Accounting for legacy nitrogen stores does not improve the accuracy of riverine nitrate load model predictions.
| Title: | Accounting for legacy nitrogen stores does not improve the accuracy of riverine nitrate load model predictions. |
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| Authors: | Carleton JN; Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency (Mail Code 8623R), 1200 Pennsylvania Ave NW, Washington, DC 20460, United States of America.; Sabo RD; Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency (Mail Code 8623R), 1200 Pennsylvania Ave NW, Washington, DC 20460, United States of America. |
| Source: | Environmental research. Water [Environ Res Water] 2025 Sep; Vol. 1 (3), pp. 035006. Date of Electronic Publication: 2025 Oct 10. |
| Publication Type: | Journal Article |
| Language: | English |
| Journal Info: | Publisher: IOP Publishing Country of Publication: England NLM ID: 9919210172406676 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 3033-4942 (Electronic) Linking ISSN: 30334942 NLM ISO Abbreviation: Environ Res Water Subsets: PubMed not MEDLINE |
| Imprint Name(s): | Original Publication: [Bristol, England] : IOP Publishing, 2025- |
| Abstract: | Legacy stores of nitrogen (N) have been proposed as an explanation for time lags between implementation of nutrient management practices and discernable declines in riverine N loads, particularly in agricultural watersheds. Process models that treat the environment as being divided into linked homogeneous pools or compartments have been used recently to estimate legacy N stores and infer time lags. However, questions have been raised regarding equifinality, i.e. the idea that acceptable estimates might be obtained using models with different structures and/or sets of parameters, creating uncertainty in model interpretation. To further advance understanding of legacy stores and lags in watershed N delivery, we developed six fate and transport models that vary in simplicity and physicochemical detail. Using published annual N surplus and riverine N load datasets, we calibrated the models to minimize summed squared errors compared with multidecadal NO3-N (nitrate N) yield time series at 254 riverine sites across the continental United States. All models fit most datasets well, with calibration results suggesting little if any lagged contribution from either biogeochemical or hydrologic legacy stores. The highest quality model in terms of adjusted Akaike information criterion was the simplest, comprising a single, well-mixed compartment that lacks any mechanism to represent time lags between N input and output. Calibrated model results thus fail to provide evidence of influential legacy N stores. However, results using incrementally lagged watershed N inputs (themselves shown to be temporally autocorrelated), also imply that delivery lags of up to about a decade cannot be ruled out. |
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| Grant Information: | EPA999999 United States ImEPA Intramural EPA |
| Contributed Indexing: | Keywords: legacy nutrients; nitrogen yield; rivers; time lag |
| Entry Date(s): | Date Created: 20260126 Latest Revision: 20260131 |
| Update Code: | 20260131 |
| PubMed Central ID: | PMC12828579 |
| DOI: | 10.1088/3033-4942/ae09d6 |
| PMID: | 41583938 |
| Database: | MEDLINE |
Journal Article