Featured Research

from universities, journals, and other organizations

Atmosphere's self-cleaning capacity surprisingly stable

Date:
January 10, 2011
Source:
National Oceanic and Atmospheric Administration
Summary:
The atmosphere's capacity for cleansing itself of air pollutants is more stable than previously thought, according to a new study

Aidan Colton at NOAA's Mauna Loa Observatory (MLO) demonstrates how early flask samples were filled at the site. Air collected year-round at MLO and eight other remote sites around the world has been analyzed for the industrial solvent methyl chloroform. Variability in the decay of this chemical has helped scientists understand the oxidizing or cleansing power of the global atmosphere and its sensitivity to natural and human-induced perturbations.
Credit: NOAA

An international, NOAA-led research team took a significant step forward in understanding the atmosphere's ability to cleanse itself of air pollutants and some other gases, except carbon dioxide. The issue has been controversial for many years, with some studies suggesting the self-cleaning power of the atmosphere is fragile and sensitive to environmental changes, while others suggest greater stability. And what researchers are finding is that the atmosphere's self-cleaning capacity is rather stable.

New analysis recently published in the journal Science shows that global levels of the hydroxyl radical, a critical player in atmospheric chemistry, do not vary much from year to year. Levels of hydroxyl, which help clear the atmosphere of many hazardous air pollutants and some important greenhouse gases -- but not carbon dioxide -- dip and rise by only a few percent every year; not by up to 25 percent, as was once estimated.

"The new hydroxyl measurements give researchers a broad view of the 'oxidizing' or self-cleaning capacity of the atmosphere," said Stephen Montzka, the study's lead author and a research chemist at the Global Monitoring Division of NOAA's Boulder, Colo., laboratory.

"Now we know that the atmosphere's ability to rid itself of many pollutants is generally well buffered or stable," said Montzka. "This fundamental property of the atmosphere was one we hadn't been able to confirm before."

The new finding adds confidence to projections of future air pollutant loads. The hydroxyl radical, comprised of one oxygen atom and one hydrogen atom, is formed and broken down so quickly in the atmosphere that it has been extremely difficult to measure on global scales.

"In the daytime, hydroxyl's lifetime is about one second and is present at exceedingly low concentrations," said Montzka. "Once created, it doesn't take long to find something to react with."

The radical is central to the chemistry of the atmosphere. It is involved in the formation and breakdown of surface-level ozone, a lung- and crop-damaging pollutant. It also reacts with and destroys the powerful greenhouse gas methane and air pollutants including hydrocarbons, carbon monoxide and sulfur dioxide. However, hydroxyl radicals do not remove carbon dioxide, nitrous oxide or chlorofluorocarbons.

To estimate variability in global hydroxyl levels -- and thus the cleansing capacity of the atmosphere -- researchers turned to studying longer-lived chemicals that react with hydroxyl.

The industrial chemical methyl chloroform, for example, is destroyed in the atmosphere primarily by hydroxyl radicals. By comparing levels of methyl chloroform emitted into the atmosphere with levels measured in the atmosphere, researchers can estimate the concentration of hydroxyl and how it varies from year to year.

This technique produced estimates of hydroxyl that swung wildly in the 1980s and 1990s. Researchers struggled to understand whether the ups and downs were due to errors in emissions estimates for methyl chloroform, for example, or to real swings in hydroxyl levels. The swings would be of concern: Large fluctuations in hydroxyl radicals would mean the atmosphere's self-cleaning ability was very sensitive to human-caused or natural changes in the atmosphere.

To complicate matters, when scientists tried to measure the concentration of hydroxyl radical levels compared to other gases, such as methane, they were seeing only small variations from year to year. The same small fluctuation was occurring when scientists ran the standard global chemistry models.

An international agreement helped resolve the issue. In response to the Montreal Protocol -- the international agreement to phase out chemicals that are destroying the Earth's protective stratospheric ozone layer -- production of methyl chloroform all but stopped in the mid 1990s. As a result, emissions of this potent ozone-depleting gas dropped precipitously.

Without the confounding effect of any appreciable methyl chloroform emissions, a more precise picture of hydroxyl variability emerged based on the observed decay of remaining methyl chloroform. The scientists studied hydroxyl radicals both by making measurements of methyl chloroform from NOAA's international cooperative air sampling program and also by modeling results with state-of-the-art models.

The group's findings improve confidence in projecting the future of Earth's atmosphere.

"Say we wanted to know how much we'd need to reduce human-derived emissions of methane to cut its climate influence by half," Montzka said. "That would require an understanding of hydroxyl and its variability. Since the new results suggest that large hydroxyl radical changes are unlikely, such projections become more reliable."


Story Source:

The above story is based on materials provided by National Oceanic and Atmospheric Administration. Note: Materials may be edited for content and length.


Journal Reference:

  1. S. A. Montzka, M. Krol, E. Dlugokencky, B. Hall, P. Jockel, J. Lelieveld. Small Interannual Variability of Global Atmospheric Hydroxyl. Science, 2011; 331 (6013): 67 DOI: 10.1126/science.1197640

Cite This Page:

National Oceanic and Atmospheric Administration. "Atmosphere's self-cleaning capacity surprisingly stable." ScienceDaily. ScienceDaily, 10 January 2011. <www.sciencedaily.com/releases/2011/01/110106145434.htm>.
National Oceanic and Atmospheric Administration. (2011, January 10). Atmosphere's self-cleaning capacity surprisingly stable. ScienceDaily. Retrieved October 1, 2014 from www.sciencedaily.com/releases/2011/01/110106145434.htm
National Oceanic and Atmospheric Administration. "Atmosphere's self-cleaning capacity surprisingly stable." ScienceDaily. www.sciencedaily.com/releases/2011/01/110106145434.htm (accessed October 1, 2014).

Share This



More Earth & Climate News

Wednesday, October 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: 12 More Bodies Found on Japan Volcano

Raw: 12 More Bodies Found on Japan Volcano

AP (Oct. 1, 2014) — A dozen more bodies were found Wednesday as Japanese rescuers resumed efforts to find survivors and retrieve bodies of those trapped by Mount Ontake's eruption. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Cultural Learning In Wild Chimps Observed For The First Time

Cultural Learning In Wild Chimps Observed For The First Time

Newsy (Oct. 1, 2014) — Cultural transmission — the passing of knowledge from one animal to another — has been caught on camera with chimps teaching other chimps. Video provided by Newsy
Powered by NewsLook.com
Raw: Trapped Scientist Rescued from Cave in Peru

Raw: Trapped Scientist Rescued from Cave in Peru

AP (Oct. 1, 2014) — A Spanish scientist, who spent 12 days trapped about 1300 feet underground in a cave in Peru's remote Amazon region, was rescued on Tuesday. (Oct. 1) Video provided by AP
Powered by NewsLook.com
Media, Industry Groups React To Calif. Plastic Bag Ban

Media, Industry Groups React To Calif. Plastic Bag Ban

Newsy (Sep. 30, 2014) — California is the first state in the country to ban single-use plastic bags in grocery, liquor and convenience stores. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins