A Report on Laboratory and Field Testing of Current and Advanced Ozone Monitoring Technology

摘要

Ozone in the lower atmosphere is formed by photochemical processes involving sunlight, nitrogen oxides (NO_x) and volatile organic compounds (VOC). The Clean Air Act has established air quality standards for ozone and it requires that state and local authorities monitor ambient ozone levels to assess compliance with those standards. Areas that do not comply must propose and implement pollution control strategies to bring ozone concentrations into attainment. These strategies usually involve expensive reductions in VOC emissions, NO_x emissions, or both. Billions of dollars are spent on strategies to control ambient air ozone levels in the U.S. so it is essential that the measurements made to assess compliance with regulations be accurate. The method that is almost universally employed for ambient air ozone monitoring is ultraviolet (UV) photometry. In current practice the instrumentation utilizes a "scrubber" to remove ozone from the air stream to provide a reference or "zero" signal. Unfortunately the scrubbers have been shown to remove some atmospheric constituents that absorb light at the same wavelength as ozone, thus causing interference in the ozone measurement. Water vapor has also been found to interfere with the measurement under some circumstances.