The Airshed for Ozone and Fine Particulate Pollution in the Eastern United States

— To examine the spatial scales associated with atmospheric pollutants such as ozone (O₃) and fine particulate matter (PM_2.5), we employ the following five techniques: (1) Analysis of the persistence of high O₃ concentrations aloft; (2) spatial and lag correlations between the short-term components (i.e., weather-induced variations) in the time series of O₃ and PM_2.5 throughout the eastern United States; (3) analysis of mixed-layer forward trajectories compiled at different locations on a climatological basis to identify the potential region covered in 1-day of atmospheric transport; (4) analysis of three-dimensional Lagrangian trajectories of tracer particles for three high-O₃ episode events in the summer of 1995; and (5) analysis of the spatial extent over which emissions have an impact through photochemical model simulations. Regardless of the method chosen, the results demonstrate that pollutants such as O₃ and PM_2.5 have the potential to affect regions having spatial scales of several hundred kilometers. This finding has implications to regulatory policies for addressing the pollution problem, and for optimally designing monitoring networks for such pollutants.