Ozone is a colorless and odorless gas. It is the main component of smog and the most widespread air pollutant. Ozone is not emitted directly into the air, but is formed by reactions in the presence of sunlight and heat. Ozone can easily be transported and therefore its health endangering occurrence is not bound to its specific sources.
The diffusive sampler is based on the diffusion of ozone along a tube to an absorbing medium. The chemisorption of ozone takes place by reaction with Sodium nitrite. In the presence of ozone, the nitrite ion are oxidized to nitrate ions : NO2 – + O3 NO3 – + O2 The passive samplers are constructed with a polypropylene housing with an opening of 20 mm in diameter. To reduce wind disturbance a membrane is attached, supported by a wire net. At the closed end there is a glass fibre filter dipped in a solution of sodiumnitrite in acetic acid. The amount of nitrate is determined by ion hromatography.