The Determination of Ozone in Ambient Air with Free Hanging Filters as Passive Samplers
2012
Adema, E. H. | Heeres, P. | Rahayuningsih, H Aprita | Rineksa, S.
This paper describes the use of dry free hanging filters, as passive samplers to determine ozone in the ambient air. The filters, with a diameter of 25 mm, were impregnated with 5,5′-disodium indigo disulphonate (IDS), a reagent for ozone. From the amount of reacted indigo compound, found on the filter, and the ozone concentration in the ambient air, a pseudo rate constant k ₁, of the reaction between ozone (O₃) and IDS on the filter, is calculated. The range of measurement is between 9 and 205 μg/m³ ambient ozone. The dry filter method is specific for ozone, while the Dutch standard method NEN2789, based on an aqueous solution of IDS, has to be corrected for the presence of NO ₓ . From wind tunnel and field experiments, k ₁ proved to vary between 0.7 and 1.5 × 10⁻⁶ m³ s⁻¹ (μg O₃)⁻¹ at wind velocities between 1 and 3 m/s and at an exposure time of 60 min. Within these conditions, ozone concentrations have been determined with free hanging filters in four busy streets in Yogyakarta, Indonesia and at two background sites using an average value of k ₁ of 1.2 × 10⁻⁶. Subsequently, the traffic NO emission was estimated from the difference of the O₃ concentrations at both sides of a road. For an arbitrary situation, an NO emission of 255 μg/s per metre road length was calculated. The filter method is inexpensive and practical, needs no electricity, is easily assembled and can be used to perform measurements in remote areas. It is shown here that this simple measurement technique may support air quality studies, e.g., in developing countries.
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