During heat waves, urban trees can increase ground-level ozone

May 17, 2017
Credit: Yinan Chen/public domain

Planting trees is a popular strategy to help make cities "greener," both literally and figuratively. But scientists have found a counterintuitive effect of urban vegetation: During heat waves, it can increase air pollution levels and the formation of ozone. Their study appears in ACS' journal Environmental Science & Technology.

Previous research has shown that in cities can have multiple benefits, including storing carbon, controlling storm water and cooling areas off by providing shade. This has spurred efforts in cities across the U.S. and Europe to encourage the practice. However, it's also known that trees and other plants release , or VOCs, that can interact with other substances and contribute to air pollution. And when it's hot, plants release higher levels of VOCs. Galina Churkina and colleagues wanted to investigate what effects and urban vegetation might have on air pollution.

The researchers compared computer models of air pollutant concentrations in the Berlin-Brandenburg metropolitan area in Germany in the summer of 2006, when there was a wave, and the summer of 2014, which had more typical seasonal temperatures. The simulation showed that during the summer of 2006, VOCs from urban greenery contributed to about 6 to 20 percent of the ozone formation, and that during the heat wave period, the contribution spiked to up to 60 percent. The researchers suggest that in addition to tree-planting campaigns, efforts to improve cities' environments should include other measures such as reducing vehicular traffic, a major source of nitrogen oxides that can react with VOCs and form ozone.

Explore further: Using Google to map our ecosystem

More information: Effect of VOC Emissions from Vegetation on Air Quality in Berlin during a Heatwave, Environmental Science & Technology (2017). pubs.acs.org/doi/abs/10.1021/acs.est.6b06514

Related Stories

Using Google to map our ecosystem

February 28, 2017

Researchers in the Singapore-ETH Centre's Future Cities Laboratory developed a method to quantify ecosystem services of street trees. Using nearly 100,000 images from Google Street View, the study helps further understanding ...

Bright facades and trees against heat and smog

May 26, 2015

Cities represent "heat islands" within their surroundings, which are characterized by many heat sources and small air flows. In southern Europe, bright buildings produce relief and provide for a cooler urban climate. Simulation ...

Arnhem plants the world's first 'urban climate tree'

August 18, 2014

Arnhem has planted the world's first ever stadsklimaatboom ('urban climate tree') in the Sonsbeekkwartier. This district is experiencing serious heat problems, which are known as the 'urban heat island effect'. The tree will ...

Recommended for you

New research could predict La Nina drought years in advance

November 16, 2017

Two new studies from The University of Texas at Austin have significantly improved scientists' ability to predict the strength and duration of droughts caused by La Niña - a recurrent cooling pattern in the tropical Pacific ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.