Navigation Links
NOAA-led team measures atmosphere's self-cleaning capacity
Date:1/6/2011

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 published online today 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."


'/>"/>

Contact: Jana Goldman
jana.goldman@noaa.gov
301-734-1123
NOAA Headquarters
Source:Eurekalert

Related biology news :

1. New test measures DNA methylation levels to predict colon cancer
2. Mathematical model may result in better environment measures for the Baltic
3. Panel finds insufficient evidence for Alzheimers disease preventive measures
4. UI study measures levels of PCBs flowing from Indiana canal to air and water
5. Prototype NIST method detects and measures elusive hazards
6. NIST calculations may improve temperature measures for microfluidics
7. PRS And EmSense Partner To Integrate Bio-Sensory Measures In Packaging Research Studies
8. Broecker: What we need are tougher measures against climate change
9. Cost-effective measures could stop child pneumonia deaths
10. Illinois Soil Nitrogen Test measures microbial nitrogen
11. Free online toolkit provides standard measures for genome and population studies
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:11/29/2016)... 2016 BioDirection, a privately held medical device ... objective detection of concussion and other traumatic brain injury ... a meeting with the U.S. Food and Drug Administration ... Package. During the meeting company representatives reviewed plans for ... to commencement of a planned pilot trial. ...
(Date:11/22/2016)... -- According to the new market research report "Biometric System ... Voice), Multi-Factor), Component (Hardware and Software), Function (Contact and Non-contact), Application, and ... expected to grow from USD 10.74 Billion in 2015 to reach USD ... 2022. Continue Reading ... ...
(Date:11/17/2016)...  AIC announces that it has just released a new white paper authored by ... plus high speed data transfer storage solutions. Photo - http://photos.prnewswire.com/prnh/20161116/440463 ... ... ... Setting up a high performance computing or HPC system can ...
Breaking Biology News(10 mins):
(Date:12/5/2016)... 5, 2016 NxGen MDx announced today that it brought its ... house, we,ve been able to improve customer service through shortened turnaround times ... Alan Mack , CEO of NxGen MDx. ... , A decrease in turnaround ... to more job opportunities at the Grand Rapid headquarters. The ...
(Date:12/5/2016)... -- Research and Markets has announced the addition ... Markets and Companies" to their offering. ... , , ... genome variations, development of sequencing technologies, and their applications. Current ... developing them. Various applications of sequencing are described including those ...
(Date:12/4/2016)... ... December 02, 2016 , ... A proposed five-year extension for ... funded research and development is welcome news for the photonics community, say leaders ... As part of the National Defense Authorization Act (NDAA) compromise agreement finalized today ...
(Date:12/4/2016)... 2016  In five studies being presented today during ... and Exposition in San Diego , ... the delivery of life-saving treatments to patients with a ... to carry therapies directly to the sites in the ... a substantial advantage over traditional, systemic methods. The studies ...
Breaking Biology Technology: