Background 

The measurement of gaseous pollutants in air is a sensitive and priority issue as it has large impact on human health and environment. The European Directive on “Ambient air quality and cleaner air for Europe” (2008/50/EC) sets limit values and data quality objectives for the measurement in the EU member states of air pollutants in ambient air. Although no harmonized legislation is currently present for the monitoring of indoor air, the concern on the exposure to indoor chemical pollutants is clearly increasing.

Identified need 

MACPoll addresses the need for improving the metrological traceability and comparability of measurement results in current air monitoring techniques and the need for setting-up the metrological bases for the new sensor technology used in air quality applications.

These needs are demonstrated by:

• Poor agreement between standards prepared by NMIs for the calibration of air monitoring equipment;

• Lack of a reliable “zero gas” for the zeroing of analyzers and preparation of gas standards used in ambient air monitoring;

• Lack of accurate reference methods and traceable reference materials for the measurement of (semi)volatile organic compounds in indoor air and constant emitting (S)VOC materials;

• Lack of low-cost indicative measurement methods for Air Quality assessment that allow proper spatial coverage.

Project description 

One of the main objectives of this project is to comply with the challenging requirements of the calibration gases, both for span and for zero gas, set in documentary EN standards related to the air quality directive (2008/50/EC) reference methods. In order to achieve this goal, the research work will focus on:

• Current metrological issues related to the lack of stable Certified Reference Materials (CRM) in cylinders for reactive gases, namely nitrogen dioxide and sulphur dioxide at the limit values mandated by the air quality directive. Normally, CRMs are used for the calibration of gas analyzers. Alternative gas mixture preparation methods, such as dynamic and static dilution, are considered a proper alternative. The outcome of the fundamental revisit of these preparation methods will provide the degree of comparability and of uncertainty of these techniques and their suitability for implementation at monitoring networks.

• Development of a new approach for the single and simultaneous assessment of impurities in zero gas. Nitrogen and pure air, used for zeroing gas analyzers and for dilution purposes, should be free of contaminants that may interfere with the measurements. Special focus will be dedicated to nitrogen oxides, sulphur dioxide, ammonia and hydrogen sulphide. These impurities have to be minimized to (sub)-ppb level and their presence quantified by traceable measurements using optical systems, such as Cavity Ring Down Spectroscopy (CRDS). Once this measurement approach is fully traceable, a protocol for the certification of the impurity composition of zero gas will be available.

The needs identified in indoor air pollution are related to the development of references systems for (semi) volatile organic compounds. The JRP will:

• Improve reference methods and develop reference materials with special attention to the semi-volatile organic compounds (SVOC), harmful compounds originating from emission of building materials, for which not much information on sampling and measurement systems is available yet.

• Research the production of a constant emitting reference material for the quality control of emission test chamber measurements.

MACPoll will also deal with micro-sensors and their applicability in air quality monitoring. Micro-sensors are identified as emerging measuring devices for “indicative measurements” specified in the air quality directive, because they provide fast results, are cheap and allow good spatial coverage. The project will:

• Carry out the validation of existing sensor systems and in particular the metrological aspects (traceability and uncertainty of the results) will be investigated.

• Develop a new highly sensitive and selective NO2 sensor using the promising 2 dimensional material graphene.

Project Impact 
 

The JRP has direct impact on NMIs dealing with the measurement of trace levels gases. The outcome of the project will certainly improve the measurement capabilities of these organizations in terms of better standards and lower uncertainties. A number of JRP partners are designated Air Quality National Reference Laboratories (NRLs). Their task of ensuring traceability and comparability to the air monitoring networks will profit from the project results.

NRLs and air monitoring networks will also profit from the research work on micro-sensors for air pollution applications, because, if successful, it will impact the implementation of the EU Air Quality Directive (2008/50/EC) and in particular the use of indicative methods for ambient air monitoring.

The development of measurement standards and methods for (S)VOC will impact on the emission labelling schemes, responsible for the detection of hazardous compounds emitted by building materials. By improving the quality of these schemes, the risk of indoor pollutants in buildings will be reduced.

All JRP-Partners are closely linked to the stakeholders and to the end-users of this project, by being members of key environmental networks, such as the AQUILA (Air Quality Reference Laboratories) European network, by participating in standardization activities (CEN/TC264 Air Quality, ISO/TC146 Air Quality and ISO/TC158 Gas Analysis), by collaborating with National Environmental Institutes or simply by providing traceable calibrations standards to air quality monitoring networks. The impact of this project is therefore ensured by the composition of the JRP Consortium.

Besides that, a specific work package will focus on on-going communication of the project activities to the relevant stake-holders and on activities for the knowledge transfer and the dissemination of the scientific results obtained in the technical work packages.