New Research: Climate and Aerosols

 

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“While soot emitted from sources like diesel engines and electric 

power plants is a focus of study, not all aerosols are man-made. The 

deserts and arid landscapes of the world produce an estimated 10 to 

20 billion tons of mineral aerosols a year. The air is full of 

biological aerosols as well – microbes, cells, and particles 

containing organic compounds. ”

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Public release date: 25-Jul-2008

Boston College

 

Contact: Ed Hayward

ed.hayward@bc.edu

617-552-4826

 

Scientists search for answers from the carbon in the clouds

Latest technology examines aerosol particles in the sky

 

 

CHESTNUT HILL, MA (JULY 25, 2008) – An aerosol mass spectrometer 

developed by chemists from Aerodyne Research Inc. and Boston College 

is giving scientists who study airborne particles the technology they 

need to examine the life cycles of atmospheric aerosols – such as 

soot – and their impact on issues ranging from climate change to 

public health.

 

BC Chemistry Professor Paul Davidovits and Aerodyne Principal 

Scientist Timothy B. Onasch say their novel spectrometer allows 

researchers to better understand what happens to these 

sub-microscopic particles that can absorb and scatter light and 

influence the lifetime of clouds.

 

“For scientists looking at climate change, the biggest uncertainty 

has to do with the effect of aerosol particles in the air,” says 

Davidovits. “The issue is made that much more complex because 

aerosols can have different effects on climate. That means the target 

is constantly shifting.”

 

The historic role of carbon-laden soot in climate change has been 

identified by researchers, particularly through ice samples taken 

from glaciers. Now scientists are focusing on tiny airborne particles 

of black carbon released into the atmosphere today in order to better 

understand the lifecycle of these aerosols in the atmosphere.

 

To that end, nearly 20 researchers from across the country brought 

other devices to the Davidovits lab this month to test and fine-tune 

these new tools developed by scientists from universities, industry 

and national laboratories at the forefront of this path-breaking 

science of the sky.

 

Hosted by Davidovits and Onasch, also an associate research professor 

at BC, the visiting researchers ran streams of laboratory-generated 

soot through devices able to analyze minute aerosol particles by 

mass, shape, chemical make-up, even the sound they make when warmed 

by light – a “pop” inaudible to the human ear.

 

“This is the cutting edge,” says Dan Lack, a research scientist with 

the National Oceanic and Atmospheric Administration’s Earth System 

Research Laboratory in Boulder, Colo. “Much of the technology in this 

room didn’t exist until a few years ago. And there isn’t another 

place in the country where you have all this technology running 

together in concert. It’s a rare opportunity.”

 

Among the 18 devices involved in the project are Billerica, MA-based 

Aerodyne’s Aerosol Mass Spectrometer, Boulder-based Droplet 

Technologies’ Single Particle Soot Photometer, and the NOAA-developed 

Cavity Ring-Down Aerosol Extinction and Photoacoustic Spectrometers, 

which shoot a laser beam into black carbon, causing the particle to 

“pop”, emitting a frequency that’s measured to gauge how much light 

carbon absorbs.

 

A technological focal point is a unique soot-particle generating 

apparatus operated by doctoral student Eben Cross, undergraduate Adam 

Ahern ’09 and recent graduate Billy Wrobel ’08. The design, 

construction, and operation of the device were funded by the 

atmospheric chemistry programs of the Department of Energy and the 

National Science Foundation.

 

In the race to determine the scope and speed of climate change and 

the influence of human activities on it, huge scientific efforts have 

focused on carbon dioxide gasses emitted largely from the burning of 

fossil fuels. Scientists believe particulates like black carbon may 

also contribute significantly to global warming.

 

For more than 15 years, Davidovits and his Aerodyne colleagues have 

pioneered the study of soot particles and gas-particle interactions, 

strengthening an understanding of the role of cloud and aerosol 

chemistry in acid rain, ozone depletion and climate change.

 

Aerosols raise temperatures, such as when black particles of soot 

rise in the sky, absorb sunlight and turn it into heat. Aerosols also 

can cool by reflecting light away from the earth. Clouds overstuffed 

with aerosols can inhibit rainfall.

 

While soot emitted from sources like diesel engines and electric 

power plants is a focus of study, not all aerosols are man-made. The 

deserts and arid landscapes of the world produce an estimated 10 to 

20 billion tons of mineral aerosols a year. The air is full of 

biological aerosols as well – microbes, cells, and particles 

containing organic compounds.

 

Aerosols are somewhat fleeting. Unlike carbon dioxide, which can 

remain in the atmosphere for years, aerosols have an atmospheric life 

of about 10 to 20 days. In that time, they can absorb other molecules 

that alter their original state.

 

Measuring the many forms of atmospheric aerosols has led researchers 

to invent new devices, known as research-grade aerosol particle 

characterizing instruments, says Davidovits. The challenge now is to 

fine-tune those instruments in concert with each other in order to 

set reliable scientific benchmarks for future study.

 

Linked closely to the atmospheric effects of aerosols is a range of 

public health concerns, says Onasch.

 

“There is a need on many fronts – from the climate to public health – 

for greater understanding of the role aerosol particles play in our 

lives and what’s happening here is the scientific community rising to 

meet those needs,” says Onasch.

 

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For more information about the Davidovits lab, please see: 

http://www.bc.edu/schools/cas/chemistry/faculty/davidovits.html

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