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| Titel |
The effect of coal-fired power-plant SO2 and NOx control technologies on aerosol nucleation in the source plumes |
| VerfasserIn |
C. R. Lonsdale, R. G. Stevens, C. A. Brock, P. A. Makar, E. M. Knipping, J. R. Pierce |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 23 ; Nr. 12, no. 23 (2012-12-04), S.11519-11531 |
| Datensatznummer |
250011644
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| Publikation (Nr.) |
 copernicus.org/acp-12-11519-2012.pdf |
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| Zusammenfassung |
| Nucleation in coal-fired power-plant plumes can greatly contribute to
particle number concentrations near source regions. The changing emissions
rates of SO2 and NOx 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 NOx
emissions were reduced by ~90% and SO2 emissions decreased by
~30%. Increases in plume OH (due to the reduced NOx)
produced enhanced SO2 oxidation and an order-of-magnitude increase in
particle nucleation in the plume despite the reduction in SO2 emissions.
These results suggest that NOx 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 SO2
and NOx emissions-control technologies. Particle formation
generally increases with SO2 emission, while NOx shows two
different regimes: increasing particle formation with increasing NOx
under low-NOx emissions and decreasing particle formation with
increasing NOx under high-NOx 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 NOx
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 NOx controls (90%
reduction) implemented at the W. A. Parish plant (with relatively weak
SO2 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 NOx and
SO2 emissions in each plant. More extensive plume measurements for a
range of emissions of SO2 and NOx and in varying background
aerosol conditions are needed, however, to better quantify these effects. |
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