COMPARISON OF PASSIVE AND ACTIVE SAMPLING METHODS FOR THE DETERMINATION OF NITROGEN-DIOXIDE IN URBAN AIR

Three different methods for sampling and determination of nitrogen dio xide in urban air are compared: an NO/NOx-monitor and an active (pumpe d) and a passive sampling method. For the latter two methods, sodium i odide is used as absorbent. For weekly averages the results from the p assive sampler are within 10-20% of the results for the two other meth ods in the concentration range 15-30 mu g NO2/m(3). The detection limi t for the passive sampler is 1 mu g NO2/m(3) (7 days), the precision i s 5% and the accuracy is estimated to 20%. The active iodide method ag rees very well with the NO/NOx-monitor. Compared on 24 h basis for a p eriod of 3 months, covering a concentration range of 5-45 mu g NO2/m(3 ), the deviation between the two methods is within 5%, and the absorpt ion capacity of the iodide reagent is excellent as the breakthrough is below 1%.