The atmosphere interacts with the terrestrial watersheds below in many ways. Air pollution disperses quickly over large regions. Figures 3.12 through 3.15 show regional patterns of estimated annual sulfate and nitrate deposition and cumulative annual ozone concentrations, averaged over several years. The lowest levels occur in central and southern Virginia, and along the extreme western portion of the region. This regional pattern of nitrate deposition may reflect prevailing winds from the west that carry air pollutants from other regions.
Terrestrial features can influence pollution deposition indirectly.
The surface maps of sulfate and nitrate deposition appear almost identical because the measurement scales have been normalized to make it easier to see relative trends across the region. This also helps to highlight the topographic effect on air pollution deposition. The ozone index is not closely associated with topography, but rather with the distribution of urban and agricultural areas. Even at this coarse scale, there are obvious differences across the mid-Atlantic. J. Lynch, Pennsylvania State University.