AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Effect of Coal-Fired Power Plant SO2, NOX Control Technologies and Background Particle Concentrations on Aerosol Nucleation and Growth in Source Plumes
CHANTELLE LONSDALE, Robin Stevens, Charles Brock, Paul Makar, Jeffrey Pierce, Dalhousie University
Abstract Number: 97 Working Group: Aerosol Nucleation: From Clusters to Nanoparticles
Abstract Nucleation and growth in coal-fired power-plant plumes can greatly contribute to particle number concentrations in plumes near source regions. The changing emissions rates of SO2 and NOx due to pollution-control technologies over recent decades may have a significant affect on aerosol formation and growth in the plumes, with ultimate implications for climate and human health. We use the System for Atmospheric Modelling (SAM) Large-Eddy simulation model with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm to model the nucleation and growth in the plume of coal-fired units. We test a range of cases with varying emissions to simulate the implementation of clean technologies between 1997 and 2010. For the W.A. Parish power plant (near Houston, TX) during this time period, NOx emissions were reduced by about a factor of 10 due to the addition of Selective Catalytic Reduction (SCR) technology, leading to a predicted increase in OH concentrations by about a factor of 10, while SO2 emissions have only decreased by ~30%. This increase in OH leads to faster production of H2SO4 in the plume, and nucleation and growth even though SO2 emissions were somewhat decreased. These results suggest that controlling NOx more strongly than SO2 may lead to increased nucleation and growth in power-plant plumes. We also compare our predictions for the W.A. Parish power plant to NOAA aircraft measurements through this plume taken during 2000 and 2006. Although variability in pre-existing aerosol concentrations between the measurement days dominates the difference between measurements, the measurements do suggest the influence of the emission-control changes on particle formation. Next, we use the case study results to understand more generally how NOx and SO2 emissions affect particle formation/growth and contribute to regional aerosol number concentrations through testing a wide range of NOx and SO2 emissions rates. Finally, we calculate statistics on how emissions controls added to all of the power plants in the US since 1997 may have effected particle formation in their plumes.