Department of Groundwater and Quaternary Geology Mapping, Geological Survey of Denmark and Greenland (GEUS), C.F. Møllers Allé 8, Building 1110, 8000 Aarhus, Denmark.
Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, 1350 Copenhagen, Denmark.
Environ Sci Technol. 2021 Dec 7;55(23):15821-15830. doi: 10.1021/acs.est.1c04593. Epub 2021 Nov 22.
The spatial and temporal variability of denitrification makes it challenging to integrate conceptual, process-based understandings of nitrate transport and retention into numerical modeling at the catchment scale, although it is critical for the realism and predictive power of the model. In this study, we propose a novel approach where the conceptual understandings of the spatial structure of denitrification zones and the corresponding representative denitrification rates are transformed into a form that can be integrated into a multi-point statistical simulation framework. This is done by constructing a denitrification training image (TI) coupled to a geophysically based TI of the hydrogeological structure. The field observations and laboratory analyses of denitrification rates and the chemistry of water and sediment revealed that the study catchment's subsurface can be characterized by three zones: (1) the oxic zone with no nitrate reduction; (2) the slow-denitrification zone (mean of ln-transformed rate = -1.19 ± 0.52 mg N L yr); and (3) the high-denitrification zone (mean of ln-transformed rate = 3.86 ± 1.96 mg N L yr). The underlying controls on the spatial distribution of these zones and the representativeness of denitrification rates were investigated. Then, a TI illustrating the subsurface structure of the denitrification zone was constructed by synthesizing the results of these geochemical interpretations and the hydrogeology TI.
反硝化的时空变异性使得将硝酸盐输运和保留的概念性、基于过程的理解整合到流域尺度的数值模型中具有挑战性，尽管这对于模型的现实性和预测能力至关重要。在本研究中，我们提出了一种新方法，即将反硝化带空间结构的概念性理解和相应的代表性反硝化速率转化为可以整合到多点统计模拟框架中的形式。这是通过构建一个与基于地球物理的地下水文结构 TI 耦合的反硝化训练图像 (TI) 来实现的。对反硝化速率以及水和沉积物化学的现场观测和实验室分析表明，研究流域的地下可以用三个区来描述：(1) 没有硝酸盐还原的好氧区；(2) 慢速反硝化区（ln 转化速率的平均值 = -1.19 ± 0.52 mg N L yr）；和 (3) 高反硝化区（ln 转化速率的平均值 = 3.86 ± 1.96 mg N L yr）。调查了这些区的空间分布和反硝化速率的代表性的潜在控制因素。然后，通过综合这些地球化学解释和地下水文 TI 的结果，构建了一个说明反硝化区地下结构的 TI。
