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Dutch paving stones clean air pollution

By mixing a photocatalyst with concrete, Dutch researchers have built a "green" paving stone that absorbs smog-causing pollution, cleaning the road in the process.

A Dutch University will see if chemically tricked-out paving stones can clean the air.

The University of Twente (UT) has devised a concrete capable of converting the nitrogen oxide from car exhaust--the source of smog and acid rain--into a nitrate, another chemical that will wash away in the rain.

Green chemistry: how green bricks convert nitrogen oxide air pollution into nitrates with the sun. University of Twente

When fertilizers are applied heavily, high levels of nitrates can enter the soil or water and be toxic to humans or livestock. Jos Brouwers from the University of Twente said that the nitrate production from its paving stones will be "harmless" and well below Dutch water standards.

The researchers came up with the air-purifying paving stones by tapping the properties of titanium dioxide, a chemical that catalyzes chemical reactions when exposed to light.

The top layer of the University of Twente paving stones contains the material mixed with concrete. So when sun shines, smog-producing pollutants will convert into nitrates and then wash away, keeping the stones surface clean in the process.

The university received a sustainability grant to test its invention in the municipality of Hengelo.

By the end of this year, researchers expect to complete construction of a road where one side is built with the specially coated paving stones. The other half will have tradition materials.

The results of how much the stones reduce air pollution should be ready by next year. If successful, the tests could be expanded further, the university said.

It's not the first time that the Dutch have been inventive with road construction. A civil engineering firm has devised a paving technique to absorb heat from asphalt to melt ice and heat neighboring buildings.