Green Walls May Cut Pollution in Cities

Vertical garden: Living walls can be indoors or outdoors, such as this one blooming on the Citi Data Centre in Frankfurt, Germany.

These vegetated surfaces don't just look pretty. They have other benefits as well, including cooling city blocks, reducing loud noises, and improving a building's energy efficiency.

What's more, a recent modeling study shows that green walls can potentially reduce large amounts of air pollution in what's called a "street canyon," or the corridor between tall buildings.

For the study, Thomas Pugh, a biogeochemist at the Karlsruhe Institute of Technology in Germany, and his colleagues created a computer model of a green wall with generic vegetation in a Western European city. Then they recorded chemical reactions based on a variety of factors, such as wind speed and building placement.

The simulation revealed a clear pattern: A green wall in a street canyon trapped or absorbed large amounts of nitrogen dioxide and particulate matter—both pollutants harmful to people, said Pugh. 

Compared with reducing emissions from cars, little attention has been focused on how to trap or take up more of the pollutants, added Pugh, whose study was published last year in the journal Environmental Science & Technology.

That's why the green-wall study is "putting forward an alternative solution that might allow governments to improve air quality in these problem hot spots," he said.

Different green walls are as captioned below.

 

 Living wall: This living wall bursts with vegetation at Paris's Musee du Quai Branly —a type of green wall that's catching on in some big cities.

Green gold: A vertical garden (pictured) won the gold medal in the 2011 Chelsea Flower Show  in London

 Going green: In Madrid, plants turn a wall in the Paseo del Prada bright green.

Colourful Tableau: A green wall creates a colorful tableau in Copenhagen's Kongens Nytorv (Royal Square).

National Geographic