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Characterizing the contrasting long-term trends in atmospheric nitrogen deposition across the Northern Hemisphere due to changing emission patterns during the 1990-2010 period
Citation:
Mathur, R., C. Hogrefe, Y. Zhang, J. Xing, AND H. Sharif. Characterizing the contrasting long-term trends in atmospheric nitrogen deposition across the Northern Hemisphere due to changing emission patterns during the 1990-2010 period. 2018 AGU Fall Meeting, Washington, DC, December 10 - 14, 2018.
Impact/Purpose:
The impacts of contrasting changes in emission patterns across the northern hemisphere, i.e., reductions in North America and Europe vs. increases across regions in Asia, on changing deposition amounts over terrestrial and aquatic ecosystems in these regions is analyzed and suggest that the exceedance of critical load thresholds has decreased at many locations in North America and Europe, but has increased across Asia. Thus, emission reductions directed at improving air quality have also helped reduce the amounts of nutrients and acidic substances deposited to sensitive ecosystems across the U.S.
Description:
A detailed understanding of the distribution and fate of atmospheric sulfur (SOx) and reactive nitrogen compounds (NOy and NHx) is desirable given their role in determining tropospheric acidic substances and particulate matter budgets and potential altering of sensitive ecosystems resulting from their atmospheric deposition. The ultimate fate of airborne SOx, NOy and NHx is removal by wet scavenging and dry deposition, which in turn lead to a variety of environmental effects including altering net primary production, acidification, eutrophication and other nutrient loading effects. The gas-particle partitioning of airborne reactive nitrogen regulates its transport distance since dry deposition velocity for fine particles is relatively low, and consequently their primary atmospheric sink is wet scavenging. Changing emissions patterns of NOx, NH3, and SO2 have altered both their atmospheric transport distances as well as deposition patterns and amounts. We model the changes in wet and dry deposition amounts of reactive nitrogen and sulfur over the 1990-2010 period using the Community Multiscale Air Quality model (CMAQ) coupled with the Weather Research and Forecast model (WRF). WRF-CMAQ simulations for this 21-year period were conducted over a domain covering the northern hemisphere using a horizontal resolution of 108km. Long-term trends in model wet deposition amounts, relative amounts of oxidized and reduced nitrogen, and relative amounts of wet and dry deposition of N and S, are compared with those inferred from available measurements. The impacts of contrasting changes in emission patterns across the northern hemisphere, i.e., reductions in North America and Europe vs. increases across regions in Asia, on changing deposition amounts over terrestrial and aquatic ecosystems in these regions is analyzed and suggest that the exceedance of critical load thresholds has decreased at many locations in North America and Europe, but has increased across Asia.
