Evaluation Of Oxidant Results At Camp Sites In The United States

Abstract

The oxidant measurements available between 1964 and 1973 at the six CAMP sites (Chicago, Cincinnati, Denver, Philadelphia, St. Louis, and Washington, D. C.) have been evaluated.Elevated oxidant concentrations have been characterized by season of the year, hour of the day, Sunday compared to weekdays, sampling site, trend with time.Differences in results among the CAMP sites can be associated with effects of altitude, local climatology, and chemical characteristics.With the exception of Chicago, a large downward trend in oxidant concentrations has been occurring at CAMP sites.However, there also are experimental results indicating that the factors responsible for this downward trend in central city locations may not be causing a proportional downward trend at suburban sites within urban areas or downwind sites outside urban areas.These CAMP results are consistent with other results obtained elsewhere in the United States.However, the present experimental results appear inadequate to permit proper optimization of control strategies.Adequate attention to these problems is urgently needed in view of their implications, not only with respect to air standards, but to transportation controls, land use, and energy policy.Eight or more years of oxidant concentration measurements are available from 1964 through 1973 from the continuous air monitoring program (CAMP) sites in Chicago, Cincinnati, Denver, Philadelphia, St. Louis, and Washington, D. C. Based on these results, various associations of oxidant with season of year, Sundays compared to weekdays, hour of day, concentration interval, and site have been developed.A definite trend downward occurred in frequency of days and highest concentration values above the EPA oxidant standard of 0.08 ppm during the time period investigated.The results at CAMP sites also are compared with those available at other sites in the U. S. ProcedureDays were tabulated on which the maximum total oxidant concentration equalled or exceeded 0.07 ppm for one or more hours per 24 hr period.These results were obtained from the hourly aerometric records for the CAMP sites in Chicago, Cincinnati, Denver, Philadelphia, St. Louis, and Washington, D. C. 1 Atmospheric oxidants were measured by use of colorimetric analyzers in which the oxidants in the sample gases were reacted with a buffered 10% potassium iodide solution.The oxidants react with potassium iodide to free iodide.Double beam colorimeter cells were used to measure the triiodide ion spectrophotometrically at 352 pm. 2 A chromic acid paper absorber was added to remove sulfur dioxide from the sample stream starting in 1964. 3Oxidant