Featured Research

from universities, journals, and other organizations

Paving 'slabs' that clean the air

Date:
August 18, 2010
Source:
Fraunhofer-Gesellschaft
Summary:
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.

Initial tests in the measuring chamber confirm that paving slabs coated with titanium dioxide can reduce ambient nitrogen oxide levels.
Credit: Copyright Fraunhofer IME

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 traffic 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 efficiency 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," confirms Herrchen. During an extended time field 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 benefit 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 finally ending up on a farmer's field or in the groundwater. The maximum possible nitrate concentration traceable back to photocatalytic reactions is around five 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 significantly improves the air quality within a short space of time, and thus helps protect the environment."


Story Source:

The above story is based on materials provided by Fraunhofer-Gesellschaft. Note: Materials may be edited for content and length.


Cite This Page:

Fraunhofer-Gesellschaft. "Paving 'slabs' that clean the air." ScienceDaily. ScienceDaily, 18 August 2010. <www.sciencedaily.com/releases/2010/08/100818090016.htm>.
Fraunhofer-Gesellschaft. (2010, August 18). Paving 'slabs' that clean the air. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2010/08/100818090016.htm
Fraunhofer-Gesellschaft. "Paving 'slabs' that clean the air." ScienceDaily. www.sciencedaily.com/releases/2010/08/100818090016.htm (accessed October 21, 2014).

Share This



More Earth & Climate News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) — He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) — Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
White Rhino's Death In Kenya Means Just 6 Are Left

White Rhino's Death In Kenya Means Just 6 Are Left

Newsy (Oct. 20, 2014) — Suni, a rare northern white rhino at Ol Pejeta Conservancy, died Friday. This, as many media have pointed out, leaves people fearing extinction. Video provided by Newsy
Powered by NewsLook.com
New Organic Fertilizer Helps Reforestation of Monarch Butterflies’ Winter Retreat

New Organic Fertilizer Helps Reforestation of Monarch Butterflies’ Winter Retreat

Reuters - Innovations Video Online (Oct. 20, 2014) — Using an organic fertiliser, a conservationist from the National Autonomous University of Mexico (UNAM), leads an award-winning project to reforest the sanctuary of monarch butterflies. Sharon Reich reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins