Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Airborne Particles Smuggle Pollutants to Far Reaches of Globe

19.11.2012
Symbiotic relationship between pollutants and airborne particles explains how city pollution ends up in Arctic

Pollution from fossil fuel burning and forest fires reaches all the way to the Arctic, even though it should decay long before it travels that far. Now, lab research can explain how pollution makes its lofty journey: rather than ride on the surface of airborne particles, pollutants snuggle inside, protected from the elements on the way. The results will help scientists improve atmospheric air-quality and pollution transport models.


Zelenyuk/PNNL

When airborne particles (green) form before pollutants known as PAHs (yellow) glob on, both the pollutants and particles dissipate quickly, as shown in the top row. But when the particles form in the presence of pollutants, which is what likely happens in nature, the long-lasting particles can take the pollutants for a long-distance ride (bottom)

The results also show that the particles that envelop pollutants also benefit from this arrangement. The new study in Environmental Science & Technology shows that the airborne particles, made from natural molecules mostly given off by live or burning plants, last longer with a touch of pollutant packed inside. The pollutants are known as polycyclic aromatic hydrocarbons, or PAHs, and are regulated by environmental agencies due to their toxicity.

"What we've learned through fundamental studies on model systems in the lab has very important implications for long-range transport of pollutants in the real world," said physical chemist Alla Zelenyuk of the Department of Energy's Pacific Northwest National Laboratory. "In this study, we propose a new explanation for how PAHs get transported so far, by demonstrating that airborne particles become a protective vessel for PAH transport."

Floating in the air and invisible to the eye, airborne particles known as secondary organic aerosols live and die. Born from carbon-based molecules given off by trees, vegetation, and fossil fuel burning, these airborne SOA particles travel the currents and contribute to cloud formation. Along for the ride are pollutants, the PAHs, that have long been thought to coat the particles on their surface.

For decades, atmospheric scientists have been trying to explain how atmospheric particles manage to transport harmful pollutants to pristine environments thousands of miles away from their starting point. The particles collected in areas such as the Arctic also pack higher concentrations of pollutants than scientists' computer models predict.

The predictions are based on the assumption that the particles are like liquid spheres, whose fluidity allows PAHs to escape. But they don't escape, and one recent advance has helped to pin down why PAHs are remaining stuck in their particle lairs. Zelenyuk and her colleagues at EMSL, DOE's Environmental Molecular Sciences Laboratory at PNNL, developed an ultra-sensitive instrument that can determine the size, composition and shape of individual particles.

Called SPLAT II, the instrument can analyze millions of tiny particles one by one. The ability of this novel instrument to characterize individual particles provides unique insight into their property and evolution.

Using SPLAT II to evaluate laboratory-generated SOA particles from alpha-pinene, the molecule that gives pine trees their piney smell, Zelenyuk has already discovered that SOA particles aren't liquid at all. Her team's recent work revealed they are more like tar -- thick, viscous blobs that are too solid to be liquid and too liquid to be solid.

Armed with this data, Zelenyuk and researchers from Imre Consulting in Richland and the University of Washington in Seattle set out to determine the relation between the SOA particle and the PAHs. Again they used alpha-pinene for the SOA. For the PAH, they used pyrene, a toxic pollutant produced by burning fossil fuels or vegetation such as forests.

They created two kinds of particles. The first kind exemplified the classical SOA: first they produced the particles with alpha-pinene and then coated them with pyrene. The second kind resembled what likely happens in nature: they mixed alpha-pinene and pyrene and let the particles form with both molecules present. Then they sent the particles through SPLAT and watched what happened to them over time.

With the pyrene-coated particles, the team found the PAH pyrene evaporating off the surface of the particle quickly, all of it gone after four hours. By the next day, the particle itself had shrunk by about 70 percent, showing that the alpha-pinene SOA also evaporates, although more slowly than pyrene.

When they created the particles in the presence of both SOA and PAH, the PAH evaporated much more slowly. Fifty percent of the original PAH still remained in the particle after 24 hours. In addition, the SOA particle itself stayed bulky, losing less than 20 percent of its volume.

These results showed the team that PAHs become trapped within the highly viscous SOA particles, where they remain protected from the environment. The symbiotic relationship between the atmospheric particles and pollutants surprised Zelenyuk: SOAs help PAHs travel the world, and the PAHs help SOAs survive longer.

Zelenyuk and her colleagues performed comparable experiments with other PAHs and SOAs and found similar results.

In the real world, Zelenyuk said, the evaporation will be even slower. These results will help modelers better simulate atmospheric SOA particles and transport of pollutants over long distances.

This work was supported by the Department of Energy Office of Science and PNNL's Chemical Imaging Initiative.

Reference: Alla Zelenyuk, Dan Imre, Josef Beránek, Evan Abramson, Jacqueline Wilson and Manish Shrivastava, Synergy between Secondary Organic Aerosols and Long-Range Transport of Polycyclic Aromatic Hydrocarbons, Environmental Science & Technology, Nov. 7, 2012, doi: 10.1021/es302743z. (http://pubs.acs.org/doi/abs/10.1021/es302743z)

EMSL, the Environmental Molecular Sciences Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science. Located at Pacific Northwest National Laboratory in Richland, Wash., EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. Its integrated computational and experimental resources enable researchers to realize important scientific insights and create new technologies. Follow EMSL on Facebook, LinkedIn and Twitter.

Interdisciplinary teams at Pacific Northwest National Laboratory address many of America's most pressing issues in energy, the environment and national security through advances in basic and applied science. PNNL employs 4,500 staff, has an annual budget of nearly $1 billion, and has been managed for the U.S. Department of Energy by Ohio-based Battelle since the laboratory's inception in 1965. For more, visit the PNNL's News Center, or follow PNNL on Facebook, LinkedIn and Twitter.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Mary Beckman | Newswise Science News
Further information:
http://www.pnnl.gov

More articles from Ecology, The Environment and Conservation:

nachricht New approach for environmental test on livestock drugs
27.07.2016 | Universität Zürich

nachricht Managing an endangered river across the US-Mexico border
18.07.2016 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: X-ray optics on a chip

Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.

In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...

Im Focus: Piggyback battery for microchips: TU Graz researchers develop new battery concept

Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.

Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...

Im Focus: UCI physicists confirm possible discovery of fifth force of nature

Light particle could be key to understanding dark matter in universe

Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...

Im Focus: Wi-fi from lasers

White light from lasers demonstrates data speeds of up to 2 GB/s

A nanocrystalline material that rapidly makes white light out of blue light has been developed by KAUST researchers.

Im Focus: Every atom counts

Malignant cancer cells not only proliferate faster than most body cells. They are also more dependent on the most important cellular garbage disposal unit, the proteasome, which degrades defective proteins. Therapies for some types of cancer exploit this dependence: Patients are treated with inhibitors, which block the proteasome. The ensuing pile-up of junk overwhelms the cancer cell, ultimately killing it. Scientists have now succeeded in determining the human proteasome’s 3D structure in unprecedented detail and have deciphered the mechanism by which inhibitors block the proteasome. Their results will pave the way to develop more effective proteasome inhibitors for cancer therapy.

In order to understand how cellular machines such as the proteasome work, it is essential to determine their three-dimensional structure in detail. With its...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

A week of excellence: 22 of the world’s best computer scientists and mathematicians in Heidelberg

12.08.2016 | Event News

Towards the connected, automated and electrified automobiles: AMAA conference in Brussels

02.08.2016 | Event News

Clash of Realities 2016: 7th Conference on the Art, Technology and Theory of Digital Games

29.07.2016 | Event News

 
Latest News

New microchip demonstrates efficiency and scalable design

23.08.2016 | Information Technology

Genetic Regulation of the Thymus Function Identified

23.08.2016 | Life Sciences

Biomass turnover time in ecosystems is halved by land use

23.08.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>