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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-12-11519-2012</article-id>
<title-group>
<article-title>The effect of coal-fired power-plant SO&lt;sub&gt;2&lt;/sub&gt; and NO&lt;sub&gt;x&lt;/sub&gt; control technologies on aerosol nucleation in the source plumes</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Lonsdale</surname>
<given-names>C. R.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Stevens</surname>
<given-names>R. G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Brock</surname>
<given-names>C. A.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Makar</surname>
<given-names>P. A.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Knipping</surname>
<given-names>E. M.</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Pierce</surname>
<given-names>J. R.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Canada</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>NOAA Earth System Research Laboratory, Boulder, CO, USA</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Environment Canada, Downsview, Toronto, Canada</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Electric Power Research Institute, Palo Alto, CA, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>04</day>
<month>12</month>
<year>2012</year>
</pub-date>
<volume>12</volume>
<issue>23</issue>
<fpage>11519</fpage>
<lpage>11531</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
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<self-uri xlink:href="http://www.atmos-chem-phys.net/12/11519/2012/acp-12-11519-2012.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/11519/2012/acp-12-11519-2012.pdf</self-uri>
<abstract>
<p>Nucleation in coal-fired power-plant plumes can greatly contribute to
particle number concentrations near source regions. The changing emissions
rates of SO&lt;sub&gt;2&lt;/sub&gt; and NO&lt;sub&gt;x&lt;/sub&gt; due to pollution-control technologies over
recent decades may have had a significant effect on aerosol formation and
growth in the plumes with ultimate implications for climate and human health.
We use the System for Atmospheric Modeling (SAM) large-eddy simulation model
with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm to model
the nucleation in plumes of coal-fired plants. We test a range of cases with
varying emissions to simulate the implementation of emissions-control
technologies between 1997 and 2010. We start by simulating the W. A. Parish
power plant (near Houston, TX) during this time period, when NO&lt;sub&gt;x&lt;/sub&gt;
emissions were reduced by ~90% and SO&lt;sub&gt;2&lt;/sub&gt; emissions decreased by
~30%. Increases in plume OH (due to the reduced NO&lt;sub&gt;x&lt;/sub&gt;)
produced enhanced SO&lt;sub&gt;2&lt;/sub&gt; oxidation and an order-of-magnitude increase in
particle nucleation in the plume despite the reduction in SO&lt;sub&gt;2&lt;/sub&gt; emissions.
These results suggest that NO&lt;sub&gt;x&lt;/sub&gt; emissions could strongly regulate
particle nucleation and growth in power-plant plumes. Next, we test a range
of cases with varying emissions to simulate the implementation of SO&lt;sub&gt;2&lt;/sub&gt;
and NO&lt;sub&gt;x&lt;/sub&gt; emissions-control technologies. Particle formation
generally increases with SO&lt;sub&gt;2&lt;/sub&gt; emission, while NO&lt;sub&gt;x&lt;/sub&gt; shows two
different regimes: increasing particle formation with increasing NO&lt;sub&gt;x&lt;/sub&gt; 
under low-NO&lt;sub&gt;x&lt;/sub&gt; emissions and decreasing particle formation with
increasing NO&lt;sub&gt;x&lt;/sub&gt; under high-NO&lt;sub&gt;x&lt;/sub&gt; emissions. Next, we
compare model results with airborne measurements made in the W. A. Parish
power-plant plume in 2000 and 2006, confirming the importance of NO&lt;sub&gt;x&lt;/sub&gt; 
emissions on new particle formation and highlighting the substantial
effect of background aerosol loadings on this process (the more polluted
background of the 2006 case caused more than an order-of-magnitude reduction
in particle formation in the plume compared to the cleaner test day in 2000).
Finally, we calculate particle-formation statistics of 330 coal-fired power
plants in the US in 1997 and 2010, and the model results show a median
decrease of 19% in particle formation rates from 1997 to 2010 (whereas
the W. A. Parish case study showed an increase). Thus, the US power plants,
on average, show a different result than was found for the W. A. Parish plant
specifically, and it shows that the strong NO&lt;sub&gt;x&lt;/sub&gt; controls (90%
reduction) implemented at the W. A. Parish plant (with relatively weak
SO&lt;sub&gt;2&lt;/sub&gt; emissions reductions, 30%) are not representative of most power
plants in the US during the past 15 yr. These results suggest that there may
be important climate implications of power-plant controls due to changes in
plume chemistry and microphysics, but the magnitude and sign of the aerosol
changes depend greatly on the relative reductions in NO&lt;sub&gt;x&lt;/sub&gt; and
SO&lt;sub&gt;2&lt;/sub&gt; emissions in each plant. More extensive plume measurements for a
range of emissions of SO&lt;sub&gt;2&lt;/sub&gt; and NO&lt;sub&gt;x&lt;/sub&gt; and in varying background
aerosol conditions are needed, however, to better quantify these effects.</p>
</abstract>
<counts><page-count count="13"/></counts>
</article-meta>
</front>
<body/>
<back>
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