Hydrologic regimes drive nitrate export behavior in human-impacted watersheds
Hydrologic regimes drive nitrate export behavior in human-impacted watersheds
复制标题
水文状况驱动受人类影响的流域的硝酸盐输出行为
DOI：
10.5194/hess-25-1333-2021
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发表时间：
2021
影响因子：
6.3
通讯作者：
M. Zimmer
中科院分区：
文献类型：
--
作者：
G. Gorski;M. Zimmer
摘要。农业流域是造成下游养分过剩问题的重要因素。这些流域养分动员的时间和规模是由一系列时空尺度上的人为、水文和生物地球化学因素共同驱动的。然而，这些复杂因素如何、何时以及在何处驱动养分动员，以前很难用低频或空间有限的数据集来捕捉。为了解决这一知识差距，我们分析了美国中西部五个巢式农业流域4年（2016-2019年）的每日硝酸盐浓度(c)和排放量(Q)数据，这些数据为墨西哥湾提供了营养负荷。这些记录使我们能够以以前不可能的时间和空间分辨率调查营养动员模式。由于冰川历史的不同，流域跨越了两种截然不同的地貌，这导致了自然土壤性质的不同，需要在研究区域内建立不同的排水基础设施。为了研究不同水文条件下的养分输出模式，我们将水文曲线划分为暴雨期和基流期，并通过分析它们在年、季节和事件时间尺度上的浓度-流量（c-Q）关系来分别考察这两个时期。暴雨流在各季节表现出一致的化学静态模式，而基流则表现出季节动态的c-Q模式。基流在夏季和秋季表现为化学动力状态，而在冬季和春季表现为化学稳态状态，表明水源对基流的贡献是非平稳的。基流化学动力学行为是由低流量、低NO3-条件驱动的，在此条件下，流内和近流生物处理可能会调节流内NO3-浓度。此外，深层地下水的输入，其停留时间较长，no3 -浓度较低，可能是造成河流低no3 -状况的原因，特别是在较大的流域。暴雨流c-Q行为在整个流域是一致的，但基流c-Q行为与农业强度和已建排水基础设施的密度有关，更多的排水基础设施与更高的负荷和更多的流域化学稳态输出模式相关。这表明，人类根据地质条件重新调整地下的方式对水文连通性、源区的均质化以及随后在基流和暴雨流期间的养分输出都有影响。我们的分析还表明，异常流量周期极大地影响了总体c-Q模式，这表明在解释季节或年模式时，多尺度高分辨率记录的分析至关重要。
Abstract. Agricultural watersheds are significant contributors to downstream nutrient excess issues. The timing and magnitude of nutrient mobilization in these watersheds are driven by a combination of anthropogenic, hydrologic, and biogeochemical factors that operate across a range of spatial and temporal scales. However, how, when, and where these complex factors drive nutrient mobilization has previously been difficult to capture with low-frequency or spatially limited data sets. To address this knowledge gap, we analyzed daily nitrate concentration (c) and discharge (Q) data for a 4-year period (2016–2019) from five nested, agricultural watersheds in the midwestern United States that contribute nutrient loads to the Gulf of Mexico. These records allow us to investigate nutrient mobilization patterns at a temporal and spatial resolution not previously possible. The watersheds span two distinct landforms shaped by differences in glacial history, resulting in natural soil properties that necessitated different drainage infrastructure across the study area. To investigate nutrient export patterns under different hydrologic conditions, we partitioned the hydrograph into stormflow and baseflow periods and examined those periods separately through the analysis of their concentration–discharge (c–Q) relationships on annual, seasonal, and event timescales. Stormflow showed consistent chemostatic patterns across all seasons, while baseflow showed seasonally dynamic c–Q patterns. Baseflow exhibited chemodynamic conditions in the summer and fall and more chemostatic conditions in the winter and spring, suggesting that water source contributions during baseflow were nonstationary. Baseflow chemodynamic behavior was driven by low-flow, low-NO3- conditions during which in-stream and near-stream biological processing likely moderated in-stream NO3- concentrations. Additionally, inputs from deeper groundwater with longer residence times and lower-NO3- concentration likely contributed to low-NO3- conditions in stream, particularly in the larger watersheds. Stormflow c–Q behavior was consistent across watersheds, but baseflow c–Q behavior was linked to the intensity of agriculture and the density of built drainage infrastructure, with more drainage infrastructure associated with higher loads and more chemostatic export patterns across the watersheds. This suggests that the way humans replumb the subsurface in response to geologic conditions has implications for hydrologic connectivity, homogenization of source areas, and, subsequently, nutrient export during both baseflow and stormflow. Our analysis also showed that anomalous flow periods greatly influenced overall c–Q patterns, suggesting that the analysis of high-resolution records at multiple scales is critical when interpreting seasonal or annual patterns.
影响因子：
18.3
作者：
Hansen, Amy T.;Dolph, Christine L.;Finlay, Jacques C.
通讯作者：
Finlay, Jacques C.
影响因子：
4
作者：
W. Wollheim;Susana Bernal;Douglas A. Burns;J. Czuba;Charles T. Driscoll;Amy T. Hansen;Robert T. Hensley;Jacob D. Hosen;Shreeram Inamdar;S. Kaushal;L. Koenig;YueHan Lu;A. Marzadri;Peter A. Raymond;Durelle T. Scott;R. J. Stewart;P. Vidon;Ellen Wohl
通讯作者：
W. Wollheim;Susana Bernal;Douglas A. Burns;J. Czuba;Charles T. Driscoll;Amy T. Hansen;Robert T. Hensley;Jacob D. Hosen;Shreeram Inamdar;S. Kaushal;L. Koenig;YueHan Lu;A. Marzadri;Peter A. Raymond;Durelle T. Scott;R. J. Stewart;P. Vidon;Ellen Wohl
影响因子：
9.8
作者：
Bowes, M. J.;Jarvie, H. P.;Palmer-Felgate, E. J.
通讯作者：
Palmer-Felgate, E. J.