Using multi-tracer inference to move beyond single-catchment ecohydrology

Abbott, Benjamin W.; Baranov, Viktor; Mendoza‐Lera, Clara; Nikolakopoulou, Myrto; Harjung, Astrid; Kolbe, Tamara; Balasubramanian, M.; Vaessen, Timothy N.; Ciocca, Francesco; Campeau, Audrey; Wallin, Marcus B.; Romeijn, Paul; Antonelli, Marta; Gonçalves, José Artur Teixeira; Datry, Thibault; Laverman, Anniet M.; Dreuzy, Jean‐Raynald de; Hannah, David M.; Krause, Stefan; Oldham, Carolyn; Pinay, Gilles

doi:10.1016/j.earscirev.2016.06.014

Cited by 149 publications

(170 citation statements)

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“…The work of Ocampo et al (15) suggested interpreting NO3 transport and transformation within a riparian zone using a Damköhler number, which is the ratio of a characteristic residence time, with importance (28) that has been documented by several empirical (5,16,17) and numerical (29,30) investigations, to the characteristic time of the pertinent biogeochemical reaction. Recent investigations also proposed this approach to interpret hyporheic processes (31,32), and they adapted it to quantify the hyporheic biogeochemical response at both bedform (33) and reach (34) scales. Here, we capitalized on these advances to depict the observed scaling effect on N 2 O emissions across riverine networks (Fig.…”

Section: Resultsmentioning

confidence: 99%

Role of surface and subsurface processes in scaling N₂O emissions along riverine networks

Marzadri

Dee

Tonina

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

127

147

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Riverine environments, such as streams and rivers, have been reported as sources of the potent greenhouse gas nitrous oxide (N 2 O) to the atmosphere mainly via microbially mediated denitrification. Our limited understanding of the relative roles of the nearsurface streambed sediment (hyporheic zone), benthic, and water column zones in controlling N 2 O production precludes predictions of N 2 O emissions along riverine networks. Here, we analyze N 2 O emissions from streams and rivers worldwide of different sizes, morphology, land cover, biomes, and climatic conditions. We show that the primary source of N 2 O emissions varies with stream and river size and shifts from the hyporheic-benthic zone in headwater streams to the benthic-water column zone in rivers. This analysis reveals that N 2 O production is bounded between two N 2 O emission potentials: the upper N 2 O emission potential results from production within the benthic-hyporheic zone, and the lower N 2 O emission potential reflects the production within the benthic-water column zone. By understanding the scaling nature of N 2 O production along riverine networks, our framework facilitates predictions of riverine N 2 O emissions globally using widely accessible chemical and hydromorphological datasets and thus, quantifies the effect of human activity and natural processes on N 2 O production.riverine networks | greenhouse gas | N 2 O | emission scaling law | N 2 O emission potentials R iverine environments, such as streams and rivers, have been identified as hotspots of microbially mediated denitrification, where nitrate (NO3) is converted to both nitrogen gas (N2), which constitutes the majority of Earth's atmosphere, and nitrous oxide (N 2 O), the potent greenhouse gas responsible for stratospheric ozone destruction (1). Denitrification has been observed to occur within both bulk-oxic (2) and anoxic environments (3-5) of both benthic (i.e., sediment-water interface) and hyporheic (i.e., near-subsurface) zones of streams and rivers. Whereas the benthic zone is the ecological region of the streambed, where both aquatic fauna and flora can be found (4, 6), the latter is the band of streambed material mainly saturated of stream water (7). The benthic zone is at the interface between water and sediment and the upper boundary of the fluvial hyporheic zone. Current understanding suggests that riverine N 2 O production occurs predominantly in these two environments, reflecting two distinct biogeochemical transformation zones (6), irrespective of system size from headwater streams to rivers. The produced N 2 O is then exchanged with the atmosphere through diffusive evasion, with dynamics that depend on N 2 O concentrations of the water in relation to atmospheric equilibrium (6, 8), stream hydrodynamics, temperature, and the air-water gas exchange rate (9). Although it is understood that microbially mediated denitrification is responsible for a large proportion of N 2 O production in riverine networks (6, 10, 11), quantifying these emissions is challenging becau...

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Section: Resultsmentioning

confidence: 99%

Role of surface and subsurface processes in scaling N₂O emissions along riverine networks

Marzadri

Dee

Tonina

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

127

147

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“…Spatial and temporal scales for use of different hydrological tracers (Abbott et al, ; Aggarwal, ; Newman et al, ). The black box represents groundwater age tracers applicable on scales from small catchments to large basins that span different temporal scales.…”

Section: Quantifying Water Ages In the Critical Zonementioning

confidence: 99%

The Demographics of Water: A Review of Water Ages in the Critical Zone

Sprenger

Stumpp

Weiler

et al. 2019

Reviews of Geophysics

233

214

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The time that water takes to travel through the terrestrial hydrological cycle and the critical zone is of great interest in Earth system sciences with broad implications for water quality and quantity. Most water age studies to date have focused on individual compartments (or subdisciplines) of the hydrological cycle such as the unsaturated or saturated zone, vegetation, atmosphere, or rivers. However, recent studies have shown that processes at the interfaces between the hydrological compartments (e.g., soil‐atmosphere or soil‐groundwater) govern the age distribution of the water fluxes between these compartments and thus can greatly affect water travel times. The broad variation from complete to nearly absent mixing of water at these interfaces affects the water ages in the compartments. This is especially the case for the highly heterogeneous critical zone between the top of the vegetation and the bottom of the groundwater storage. Here, we review a wide variety of studies about water ages in the critical zone and provide (1) an overview of new prospects and challenges in the use of hydrological tracers to study water ages, (2) a discussion of the limiting assumptions linked to our lack of process understanding and methodological transfer of water age estimations to individual disciplines or compartments, and (3) a vision for how to improve future interdisciplinary efforts to better understand the feedbacks between the atmosphere, vegetation, soil, groundwater, and surface water that control water ages in the critical zone.

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“…While this large labile DOC addition in Experiment 4 demonstrated that an increased supply of acetate promotes increased NO 3 − removal, it did not have a strong effect on overall denitrification rates, suggesting that denitrification in this lake SWI is not primarily controlled by N or C reaction substrate limitations. Thus, it is likely limited by exposure timescales of the solutes in the SWI, which are controlled by the prevailing transport conditions, similar to those seen in other freshwater SWIs (Abbott et al, ; Briggs et al, ; Marzadri et al, ; Zarnetske et al, ). In this experiment, the median residence time through the SWI was only 0.97 hr, which was slightly less than previous experiments when lake levels were higher (Table ).…”

Section: Resultsmentioning

confidence: 93%

Residence Time Controls on the Fate of Nitrogen in Flow‐Through Lakebed Sediments

et al. 2019

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For many glacial lakes with highly permeable sediments, water exchange rates control hydrologic residence times within the sediment‐water interface (SWI) and the removal of reactive compounds such as nitrate, a common pollutant in lakes and groundwater. Here we conducted a series of focused tracer injection experiments in the upper 20 cm of the naturally downwelling SWI in a flow‐through lake on Cape Cod, MA. We systematically varied residence time and reactant controls on nitrate processing, using isotopically labeled 15N nitrate to monitor the effect of these changes on nitrate removal via denitrification. The addition of acetate, a labile carbon compound, triggered the lake SWI to switch from net production to net removal of nitrate. When acetate was combined with increased residence time created by controlled reductions in water flux, we observed a fivefold increase in nitrate removal, a 26‐fold increase in N2 production, and a 42‐fold increase in N2O production. We demonstrate that water residence time is an important control on the fate of nitrate in these lake SWIs and illustrate that seasonal conditions that alter lake exchange rates and variability in lake carbon may predict dynamic nitrate removal across the SWI. Additionally, observed N2O production during the oxic pore water experiments paired with geophysical characterization of the sediment porosity revealed that the lake SWI has less mobile pores occupying upward of 50% of the total porosity volume, which function as reactive microzones for nitrate processing.

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Using multi-tracer inference to move beyond single-catchment ecohydrology

Cited by 149 publications

References 377 publications

Role of surface and subsurface processes in scaling N₂O emissions along riverine networks

Role of surface and subsurface processes in scaling N₂O emissions along riverine networks

The Demographics of Water: A Review of Water Ages in the Critical Zone

Residence Time Controls on the Fate of Nitrogen in Flow‐Through Lakebed Sediments

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Using multi-tracer inference to move beyond single-catchment ecohydrology

Cited by 149 publications

References 377 publications

Role of surface and subsurface processes in scaling N2O emissions along riverine networks

Role of surface and subsurface processes in scaling N2O emissions along riverine networks

The Demographics of Water: A Review of Water Ages in the Critical Zone

Residence Time Controls on the Fate of Nitrogen in Flow‐Through Lakebed Sediments

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Product

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Role of surface and subsurface processes in scaling N₂O emissions along riverine networks

Role of surface and subsurface processes in scaling N₂O emissions along riverine networks