installed down- wind of the source in the nearest residential area. Where the background concentration is not known, an additional sampling point shall be situated within the main wind direction;

(f) Sampling points shall, where possible, also be representative of similar locations not in their

immediate vicinity; (g) Account shall be taken of the need to locate sampling points on islands where that is necessary

for the protection of human health. (h) Ozone monitoring stations targeted at the protection of human health shall cover the following

types of areas: • urban background • suburban background • rural background as far as representative for the exposure of population.

In case of agglomerations or other areas with significant regional ozone formation potential, suburban ozone monitoring sites shall cover both upwind and downwind locations with respect to the main wind directions.

Ozone monitoring stations are recommended to be located in well vented locations away from the influence of local emissions, such as major roads and petrol stations.

2. Protection of vegetation and natural ecosystems

Sampling points targeted at the protection of vegetation and natural ecosystems shall be sited more than 20 km away from agglomerations or more than 5 km away from other built-up areas, industrial installations or motorways or major roads with traffic counts of more than 50 000 vehicles per day,

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which means that a sampling point must be sited in such a way that the air sampled is representative of air quality in a surrounding area of at least 1 000 km2. A Member State may provide for a sampling point to be sited representative of air quality in a less extended area, taking account of geographical conditions or of the opportunities to protect particularly vulnerable areas.

Ozone monitoring stations targeted at the protection of vegetation are not recommended in locations

which are representative for only small areas due to local temperature inversions or due to local

diurnal wind systems (sea breeze circulation, slope wind circulation).

For rural and rural background stations the location shall, where appropriate, be coordinated with the monitoring requirements of Commission Regulation (EC) No 1737/2006 of 7 November 2006 laying down detailed rules for the implementation of Regulation (EC) No 2152/2003 of the European Parliament and of the Council concerning moni- toring of forests and environmental interactions in the Community (OJ L 334, 30.11.2006, p. 1). Account shall be taken of the need to assess air quality on islands.

C. Micro scale siting of sampling points

In so far as is practicable, the following shall apply:

- the flow around the inlet sampling probe shall be unrestricted (in general free in an arc of at least 270° or 180° for

sampling points at the building line) without any obstruc tions affecting the airflow in the vicinity of the sampler

(normally some metres away from buildings, balconies, trees and other obstacles and at least 0,5 m from the

nearest building in the case of sampling points representing air quality at the building line),

- in general, the inlet sampling point shall be between 1.5 m (the breathing zone) and 4 m above the ground.

Higher positions (up to 8 m) may be necessary in some circumstances. Higher siting may also be appropriate if the

station is representative of a large area, in general, the inlet sampling point shall be between 1.5 m (the

breathing zone) and 4 m above the ground. Higher positions may be necessary in some circumstances due to

technical reasons that should be fully documented. Higher siting may also be appropriate if the station is

representative of a large area,

- the inlet probe shall not be positioned in the immediate vicinity of sources in order to avoid the direct intake

of emissions unmixed with ambient air,

- the sampler’s exhaust outlet shall be positioned so that recirculation of exhaust air to the sampler inlet is avoided,

- for all pollutants, traffic-orientated sampling probes shall be at least 25 m from the edge of major junctions

and no more than 10 m from the kerbside. A “major junction” to be considered here is a junction which

interrupts the traffic flow and causes different emissions (stop&go) from the rest of the road.

The following factors may also be taken into account:

interfering sources,

security,

access,

availability of electrical power and telephone communications,

visibility of the site in relation to its surroundings,

safety of the public and operators,

the desirability of co-locating sampling points for different pollutants,

planning requirements.,

Any deviation from the criteria listed above shall be fully documented through the procedures

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described in section D of this Annex.

D. Documentation and review of site selection

The site-selection procedures shall be fully documented at the classification stage by such means as

compass-point pho- tographs of the surrounding area and a detailed map. Sites shall be

reviewed at regular intervals with repeated docu- mentation to ensure that selection criteria

remain valid over time.

An assessment strategy shall be made available by the national authorities responsible for air

quality assessment for all zones and agglomerations. This strategy shall provide full

documentation of the site-selection procedures and provide information to support the network

design and choice of location for all monitoring sites. Compass-point photographs of the area

surrounding monitoring sites and detailed maps should be provided. Where supplementary

methods are used within a zone or agglomeration, the assessment strategy shall include details

of these methods and information on how the criteria listed in Article 7 (3) are met. Assessment

strategies shall be updated as necessary and reviewed at least every 5 years with repeated

documentation, to ensure that selection criteria, network design and monitoring site locations

remain valid and optimal over time.

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ANNEX VIII (deleted)

Criteria for classifying and locating sampling points for assessments of ozone

concentrations

The following apply to fixed

measurements: A. Macroscale

siting

Type of station Objectives of measurement Representative-

ness (1)

Macroscale siting criteria

Urban Protection of human health:

to assess the exposure of the urban population to ozone, i.e. where population density and ozone concentration are relatively high and representative of the exposure of the general popula- tion

A few km2 Away from the influence of local emissions such as traffic, petrol stations, etc.;

vented locations where well mixed levels can be measured;

locations such as residential and commercial areas of cities, parks (away from the trees), big streets or squares with very little or no traffic, open areas characteristic of educational, sports or recreation facilities

Suburban Protection of human health and vegetation:

to assess the exposure of the population and vegetation located in the outskirts of the agglomeration, where the highest ozone levels, to which the popu- lation and vegetation are likely to be directly or indirectly exposed occur

Some tens of km2

At a certain distance from the area of maximum emissions, downwind following the main wind direction/directions during conditions favour- able to ozone formation;

where population, sensitive crops or natural eco- systems located in the outer fringe of an agglom- eration are exposed to high ozone levels;

where appropriate, some suburban stations also upwind of the area of maximum emissions, in order to determine the regional background lev- els of ozone

Rural Protection of human health and vegetation:

to assess the exposure of popula- tion, crops and natural ecosys- tems to sub-regional scale ozone concentrations

Sub-regional levels

(some hundreds of km2)

Stations can be located in small settlements and/or areas with natural ecosystems, forests or crops;

representative for ozone away from the influ- ence of immediate local emissions such as indus- trial installations and roads;

at open area sites, but not on summits of higher mountains

Rural background

Protection of vegetation and human health:

to assess the exposure of crops and natural ecosystems to regional-scale ozone concentra- tions as well as exposure of the population

Regional/ national/ continental levels

(1 000 to

10 000 km2)

Station located in areas with lower population density, e.g. with natural ecosystems, forests, at a distance of at least 20 km from urban and industrial areas and away from local emissions;

avoid locations which are subject to locally enhanced formation of ground-near inversion conditions, also summits of higher mountains;

coastal sites with pronounced diurnal wind cycles of local character are not recommended.

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(1) Sampling points should, where possible, be representative of similar locations not in

their immediate vicinity.

For rural and rural background stations the location shall, where appropriate, be coordinated with the monitoring requirements of Commission Regulation (EC) No 1737/2006 of 7 November 2006 laying down detailed rules for the implementation of Regulation (EC) No 2152/2003 of the European Parliament and of the Council concerning moni- toring of forests and environmental interactions in the Community (1).

(1) OJ L 334, 30.11.2006, p. 1.

4. Proposed guidance for the implementation of current legislation

by Member States

In order to aid Member States in developing effective assessment strategies, with

appropriately placed monitoring stations, there is a need for more detailed and practical

guidance to be developed. This should include examples of where monitoring should take

place, how these locations should be identified, and how these should be kept under

review, etc. Modelling can play a vital role here and we note that in FAIRMODE’s current

draft recommendations for the review, they intend to produce a guide on the optimisation

of monitoring and network design. This work is highly relevant and it is proposed that this

will be developed in partnership with AQUILA, with a view to developing a common

guidance document on the development of effective assessment strategies. Since the use of

modelling is not to be made mandatory, it is also essential that guidance also focuses on

how assessment strategies can be developed without the use of modelling.

Some useful information to inform this work can be found in an old guidance report on

preliminary assessment under EC air quality directives from 1998. The updated guidance

should be incorporated within the Commission’s Guidance on Assessment under the EU Air

Quality Directives.