The fresh scent of pine has helped atmospheric scientists find missing sources of organic molecules in the air -- which, it could well turn out, aren't missing after all. In work appearing in this week's Proceedings of the National Academy of Sciences Early Edition Online, researchers examined what particles containing compounds such as those given off by pine trees look like and how quickly they evaporate. They found the particles evaporate more than 100 times slower than expected by current air-quality models.
"This work could resolve the discrepancy between field observations and models," said atmospheric chemist Alla Zelenyuk. "The results will affect how we represent organics in climate and air quality models, and could have profound implications for the science and policy governing control of submicron particulate matter levels in the atmosphere."
Zelenyuk and colleagues at the Department of Energy's Pacific Northwest National Laboratory were able to measure evaporation from atmospheric particles in a much more realistic manner than ever before. This allowed them to show that they are not liquids, as has been assumed for two decades, and to get an accurate read on how fast these particles evaporate. What researchers previously thought takes seconds actually takes days.
Secondary organic aerosols are tiny bits of chemically modified organic compounds floating in the air. They absorb, scatter or reflect sunlight, and serve as cloud nuclei, making them an important component of the atmosphere.
For a couple of decades, researchers have interpreted laboratory and field measurements under the assumption that these particles are liquid droplets that evaporate fast, which is central to the way these particles are modeled. However, to this day researchers have failed to explain the high amounts observed in the real atmosphere. The never-ending search for extra sources of organics has been frustrating for scientists studying these aerosols.
To re-examine the assumption, researchers at PNNL used equipment that could study the particles under realistic conditions. Zelenyuk developed a sensitive and high-precision instrument called SPLAT II that can count, size and measure the evaporation characteristics of these particles at room temperature. Research and development for SPLAT II occurred partly in EMSL, DOE's Environmental Molecular Sciences Laboratory at PNNL.
First, the researchers created secondary organic aerosol particles in the lab by oxidizing alpha-pinene, the molecule that makes pine trees smell like pine. Oxidation is the same thing that happens to iron when it rusts, and happens a lot in the atmosphere when aerosols come into contact with gases such as ozone, which is a pollutant when it is low in the atmosphere.
For comparison, the researchers also made particles from other, well-understood organic molecules that are known to form solids or liquid droplets, such as one called DOP. Lastly, they allowed these other organic molecules and the pine-scented SOA particles to mingle to simulate what likely happens in the outdoors.
Monitoring the various particles with SPLAT II for up to 24 hours, the research team found that DOP particles behaved as expected. Organics evaporated from the particles quickly, and faster if the particle was smaller, which is how liquid particles evaporate.
But the pinene-based particles did not. About 50 percent of their volume evaporated away within the first 100 minutes. Then they clammed up, and only another 25 percent of their volume dissipated in the next 23 hours. In addition, this fast-slow evaporation occurred similarly whether the particle was big or small, indicating the particles were not behaving like a liquid.
This lack of evaporation could account for the inability of scientists to find other sources of atmospheric organics. "Our findings indicate that there may, in fact, be no missing SOA," said Zelenyuk.
In the world, the SOAs from pinene co-exist with other organic molecules, and some of these slam onto the particle and coat it. Experiments with the co-mingled SOAs and organic compounds showed the researchers that coated particles evaporate even slower than single-source SOA.
Zelenyuk then tested how close to reality their lab-based SOAs were. Using air samples gathered in Sacramento, Calif., the team found the behavior of atmospheric SOAs (whether from trees and shrubs or pollution) paralleled that of the co-mingled pinene-derived SOAs in the lab and did not behave like liquids.
The results suggest that in the real atmosphere, SOA evaporation is so slow that scientists do not need to include the evaporation in certain models. The researchers hope that incorporating this information into atmospheric models will improve the understanding of aerosols' role in the climate.
More on http://www.emsl.pnl.gov/news/viewArticle.jsp?articleId=106">SPLAT II
More on the Sacramento CARES campaign
Reference: Timothy D. Vaden, Dan Imre, Josef Beránek, Manish Shrivastava, and Alla Zelenyuk, On the Evaporation Kinetics and Phase of Laboratory and Ambient Secondary Organic Aerosol, Proc Natl Acad Sci U S A, Early Edition online the week of January 24, DOI 10.1073/pnas.1013391108 (http://www.pnas.org/cgi/doi/10.1073/pnas.1013391108).
This work was supported by the U.S. Department of Energy Office of Science.
EMSL, the Environmental Molecular Sciences Laboratory located at Pacific Northwest National Laboratory, is a national scientific user facility sponsored by the Department of Energy's Office of Science. EMSL offers an open, collaborative environment for scientific discovery to researchers around the world. EMSL’s technical experts and suite of custom and advanced instruments are unmatched. Its integrated computational and experimental capabilities enable researchers to realize fundamental scientific insights and create new technologies. EMSL's Facebook page.
Pacific Northwest National Laboratory is a Department of Energy Office of Science national laboratory where interdisciplinary teams advance science and technology and deliver solutions to America's most intractable problems in energy, national security and the environment. PNNL employs 4,900 staff, has an annual budget of nearly $1.1 billion, and has been managed by Ohio-based Battelle since the lab's inception in 1965. Follow PNNL on Facebook, LinkedIn and Twitter.
Mary Beckman | Newswise Science News
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Life Sciences
23.03.2018 | Materials Sciences
23.03.2018 | Process Engineering