Ozone Levels in the Vicinity of 33 Cities

Abstract

Hourly concentrations of ozone were measured by the chemiluminescence method during the summer of 1971 in the vicinity of 33 cities. A listing was made of the percent of time the National Air Quality Standard for photochemical oxidants was violated. At 4 selected cities the daytime and nighttime average concentrations were related to wind directions showing the direction to source areas. Another set of tables and graphs was used to show the source directions for high concentrations (equal to or above 120 µg/m³) and disregarding the times of more usual or background concentrations. Numerous occasions of high ozone concentrations occurred when wind directions were apparently from areas with low concentrations of the known precursors. Because of this, other sources of ozone were considered such as thunderstorms and the transport of ozone for long distances. Examples of ozone concentrations during thunderstorms or related to long distance transport are cited.