Los Angeles, London, New Delhi or Beijing – all are mega cities in which millions of people suffer from breathing problems and burning eyes. The cause is smog. Often it is so thick that the tops of the skyscrapers disappear and the sun cannot be seen for days.
A big smog layer is visible over the American mega city Los Angeles.
Steve Buss, from flickr
Under certain weather conditions smog – a mixture of particles and gaseous pollutants like ozone - develops due to traffic, industrial activities, or combustion of biomass, coal and wood. The main component of urban smog is the so-called secondary organic aerosol (SOA). The SOA particles develop from organic compounds oxidized by ozone and hydroxyl radicals. The organic molecules are for example released by burning fossil and renewable fuels.
The processes and mechanisms for the formation of these smog particles are still poorly understood. It has been difficult to accurately predict size and mass of the particles, which determines atmospheric visibility, i.e. the smog thickness and the extent of adverse health effects.
An improved view on smog has now been obtained by a team led by the Max Planck researcher Manabu Shiraiwa. "So far, it is considered that only the gas reactions are important for smog formation," says Shiraiwa, lead author of a recently published study. "We found out that it is more important what happens inside the particles, which is a typical multiphase reaction and needs to be included in the model forecasts," adds the 30 years old Japanese scientist, who conducted the study at the California Institute of Technology in the U.S. and who came back to the Max Planck Institute for Chemistry in Mainz in April 2013 where he had working before.
The researchers generated smog which mimicked the urban air in the laboratory. They used the volatile organic molecule dodecane as particle source. Dodecane belongs to the alkanes, which consist only of carbon and hydrogen atoms, and is also emitted into the atmosphere by incomplete combustion of biomass. In a giant special reaction chamber they added hydroxyl radicals (OH) for photooxidation leading to the formation of smog particles. Hydroxyl radicals are a kind of cleaning agent of the atmosphere, which quickly reacts with volatile organic molecules such as methane or alkanes. After the oxidation the researchers measured the size of the SOA particles developed in the chamber. About five hours later they observed a steep increase in mass and size of the particles.
The traditional model however predicts a much slower increase. Shiraiwa and his colleagues concluded that the gase phase reactions are not sufficient enough for the particle growth. Mass spectrometry measurements confirmed that the small volatile organic molecule dodecane reacts to bigger, less volatile organic molecules. As these molecules do not evaporate from the particle phase the particles grow bigger. Since these multiphase reactions have so far never been considered in air quality models the researcher hope that including the findings will lead to better prediction of air quality in the urban air.
Shiraiwa who currently establishes a research group at the Max Planck Institute for Chemistry will continue studying the chemical aging of organic aerosols and related topics. He received his Bachelor and Master degree at the University of Tokyo, and his Ph.D. degree at the Max Planck Institute for Chemistry in Mainz where he developed the kinetic model for the reactions of atmospheric particles. In 2012 he has been awarded the Otto Hahn Medal of the Max Planck Society and Paul Crutzen Prize of German Chemical Society for his path-breaking discoveries about the progression of chemical reactions on the surface of and inside aerosol particles.Original publication
PNAS, 110(29), 11746-11750, doi: 10.1073/pnas.1307501110
Dr. Susanne Benner | Max-Planck-Institut
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences