Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Jelly-like atmospheric particles resist chemical aging

Findings will affect scientific models of cloud formation and light absorption
Atmospheric chemists at the Harvard School of Engineering and Applied Sciences (SEAS) have found that when it comes to secondary organic material in the atmosphere, there are two distinct breeds: liquids and jellies.

Secondary organic materials (SOM) are airborne particles that have begun to react with gases in the atmosphere. In the last 20 years' research and climate modeling, these SOM particles have been assumed to drift as liquids. In a liquid phase, the organic materials would absorb other compounds like ammonia or ozone very easily and then progress through a series of chemical changes (known as chemical aging) to form particles that reflect or absorb sunlight, or form clouds.

Now, experiments at Harvard, using particles of á-pinene SOM and adipic acid, have shown that a drop in humidity can send these common aerosols into a jelly-like phase, in which they resist chemical aging almost entirely. The findings, published in the Proceedings of the National Academy of Sciences, may call for a revision of regional and global climate models.

"Our research provides the first experimental evidence that the chemical aging process of atmospheric particles is limited by phase," says principal investigator Scot Martin, Gordon McKay Professor of Environmental Chemistry at SEAS and in Harvard's Department of Earth and Planetary Sciences. "Solid or semi-solid aerosol particles will only react with other molecules at the surface of the droplet, instead of mixing homogeneously. What this means is that the time scale of important chemical aging processes may be much longer than what is reflected in current models."

The two particles chosen for this study, á-pinene and adipic acid, are common in the Earth's atmosphere; á-pinene is essentially a scent released by coniferous trees (including pines—hence the name), and adipic acid comes from both anthropogenic sources (such as car exhaust) and natural chemical reactions.

In the atmosphere, the particles of á-pinene SOM and adipic acid behave rather like gelatin; in moist conditions, the droplets absorb water and remain liquid. In dry conditions, they solidify without crystallizing. Lead author Kuwata Mikinori, a postdoctoral fellow at SEAS, compares these semi-solid atmospheric particles to chunks of tofu, another high-viscosity, amorphous solid.

"If you pour soy sauce onto a block of tofu at room temperature, the liquid will just sit on the surface of the tofu. It won't sink in," Kuwata explains. "But if you cook tofu in a sauce at a high heat for a long time, the tofu will eventually absorb the taste of the sauce. That's the same kind of effect we're seeing in the atmosphere. Eventually these semi-solid aerosols do blend with other reactants, but it takes a long time, a higher temperature, or enough ambient humidity to encourage a phase change back to liquid."

The researchers selected ammonia as the reactant in their study partly because its nitrogen component is easy to detect using mass spectrometry, but also because of its current environmental relevance. Atmospheric ammonia has been on the increase in the past few years as a byproduct of fertilizer use and livestock farming, and as a result of increasing temperatures.

"For the environment, ammonia is a very tricky compound," says Kuwata. "It neutralizes sulfuric acid, helping prevent acid rain, but its nitrogen component can also fertilize open bodies of water, which can be bad news for ecosystems. When ammonia reacts with SOM, it can form ammonium salts, which are thought to affect cloud nucleation activity, and organic nitrogen, which forms light-absorbing compounds."

Martin and Kuwata conducted their experiments in the Harvard Environmental Chamber, a 5-cubic-meter Teflon bag that hangs from the ceiling of an environmentally controlled laboratory room at SEAS. In trials within this chamber, they recreated various atmospheric conditions while adjusting the humidity, and exposed particles of either á-pinene SOM or adipic acid to ammonia for approximately seven minutes.

Following that exposure, they measured the diameter of the resulting particles and determined the mass and composition of each one to understand the extent of chemical aging that had occurred.

"Our results challenge basic assumptions about the rate of chemical reactions in the atmosphere," says Kuwata. "These results ought to change the way we evaluate the impacts of atmospheric aerosol particles on the climate."

This work was supported by the U.S. Department of Energy and by a postdoctoral fellowship from the Japan Society for the Promotion of Science.

Caroline Perry | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>