Back
Detecting Past and Future Trends in Nitrogen Deposition: A Modeling
Study to Guide the
Placement of Future Monitoring Sites
Robert W. Pinder, Alice B. Gilliland, Robin L. Dennis
ASMD, NOAA, ALR, RTP, NC, 27711
In partnership with NERL, USEPA
| Previous studies have reported large changes
in concentrations and deposition fluxes observed in the national monitoring
networks (NADP, CASTNet, and STN). However, as the focus of regulated
emission reductions turns from SO2 to NOx, it is important to re-assess
the location of the network monitoring sites to ensure sufficient coverage
in order to evaluate the effectiveness of the regulated emission changes.
This research examines the sensitivity of monitored concentrations and
deposition fluxes to emission changes for two cases: (1) previous emission
reductions during the NOx SIP call (2002 – 2005) and (2) future
projected emission changes planned for the Clean Air Interstate Rule (2010
and 2020). To estimate this sensitivity, we use the Community Multiscale
Air Quality (CMAQ) model. First, using the well-known emission changes
of the NOx SIP Call, we evaluate the CMAQ model predicted sensitivity
using monitoring network observations of concentration and deposition
for that time period. Second, we apply CMAQ to estimate concentrations
and deposition for the future years of 2010 and 2020 in response the Clean
Air Interstate Rule. By the year 2020, after substantial reductions in
SO2 and NOx emissions, we estimate large changes in the composition and
spatial extent of inorganic aerosol. This causes a highly variable change
in the spatial distribution of reduced nitrogen (NH3 + NH4 +) deposition.
Given only current monitoring network locations and speciation, this change
will not be well quantified. DISCLAIMER: The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. This work constitutes a contribution to the NOAA Air Quality Program. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views. |