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

Abstract

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 dm(3) min(-1). NO was collected using guaiacol by oxidizing it to NO2 with potassium permanganate at a 0.3 dm(3) 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 dm(3) 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.