Measurements of air concentrations of SO2, NO2 and NH3 at rural and remote sites in Asia

Sensitive diffusive samplers for concentration measurements in ambient air have been used successfully in Sweden for several years. The samplers have the advantage of being stable at room temperature before, as well as after, sampling, easy to handle, and cost-efficient. Furthermore, they do not require electricity or field calibration. In order to test their use in tropical and subtropical environments and to obtain a preliminary set of data to validate atmospheric chemistry transport models in this part of the world, duplicate samples were collected at 11 sites every second month during one year. Eight of the sites were background sites in Asia. It was not possible within the project to compare the measured concentrations with other measurement techniques. However, the reproducibility of the duplicates was satisfactory over the whole measuring range (almost three orders of magnitude of the concentration for SO2) and reasonable agreement with model calculations was obtained at least for SO2 and NH3. Further testing of the measuring technique in tropical areas is, however, warranted.