Simultaneous Sampling of NO, NO2, HONO and HNO3 in the Atmosphere by a Filter-Pack Method

　　A simultaneous sampling method for gaseous nitric oxide (NO), nitrogen dioxide (NO2), nitrous acid (HONO) and nitric acid (HNO3) was developed by a filter-pack sampling method to measure these concentrations at low cost in areas where monitoring stations are not available or at multiple locations. HONO and HNO3 gases were collected with a conventional filter-pack method. NO2 was collected with a guaiacol-impregnated filter at a flow rate of 0.3 dm3 min?1. NO was collected using guaiacol by oxidizing it to NO2 with potassium permanganate at a 0.3 dm3 min?1 flow rate. The optimum concentration of KMnO4 in the immersion solution for the impregnated filter was 0.16 mol dm?3 (in 0.51 mol dm?3 H2SO4). The concentrations of NO and NO2 measured by the filter-pack method were in good agreement with those measured by the chemiluminescence method. It was calculated that 60 ppb NO could be oxidized to NO2 with the KMnO4-impregnated filter for 183 hours at a 0.3 dm3 min?1 flow rate. This is enough time for sampling in a real environment. This method was applied to measure NO, NO2, HONO and HNO3 in the atmosphere at three points around Osaka, Japan.

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