Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Paving slabs that clean the air

19.08.2010
The concentrations of toxic nitrogen oxide that are present in German cities regularly exceed the maximum permitted levels. That’s now about to change, as innovative paving slabs that will help protect the environment are being introduced. Coated in titanium dioxide nanoparticles, they reduce the amount of nitrogen oxide in the air.

In Germany, ambient air quality is not always as good as it might be – data from the federal environment ministry makes this all too clear. In 2009, the amounts of toxic nitrogen oxide in the atmosphere exceeded the maximum permitted levels at no fewer than 55 percent of air monitoring stations in urban areas. The ministry reports that road traffi c is one of the primary sources of these emissions. In light of this fact, the Baroque city of Fulda is currently embarking on new ways to combat air pollution.

Special paving slabs that will clean the air are to be laid the length of Petersberger Straße, where recorded pollution levels topped the annual mean limit of 40 micrograms per cubic meter (μg/m3) last year. These paving slabs are coated with titanium dioxide (TiO2), which converts harmful substances such as nitrogen oxides into nitrates. Titanium dioxide is a photocatalyst; it uses sunlight to accelerate a naturallyoccurring chemical reaction, the speed of which changes with exposure to light. The »Air Clean« nitrogen oxide-reducing paving slabs were developed by F. C. Nüdling Betonelemente. Proof of their effectiveness has subsequently been provided by the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Schmallenberg, where researchers also determined the risk to the environment posed by the resulting nitrates. Their work was funded by the German Environment Foundation.

Dr. Monika Herrchen, a scientist at the IME, says: »Experiments in Italian cities had already shown that photocatalytic paving slabs can improve the air quality. We wanted to see if they would also be effective here in Germany, where we have lower levels of light intensity and fewer hours of sunshine. Of course, the more intense the sunshine, the quicker the degradation of harmful substances, so our aim was to identify the formula with the highest photocatalytic effi ciency rating.«

To begin with, concrete manufacturer F.C. Nüdling produced a range of sample slabs incorporating different surfaces, colors, types of cement and TiO2 contents. Since the nitrogen oxide degradation rates achieved using standard commercial photocatalytic cement (i.e. cement that reacts to solar radiation) proved unsatisfactory, the company ultimately had to develop its own, more effective formula. »We were able to verify the effectiveness of the optimized slabs in a variety of tests,« confi rms Herrchen. During an extended time fi eld test, the scientist and her team recorded nitrogen oxide degradation rates of 20 to 30 percent in specially-created street canyons. The measurements were taken at a height of three meters above the photocatalytic slabs, in variable wind and light conditions. When the wind was still, the experts recorded degradation rates as high as 70 percent for both nitrogen monoxide (NO) and nitrogen dioxide (NO2). Measurements likewise taken at a height of three meters above the Gothaer Platz in Erfurt, which is already paved with Air Clean paving slabs, revealed an average degradation rate of 20 percent for NO2 and 38 percent for NO.

Herrchen points out an additional benefi t of these paving slabs: »They also remain stable over the long term. Measurements recorded from 14 to 23 months after they were laid revealed no change from the initial degradation capability.« Furthermore, the nitrate that is generated during the conversion process poses absolutely no risk to the environment. It runs off into the drainage system, then into a wastewater treatment plant, before fi nally ending up on a farmer’s fi eld or in the groundwater. The maximum possible nitrate concentration traceable back to photocatalytic reactions is around fi ve milligrams per liter (mg/l), while the maximum permitted concentration of nitrate in groundwater is 50 mg/l. Herrchen sums up: »All in all, it’s possible to say that Air Clean signifi cantly improves the air quality within a short space of time, and thus helps protect the environment.«

Dr. Monika Herrchen | EurekAlert!
Further information:
http://www.fraunhofer.de/en/press/research-news/2010/08/paving-slabs-that-clean-the-air.jsp

Further reports about: IME Molecular Biology NO2 TiO2 harmful substances measurements nitrogen oxide

More articles from Ecology, The Environment and Conservation:

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>