MEASUREMENT OF AMBIENT OZONE USING A NITRITE-COATED FILTER

Standard ozone monitoring techniques utilize large, heavy, and expensive instruments that are not easily adapted for personal or microenvironmental monitoring. For large-scale monitoring projects, where spatial variations of a pollutant and human exposure assessments are of interest, passive sampling devices can provide the methodology to meet monitoring and statistical goals. Recently we developed a coated filter for ozone collection that we used in a commercially available passive sampling device. Results from the ozone sampler validation tests are presented. The passive ozone sampler used in field and laboratory experiments consists of a badge clip supporting a barrel-shaped body which contains two coated glass fiber filters. The principal component of the coating is nitrite ion, which in the presence of ozone is oxidized to nitrate ion on the filter medium, NO2- + O3 --> NO3- + O2. After sample collection, the filters are extracted with ultrapure water and analyzed for nitrate ion by ion chromatography. The results from laboratory and field validation tests indicate excellent agreement between the passive method and standard ozone monitoring techniques. We have determined that relative humidity (ranging from 10 to 80 %) and temperature (ranging from 0 to 40-degrees-C) at typical ambient ozone levels (40-100 ppb) do not influence sampler performance. Face velocity and sampler orientation with respect to wind direction affected the sampler's collection rate of ozone. By using a protective cup which acts as both a wind screen and a rain cover, we were able to obtain a constant collection rate over a wide range of wind speeds.