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We developed an automated system for measuring a) simultaneous vertical profiles (three levels) of Radon (222Rn (here Rn)) and Thoron (220Rn (here Tn)), and b) soil fluxes of Rn and CO2 with three static chambers. For the Rn/Tn profiles three Rn/Tn-discriminative RAD7 monitors (Durridge, USA) were used. The static chambers were sequentially closed, and the measurements of Rn and CO2 were performed using an ALPHAGUARD (Saphymo, Germany) and a GMT222 (Vaisala, Finland), respectively. This system was complemented by simultaneous profile measurements of NO, NO2, O3, CO2, and H2O. Measurements were performed during two month (28th of July - 26th of September 2011) on the estate of the Mainz Finthen Airport (Mainz, Germany (49.969° N, 8.148° E)). The vegetation type at the site is classified as a nutrient-poor steppe-like grassland ecosystem. The inlets of the Rn/Tn and trace gas profiles were installed within the canopy at 0.04m, 0.20m and 0.80m above ground level. We will present the setup of our Rn/Tn system and investigate the performance. The residence time of the air (τturb) within the grass canopy will be determined at different levels including rigorous error estimation. Additionally, we will present calculated bulk diffusion coefficients (Kbulk) within the canopy by using the Rn and CO2 profiles in combination with the soil fluxes. We will compare τturb and the chemical conversion timescales (τchem) within the NO-NO2-O3-triad represented by the Damköhler numbers (DA = τturb / τchem). Using this method, the influence of chemical divergence on exchange fluxes within and above the canopy can be studied. |
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