Status of black carbon monitoring in ambient air in Europe

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Courtesy of European Environment Agency (EEA)

Black carbon (BC) is increasingly discussed in science and environmental policy areas as an example of an air pollutant that affects both human health and contributes to climate change (e.g. WHO, 2012; UNEP/WMO, 2011; Bond et al., 2013; IPCC, 2013). In order to be able to make comparable measurements of BC in ambient air and to relate BC monitoring to health impacts and climate change it is important to understand how BC is defined.

This report provides a summary of BC definitions as discussed in the air quality monitoring community. Secondly, it provides a summary of the current status of BC-related monitoring in Europe. Information presented in the report includes an overview of available measurement techniques and associated technical issues, monitoring networks and current data reporting practices.

BC is a light-absorbing, carbon-containing constituent of particulate matter (PM) formed by the incomplete combustion of fossil fuels, biomass and biofuels. BC is directly emitted into the air. Major sources include vehicles (particularly diesel.driven road vehicles), non.road mobile machinery (e.g. forest machines), ships, residential heating (e.g. small coal or wood burning stoves) and open biomass burning (e.g. forest fires or burning of agricultural waste).

In terms of the potential to harm human health, PM is one of the most important air pollutants as it penetrates into sensitive regions of the respiratory system, and can cause or aggravate cardiovascular and lung diseases. BC is mainly present in the so-called ultrafine fraction of particulate matter (PM0.1 (1)). Due to their small size, PM0.1 particles can be transported through the respiratory tract and across the lung membranes. Once absorbed directly into the bloodstream they can relocate to other organs. BC is a major component of diesel soot, which has been declared as a substance that can cause cancer by the World Health Organization (WHO, 2012).

As regards its climate-related impacts, BC scatters and absorbs solar radiation (light) entering the Earth's atmosphere. It is the component of airborne PM which most absorbs light and is viewed as a major contributor to climate change (e.g. Bond et al., 2013). BC acts over a much shorter period than classic greenhouse gases (GHG) such as carbon dioxide (CO2) because it has a shorter life time in the air. According to current research BC contributes to the warming of the atmosphere (US EPA, 2012; Ramanathan and Carmichael, 2008; Bond et al., 2013).

The report highlights BC measurement work carried out in air quality monitoring networks, particularly in urban networks. The monitoring community uses measurements from a method to analyse light.absorbing properties of BC-containing particles in order to gain a light absorption coefficient. This coefficient can be translated into a unit that measures particle mass so that the results can be used to assess possible health impacts.

The European Union's Air Quality (AQ) Directive (EC, 2008) requires Member States to sample, analyse and report fine particulate matter (PM2.5 (2)) concentrations. For stations in rural areas, the Member States also have to report how much BC.related components the measured PM2.5 contains. The report notes that this reporting has yet to be fully implemented (EC, 2011). Monitoring of BC in ambient air at urban background and traffic sites is not required by EU legislation. Overall the information on BC measurements is largely missing in the Europe-wide AirBase database (3) (EEA, 2013a). For 2011 AirBase includes such measurement data for stations located in Finland (two), Germany (eight), Ireland (two), and one each in Malta, the Netherlands and Poland.

In view of the different methodologies used to monitor BC levels, this report also provides a summary of the current networks and applied practices for measurements, irrespective of whether they have been reported to the AirBase database or not. The current review shows that BC monitoring is part of several urban national air quality monitoring networks, mostly as a continuation of the 'black smoke' or 'soot' monitoring that had been put in place based on Member State regulations. For example Germany, Switzerland and the United Kingdom have long-standing and continued urban BC monitoring networks (Map ES.1).

The report notes that measurements at regional background monitoring sites of the European Monitoring and Evaluation Programme (EMEP) focus on climate change aspects, alongside possible impacts on health and ecosystems (Torseth et al., 2012). Monitoring sites are also run in cooperation with the World Meteorological Organization's (WMO) Global Atmosphere Watch (GAW) programme. Another aim of the EMEP (4) monitoring sites is to harmonise approaches on measurement and efforts related to global climate change issues via the World Data Centre on Aerosols (GAW-WDCA, 2013). In addition, the monitoring database (EBAS) is addressed within the report as an example of a well-established monitoring network. BC-related mass concentration data from twenty.one stations in thirteen European countries over the period 2010.2012 were reported to the database. Twenty-two European stations reported absorption coefficient data for the same period (EBAS, 2013).

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