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Pan-European research project for clean air

Metrology institutes develop novel measuring methods for soot particles in diesel exhaust gases, as well as for platinum and mercury residues in the air

06.06.2011

Sie können Lungenkrebs und andere schwere Erkrankungen verursachen: die winzigen Rußpartikel aus den Abgasen von Dieselfahrzeugen. Deren Anzahl hat stetig zugenommen. Um dennoch die Gesundheitsbelastung durch Rußpartikel gering zu halten, sind die Grenzwerte für Dieselruß Schritt für Schritt drastisch gesenkt worden, von 180 mg/km (EURO 1, 1993) bis hin zu 5 mg/km in der EURO-Norm 5, die ab September dieses Jahres für neue Modelle gilt. In dieser Norm wird nicht mehr nur die Massen-Konzentration von Rußpartikeln, sondern deren Anzahl betrachtet, weil dieser Wert viel relevanter für die Gesundheitsgefahren ist. Dafür müssen neue Messgeräte zugelassen werden. Um das gesamte Messsystem von Zulassungsprüfungen über Kalibrierungen bis hin zu den regelmäßigen Abgasüberprüfungen an die neuen Vorgaben anzupassen, ist nun ein europaweites Projekt gestartet worden. Unter Federführung der Physikalisch-Technischen Bundesanstalt (PTB) arbeiten darin mehrere nationale Metrologieinstitute mit Kooperationspartnern aus der Industrie zusammen. Das Projekt ist auf drei Jahre angelegt. Neben dem Dieselruß widmet es sich auch zwei weiteren gesundheitlich problematischen Stoffen, die die Luft verschmutzen: kleinsten Teilchen von Platin und anderen Elementen aus Katalysatoren sowie jenen Quecksilberverbindungen, die bei der Verbrennung von fossilen Energieträgern in Kraftwerken entstehen. Das Projekt begann mit einem Kick-Off-Workshop am 6./7. Juni in der PTB.

Bei der regelmäßigen Abgasuntersuchung wird auch der Anteil an Rußpartikeln bestimmt.

Bei der Abgasuntersuchung für Dieselfahrzeuge sollen in Zukunft Rußsensoren oder Partikelzähler eingesetzt werden.

They can cause lung cancer and other severe diseases: the minute soot particles from the exhaust gas of diesel-engined vehicles. The quantity of these particles has increased steadily. In order to nevertheless keep the harmful effects to one's physical health due to soot particles low, the limit values for diesel soot have been lowered drastically step by step, from 180 mg/km (EURO 1, 1993) down to 5 mg/km in EURO Standard 5, which is valid for new models, effective September of this year. In this standard, it is no longer only the mass concentration of soot particles which is considered, but their number, because this value is much more relevant for health hazards. To this end, novel measuring instruments must be approved. In order to adapt the entire measuring system – from approval tests to calibrations and to the exhaust inspections at regular intervals – to the new specifications, a pan-European project has been started. Under the auspices of the Physikalisch-Technische Bundesanstalt (PTB), several national metrology institutes are working together therein with cooperation partners from industry. The project is laid out for three years. Besides the diesel soot, it also addresses two additional materials problematic for health which pollute the air: smallest particles of platinum and other elements from catalyzers as well as those mercury compounds which are created in the combustion of fossil energy sources in power plants. The project began with a kickoff workshop on 6/7 June at PTB.

Whereas in 1980, only two percent of all new approved passenger cars were diesel-engined vehicles, today the proportion is already somewhat above 50 percent, in the case of some car models, even more than 90 percent. Actually, the proportion of coarse soot particles – and thus the total mass – in diesel exhaust gases were reduced in recent years. These are, however, not such a great hazard, but rather the respirable, very small soot particles are. They are, in part, smaller than 0.1 micrometer (µm) or 100 nanometers (nm); that is, one thousandth of the diameter of a human hair. Due to, among other things, new diesel injection techniques, the amount of the fine (2.5 µm) and ultrafine (smaller than 0.1 µm) soot particles has increased, and metrology is thus confronted with large problems. For periodic exhaust gas inspections, meters of opaqueness, so-called opacimeters, are still used; these show their weaknesses precisely with the very minute particles. Thus, in future, the entire measurement technology should be upgraded, perhaps with soot sensors or also with particle counters which do not measure the quantity but rather the number of particles – and they do this, above all, more precisely.

The aim of the pan-European project is to compare the individual approaches, to further develop measuring instruments and to attend to correct traceability of measuring results. To this end, internationally harmonized standards are to be developed on the basis of the number of particles (instead of their mass, as hitherto), which then will facilitate the approval and calibration of measuring instruments. "Precisely regarding the subject of air pollution prevention, cross-border cooperation lends itself well. After all, air does not stop at national borders", Martin Thedens, PTB's project coordinator, points out. The project laid out for three years is a so-called Joint Research Project (JRP) within the scope of the European Metrology Research Progamme EMRP. Besides the experts of PTB and the Bundesanstalt für Materialforschung und -prüfung (BAM) (Federal Institute for Materials Research and Testing), colleagues from Denmark, Switzerland, Slovenia, France, Finland, Great Britain, the Netherlands and the Joint Research Centre JRC of the EU Commission are participating. The significance of the subject also for industry is indicated by the large number of partners from the ranks of the measuring instruments manufacturers and from the automobile industry.

Also, the two other subjects present particular challenges for metrology. In the first case, it deals with the so-called platinum-group elements (platinum, palladium and rhodium) which escape as "abrasion" from catalyzers in the air and pose a health problem. In order to be able to better assess this problem, one must first know more precisely what quantities are actually involved. The same problem arises with mercury, which does not, however, come from motor vehicles, but rather essentially from coal-fired power plants. Mercury is present in very small quantities in fossil fuels, such as perhaps coal – but there are a large number of such power plants in Europe. So far, the estimations still fluctuate between 4800 tons and 8300 tons – thus, there is a clear need for action for the measuring experts.

The project intends to improve the measuring methods in all these areas. And then, the goal is to create more uniformity. Even though the legal specifications are the same all over Europe, the controls are not yet the same. "That must change", says Martin Thedens. "Ultimately, this is supposed to create the same competitive requirements for all European countries. And we have to be equipped to participate in the international market on a long-term basis." After all, also in other countries very strict environmental regulations are being put into effect or are in effect already. The European automobile industry and its suppliers have to stay on the ball in order to sustainably retain their good global market position. The metrology institutes will help to achieve this.

Contact at PTB
Dr. Martin Thedens,
telephone: +49 (0)531 592 3510,
e-mail: martin.thedens(at)ptb.de