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A research team at the Eindhoven University of Technology
(TU/e) in the Netherlands have invented a type of paving material
that can be mixed in with normal asphalt or concrete that
actually removes some pollutants from the air as cars travel
over the surface.
The effect works well enough to remove some 25 percent to
45 percent of nitrogen oxides from vehicle emissions.
The best part - the material reportedly doesn't even cost
that much more than a normal roadway to construct.
Although modern vehicles are equipped with stringent emissions
control equipment, exhaust still contains enough nitrogen
oxides (NOx) to create concern for causing
acid rain and smog. To combat this problem in a way that's
agnostic of the vehicle type, the TU/e
researchers impregnated a paving material with titanium dioxide.
The titanium dioxide works in conjunction with sunlight to
cause a chemical reaction that removes the nitrogen oxide
from the air and converts it into nitrate. The researchers
say that the nitrate is then rinsed away by rain.
The research team has been working on the material for quite
some time, but was only able to conduct its first area-wide
tests this past year. Last autumn, around 1,000 square meters
of existing road surface were covered with the air-purifying
concrete paving stones and a further 1,000 square meters was
surfaced with normal paving stones for comparison.
Taking measurements at various levels between 0.5 and 1.5
meters above the road surface on both types of paving stones,
the researchers found that the nitrogen oxides are reduced
by almost one-half from the air immediately around the vehicles.
According to the researchers, the material also has another
advantage - it can break down algae and dirt, keeping the
surface relatively clean.
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