Plants can reduce street-level concentrations of nitrogen dioxide
A study suggested that urban planners consider the benefits of planting trees in these areas
Thomas Pugh explains that concentrations of nitrogen dioxide and microscopic particulate matter — both of which can be harmful to human health — exceed safe levels on the streets of many cities. Past research suggested that trees and other green plants can improve urban air quality by removing those pollutants from the air. However, the reduction seemed to be small, typically less than 5 percent.
The study sought a better understanding of the effects of green plants in the sometimes stagnant air of city streets bounded by buildings, which the authors term “urban street canyons.” It concluded that careful placement of grass, climbing ivy and other plants in urban canyons can reduce street-level concentrations of nitrogen dioxide by up to 40 percent and particulate matter by 60 percent. That is much more than previous studies indicated.
Pugh also pointed out, however, that trees actually could worsen street-level air quality in the most polluted urban canyons. In these areas, trees might trap more pollutants than they could remove. The study suggested that urban planners consider the benefits of planting trees in these areas