Diffusive sampling is suitable for two or three-dimensional mapping - weekly to

monthly measurements - of air concentrations in an urban area. Diffusive samplers are

simple and cheap and the procedure can produce a large amount of long term air

quality data to a fairly low cost. In combination with other measurements with higher

temporal resolution, the passive sampling is valuable for the total air quality

assessment. However the diffusive samplers need validation.

The NO2 collected on the impregnated filter is extracted from the filter with water and

determined by chemical analysis. When calculating the concentration, the ambient air

temperature must be taken into consideration, since the diffusion velocity is

temperature dependent. Studies on the accuracy of diffusive samplers in comparison

with other monitoring techniques for NO2 show a good agreement with

chemiluminescence measurements, as well as with the potassium iodide method

(Svanberg et al., 1994, Ferm & Svanberg 1997), (Saeger, 1996).The diffusive

sampling technique for other urban pollutants, such as NO has also been recently

developed by the Ogawa Co, and by other organisations (Ferm and Sjödin, 1993;

Saeger, 1996), for SO2 (Carmichael et al. 1995; Ferm and Svanberg, 1997), for VOC

(Svanberg et al., 1994, 1995) and for O3 (Koutrakis et al., 1993).

 

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