Research project CG/DD1/03 (Research action CG)
Context
Atmospheric aerosol particles have an impact on climate. They reflect or absorb incoming solar radiation (direct effect) and serve as condensation nuclei for clouds, which in turn reflect solar radiation (indirect effect). The climatic impact of aerosols depends strongly on the size of the particles and on their chemical composition.
Objectives
The project aims to advance our knowledge on the sources, spatial distribution, and properties of tropospheric aerosols which are important for climate.
To this end, studies are conducted at sites which are representative for a large area or which are situated within (or downwind of) regions for which a large radiative forcing by anthropogenic aerosols is expected. Both in long-term programs and in intensive measuring campaigns, the chemical, physical, and optical (radiative) properties of the fine (submicrometer) aerosol are investigated. The relative contributions of the important radiatively active aerosol types are determined, the natural and anthropogenic contributions for a number of these aerosol types are distinguished, and the sources, source processes, source regions and transport mechanisms of the aerosols are examined. It is investigated to which extent the fine aerosol mass can be reconstituted on the basis of the measured aerosol types (and thus mass closure can be obtained), and the various aerosol data sets are related to each other and used for model calculations of the optical aerosol properties or of the radiative forcing. As part of the project, novel methods and techniques for aerosol collection, for bulk and individual particle analysis, and for the interpretation and interrelation of the data are developed and implemented.
Partners
Structure of the cooperation:
1. Coordinator:
Willy Maenhaut, University of Gent (RUG), Department of Analytical Chemistry, Research group Tropospheric Aerosol Research and Nuclear Microanalysis
2. Other promoters:
a. Freddy Adams, University of Antwerp (UIA), Micro and Trace Analysis Centre (MiTAC)
b. Magda Claeys, University of Antwerp (UIA), Department of Pharmaceutical Sciences, Research group Bio-organic Mass Spectrometry
The team of the coordinator is responsible for the collection and selection of the aerosol samples which are examined by the two UIA teams. At meetings, which normally take place at the UIA, the progress in the research is discussed and the results are evaluated. The joint research is presented at international conferences and written up in scientific articles.
Methodologies
The RUG team takes care of the aerosol collections and performs most of the bulk analyses. Most of the samplings are done with filters or filter cassettes, whereby the fine (PM2.5) aerosol is collected separately or whereby the aerosol is separated in two size fractions (fine and coarse). In intensive campaigns, also cascade impactors are deployed in order to obtain a separation in several particle size classes (up to 10 or more). The RUG bulk analyses include the measurement of the particle mass, of organic and soot carbon, of water soluble ionic components (e.g., sulphate), and of major, minor and trace elements. Organic and soot carbon are determined by a thermal-optical technique. Ion chromatography is used for measuring sulphate and other ions and the multielemental analyses are performed by particle-induced X-ray emission spectrometry and neutron activation analysis. The RUG team has a close cooperation with a number of foreign research teams in order to complement the chemical aerosol measurements with purely physical and optical/radiative measurements. These include determinations of the particle number size distribution and of the aerosol scattering and absorption coefficients.
MiTAC performs microscopical examinations on the aerosol particles. Electron probe X-ray microanalysis and scanning transmission electron microscopy are the main techniques. They are used to determine the size, shape, and elemental composition of individual aerosol particles. This information allows us to identify the sources of the particles and to examine the transformations which take place during atmospheric transport. The characteristics of individual aerosol particles are also very useful for assessing their impact on climate. Pilot research is done with novel microscopical techniques such as static micro secondary ion mass spectrometry.
The research group Bio-organic Mass Spectrometry of the UIA focuses on the development and application of chemical analysis methods for measuring organic compounds in the aerosol. It is examined which organic compounds or classes of compounds are predominant contributors to the organic aerosol mass. Furthermore, a number of marker compounds are measured to differentiate between the contributions from natural sources and of human activities. For the chemical analysis of the organic compounds use is made of capillary gas chromatography (GC) with flame ionisation detection and of capillary GC/mass spectrometry.
Deliverables and expected results
The climatic impact of atmospheric aerosols and the anthropogenic perturbation therein have a large associated uncertainty. This is due to our limited knowledge of the sources, distributions and characteristics of aerosols on a global scale. With our research we contribute to reducing that uncertainty. Our data sets are also useful for assessing model calculations on the formation, distribution and climatic impact of aerosols.
Scientific collaboration
Several foreign research groups contribute to the research project. The major ones are the Department of Biogeochemistry of the Max Planck Institute for Chemistry (MPIC), Mainz, Germany, and the Institute of Physics, University of Sao Paulo (USP), Brazil. Within Europe there is also cooperation with groups from Finland, Sweden, Norway and France, and outside of Europe with teams from Israel, southern Africa and Australia.
Sources, physico-chemical characteritics and climate forcing of atmospheric aerosols: final report
Maenhaut, Willy - Adams, Freddy - Claeys, Magda Brussels: OSTC, 2001 (SP0983)
[To download]
[Exhausted]
Sources, caractéristiques physico-chimiques et forçage climatique des aérosols atmosphériques: synthèse
Bruxelles: SSTC, 2001 (SP0997)
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Sources, physico-chemical characteristics, and climate forcing of atmospheric aerosols: synthesis
Brussels: OSTC, 2001 (SP0998)
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Bronnen, fysico-chemische eigenschappen en klimaat "forcing" van atmosferische aërosolen: synthese
Brussel: DWTC, 2001 (SP0999)
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