Spatiotemporal dynamics of N and C biogeochemistry along a wetland-stream sequence Patrick Hurley 1 | H. Maurice Valett 1 | Marc Peipoch 2 1 University of Montana | 2 Stroud Water Research Center | patrick1.hurley@umontana.edu 3. Groundwater flowpaths drive N processing 1. Lost Creek Dutchman Complex (LCDC) REACH IV Figure 4. For all reaches, total change in NO 3 load (∆L NO3 ) is driven by groundwater dissolved inorganic N inputs (L gwDIN ). Removal of 1 outlier explains 30% of changes in ∆ L NO3 over space and time (P=0.00064). Clustering of symbols suggest spatially- discrete nutrient process domains (NPD) based on biogeochemical character. Upper Figure 1. NO 3 -N (a) & DOC (b) Figure 5. δ 18 O NO3 and concentration on a 23 km longitudinal Clark Warm δ 15 N NO3 signatures from all gradient. NO 3 increases dramatically Springs Fork sites fall within the range in reach II during both peak and base for nitrification of NH 4 from flows in contrast to DOC. DOC was River soil and/or septic sources higher during spring runoff and and show spatial variability increased in reach III and IV. Dutchman Cr in N processing. Yellow Figure 2. Aerial photo of the LCDC as circles are from above the N it flows towards the Upper Clark Fork wetland complex; purple 1 km River (UCFR). triangles from Dutchman Cr and reach II zones; red diamonds are closest to the UCFR. Slopes between 2. Nutrient Patterns over Time and Space 0.5 and 1.0 typically indicate denitrification fractionation. 4. Contributions to the UCFR Figure 6. LCDC inputs to the river are 11,431% 1,1447% 1,328% NO 3 -N (kg d -1 ) presented as % increase of NO 3 , DOC, and hydrologic load (Q), relative to the UCFR at Perkins Rd. DOC (kg d -1 ) Q (L sec -1 ) Figure 3. Long-term nutrient concentrations from the five main channel sites between Sept 2017 – Oct 2018. NO 3 (a) is high from fall until peak runoff, then rebounds during the summer. NH 4 (b) is Figure 7. Difference in C NO3 of the low throughout the year. PO 4 (c) and DOC (d) peak during spring runoff and return to UCFR above and below the LCDC background concentrations over the growing season. inputs.
Spatiotemporal dynamics of N and C biogeochemistry along a wetland-stream sequence Patrick Hurley 1 | H. Maurice Valett 1 | Marc Peipoch 2 1 University of Montana | 2 Stroud Water Research Center | patrick1.hurley@umontana.edu 3. Groundwater flowpaths drive N processing 1. Lost Creek Dutchman Complex (LCDC) REACH IV Figure 4. For all reaches, total change in NO 3 load (∆L NO3 ) is driven by groundwater dissolved inorganic N inputs (L gwDIN ). Removal of 1 outlier explains 30% of changes in ∆ L NO3 over space and time (P=0.00064). Clustering of symbols suggest spatially- discrete nutrient process domains (NPD) based on biogeochemical character. Upper Figure 1. NO 3 -N (a) & DOC (b) Figure 5. ∂ 18 O NO3 and concentration on a 23 km longitudinal Clark Warm ∂ 15 N NO3 signatures from all gradient. NO 3 increases dramatically Springs Fork sites fall within the range in reach II during both peak and base for nitrification of NH 4 from flows in contrast to DOC. DOC was River soil and/or septic sources higher during spring runoff and and show spatial variability increased in reach III and IV. Dutchman Cr in N processing. Yellow Figure 2. Aerial photo of the LCDC as circles are from above the N it flows towards the Upper Clark Fork wetland complex; purple 1 km River (UCFR). triangles from Dutchman Cr and reach II zones; red diamonds are closest to the UCFR. Slopes between 2. Nutrient Patterns over Time and Space 0.5 and 1.0 typically indicate denitrification fractionation. 4. Contributions to the UCFR Figure 3. Long-term nutrient concentrations from the five main channel sites between Sept 2017 – Oct 2018. NO 3 (a) is high from fall until peak runoff, then rebounds during the summer. NH 4 (b) is low throughout the year. PO 4 (c) and DOC (d) peak during spring runoff and return to background concentrations over the growing season.
Dynamics of Biogeochemical Process Domains: Wetland Influences on a Contaminated River Patrick Hurley 1 | H. Maurice Valett 1 | Marc Peipoch 2 1 University of Montana | 2 Stroud Water Research Center | patrick1.hurley@umontana.edu 2. Nitrogen Sources to the UCFR 1. Question & Hypothesis SITE V Q: SITE IV How do nutrient process domains (NPDs) NH 4 -N (µg/L) 140 NO 3 -N (µg/L) characterize discrete biogeochemical zones that influence 100 whole-stream nutrient budgets within linked aquatic SITE III ecosystems? 60 H: Hydrologic, geomorphic, and biologic factors drive 20 nutrient cycling and dictate dominant biogeochemical behavior that distinguish nutrient fates among NPDs. 0 10 20 30 40 Distance Downstream (km) SITE II Figure 1. Longitudinal trends in nitrogen of the UCFR show reaches of significant gains. 3. Seasonal & Spatial Trends • Longitudinal sampling of the SITE I Upper Clark Upper Clark Fork River (UCFR) Fork River identified Lost Creek-Dutchman 4.5 0.6 Q (m 3 /s) NO 3 -N (mg/L) Complex (LCDC) as a zone of Lost Creek Dutchman Creek a. b. substantial N contributions (yellow 3.0 0.4 stars) N • Reaches may be nutrients donors, 1 km Lost Creek-Dutchman transformers, conveyors, or 1.5 0.2 Oct 2017 Feb 2018 removers. Apr 2018 Complex • Segmented study reaches 0 0 2012 2014 2016 2018 Site 1 2 3 4 5 (colored) provide a Figure 2. Aerial photo of Lost Creek-Dutchman comprehensive assessment of the 8 Complex (LCDC) – an identified source of PO 4 -P (kg/d) dynamics of each potential NPD 0.2 d. c. NO 3 -N (kg/d) inorganic nitrogen – as it flows towards the within the LCDC 6 PO 4 -P (mg/L) Upper Clark Fork River (UCFR). 4 0.1 NH 4 -N (kg/day) 4. Future Mass Balance Study 2 NO 3 -N (mg/L) NH 4 -N (mg/L) 0 0 4 1 2 3 5 Site Site 1 2 3 4 5 Figure 3. a) LCDC discharge (m 3 /s), b) Seasonal and downstream trends in nitrate (kg NO 3 -N • Develop theoretical bases for NPD as important influences on catchment- d -1 ); Dutchman Creek (red triangle) confluence in between sites I & II c) Nitrate loads at the base of each reach d) Ammonium & phosphate loads among reaches. wide stream dynamics and biogeochemical function • Hydrologic variation is associated with summer drought and • 6-month biogeochemical and hydrologic assessment using mass balance to agricultural drawdown. determine nutrient sources and sinks and characterize NPDs along a • Nutrient loads fluctuate with discharge and biologic influences landscape-scale wetland-stream sequence • Inorganic N loads predicted to be related to the seasonal • Evaluate input & output nutrient loads across four spatially distinct reaches capacity for nutrient uptake by in-stream biota. • Quantify seasonal variability in NPD behavior • Potential for buried peat-wetland to support large-scale • Quantify total annual loads to UCFR to inform nutrient reduction efforts mineralization & nitrification and act as N donor
1. Lost Creek Dutchman Complex (LCDC) REACH IV REACH II REACH I REACH III Warm Dutchman Cr Springs 1 km Upper Clark Fork River Figure 1. NO 3 -N & DOC concentration on a 23 km longitudinal gradient. NO 3 increases dramatically in reach II Figure 2. Aerial photo of the LCDC as it during both peak and base flows in flows towards the Upper Clark Fork River contrast to DOC. DOC was higher (UCFR). during spring runoff and increased in reach III and IV.
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