Plants play larger role than thought in cleaning up air pollution

Oct 21, 2010
Deciduous trees in hardwood forests remove harmful chemicals from the atmosphere. Credit: USDA

(PhysOrg.com) -- Vegetation plays an unexpectedly large role in cleansing the atmosphere, a new study finds. The research, led by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., uses observations, gene expression studies, and computer modeling to show that deciduous plants absorb about a third more of a common class of air-polluting chemicals than previously thought.

The new study, results of which are being published this week in , was conducted with co-authors from the University of Northern Colorado and the University of Arizona. It was supported in part by the National Science Foundation (NSF), NCAR's sponsor.

"Plants clean our air to a greater extent than we had realized," says NCAR scientist Thomas Karl, the lead author. "They actively consume certain types of air pollution."

The research team focused on a class of chemicals known as oxygenated (oVOCs), which can have long-term impacts on the environment and human health.

"The team has made significant progress in understanding the complex interactions between plants and the atmosphere," says Anne-Marie Schmoltner of NSF's Division of Atmospheric and Geospace Sciences, which funded the research.

The compounds form in abundance in the atmosphere from hydrocarbons and other chemicals that are emitted from both natural sources--including plants--and sources related to human activities, including vehicles and construction materials.

The compounds help shape atmospheric chemistry and influence climate.

Eventually, some oVOCs evolve into tiny airborne particles, known as aerosols, that have important effects on both clouds and human health.

By measuring oVOC levels in a number of ecosystems in the United States and other countries, the researchers determined that deciduous plants appear to be taking up the compounds at an unexpectedly fast rate--as much as four times more rapidly than previously thought.

The uptake was especially rapid in dense forests and most evident near the tops of forest canopies, which accounted for as much as 97 percent of the oVOC uptake that was observed.

Karl and his colleagues then tackled a follow-up question: How do plants absorb such large quantities of these chemicals?

The scientists moved their research into their laboratories and focused on poplar trees. The species offered a significant advantage in that its genome has been sequenced.

The team found that when the study trees were under stress, either because of a physical wound or because of exposure to an irritant such as ozone pollution, they began sharply increasing their uptake of oVOCs.

At the same time, changes took place in expression levels of certain genes that indicated heightened metabolic activity in the poplars.

The uptake of oVOCs, the scientists concluded, appeared to be part of a larger metabolic cycle.

Plants can produce chemicals to protect themselves from irritants and repel invaders such as insects, much as a human body may increase its production of white blood cells in reaction to an infection.

But these chemicals, if produced in enough quantity, can become toxic to the plant itself.

In order to metabolize these chemicals, the plants start increasing the levels of enzymes that transform the chemicals into less toxic substances.

At the same time, as it turns out, the plant draws down more oVOCs, which can be metabolized by the enzymes.

"Our results show that plants can actually adjust their metabolism and increase their uptake of atmospheric chemicals as a response to various types of stress," says Chhandak Basu of the University of Northern Colorado, a co-author.

"This complex metabolic process within plants has the side effect of cleansing our atmosphere."

Once they understood the extent to which plants absorb oVOCs, the research team fed the information into a computer model that simulates chemicals in the atmosphere worldwide.

The results indicated that, on a global level, plants are taking in 36 percent more oVOCs than had previously been accounted for in studies of .

Additionally, since plants are directly removing the oVOCs, fewer of the compounds are evolving into .

"This really transforms our understanding of some fundamental processes taking place in our atmosphere," Karl says.

Explore further: Conservation scientists asking wrong questions on climate change impacts on wildlife

Related Stories

Scientists close in on missing carbon sink

Jun 21, 2007

Forests in the United States and other northern mid- and upper-latitude regions are playing a smaller role in offsetting global warming than previously thought, according to a study appearing in Science this week.

Man-Made Activities Affect Blue Haze (w/ Video)

Oct 06, 2009

(PhysOrg.com) -- "Blue haze," a common occurrence that appears over heavily forested areas around the world, is formed by natural emissions of chemicals, but human activities can worsen it to the point of affecting the world's ...

Plants absorb more carbon under hazy skies

Apr 22, 2009

Plants absorbed carbon dioxide more efficiently under the polluted skies of recent decades than they would have done in a cleaner atmosphere, according to new findings published this week in Nature.

Recommended for you

Big data confirms climate extremes are here to stay

18 hours ago

In a paper published online today in the journal Scientific Reports, published by Nature, Northeastern researchers Evan Kodra and Auroop Ganguly found that while global temperature is indeed increasing, so too is the variab ...

Peru's carbon quantified: Economic and conservation boon

19 hours ago

Today scientists unveiled the first high-resolution map of the carbon stocks stored on land throughout the entire country of PerĂº. The new and improved methodology used to make the map marks a sea change ...

How might climate change affect our food supply?

19 hours ago

It's no easy question to answer, but prudence demands that we try. Thus, Microsoft and the United States Department of Agriculture (USDA) have teamed up to tackle "food resilience," one of several themes ...

Groundwater is safe in potential N.Y. fracking area

20 hours ago

Two Cornell hydrologists have completed a thorough groundwater examination of drinking water in a potential hydraulic fracturing area in New York's Southern Tier. They determined that drinking water in potable ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

Noumenon
not rated yet Oct 21, 2010
Ironically, it appears that trees don't like to be hugged :)
Graeme
5 / 5 (1) Oct 21, 2010
Hopefully bacteria are also helping out. Plants must also be creating VOC, if you can smell it it must be putting something in the air.
Noumenon
not rated yet Oct 22, 2010
I posted here months ago that I thought vegetation would grow more vigorously with increased co2 and received a face full of 1's.
Our results show that plants can actually adjust their metabolism and increase their uptake of atmospheric chemicals as a response to various types of stress
This prooves that trees don't like to be hugged.
GSwift7
1 / 5 (1) Oct 25, 2010
So, this implies that other parts of the system are accountable for absorbing a smaller portion of the observed gasses. (assuming the total observed amounts haven't changed, just the percent accounted in one way versus another).

This agrees with studies which have observed an increase in the root to shoot ratio in plants exposed to higher concentrations of organic gases/CO2.

I have no idea how much this impacts any of the global climate models. Any opinions from the peanut gallery? It certainly sounds like a major departure from certain assumptions, if these people are correct.