Clean air through paving stones
In German cities the allowable limits for harmful nitrogen oxide are regularly exceeded. An important contribution to environmental protection are now to provide new paving stones. They are coated with nanoparticles of titanium dioxide and nitrogen oxide can reduce concentrations in the air.
The air quality in Germany, it is not very good. As evidenced by the data of the Federal Environmental Agency for the year 2009 at 55 percent of air monitoring stations in urban areas exceeded the permissible limits are of toxic nitric oxide. One of the main sources of emissions, according to EPA traffic. New approaches in the fight against air pollution is now the baroque city of Fulda. Peter Around the mountain road where the annual limit was exceeded 40 micrograms per cubic meter of air (ug/m3), 2009, to air-purifying Pfl aster stones are laid.
Their surfaces are Ach with titanium dioxide (TiO2) coated, which converts the pollutants such as nitrogen oxide into nitrates. The titanium dioxide as a photo catalyst uses for this chemical process in the sunlight. That is, it changes the speed of the reaction under Lichteinfl uss.
It was developed nitric oxide-reducing pavement air clean called by the company FC Nudling concrete. The proof of the effectiveness of the stones gave the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Schmallenberg. The IME researchers have also identified the environmental risk of the resulting product nitrate. The project was funded by the German Federal Environmental Foundation.
“That photo catalytic Pfl aster blocks can improve the air quality have already been shown in studies Italian cities. We wanted to examine to what extent these effects also in Germany – at a lower light intensity and sunshine duration – can be measured. For the more intense the sunlight is, the faster the degradation of pollutants. The aim was therefore to find a recipe with the highest photo catalytic efficiency, “explained Dr. Monika owner, a scientist at the IME.
We originally made of concrete producers protoset, with surface next car price, color, type of cement and TiO 2 content were varied. Since the degradation rates of nitric oxide with commercial photo catalytic active, ie sunlight reacting cement had not been sufficient to develop the company FC Nudling its own, more effective formula. “In tests we were able to” demonstrate the effectiveness of the optimized stones, confirmed owner.
In the long-term field experiment reported by the researcher and her team in specially constructed street canyons nitrogen oxide reduction rates of 20 to 30 percent. The measurements were made at a height of three meters above the photo catalytic paving for changing wind and light conditions. In calm weather, the experts even degradation rates for nitric oxide (NO) and nitrogen dioxide (NO2), each set up to 70 percent.
During measurements on the cobblestone AirClean already occupied space in Erfurt Gotha was achieved in three meters, an average reduction rate of about 20 percent and 38 percent with respect to NO2 NO.
“The paving stones are also long-term stability. In the period of 14 to 23 months after the laying of the floor we could “find no change in the initial degradation capacity, says the scientist. Also an environmental risk from nitrate, formed in the photo catalytic degradation of nitrogen oxides, there is not. It gets into the sewers, from there the trail leads to the treatment plant and finally it lands on the field and in the groundwater. But the maximum concentration of nitrate, which can be attributed to photo catalytic reactions is, at five milligrams per liter (mg / l). By comparison, the nitrate limit for groundwater is 50 mg / l. Everything is “in everything you say, that sums up AirClean signifi cantly improves air quality and fast and so contribute to environmental protection,” the researcher.
