Air chemistry data from South Korea field study puts models to the test


Date:
February 15, 2022
Source:
Penn State
Summary:
An international effort to measure air quality in South Korea, a
region with complex sources of pollution, may provide new insights
into the atmospheric chemistry that produces ozone pollution,
according to a team of scientists.



FULL STORY ==========================================================================
An international effort to measure air quality in South Korea, a region
with complex sources of pollution, may provide new insights into the atmospheric chemistry that produces ozone pollution, according to a team
of scientists.


========================================================================== "This study shows that observations of the hydroxyl radical -- OH --
and hydroperoxyl radical -- HO2 provide valuable tests of the ability of
our photochemical models to correctly represent atmospheric chemistry, especially in environments with high levels of pollution," said William
H. Brune, distinguished professor of meteorology at Penn State.

The hydroxyl radical initiates important chemical reactions throughout
the atmosphere, including in the troposphere, the lowest region reaching
to the Earth's surface, where its reactions clean the air but also lead
to ozone pollution in cities, the scientists said.

The team analyzed airborne measurements of the hydroxyl radical,
hydroperoxyl radical and about a 100 other chemical species taken during flights over South Korea in 2016 as part of a joint field study between
NASA and the Republic of Korea, called Korea-U.S. Air Quality (KORUS-AQ).

The airborne measurements of the hydroxyl and hydroperoxyl radicals
agreed with values produced by separate models running at NASA Langley
Research Center and Penn State when the uncertainties in the measurements
and models are considered, the researchers said.

"One major finding is -- even in a complex environment like this -- we
have a good handle on the basic chemistry in our models," Brune said. "We
can really say this chemistry is correct within the uncertainties,
and that tells us something about ozone production." Ozone forms when
nitrogen oxides -- like from vehicle and power plant emissions -- and
volatile organic compounds -- produced naturally by plants but also by
solvents and other harsh human-made chemicals -- mix in the atmosphere
in the presence of sunlight, the scientists said.



==========================================================================
"But these elements can't do much themselves, they need something to
make the chemistry active, and that is the hydroxyl radical," Brune
said. "It drives the chemistry, kind of like a low-temperature version
of the flame heating your house." While the hydroxyl radical measured
during the flights generally agreed with the models, the scientists found
less agreement when they looked at their measurements of the radical's reactivity, which is the sum of reactions between the hydroxyl radical
and all chemical species.

"It's really a key number because a very high hydroxyl radical reactivity
means you're in a very polluted environment, or an environment that has a
lot of things being emitted that are reacting with the hydroxyl radical,"
Brune said.

When the measured hydroxyl radical reactivity was compared to the hydroxyl radical reactivity calculated using all the other measurements, it was not possible to account for as much as half of the hydroxyl radical reactivity
in some cases, said the scientists, who reported their findings in the
journal Atmospheric Environment.

This missing hydroxyl radical reactivity originated primarily from the
Korean peninsula, potentially helping to distinguish the sources between pollution emitted by industry in South Korea and older pollution that
blows in from China, the scientists said.



==========================================================================
"We invented this idea of measuring hydroxyl radical reactivity about 25
years ago and we've found missing reactivity in forests and all kinds of
other places," Brune said. "And while we are now much better at closing
the gap between measured and calculated hydroxyl radical reactivity,
in South Korea we thought we were measuring everything, and we clearly
weren't measuring everything." Improving our understanding of this
reactive chemistry is important, Brune said, because that information
can inform regional and global air quality models.

"These models have a hard time predicting really harmful amounts of
ozone," he said. "Hopefully our results will help them figure out the
problem so that they can be used by policy makers to efficiently reduce
ozone levels, not just in the U.S., but around the world." Other Penn
State researchers on this project were David Miller, assistant research professor and Alexander Thames and Alexandra Brosius, graduate students.

Scientists from the University of California, Irvine, NASA Langley
Research Center, University of Colorado, Boulder, NASA Goddard Space
Flight Center, Georgia Institute of Technology, California Institute of Technology, University of Virginia, University in Innsbruck and University
of Oslo also participated.

NASA provided funding for several researchers involved in the study.

========================================================================== Story Source: Materials provided by Penn_State. Original written by
Matthew Carroll. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. William H. Brune, David O. Miller, Alexander B. Thames, Alexandra L.

Brosius, Barbara Barletta, Donald R. Blake, Nicola J. Blake, Gao
Chen, Yonghoon Choi, James H. Crawford, Joshua P. Digangi, Glenn
Diskin, Alan Fried, Samuel R. Hall, Thomas F. Hanisco, Greg L. Huey,
Stacey C. Hughes, Michelle Kim, Simone Meinardi, Denise D. Montzka,
Sally E. Pusede, Jason R. Schroeder, Alex Teng, David J. Tanner,
Kirk Ullmann, James Walega, Andrew Weinheimer, Armin Wisthaler,
Paul O. Wennberg. Observations of atmospheric oxidation and ozone
production in South Korea. Atmospheric Environment, 2022; 269:
118854 DOI: 10.1016/j.atmosenv.2021.118854 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220215125513.htm
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