Nuisance "for air pollutants on the Jungfraujoch

First evidence of new fluorocarbons in the atmosphere

The high-alpine research station on the Jungfraujoch at 3580 meters above sea level is ideal for determining the pollutant load of the air; It serves as a so-called background station within the Swiss Air Pollution Monitoring Network (NABEL), which is operated by the Federal Office for the Environment (FOEN) and Empa. © Empa
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Hardly produced and released into the atmosphere, new air pollutants can already be detected by researchers. More and more sensitive environmental analytical instruments make this possible. Empa's environmental scientists have now been able to detect two new hydrofluorocarbons during measurements on the Jungfraujoch.

This allows estimates of the global emissions of these climate-relevant substances and thus provides information that is essential for a better understanding of the chemical processes in the atmosphere and the role of these substances in global warming. Although the two substances are only in relatively small amounts in the atmosphere, but show a rapid increase.

The Montreal Protocol, which came into force in 1987, resulted in a phased ban on certain ozone-depleting halogenated hydrocarbons, such as the notorious "ozone killer" CFCs (chlorofluorocarbons). These were used, inter alia, as a foaming agent in the plastics industry, for example for the production of insulation or packaging foams. Therefore, the industry was forced to introduce substitutes on a regular basis.

The CFCs were followed by the so-called HCFCs with a lower chlorine content, which in the meantime have also been banned in Europe. Currently, the "third generation" of foaming agents on the market, the fluorocarbons (HFCs), which contain no chlorine and therefore do not attack the ozone layer. The thing is, however, a catch: HFCs are like the classic greenhouse gas carbon dioxide (CO2) climate-warming, some even up to 10, 000 times stronger.

"Nose" for air pollutants on the Jungfraujoch

In order to better understand the contribution of HFCs to global warming, as well as their chemical turnover in the atmosphere, the amounts of these substances in the atmosphere must be estimated. This is especially difficult at the beginning of the "life cycle" of a substance when production volumes and emissions are low. For example, for the two foaming agents pentafluoropropane - FKW-245fa - and pentafluorobutane - HFC-365mfc. display

"We knew that these substances were produced since 2002 and since 2003. The question now was: is this also visible in the atmosphere and if so, when?" says Empa researcher Martin Vollmer. A task for the highly sensitive measuring devices of Empa in the research station Jungfraujoch. Due to its high alpine and central location in the midst of the highly industrialized Europe and the low local pollution, it is particularly well suited for the investigation of pollutant emissions.

Tracing airborne pollutants: Three halogenated pollutants, whose emissions and source regions were determined by Empa researchers to be measured on the Jungfraujoch, show various trends. While the emissions of the now banned substances CFC-11 (CFC-11) and HCFC-141b (HCFC-141b) have been decreasing for four years, the emission of the substitute FKW-365mfc (HFC-365mfc ) at. With the aid of meteorological models, even the regions of origin of HKW-365mfc can be identified: the production plant in Tavaux, France, and the Po Valley, where the material is processed. Empa

However, air samples from partner stations within the global AGAGE ("Global Atmospheric Gases Experiment") monitoring network - for example from Mace Head on the west coast of Ireland and Cape Grim in Tasmania - have Vollmer and his colleague Stefan Reimann together with their Australian and European AGAGE colleagues for traces of new HFCs.

At the same time, the Empa team has analyzed the air samples for emissions of the now banned in Europe substance CFC-11, a prohibited since 1995 first-generation fumes, and on the temporary replacement, HCFC-141b, banned since 2003 Sch Second Generation Generic.

Concentration of PFCs detected in the "ppq" range

Conclusion of the study co-financed by the Federal Office for the Environment (FOEN), recently published in the scientific journals "Geophysical Research Letters" and "Environmental Science and Technology": barely produced, the substances can be Investigators already prove - and in the smallest quantities.

The concentration of the two HFCs is in the "ppq" range ("parts per quadrillion"). This means: a particle of substance X on a quadrillion particles of air, so a million times a billion. "Not many labs can do that, so we have to work extremely cleanly to avoid even minimal contamination, " says Reimann with great pride. In Tasmania, too, the materials produced and processed exclusively in the northern hemisphere are already to be found. "If a substance is blown into the atmosphere in the north, it can be detected in the southern hemisphere about one year later, " says Reimann.

Small amounts of HFC - but with a strongly increasing tendency

Overall, the global emissions of the two substances are still relatively low. "At current levels, they are negligible as climate gases compared to CO2 or methane, " says Vollmer. And that although the two substances have between 800 and 1, 000 times more impact on the climate than CO2. If the trends continue, however, HFCs could play a more important role in the climate issue in the future. Because the emissions of the two PFC foaming agents have increased massively in recent years. For example, FKW-245fa was not detectable in the atmosphere in 2002. Just one year later, Empa measurements produced global emissions of around 2, 200 tonnes; in 2005 it was already 5, 500 tons.

The situation at FKW-365mfc is similar, from 600 tonnes in 2002 to around 3200 tonnes in 2005. "This is the first time we have been able to observe newly emerging airborne pollutants in 'real time', " explains Reimann. "It gives us an excellent early detection system that gives us the ability to anticipate trends and act ahead."

In contrast to the two newcomers, the emissions of the now banned CFC-11 and HCFC-141b are falling. It is astonishing that even twelve years after the ban on CFC-11, around 3, 000 tonnes are released into the atmosphere from Europe alone, for example due to diffuse outgassing from built-up foams. "This shows that a huge amount of CFC-11 was produced, " says Vollmer.

And where do the pollutants come from?

The Jungfraujoch measuring station offers yet another advantage: If the Empa researchers combine the data collected from the long-term measurement series with meteorological models, they can trace the air pollutants back to their sources. They experienced, according to Reimann "the biggest surprise since we measure up there."

According to the "trajectory model" used by Empa researchers, the main emission source of FKW-365mfc should be in the middle of France. A look at the map confirmed the finding: right there is the only factory in which the substance is produced. As a second emission source, the model also reliably determined the Po Valley in northern Italy, where a large proportion of the foaming agent is used for foam production. "Around one third of the used HFCs get into the atmosphere during the manufacturing process, " says Empa colleague Vollmer.

Ideally, only non-climate-effective foaming agents would be used. They are indeed, for example pentane or nitrogen. However, most of the substitutes do not have all the desired properties; so they isolate about worse than HFC. These will continue to appear on the Jungfraujoch and bring the Empa measuring instruments to "knocking out". Currently, Reimann's team is working on the development of an analyzer that can measure even more substances more precisely.

(idw - Empa, 12.02.2007 - DLO)