40 per cent of the Swiss population breathes in too much fine particulate matter, particles with a diameter of less than 10 thousandths of a millimeter. The price for this is paid in terms of health – about 16,000 hospital admissions for heart and respiratory problems were due to fine particles in the year 2000, plus a further 40,000 cases of bronchitis in children. It appears that the very finest particles – soot from diesel motors – are particularly toxic.
Since 1997 the Empa, together with the Federal office for the Environment (FOEN), has been measuring fine particulates in the atmosphere as part of the National Air Pollution Monitoring Network (NABEL). According to Rudolf Weber of the FOEN, in 2004 the mean annual limits for fine particulate pollution were exceeded at 51 of a total of 72 Swiss monitoring stations
Better methods help to identify sources
At six out of the 16 NABEL monitoring stations the Empa determines not just the PM10 value but also the mass distribution of various particle sizes as well as the number of particles. This data is essential for a comprehensive understanding of the fine particle pollution situation. New measurement techniques allow the chemical constitution of the particles to be determined with high temporal resolution. “With this information it will be possible to identify sources with more confidence and to quantify their contribution more accurately,” said the Empa’s Christoph Hueglin. In addition the formation and breakdown processes can be investigated. The NABEL data also enable the effectiveness of measures announced by the federal government against fine particle emissions to be monitored.
It is known that the diesel motor represents one of the greatest sources of fine particulate matter. The composition of these of emissions and how they vary with motor type is being investigated by the Empa through dynamometer-based vehicle measurements. “Particle filters are the most effective means of reducing soot emissions” concluded the Empa’s Martin Mohr on the basis of this study. In an extension to the work, the Empa together with the Paul Scherrer Institute (PSI) and the ETH Zurich will also investigate how the particles change immediately after they are emitted.
It is not just engines that create fine particulate matter
In addition to the diesel motor there are numerous other sources of fine particulates such as combustion processes, industrial activities, tire and road surface wear, agriculture and forestry work. Fine particles can also actually form in the air through the reaction of gaseous pollutants with organic molecules. Exactly how these processes occur is the subject of research by scientists at the PSI and the ETHZ. They have discovered that under the influence of sunshine long chain organic molecules – so called polymers – are formed. The University of Bern is investigating the source of the carbon in fine particulate matter by means of radio-carbon measurements. In summer a significant proportion of the organic carbon in fine particles is of natural origin, as measurements in Zurich have shown.
A surprising result was brought to light by the PSI. In rural Roveredo in Canton Grisons the major fraction of fine particulate matter found in winter originated from wood-burning heating systems. Even in the Leventina region right next to the Gotthard motorway this source made a significant contribution to the total fine particle matter in the atmosphere. The conclusion drawn by the PSI’s André Prevot: “The fine particulate emission by wood-fired heating systems in Europe could well be generally underestimated.”
As this one day meeting at the Empa clearly demonstrated, fine particulates are a complex subject. “We already have enough knowledge, though, to be able to take effective countermeasures” according to Christoph Hueglin. Considering the numerous sources of fine particulate emissions, the packet of measures announced by Federal Councilor Moritz Leuenberger is a step in the right direction.
Author:
Irene Bättig, Oerlikon-Journalisten
Kontakt:
Dr. Christoph Hüglin, Air Pollution and Environmental Technology Lab, +41 44 823 46 54, christoph.hueglin@empa.ch
Martina Peter, Communication/Marketing Dept., +41 44 823 49 87, martina.peter@empa.ch
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