(Press-News.org) Laboratory chamber walls have been stealing vapors, causing
researchers to underestimate the formation of secondary organic
aerosol in the atmosphere.
A study published April 7 in PNAS Online Early Edition describes how
a team of scientists, including researchers from the University of
California, Davis, showed that vapor losses to the walls of
laboratory chambers can suppress the formation of secondary organic
aerosol, which in turn has contributed to the underprediction of SOA
in climate and air quality models.
SOA impacts air quality and climate and makes up a major fraction of
particulate matter in the atmosphere. Yet SOA concentrations have
been significantly underestimated in regional air quality models.
Nearly all models of secondary organic aerosols are tied to
observations of their formation in laboratory chamber experiments.
However, the effect of vapor loss to chamber walls previously had
been neglected.
"To accurately predict the health and climate impacts of particles,
we need to accurately predict their abundance in the atmosphere,"
said co-author Christopher Cappa, professor of civil and
environmental engineering at UC Davis.
Secondary organic aerosols are formed primarily through chemistry
that occurs in the gas phase.
"If, along the path from moving from the gas phase to the particle
phase, another surface steals that gas-phase material, you wouldn't
form as much of the particle as you would think," Cappa said. "That's
what we've demonstrated is happening: The walls of these chambers act
as a sponge for the vapors and compete with the particles for these
vapors."
Researchers from UC Davis and the California Institute of Technology
conducted a series of experiments in a 24 cubic meter environmental
chamber using the volatile organic compound toluene, which is emitted
from motor vehicles and is an important SOA precursor.
Cappa said the researchers' next steps are to assess the vapor effect
more broadly for other compounds to more fully understand these wall
effects and make better predictions for the future.
INFORMATION:
The study's other co-authors include Shantanu Jathar and Michael
Kleeman, both of UC Davis; and Xuan Zhang, Renee McVay, Joseph
Ensberg and John Seinfeld, all of the California Institute of
Technology.
The study was funded by the National Science Foundation, U.S.
Department of Energy and California Air Resources Board.
About UC Davis
For more than 100 years, UC Davis has been one place where people are
bettering humanity and our natural world while seeking solutions to
some of our most pressing challenges. Located near the state capital,
UC Davis has more than 33,000 students, over 2,500 faculty and more
than 21,000 staff, an annual research budget of over $750 million, a
comprehensive health system and 13 specialized research centers. The
university offers interdisciplinary graduate study and more than 100
undergraduate majors in four colleges -- Agricultural and
Environmental Sciences, Biological Sciences, Engineering, and Letters
and Science. It also houses six professional schools -- Education,
Law, Management, Medicine, Veterinary Medicine and the Betty Irene
Moore School of Nursing.
Scientists find missing piece of air particle equation hiding in the walls
2014-04-07
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