Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

MATIATOS, IOANNIS; WASSENAAR, LEONARD I.; MONTEIRO, LUCILENA R.; VENKITESWARAN, JASON J.; GOODDY, DAREN C.; BOECKX, PASCAL; SACCHI, ELISA; YUE, FU?JUN; MICHALSKI, GREG; ALONSO-HERNÁNDEZ, CARLOS; BIASI, CHRISTINA; BOUCHAOU, LHOUSSAINE; EDIRISINGHE, NANDANA V.; FADHULLAH, WIDAD; FIANKO, JOSEPH R.; GARCÍA-MOYA, ALEJANDRO; KAZAKIS, NERANTZIS; LI, SI-LIANG; LUU, MINH T. N.; PRIYADARSHANEE, SAKHILA; RE, VIVIANA; RIVERA, DIEGO S.; ROMANELLI, ASUNCIÓN; SANYAL, PRASANTA; TAMOOH, FREDRICK; TRINH, DUC A.; WALTERS, WENDELL; WELTI, NINA

Communications Earth & Environment

Nature Publishing Group

Año: 2021 vol. 2

Remediation of nitrate pollution of Earth?s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8?, n = 2902 vs +7.7 ± 4.5?, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2?, n = 2790 vs +2.3 ± 5.4?, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies.