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Title (Primary) Long-term nitrate trajectories vary by season in Western European catchments
Author Ebeling, P.; Dupas, R.; Abbott, B.; Kumar, R.; Ehrhardt, S.; Fleckenstein, J.H.; Musolff, A.
Journal Global Biogeochemical Cycles
Year 2021
Department CHS; HDG
Volume 35
Issue 9
Page From e2021GB007050
Language englisch
Topic T5 Future Landscapes
Keywords Catchment hydrology; Nitrate seasonality; Water quality; Long-term trends; Eutrophication; Controls
Abstract Human alteration of nutrient cycles has caused persistent and widespread degradation of water quality around the globe. In many regions, including Western Europe, elevated nitrate (NO3-) concentration in surface waters contributes to eutrophication and noncompliance with environmental legislation. Discharge, NO3- concentrations and the vulnerability of the aquatic ecosystems to eutrophication often exhibit a distinct seasonality. Understanding spatial patterns and long-term trends in this seasonality is crucial to improve water quality management. Here, we hypothesized that NO3- concentrations during high-flow periods would respond faster to changes in nutrient inputs than low-flow concentrations because of greater connectivity of shallow diffuse NO3- sources with the river network. To test this hypothesis, we compiled long-term NO3- and discharge time series from 290 Western European catchments. To characterize the long-term trajectories of seasonal NO3- concentration, we propose a novel hysteresis approach comparing low- and high-flow NO3- concentration in the context of multi-decadal N input changes. We found synchronous winter maxima of NO3- and discharge in 84% of the study catchments. However, contrary to our hypothesis, there were surprisingly diverse long-term trajectories of seasonal NO3- concentration. Both clockwise (faster high-flow NO3- response) and counterclockwise hysteresis (faster low-flow NO3- response) occurred in similar proportions, potentially due to a high complexity in the underlying processes. Spatial variability of seasonality in NO3- concentration across the catchments was more pronounced and better predictable than its long-term variability. This work demonstrates the value of seasonal and inter-annual hydrochemical analysis and provides new tools for water quality monitoring and management.
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Ebeling, P., Dupas, R., Abbott, B., Kumar, R., Ehrhardt, S., Fleckenstein, J.H., Musolff, A. (2021):
Long-term nitrate trajectories vary by season in Western European catchments
Glob. Biogeochem. Cycles 35 (9), e2021GB007050