Aquifers under agricultural areas are considered to be an indirect source of nitrous oxide emission (N₂O) to the atmosphere, which is the greenhouse gas (GHGs) characterized with the highest global warning potential and acts as a stratospheric ozone depletion agent. Previous investigations performed in the Cretaceous Hesbaye chalk aquifer in Eastern Belgium suggested that the dynamics of N₂O in the aquifer is controlled by overlapping biochemical processes such as nitrification and denitrification. The current study aims to obtain better insight concerning the factors controlling the distribution of N₂O concentration along a vertical dimension in the aquifer, and to capture and quantify the occurrence of nitrification and denitrification processes in the groundwater system. Low-flow groundwater sampling technique was undertaken at different depths in the aquifer to collect groundwater samples aiming at obtaining information about ambient aquifer hydrogeochemical conditions and their effect on the accumulation of GHGs. Afterwards, laboratory stable isotope experiments, using NO₃⁻ and NH₄⁺ compounds labeled with heavy ¹⁵N isotope, were applied to quantify the rates of nitrification and denitrification processes. Ambient studies suggest that the occurrence of N transformation was related to denitrification while laboratory incubation experiments did not detect it. Such controversial results might be explained by the discrepancy between real aquifer conditions and lab design studies. Thus, additional in situ tracer experiments should be carried out in areas where natural groundwater fluxes do not flush the injected tracer too rapidly. In addition, it would be useful to conduct microbiological studies to obtain better insight into the nature of subsurface biofilm biotope.

农业区下的含水层被认为是向大气排放一氧化二氮 (N ₂ O)的间接来源，这是一种温室气体 (GHG)，具有最高的全球预警潜力，并充当平流层臭氧消耗剂。先前在比利时东部白垩纪 Hesbaye 白垩含水层中进行的调查表明，含水层中 N ₂ O的动态受到重叠的生化过程（如硝化和反硝化）的控制。目前的研究旨在更好地了解控制 N ₂分布的因素。沿含水层垂直方向的 O 浓度，并捕获和量化地下水系统中硝化和反硝化过程的发生。在含水层不同深度采用低流量地下水采样技术采集地下水样品，旨在获取有关周围含水层水文地球化学条件及其对温室气体积累影响的信息。之后，实验室稳定同位素实验，使用 NO ₃ ^-和 NH ₄ ⁺化合物标记为重¹⁵N 同位素用于量化硝化和反硝化过程的速率。环境研究表明，N 转化的发生与反硝化作用有关，而实验室孵化实验未检测到。这种有争议的结果可能是由于实际含水层条件与实验室设计研究之间的差异所致。因此，应在天然地下水通量不会过快冲洗注入示踪剂的地区进行额外的原位示踪剂实验。此外，进行微生物学研究以更好地了解地下生物膜生物群落的性质将是有用的。