Assessment of HONO Measurements: The FIONA Campaign at EUPHORE

Abstract

HONO is an important source of OH-radicals, the major oxidant in the atmosphere during daytime that participates in ozone formation and can lead to photo-smog. Nevertheless, there are still many open questions about its formation and role as a source of OH-radicals. A better knowledge of HONO processes is highly desirable for the improvement of air pollution models, many of which do not currently include heterogeneous HONO production mechanisms. One reason for the uncertainties in the atmospheric role of HONO is the difficulty in measuring this species. To elucidate both aspects - chemical and instrumental issues - a HONO intercomparison campaign was carried out at the EUPHORE simulation chambers within the framework of the EUROCHAMP-2 project, in May 2010. EUPHORE provided a large and well-mixed gas volume for the simultaneous operation of multiple instruments under well controlled, realistic conditions. Ten experiments were carried out to simulate typical urban and semi-rural conditions and to address the following topics: (i) intercomparison of the different techniques, (ii) study of interferences (aerosols, nitrates, nitrites, NO2, etc.) and (iii) HONO sources (nitrophenols, vehicle emissions, ambient air, etc.). The first three experiments were part of an open-informal intercomparison while the rest of the intercomparison experiments were conducted under formally blind conditions with an external referee. The extensive participant list included the majority of groups working in this area globally, running simultaneously 18 techniques/instruments that covered nearly the whole range of techniques capable of measuring HONO. These included spectroscopic and chemical instruments. In this work, an overview of the campaign in terms of participants, instruments aim of the experiments, etc. is presented, as well as the results of a selected open experiment. © Springer Science+Business Media Dordrecht 2013.