Environ. Sei. Technol. 1083, 17, 402-407
Evidence of en Additive Effect for Ozone Plumes from Small Cities Ken Sexton Department of Environmental Science and Physiology, School of Public Health, Harvard University, Boston, Massachusetts 021 15
Results of an aerial monitoring program examining ozone plumes from small cities (population 200000) and major metropolitan areas. Oxidant transport has been documented downwind of several major U S . cities, including New York (1-3), St. Louis (4,5), Chicago (6),Milwaukee (3,Philadelphia (8, 9), Houston (10, 111, Los Angeles (12),and Boston (13). Urban plumes often stretch over 100 miles downwind, with significant effects on local pollution levels. Plumes from large cities are typically tens of miles wide and contain elevated concentrations of ozone and ozone precursors. Photochemical ozone buildup within urban plumes is commonly on the order of 100-200 ppb above ambient background levels (14). Oxides of nitrogen concentrations increase approximately 20-fold inside plume boundaries, while in-plume non-methane hydrocarbon values can be several hundred times background levels (14, 15). Official efforts to reduce photochemical ozone formation due to anthropogenic emissions have focused on hydrocarbon controls, although increasing attention is being given to the importance of nitrogen oxides (NO,) emission reductions. In general, current oxidant control strategies rely on the theory that ozone transport will be reduced or eliminated as major upwind urban areas (population >200000) are brought into control (16). One of the problems with this approach is its failure to consider the contribution of pollutant emissions from small cities (population
