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Abstract

Biogenic NOx emissions from natural and anthropogenically influenced soils are currently estimated to amount to 9 Tg a(-1), hence a significant fraction of global NOx emissions (45 Tg a(-1)). During the last three decades, a large number of field measurements have been performed to quantify biogenic NO emissions. To study biogenic NO emissions as a function of soil moisture, soil temperature, and soil nutrients, several laboratory approaches have been developed to estimate local/regional NO emissions by suitable upscaling. This study presents an improved and automated laboratory dynamic chamber system (consisting of six individual soil chambers) for investigation and quantification of all quantities necessary to characterise biogenic NO release from soil (i.e. net NO release rate, NO production and consumption rate, and respective Q(10) values). In contrast to former versions of the laboratory dynamic chamber system, the four experiments for complete characterisation can now be performed on a single soil sample, whereas former studies had to be performed on four sub-samples. This study discovered that the sub-sample variability biased former measurements of net NO release rates tremendously. Furthermore, it was also shown that the previously reported variation of optimum soil moisture (i.e. where a maximum net NO release rates occur) between individual sub-samples is most likely a methodical artefact of former versions of the laboratory dynamic chamber system.