Coordination Funds

反硝化作用是将活性氮以N2的形式返回大气的关键过程，它是硝酸盐还原过程，使微生物在厌氧条件下维持呼吸。不同的反应步骤（NO3- ->NO2- ->NO -> N2 O->N2）由广泛的原核生物和一些真核生物酶促介导。尽管人们对其进行了100多年的深入研究，但其气体产物的脱氮速率和排放量仍然不能令人满意地预测。在DASIM第一阶段，我们集中在实验室条件下的调查，从非常简单的系统，如玻璃珠重新填充土柱与热点和无热点。三个典型的中欧农业土壤被选中，其特征在于，并用于进行反硝化研究。重点是通过使用稳定同位素示踪方法（15 N和18 O）结合先进的微生物、土壤物理和土壤化学（例如有机物）调查，查明造成N2 O和N2产生的过程。此外，还通过µCT结合高分辨率3D建模对土壤微观结构进行了调查。在DASIM第二阶段，调查将转向更现实的系统，如完整的土芯和实地调查，特别是植物对根际反硝化作用的影响（如渗出模式）。将应用新的先进技术来测量N2排放，例如在减少的N2气氛下量化N2的方法或可以直接量化N2的拉曼光谱法。根据小规模测量，将开发放大功能，以便通过详细的土壤结构识别获得的信息也可以包括在生态系统模型中，特别是LandscapeDNDC中并进行测试。最终目标是更好地了解反硝化作用以及与N2 O和N2产生相关的过程及其通过数值模型进行的预测，这为获得合适的缓解技术提供了重要信息。

Denitrification, the process of nitrate reduction allowing microbes to sustain respiration under anaerobic conditions, is the key process returning reactive nitrogen as N2 to the atmosphere. The different reaction steps (NO3- ->NO2- ->NO ->N2O->N2) are enzymatically mediated by a broad range of prokaryotes and some eukaryotes. Despite being intensively studied for more than 100 years, denitrification rates and emissions of its gaseous products can still not be satisfactorily predicted. In DASIM phase I we have focused on investigations under laboratory conditions ranging from very simple systems such as glass beads to re-packed soil columns with and without hot spots. Three typical mid-European agricultural soils were selected, characterized and used to carry out denitrification studies. A focus was on the identification of processes responsible for N2O and N2 production via the use of stable isotope tracing methods (15N and 18O) in combination with advanced microbial, soil physical and soil chemical (e.g. organic matter) investigations. Moreover, investigation into the soil microsite structure were carried out via µCT in combination with high-resolution 3D modelling. In DASIM phase II the investigations will move to more realistic systems such as intact soil cores and field investigations and in particular the influence of plants (e.g. exudation pattern) on denitrification in the rhizosphere. New advanced techniques to measure N2 emissions will be applied such as a method where N2 is quantified under a reduced N2 atmosphere or Raman spectroscopy where N2 can directly be quantified. Based on the small-scale measurements, upscaling functions will be developed so that the information gained via the detailed soil structural identification can also be included and tested in ecosystems models, in particular LandscapeDNDC. The final aim is to obtain an improved understanding on denitrification and the processes associated with N2O and N2 production and their prediction with numerical models which provides important information to derive suitable mitigation techniques.