Global Technical function: Burning
Technical Function Unit: Cooling, Modelling, Software tool
Techniques: Neutral cluster and Air Ion Spectrometer
Geographic Area: Finland

EUCAARI

Aerosols are minute particles suspended in the atmosphere which have a strong influence on air quality, since they scatter and absorb solar radiation, changing the Earth radiation balance and consequently global temperature patterns. Additionally, as they act as cloud condensation nuclei, they are also influencing precipitation trends.

In urban areas their high aerosols concentrations harm citizens and can affect visibility. Nevertheless, little is known about the processes generating atmospheric particles and the influence they have on trace gases and climate change. Developing advanced instrumentation and methodologies is a key for assessing atmospheric composition changes and better understanding atmospheric processes.

The European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project was a FP6 multidisciplinary work where 48 partners (from Europe and other non-EU countries) Improved the understanding of the existing interactions between air pollution and climate. More specifically, the project aimed to halve the uncertainty of the impact of aerosol particles on climate and to quantify the relationships between regional air quality and anthropogenic aerosols. The project was coordinated by the University of Helsinki (Finland) and lasted from 2007 to 2010.

The project covered a broad scale both in the spatial and the temporal scales (from nanometres to global scale and from seconds to years). Different activities were carried out in each case: formulation of basic theories, aerosol dynamics, atmospheric chemistry, and climate modelling, laboratory experiments and field measurements. Concerning this last point, the project took advantage of a long-term observation European network which was established within the EUSAAR project, but also applied long-term measurements in economically growing countries in other continents. These measurements were also complemented with intensive
air pollution monitoring activities regarding aerosols, which were carried out in May 2008, making use of ground measurements and aircrafts. This aircraft field campaign was conducted for studying the distribution and evolution of air mass properties on a continental scale.

Thanks to this project the contribution of different sources to aerosol production could be elucidated. So, anthropogenic carbonaceous aerosols emission factors were estimated by combining data from laboratory studies and from field measurements. Particle number emissions from biomass burning, on the other hand, were determined from experimental data, founding an influence of combustion efficiency and no dependence of fuel type. A particle number based inventory of anthropogenic emissions in Europe was developed. Finally, the project provided global emission inventories for marine aerosols and developed a method for calculating them in chemical transport models.

From the technical point of view, the most relevant result was a new instrument, called
Neutral cluster and Air Ion Spectrometer (NAIS), for measuring sub-3 nm particle populations. Main advantage of this equipment with respect to conventional Air Ion Spectrometers is that NAIS can measure mobility and size distributions not only of atmospheric ions but also of neutral particles. Additionally, advanced application of digital micro-mirror array technology allows a successful separation of sub-3nm particles. This new technique was used at laboratory and field scale, revealing that sulphuric acid plays a central role in atmospheric nucleation, although other vapours are also involved. An integrated internet-based software tool for analysing the influence of emission sources and atmospheric transport on measured concentrations of trace gases and aerosols has been also developed under the scope of the project.

The critical role of aerosols in global climate change has been underlined because of this project, concluding that aerosols have been masking the authentic impact of greenhouse gases over global warming. So, these investigations have shown that the aerosol cooling effect will be strongly reduced by 2030 if air pollution is progressively abated and control technologies are increasingly used. All the relevant information can be found in a special issue of the journal Atmospheric Chemistry and Physics, whereas an online database with all the results is also freely available. A level 9 in the TRL scale can be assigned to the project.