Can Plants Reduce Urban Pollution?

Effectiveness of Green Infrastructure for Improvement of Air Quality in Urban Street Canyons (Abstract, Thomas A. M. Pugh, A. Robert MacKenzie, J. Duncan Whyatt, and C. Nicholas Hewitt, Environ. Sci. Technol., Jun. 4, 2012)

Also discussed here: Green Plants Reduce City Street Pollution Up to Eight Times More Than Previously Believed (ScienceDaily, Jul. 18, 2012)

The question whether trees reduce or add to urban pollution is frequently debated with the answer seeming to be that in a highly polluted atmosphere, some coniferous trees add aromatic gases to the mix. Today we review an interesting article that suggests that foliage (not trees) will absorb pollution through their plant surface which is more effective than the hard surfaces that make up street canyons – with reductions of 40-60% in terms of the concentrations of NO2 and PM.


 

Key Quotes:

“Street-level concentrations of nitrogen dioxide (NO2) and particulate matter (PM) exceed public health standards in many cities, causing increased mortality and morbidity”

 “Both NO2 and PM are deposited onto surfaces at rates that vary according to the nature of the surface; deposition rates to vegetation are much higher than those to hard, built surfaces”

“increasing deposition by the planting of vegetation in street canyons can reduce street-level concentrations in those canyons by as much as 40% for NO2 and 60% for PM”

“The authors even suggest building plant-covered "green billboards" in these urban canyons to increase the amount of foliage”

 “Trees were also shown to be effective, but only if care is taken to avoid trapping pollutants beneath their crowns”

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