Floodplains play a crucial role in water quality regulation via denitrification. This biogeochemical process reduces nitrate (NO 3 − ), with aquifer saturation, organic carbon (OC) and N availability as the main drivers. To accurately describe the denitrification in the floodplain, it is necessary to better understand nitrate fluxes that reach these natural bioreactors and the transformation that occurs in these surface areas at the watershed scale. At this scale, several approaches tried to simulate denitrification contribution to nitrogen dynamics in study sites. However, these studies did not consider OC fluxes influences, hydrological dynamics and temperature variations at a daily time step. This paper focuses on a new model that allows insights on nitrate, OC, discharge and temperature influences on daily denitrification for each water body. We used a process-based deterministic model to estimate daily alluvial denitrification in different watersheds showing various pedo-climatic conditions. To better understand global alluvial denitrification variability, we applied the method to three contrasting catchments: The Amazon for tropical zones, the Garonne as representative of the temperate climate and the Yenisei for cold rivers. The Amazon with a high discharge, frequent flooding and warm temperature, leads to aquifers saturation, and stable OC concentrations. Those conditions favour a significant loss of N by denitrification. In the Garonne River, the low OC delivery limits the denitrification process. While Arctic rivers have high OC exports, the low nitrate concentrations and cold temperature in the Yenisei River hinder denitrification. We found daily alluvial denitrification rates of 73.0 ± 6.2, 4.5 ± 1.4 and 0.7 ± 0.2 kgN ha −1 y −1 during the 2000–2010 period for the Amazon, the Garonne and the Yenisei respectively. This study quantifies the floodplains influence in the water quality regulation service, their contribution to rivers geochemical processes facing global changes and their role on nitrate and OC fluxes to the oceans.

中文翻译：

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对比土壤气候和人为背景下洪泛平原的每日反硝化率：流域尺度建模

漫滩通过反硝化作用在水质调节中发挥着至关重要的作用。这种生物地球化学过程减少了硝酸盐 (NO 3 - )，含水层饱和度、有机碳 (OC) 和 N 可用性是主要驱动因素。为了准确描述漫滩中的反硝化作用，有必要更好地了解到达这些天然生物反应器的硝酸盐通量以及在流域尺度这些表面区域发生的转化。在这个规模上，有几种方法试图模拟反硝化作用对研究地点氮动力学的贡献。然而，这些研究没有考虑每天时间步长的 OC 通量影响、水文动力学和温度变化。本文重点介绍一种新模型，该模型可以深入了解硝酸盐、有机碳、排放和温度对每个水体日常反硝化的影响。我们使用基于过程的确定性模型来估计显示各种土壤气候条件的不同流域的每日冲积反硝化作用。为了更好地了解全球冲积反硝化作用的变化，我们将该方法应用于三个对比鲜明的集水区：热带地区的亚马逊河、温带气候的代表加龙河和寒冷河流的叶尼塞河。亚马逊河流域流量大、洪水泛滥、温度高，含水层饱和，有机碳浓度稳定。这些条件有利于通过反硝化作用显着损失 N。在加龙河，低 OC 输送限制了反硝化过程。虽然北极河流的 OC 出口量很高，但叶尼塞河的低硝酸盐浓度和寒冷的温度阻碍了反硝化作用。我们发现亚马逊、加龙河和叶尼塞河在 2000-2010 年期间的每日冲积反硝化率分别为 73.0 ± 6.2、4.5 ± 1.4 和 0.7 ± 0.2 kgN ha -1 y -1。本研究量化了漫滩对水质调节服务的影响、它们对面临全球变化的河流地球化学过程的贡献以及它们对流入海洋的硝酸盐和 OC 通量的作用。