Dutch Town Lays Air-Purifying Concrete

eldavojohn writes "In an effort to combat air pollution, a Dutch town has paved some of its streets with air-purifying concrete. It contains a titanium dioxide-based additive that utilizes sunlight to turn car exhaust into harmless nitrates. It was shown to do this in a lab and now the scientists are interested in just how much this will affect the air quality around the road. They will sample the air quality by a normal road and by this newly paved one."

Comments

TFA interesting but light on details

[dedazo]

All passive filters I know require replacement because they get clogged, or the active elements eventually decay. Beyond making jokes about swapping the church bricks five years from now, TFA was a bit light on the details. Does anyone know how does this works, from a chemical perspective?

Re:Nitrates?

[hey!]

Anything is harmful in the wrong place and in the wrong concentrations. Nitrates are, for example harmful to fish in high concentrations.

Most systems have processes that are limited by the supply of some resource. Ocean ecosystems are nitrogen limited, whereas fresh water systems tend to be phosphorous limited. Thus if the nitrates are washed off into fresh water, they'll cause relatively little immediate damage unless the concentrations are high enough to be toxic. However, if that nitrate is carried downstream to the ocean, the plume of nitrogen rich water entering the ocean can cause blooms of organisms that use up so much oxygen that fin fish suffocate. This happens where the Mississippi enters the gulf.

So, how and where something like this is used makes a difference. If you imagine all the US cities along the Mississippi and its tributaries using it, and if there is a mechanism by which the nitrates make it into the rivers, then this could make the situation in the Gulf much worse. If you use it in a coastal city and only the runoff from that city affects the local ocean, the amount of nitrogen entering the ocean might or might not have any measurable effect.