Paving Slabs Clean the Air

Monday, August 16 2010

Innovative paving slabs that are coated in titanium dioxide nanoparticles can reduce the amount of nitrogen oxide in the air. Titanium dioxide is a photocatalyst; it uses sunlight to accelerate a naturally occurring chemical reaction, the speed of which changes with exposure to light.

The concentrations of toxic nitrogen oxide that are present in German cities regularly exceed the maximum permitted levels. 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 paving slabs are to be laid the length of Petersberger Straße in the Baroque city of Fulda, where recorded pollution levels topped the annual mean limit of 40 micrograms per cubic meter (μg/m³) last year. The "Air Clean" nitrogen oxide-reducing paving slabs were developed by concrete manufacturer F. C. Nüdling Betonelemente. Proof of their effectiveness has 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.

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."