HONO measurements with a chemical ionization mass spectrometer during FIONA

Nitrous acid (HONO) is an important source of the OH radical, the primary oxidant in the atmosphere. The chemistry of HONO and its possible sources in the atmosphere are not well understood. The aims of the FIONA (Formal Intercomparisons of Observations of Nitrous Acid) campaign are to establish a better understanding of HONO chemistry and to intercompare different measurement techniques. Data from 19 instruments from 9 countries including spectroscopy (DOAS, BBCEAS, LIF), wet chemistry, denuders and mass spectrometry were intercompared at typical urban and semi-rural conditions at the simulation chamber Euphore. During the FIONA campaign we deployed an Atmospheric chemical Ionization Mass Spectrometer (AIMS). The AIMS has extensively been calibrated to a gas-phase HONO source and interferences with other gases (particularly water) have been tested. We show first results of our mass spectrometric measurements. For specific observation conditions, the chemical ionization mass spectrometry can be used as a fast and sensitive method for the detection of HONO in the atmosphere