Deep denitrification: Stream and groundwater biogeochemistry reveal contrasted but connected worlds above and below
Deep denitrification: Stream and groundwater biogeochemistry reveal contrasted but connected worlds above and below
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深度反硝化：溪流和地下水生物地球化学揭示了上下截然不同但又相互联系的世界
DOI：
10.1016/j.scitotenv.2023.163178
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发表时间：
2023
影响因子：
9.8
通讯作者：
Vautier, Camille
中科院分区：
文献类型：
--
作者：
Severe, Emilee;Errigo, Isabella M.;Proteau, Mary;Sayedi, Sayedeh Sara;Kolbe, Tamara;Marçais, Jean;Thomas, Zahra;Petton, Christophe;Rouault, François;Vautier, Camille
农业和城市发展带来的过量养分在地球仪各地造成了一系列生态危机。营养物污染引发了大多数淡水和沿海生态系统的富营养化，导致生物多样性丧失，危害人类健康，每年造成数万亿美元的经济损失。关于养分运输和保持的研究大多集中在地表环境，因为地表环境既容易获取，又具有生物活性。然而，流域的表面特征，如土地利用和网络配置，往往不能解释在河流，湖泊和河口观察到的养分保留的变化。最近的研究表明，地下过程和特征可能比以前认为的更重要，在确定流域级营养盐通量和去除。在法国西部的一个小流域，我们使用了多示踪剂的方法来比较地表和地下硝酸盐动态在相称的时空尺度。我们结合了三维水文模型与丰富的地球化学数据集，从20个威尔斯和15个溪流位置。水化学在地表和地下表现出很高的时间变异性，但地下水的空间变异性更大，这是由于长的运输时间（10-60年）和补丁分布的铁和硫电子供体燃料自养反硝化。硝酸盐和硫酸盐的同位素揭示了根本不同的过程占主导地位的表面（异养反硝化和硫酸盐还原）和地下（自养反硝化和硫酸盐生产）。农业土地利用与地表水硝酸盐含量升高有关，但地下硝酸盐浓度与土地利用无关。溶解的二氧化硅和硫酸盐是停留时间和脱氮的可负担的示踪剂，在地表和地下环境中相对稳定。总之，这些发现揭示了地表和地下不同但相邻和相连的地球化学世界。描述这些世界是如何联系和分离的，对于实现水质目标和解决人类世的水问题至关重要。
Excess nutrients from agricultural and urban development have created a cascade of ecological crises around the globe. Nutrient pollution has triggered eutrophication in most freshwater and coastal ecosystems, contributing to a loss in biodiversity, harm to human health, and trillions in economic damage every year. Much of the research conducted on nutrient transport and retention has focused on surface environments, which are both easy to access and biologically active. However, surface characteristics of watersheds, such as land use and network configuration, often do not explain the variation in nutrient retention observed in rivers, lakes, and estuaries. Recent research suggests subsurface processes and characteristics may be more important than previously thought in determining watershed-level nutrient fluxes and removal. In a small watershed in western France, we used a multi-tracer approach to compare surface and subsurface nitrate dynamics at commensurate spatiotemporal scales. We combined 3-D hydrological modeling with a rich biogeochemical dataset from 20 wells and 15 stream locations. Water chemistry in the surface and subsurface showed high temporal variability, but groundwater was substantially more spatially variable, attributable to long transport times (10–60 years) and patchy distribution of the iron and sulfur electron donors fueling autotrophic denitrification. Isotopes of nitrate and sulfate revealed fundamentally different processes dominating the surface (heterotrophic denitrification and sulfate reduction) and subsurface (autotrophic denitrification and sulfate production). Agricultural land use was associated with elevated nitrate in surface water, but subsurface nitrate concentration was decoupled from land use. Dissolved silica and sulfate are affordable tracers of residence time and nitrogen removal that are relatively stable in surface and subsurface environments. Together, these findings reveal distinct but adjacent and connected biogeochemical worlds in the surface and subsurface. Characterizing how these worlds are linked and decoupled is critical to meeting water quality targets and addressing water issues in the Anthropocene.