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Managing nitrogen legacies to accelerate water quality improvement

Abstract

Increasing incidences of eutrophication and groundwater quality impairment from agricultural nitrogen pollution are threatening humans and ecosystem health. Minimal improvements in water quality have been achieved despite billions of dollars invested in conservation measures worldwide. Such apparent failures can be attributed in part to legacy nitrogen that has accumulated over decades of agricultural intensification and that can lead to time lags in water quality improvement. Here, we identify the key knowledge gaps related to landscape nitrogen legacies and propose approaches to manage and improve water quality, given the presence of these legacies.

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Fig. 1: Time lines of policy measures and hypoxic-zone size reveal lack of response to policy interventions across Europe and North America.
Fig. 2: Transport and retention of N across human-impacted landscapes.
Fig. 3: Relationships between stream N loads and watershed net N inputs.
Fig. 4: Strategies for solving the legacy N problem.

Data availability

Datasets for this research have been previously published13,26,41,80,84,85,86,87,89,91,92,94,95. All other data are available upon request.

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Acknowledgements

This work was financed in part through Natural Sciences and Engineering Research Council of Canada (NSERC) in the frame of the collaborative Water JPI international consortium pilot call under the project name ‘Legacies of Agricultural Pollutants (LEAP): Integrated Assessment of Biophysical and Socioeconomic Controls on Water Quality Agroecosystems’ (N.B.B., K.J.V.M., R. Brouwer, R. Bhattacharya, M.C.C., G.D., B.H.J., J.J., S.B.O. and P.V.C.) and by Lake Futures Project under the Global Water Futures umbrella, and provided through the Canada First Research Excellence Fund (N.B.B., P.V.C., R. Brouwer and R. Bhattacharya). N.B.B. was also supported by a University Research Chair appointment and by an NSERC Discovery Grant. K.J.V.M. was also supported by startup funds at The Pennsylvania State University. D.K.B. was supported by the NSERC Alexander Graham Bell Canada Graduate Scholarship.

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N.B.B. conceptualized the project, wrote the first draft, edited the paper and acquired the funding. K.J.V.M. conceptualized the project, edited the draft and wrote sections, contributed materials/analysis tools and analysed data. D.K.B. contributed materials/analysis tools, analysed data and edited the draft. P.V.C., R. Brouwer, G.D., J.J., R. Bhattacharya, B.H.J., M.C.C., G.D., N.N., S.B.O. and D.L.R. edited the draft. P.V.C. and N.B.B. acquired funding.

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Correspondence to Nandita B. Basu.

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Basu, N.B., Van Meter, K.J., Byrnes, D.K. et al. Managing nitrogen legacies to accelerate water quality improvement. Nat. Geosci. 15, 97–105 (2022). https://doi.org/10.1038/s41561-021-00889-9

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