Regensburg 2007 – scientific programme
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UP: Fachverband Umweltphysik
UP 14: Poster: Heterogene Prozesse in der Atmosphäre - gemeinsam mit dem Arbeitskreis Atmosphärenchemie (AKAC) der GDCh
UP 14.1: Poster
Tuesday, March 27, 2007, 14:00–15:00, Poster C
Light induced uptake of NO2 on submicron humic acid aerosol — •Jörg Kleffmann1, Markus Ammann2, Birger Bohn3, Yasin Elshorbany1, Christian George4, Marieme Ndour4, and Konrad Stemmler2 — 1Bergische Universität Wuppertal, Germany — 2Paul Scherrer Institut, Villigen, Switzerland — 3Forschungszentrum Jülich, Germany — 4University Claude Bernard, (UCBL-CNRS), Villeurbanne, France
Recent field studies have demonstrated that the contribution of HONO to the OH radical production during daytime has been underestimated and indicated the existence of strong photolytic sources of HONO. A potential source is the light induced heterogeneous conversion of NO2 into HONO on humic acid surfaces, which was recently investigated on bulk surfaces. In the present laboratory study, we extended these studies to humic acid aerosols, which were generated by a nebulizer. The aerosol was transferred into a flow reactor and irradiated (300-700 nm) under controlled atmospheric conditions (humidity, NO2 concentration, etc.). HONO was detected using a selective and sensitive instrument (LOPAP), while the particle surface was quantified by a SMPS and an electrostatic precipitator. Similar to our recent study on bulk surfaces, a clearly photoinduced formation of HONO was observed, which was linear correlated with the aerosol surface and the reaction time. The experimental results are compared with the bulk study and a mechanism is presented to explain the experimental observations. In addition, the contribution to the primary production of OH radicals in the atmosphere is estimated.