Beijing’s Chinese Red Pines best pollution fighter in city’s landscaping

Short and stout, with large tufts of needles – the Chinese Red Pine may be a  city planner’s best defense when  fighting  air pollution,  a recent study has found.

Comparing the ability of 6 common landscaping plants used in Beijing to absorb pollution, researchers identified Pinus tabuliformis, or the Chinese Red Pine, the most capable of combating PM10 (particulate matter up to 10 micrometers in size) and PM 2.5 – the regular guage for air pollution.

Scientists from Beijing Forest University staked out two locations to obtain samples – next to the busy 5th ring road highway and in the large botanical gardens in the city’s west.

Using the gardens as a ‘slightly polluted’ setting and the highway as a ‘heavily polluted setting, they examined six trees commonly found in the city’s landscaping  – Chinese Red Pines, Lacebark Pines, Chinese White Poplar, Ginko Biloba, Shangtung maple and Chinese Willow.

“A plants’ ability to remove atmospheric particulates mainly relies on its leaf
function and leaf structure, such as leaf surface texture, hair, grease and moisture,”  the study,  Study on the Adsorption Capacities for Airborne Particulates of Landscape Plants in Different Polluted Regions in Beijing (China), said.

With a rough, irregular surface, the two-needle sprouts of the Chinese Red Pine  catch particulate matter like a broom in the air.  A high density of needles and vertical orientation allow  particulate matter to easily shifted to the stoma, or pores, of the leaf before gradually being absorbed, making it the most  effective dust trap.

Red Pines showed an absorption capacity  3.89 micrograms per cm-2, the highest of all species tested, and almost twice that of the lowest, the Chinese White Poplar. The second highest was the Lacebark Pine, confirming coniferous species generally absorb the most pollution.

There were also significant differences in ability to absorb particulate matter in the slightly versus heavily polluted areas.

Near the highway site,  plant pores became overwhelmed with dust, stunting ability to grow.

“Unfortunately,the atmospheric particles can crimp stomas and reduce the chlorophyll content of leaves, so that gas exchange action is blocked and photosynthesis is decreased,” the study said.

The photos below show a close up of  Chinese Red Pine leaves in the botanical gardens (before)  and near the 5th Ring road (after).

“Trees can capture significant quantities of particles from the atmosphere, especially PM2.5, particles, with the potential to improve local air quality,” the study said.

“Future research will attempt to remove the urban airborne particulates, to manage the urban environment and to improve the environmental quality by increasing the urban vegetation coverage.”

It was published in the International Journal of Environmental Research and Public Health on August 14.

Comments are closed.