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- Title
Disaggregating Landscape‐Scale Nitrogen Attenuation Along Hydrological Flow Paths.
- Authors
Jawitz, J.W.; Desormeaux, A.M.; Annable, M.D.; Borchardt, D.; Dobberfuhl, D.
- Abstract
Evaluating how nitrogen (N) sources are attenuated throughout the landscape is critical to further our understanding of catchment‐scale N budgets. We developed a catchment‐scale N budget for a mixed land use karst springshed using in situ measurements (nitrate leaching fluxes and attenuation) and long‐term records (surface N inputs and spring exports) to estimate 20‐year average landscape‐scale N loading, attenuation, and export. We introduce a conceptual model framework to compute N export that can be applied consistently for point or nonpoint sources. The model is based on the product of only four components for each N source: population density or proportion of land cover, P; specific load, L; anthropogenic attenuation, A; and natural attenuation, N. The product of these components is computed for each N source and then integrated at the basin scale. The concise PLAN model framework predicted attenuation of 90% ± 3% of N inputs, in close agreement with the estimate based on measured spring mass discharge (87% ± 3%). Further, when this attenuation is disaggregated along the hydrological flow path, we estimate that 64% of inputs are lost in the surface soil, 20% in the vadose zone, and 6% in the aquifer. Livestock and human wastes were estimated to be the dominant contributors to spring N export, which was independently supported by isotopic data. The PLAN model is a simple, transferable framework that supports systematically computing N export based on proportioning of load and attenuation. Identifying the main sources of N ultimately contributing to discharged N loads is a critical step toward source‐related water‐quality management. Key Points: Our concise model framework predicted attenuation of 90% of N inputsWe found that 64% of surface N inputs were attenuated in the surface soilManure and septic‐treated wastewater were the largest contributors to spring N export
- Subjects
NITROGEN &; the environment; NITROGEN analysis; ATTENUATION (Physics); ZONE of aeration; WASTEWATER treatment
- Publication
Journal of Geophysical Research. Biogeosciences, 2020, Vol 125, Issue 2, p1
- ISSN
2169-8953
- Publication type
Article
- DOI
10.1029/2019JG005229