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SEASONAL AND REGIONAL AIR QUALITY AND ATMOSPHERIC DEPOSITION IN THE EASTERN US
Citation:
Sickles II, J. E. AND D. SHADWICK. SEASONAL AND REGIONAL AIR QUALITY AND ATMOSPHERIC DEPOSITION IN THE EASTERN US. JOURNAL OF GEOPHYSICAL RESEARCH. American Geophysical Union, Washington, DC, 112(d17302):doi:10.1029, (2007).
Impact/Purpose:
Our main objective is to assess the exposure of selected ecosystems to specific atmospheric stressors. More precisely, we will analyze and interpret environmental quality (primarily atmospheric) data to document observable changes in environmental stressors that may be associated with legislatively-mandated emissions reductions.
Description:
Dry concentration and dry and wet deposition of selected air pollutants monitored over two 5-year periods in the 1990s at or near 34 rural Clean Air Status and Trends Network (CASTNET) sites located in the eastern US are adjusted for known biases, composed into seasonal values, and examined. Similar patterns of seasonal and regional behavior are found consistently in both periods. In the east, dry concentration, deposition velocity, precipitation rate, and dry, wet, and total deposition of each of the monitored chemical constituents display regular seasonal cycles of behavior. High and low seasonal values occur in summer and winter, respectively, for dry concentration and dry deposition of SO42-, NH4+, O3, HNO3, and monitored oxidized plus reduced nitrogen (N); for dry oxidized nitrogen (Nox) deposition; for wet sulfur and H+ deposition; and for total dry plus wet Nox and N deposition. In contrast, high seasonal values of dry SO2 concentration and deposition and dry NO3- concentration occur in winter. In the east, SO2 composes a major portion (¡Ö70%) of the airborne dry sulfur concentration and is the dominant (>85%) contributor to dry sulfur deposition. Although NH4+ represents a major portion of the dry N concentration (¡Ö65%), HNO3 dominates both dry Nox (>90%) and N (>75%) deposition. Wet deposition is a major contributor to total deposition, generally peaking in summer or spring. Total sulfur, Nox, and N deposition peak in summer. Although mean O concentration is ¡Ö70% larger in summer than winter, dry O3 deposition in the east is >5 times higher in summer. Dry deposition of SO4 2-, HNO3, Nox, N, and O3 is the highest at the high elevation subset of sites, underscoring the importance of dry deposition as a stressor to high elevation ecosystems in the east.