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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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