| 1. |
- Abbott, Benjamin, et al.
(författare)
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Using multi-tracer inference to move beyond single-catchment ecohydrology
- 2016
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Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 160, s. 19-42
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Tidskriftsartikel (refereegranskat)abstract
- Protecting or restoring aquatic ecosystems in the face of growing anthropogenic pressures requires an understanding of hydrological and biogeochemical functioning across multiple spatial and temporal scales. Recent technological and methodological advances have vastly increased the number and diversity of hydrological, biogeochemical, and ecological tracers available, providing potentially powerful tools to improve understanding of fundamental problems in ecohydrology, notably: 1. Identifying spatially explicit flowpaths, 2. Quantifying water residence time, and 3. Quantifying and localizing biogeochemical transformation. In this review, we synthesize the history of hydrological and biogeochemical theory, summarize modem tracer methods, and discuss how improved understanding of flowpath, residence time, and biogeochemical transformation can help ecohydrology move beyond description of site-specific heterogeneity. We focus on using multiple tracers with contrasting characteristics (crossing proxies) to infer ecosystem functioning across multiple scales. Specifically, we present how crossed proxies could test recent ecohydrological theory, combining the concepts of hotspots and hot moments with the Damkohler number in what we call the HotDam framework.
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| 2. |
- Campeau, Audrey, et al.
(författare)
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Aquatic export of young dissolved and gaseous carbon from a pristine boreal fen : Implications for peat carbon stock stability
- 2017
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 23:12, s. 5523-5536
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Tidskriftsartikel (refereegranskat)abstract
- The stability of northern peatland's carbon (C) store under changing climate is of major concern for the global C cycle. The aquatic export of C from boreal peatlands is recognized as both a critical pathway for the remobilization of peat C stocks as well as a major component of the net ecosystem C balance (NECB). Here, we present a full year characterization of radiocarbon content (14C) of dissolved organic carbon (DOC), carbon dioxide (CO2), and methane (CH4) exported from a boreal peatland catchment coupled with 14C characterization of the catchment's peat profile of the same C species. The age of aquatic C in runoff varied little throughout the year and appeared to be sustained by recently fixed C from the atmosphere (<60 years), despite stream DOC, CO2, and CH4 primarily being sourced from deep peat horizons (2–4 m) near the mire's outlet. In fact, the 14C content of DOC, CO2, and CH4 across the entire peat profile was considerably enriched with postbomb C compared with the solid peat material. Overall, our results demonstrate little to no mobilization of ancient C stocks from this boreal peatland and a relatively large resilience of the source of aquatic C export to forecasted hydroclimatic changes.
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| 3. |
- Campeau, Audrey, et al.
(författare)
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Autumn destabilization of deep porewater CO2 store in a northern peatland driven by turbulent diffusion
- 2021
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The deep porewater of northern peatlands stores large amounts of carbon dioxide (CO2). This store is viewed as a stable feature in the peatland CO2 cycle. Here, we report large and rapid fluctuations in deep porewater CO2 concentration recurring every autumn over four consecutive years in a boreal peatland. Estimates of the vertical diffusion of heat indicate that CO2 diffusion occurs at the turbulent rather than molecular rate. The weakening of porewater thermal stratification in autumn likely increases turbulent diffusion, thus fostering a rapid diffusion of deeper porewater CO2 towards the surface where net losses occur. This phenomenon periodically decreases the peat porewater CO2 store by between 29 and 90 g C m−2 throughout autumn, which is comparable to the peatland’s annual C-sink. Our results establish the need to consider the role of turbulent diffusion in regularly destabilizing the CO2 store in peat porewater.
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| 4. |
- Campeau, Audrey
(författare)
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Carbon in Boreal Streams : Isotopic Tracing of Terrestrial Sources
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The boreal biome comprises vast areas of coniferous forests, dotted with millions of peatlands. Plants harbouring these ecosystems fix CO2 from the atmosphere, which is later incorporated into the vegetation biomass and subsequently buried in soils. Over the course of millennia, this process has led to the formation of a large repository of organic C, currently stored in boreal soils. Streams draining this landscape are typically enriched with carbon dioxide (CO2), methane (CH4) and dissolved organic carbon (DOC). As a consequence, streams tend to emit CO2 and CH4 to the atmosphere, two potent greenhouse gases, and thus contribute positively to radiative climate forcing. The sources fuelling C to boreal streams are not well understood. This thesis aims to unravel these sources, and promote a better consolidation of terrestrial and aquatic C biogeochemical processes. The work is largely based on stable and radiogenic C isotope characterization of various dissolved C forms in stream and groundwater, within contrasting ecosystem types across Sweden.This thesis identifies boreal soils as the main source of CO2 in streams. Soil respiration (i.e. biogenic sources) overwhelmingly supply CO2 to streams, leaving only a few exceptions where geogenic CO2 sources were present. An array of biological processes also transform CO2 during its transport from soils to streams. These include; methanogenesis, aquatic DOC mineralization and primary production. The majority of C in boreal streams is sustained by the decomposition of recent photosynthates, with ancient C substrates holding a negligible share of the total C export. While these results suggest that the repository of ancient soil organic C is currently stable, within boreal forests and peatlands, the close connection with recently occurring photosynthesis suggest that forecasted alterations in plant C allocation patterns, driven by climate and land-use changes, will produce a rapid response in stream CO2 emissions. Isotopic characterization of C in stream and groundwater can help reveal these sources and transformation processes, but its interpretation must be made with care.
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| 5. |
- Campeau, Audrey, et al.
(författare)
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Controls on the 14C Content of Dissolved and Particulate Organic Carbon Mobilized Across the Mackenzie River Basin, Canada
- 2020
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Ingår i: Global Biogeochemical Cycles. - : AMER GEOPHYSICAL UNION. - 0886-6236 .- 1944-9224. ; 34:12
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Tidskriftsartikel (refereegranskat)abstract
- The Mackenzie River Basin (MRB) delivers large quantities of organic carbon (OC) into the Arctic Ocean, with significant implications for the global C budgets and ocean biogeochemistry. The amount and properties of OC in the Mackenzie River's delta have been well monitored in the last decade, but the spatial variability in OC sources transported by its different tributaries is still unclear. Here we present new data on the radiocarbon (14C) content of dissolved and particulate OC (Δ14C‐DOC and Δ14C‐POC) across the mainstem and major tributaries of the MRB, comprising 19 different locations, to identify factors controlling spatial patterns in riverine OC sources. The Δ14C‐DOC and Δ14C‐POC varied across a large range, from −179.9‰ to 62.9‰, and −728.8‰ to −9.0‰, respectively. Our data reveal a positive spatial coupling between the Δ14C of DOC and POC across the MRB, whereby the most 14C‐depleted waters were issued from the mountainous west bank of the MRB. This 14C‐depleted DOC and POC likely originates from a combination of petrogenic sources, connected with the presence of kerogens in the bedrock, and biogenic sources, mobilized by thawing permafrost. Our analysis also reveals intriguing relationships between Δ14C of DOC and POC with turbidity, water stable isotope ratio and catchment elevation, indicating that hydrology and geomorphology are key to understanding riverine OC sources in this landscape. A closer examination of the specific mechanisms giving rise to these relationships is recommended. For now, this study provides a road map of the key OC sources in this rapidly changing river basin.
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| 6. |
- Campeau, Audrey, et al.
(författare)
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Current forest carbon fixation fuels stream CO 2 emissions
- 2019
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Stream CO 2 emissions contribute significantly to atmospheric climate forcing. While there are strong indications that groundwater inputs sustain these emissions, the specific biogeochemical pathways and timescales involved in this lateral CO 2 export are still obscure. Here, via an extensive radiocarbon ( 14 C) characterisation of CO 2 and DOC in stream water and its groundwater sources in an old-growth boreal forest, we demonstrate that the 14 C-CO 2 is consistently in tune with the current atmospheric 14 C-CO 2 level and shows little association with the 14 C-DOC in the same waters. Our findings thus indicate that stream CO 2 emissions act as a shortcut that returns CO 2 recently fixed by the forest vegetation to the atmosphere. Our results expose a positive feedback mechanism within the C budget of forested catchments, where stream CO 2 emissions will be highly sensitive to changes in forest C allocation patterns associated with climate and land-use changes. © 2019, The Author(s).
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| 7. |
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| 8. |
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| 9. |
- Campeau, Audrey, et al.
(författare)
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Multiple sources and sinks of dissolved inorganic carbon across Swedish streams, refocusing the lens of stable C isotopes
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- It is well established that stream dissolved inorganic carbon (DIC) fluxes play a central role in the global C cycle, yet the sources of stream DIC remain to a large extent unresolved. Here, we explore large-scale patterns in delta C-13-DIC from streams across Sweden to separate and further quantify the sources and sinks of stream DIC. We found that stream DIC is governed by a variety of sources and sinks including biogenic and geogenic sources, CO2 evasion, as well as in-stream processes. Although soil respiration was the main source of DIC across all streams, a geogenic DIC influence was identified in the northernmost region. All streams were affected by various degrees of atmospheric CO2 evasion, but residual variance in delta C-13-DIC also indicated a significant influence of in-stream metabolism and anaerobic processes. Due to those multiple sources and sinks, we emphasize that simply quantifying aquatic DIC fluxes will not be sufficient to characterise their role in the global C cycle.
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| 10. |
- Campeau, Audrey, et al.
(författare)
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Patterns in CH4 and CO2 concentrations across boreal rivers : Major drivers and implications for fluvial greenhouse emissions under climate change scenarios
- 2014
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 20:4, s. 1075-1088
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Tidskriftsartikel (refereegranskat)abstract
- It is now widely accepted that boreal rivers and streams are regionally significant sources of carbon dioxide (CO2), yet their role as methane (CH4) emitters, as well as the sensitivity of these greenhouse gas (GHG) emissions to climate change, are still largely undefined. In this study, we explore the large-scale patterns of fluvial CO2 and CH4 partial pressure (pCO(2),pCH(4)) and gas exchange (k) relative to a set of key, climate-sensitive river variables across 46 streams and rivers in two distinct boreal landscapes of Northern Quebec. We use the resulting models to determine the direction and magnitude of C-gas emissions from these boreal fluvial networks under scenarios of climate change. River pCO(2) and pCH(4) were positively correlated, although the latter was two orders of magnitude more variable. We provide evidence that in-stream metabolism strongly influences the dynamics of surface water pCO(2) and pCH(4), but whereas pCO(2) is not influenced by temperature in the surveyed streams and rivers, pCH(4) appears to be strongly temperature-dependent. The major predictors of ambient gas concentrations and exchange were water temperature, velocity, and DOC, and the resulting models indicate that total GHG emissions (C-CO2 equivalent) from the entire network may increase between by 13 to 68% under plausible scenarios of climate change over the next 50years. These predicted increases in fluvial GHG emissions are mostly driven by a steep increase in the contribution of CH4 (from 36 to over 50% of total CO2-equivalents). The current role of boreal fluvial networks as major landscape sources of C is thus likely to expand, mainly driven by large increases in fluvial CH4 emissions.
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| 11. |
- Campeau, Audrey, et al.
(författare)
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Regional contribution of CO2 and CH4 fluxes from the fluvial network in a lowland boreal landscape of Quebec
- 2014
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 28:1, s. 57-69
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Tidskriftsartikel (refereegranskat)abstract
- Boreal rivers and streams are known as hot spots of CO2 emissions, yet their contribution to CH4 emissions has traditionally been assumed to be negligible, due to the spatially fragmented data and lack of regional studies addressing both gases simultaneously. Here we explore the regional patterns in river CO2 and CH4 concentrations (pCO(2) and pCH(4)), gas exchange coefficient (k), and the resulting emissions in a lowland boreal region of Northern Quebec. Rivers and streams were systematically supersaturated in both gases, with both pCO(2) and pCH(4) declining along the river continuum. The k was on average low and increased with stream order, consistent with the hydrology of this flat landscape. The smallest streams (order 1), which represent <20% of the total river surface, contributed over 35% of the total fluvial greenhouse gas (GHG) emissions. The end of winter and the spring thaw periods, which are rarely included in annual emission budgets, contributed on average 21% of the annual GHG emissions. As a whole, the fluvial network acted as significant source of both CO2 and CH4, releasing on average 1.5 tons of C (CO2 eq) yr(-1)km(-2) of landscape, of which CH4 emissions contributed approximately 34%. We estimate that fluvial CH4 emissions represent 41% of the regional aquatic (lakes, reservoirs, and rivers) CH4 emissions, despite the relatively small riverine surface (4.3% of the total aquatic surface). We conclude that these fluvial networks in boreal lowlands play a disproportionately large role as hot spots for CO2 and more unexpectedly for CH4 emissions. Key Points pCO(2) and pCH(4) decrease, whereas the k600 increases with increasing stream order Small streams and spring thaw period play a large role in regional C balance Rivers are significant sources of CO2 and unexpectedly large sources of CH4
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| 12. |
- Campeau, Audrey, et al.
(författare)
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Sources of riverine mercury across the Mackenzie River Basin; inferences from a combined Hg C isotopes and optical properties approach
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 806, s. 150808-150808
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic terrestrial environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. ∆199Hg, d202Hg), radiocarbon content (∆14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the ∆14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older riverine OC. These findings reveal that a complex mixture of Hg sources, supplied across the MRB, will contribute to future trends in Hg export to the Arctic Ocean under rapid environmental changes.
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| 13. |
- Campeau, Audrey, et al.
(författare)
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Stable carbon isotopes reveal soil - stream DIC linkages in contrasting headwater catchments
- 2018
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 123:1, s. 149-167
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Tidskriftsartikel (refereegranskat)abstract
- Large CO2 evasion to the atmosphere occurs as dissolved inorganic carbon (DIC) is transported from soils to streams. While this physical process has been the focus of multiple studies, less is known about the underlying biogeochemical transformations that accompany this transfer of C from soils to streams. Here we used patterns in stream water and groundwater C-13-DIC values within three headwater catchments with contrasting land cover to identify the sources and processes regulating DIC during its transport. We found that although considerable CO2 evasion occurs as DIC is transported from soils to streams, there were also other processes affecting the DIC pool. Methane production and mixing of C sources, associated with different types and spatial distribution of peat-rich areas within each catchment, had a significant influence on the C-13-DIC values in both soils and streams. These processes represent an additional control on C-13-DIC values and the catchment-scale cycling of DIC across different northern landscape types. The results from this study demonstrate that the transport of DIC from soils to streams results in more than just rapid CO2 evasion to the atmosphere but also represents a channel of C transformation, which questions some of our current conceptualizations of C cycling at the landscape scale. Plain Language Summary Large carbon dioxide emission to the atmosphere occurs as rainwater percolates through soils and into streams. This physical process is important for the global carbon cycle and has been the focus of multiple studies. However, less is known about the underlying processes that accompanies this transfer of carbon dioxide from soils to streams. Here we analyze the stable isotope composition of soil and stream carbon dioxide and demonstrate that methane production and mixing of carbon sources also occur in soils and streams. These processes were linked to different types and configurations of peat-rich areas, for example, bogs, fens, and riparian zones, found within each of the three studied catchments. Our results therefore demonstrate that the export of carbon dioxide from soils to streams not only results in emissions to the atmosphere but also represents a channel of transformation. This questions some of our current conceptualization of the catchment-scale cycling of carbon dioxide.
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| 14. |
- Laudon, Hjalmar, et al.
(författare)
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On the Relationship Between Aquatic CO2 Concentration and Ecosystem Fluxes in Some of the World's Key Wetland Types
- 2024
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Ingår i: Wetlands. - 0277-5212 .- 1943-6246. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- To understand patterns in CO2 partial pressure (P-CO2) over time in wetlands' surface water and porewater, we examined the relationship between P-CO2 and land-atmosphere flux of CO2 at the ecosystem scale at 22 Northern Hemisphere wetland sites synthesized through an open call. Sites spanned 6 major wetland types (tidal, alpine, fen, bog, marsh, and prairie pothole/karst), 7 K & ouml;ppen climates, and 16 different years. Ecosystem respiration (R-eco) and gross primary production (GPP), components of vertical CO2 flux, were compared to P-CO2, a component of lateral CO2 flux, to determine if photosynthetic rates and soil respiration consistently influence wetland surface and porewater CO2 concentrations across wetlands. Similar to drivers of primary productivity at the ecosystem scale, P-CO2 was strongly positively correlated with air temperature (T-air) at most sites. Monthly average P-CO2 tended to peak towards the middle of the year and was more strongly related to R-eco than GPP. Our results suggest R-eco may be related to biologically driven P-CO2 in wetlands, but the relationship is site-specific and could be an artifact of differently timed seasonal cycles or other factors. Higher levels of discharge do not consistently alter the relationship between R-eco and temperature normalized P-CO2. This work synthesizes relevant data and identifies key knowledge gaps in drivers of wetland respiration.
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| 15. |
- Riml, Joakim, 1979-, et al.
(författare)
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Spectral Decomposition Reveals New Perspectives on CO2 Concentration Patterns and Soil-Stream Linkages
- 2019
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 124:10, s. 3039-3056
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Tidskriftsartikel (refereegranskat)abstract
- The rapid development of novel technologies to obtain high-frequency observations has provided new possibilities to observe and understand carbon cycling in inland waters. This study investigates carbon dioxide (CO2) dynamics along a boreal soil-stream transect using a state-of-the-art data set in combination with a spectral methodology to identify controls on stream CO2. The spectral decomposition of hourly observations revealed intermediate (multiday) to long-term (monthly) patterns across the upslope-riparian-stream continuum, with similar power law increases in CO2 concentration fluctuations with increasing period. High-frequency CO2 variabilities, specifically diel CO2 concentration fluctuations, were also identified at all locations but were substantially amplified in the stream compared to in the riparian groundwater. Moreover, the spectral coherence between soil and stream CO2 fluctuations was inconsistent and restricted to episodic events. In contrast, we found a strong and consistent spectral coherence between the riparian groundwater level and stream CO2 concentration, indicating a hydrological control on stream CO2 dynamics. However, during some time spans even these patterns were obscured, suggesting that additional processes, such as CO2 evasion and in-stream metabolism, modulated the influence from riparian sources. The scales and patterns of temporal coherences (or lack thereof) between CO2 at different points in the catchment, as well as with other factors, for example, groundwater levels and Photosynthetically Active Radiation, provide new perspectives on the range of processes governing stream CO2 dynamics. Thus, this study highlights the potential of using spectral decomposition of high-resolution, spatially distributed data of different types to investigate biogeochemical transformations and pathways linking terrestrial and aquatic systems.
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| 16. |
- Wallin, Marcus, 1979-, et al.
(författare)
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Carbon dioxide and methane emissions of Swedish low-order streams : a national estimate and lessons learnt from more than a decade of observations
- 2018
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Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 3:3, s. 156-167
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Tidskriftsartikel (refereegranskat)abstract
- Low-order streams are suggested to dominate the atmospheric CO2 source of all inland waters. Yet, many large-scale stream estimates suffer from methods not designed for gas emission determination and rarely include other greenhouse gases such as CH4. Here, we present a compilation of directly measured CO2 and CH4 concentration data from Swedish low-order streams (> 1600 observations across > 500 streams) covering large climatological and land-use gradients. These data were combined with an empirically derived gas transfer model and the characteristics of a ca. 400,000 km stream network covering the entire country. The total stream CO2 and CH4 emission corresponded to 2.7 Tg C yr(-1) (95% confidence interval: 2.0-3.7) of which the CH4 accounted for 0.7% (0.02 Tg C yr(-1)). The study highlights the importance of low-order streams, as well as the critical need to better represent variability in emissions and stream areal extent to constrain future stream C emission estimates.
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| 17. |
- Zdanowicz, Christian, 1966-, et al.
(författare)
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Identifying terrestrial sources of mercury in streams of the Mackenzie River Basin, NW Canada
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Mackenzie River, with a catchment >1 million km^2 and a mean water discharge of 10,000 m^3/s, is the largest conduit for freshwater and sediment delivery to the Beaufort Sea. During peak flow, the Mackenzie and its main tributaries have some of the highest Hg levels in freshwaters of the Canadian Arctic and subarctic (>> 10 ng/L). An unknown fraction of this Hg is derived from thawing permafrost soils in the northern reaches of the Mackenzie basin. This contribution is likely to increase as NW Canada warms up over the next decades at nearly twice the mean rate of the whole country. To better anticipate the future impact of warming on riverine Hg transfer to the Beaufort Sea marine ecosystem, a Swedish-Canadian research project was initiated to identify and quantify the terrestrial sources of Hg in streams of the Mackenzie basin. Water was sampled from the Mackenzie itself and selected tributaries during spring peak flow in 2018, and will also be sampled during the base flow period in 2019. Water samples are being analysed for isotopic ratios of O and H in water, C and Hg (dissolved and particulate), as well as the optical properties of dissolved organic matter, to help in the source apportionment of Hg between various terrestrial pools such as rocks and organic soils. These data will be used to constrain a mixing model of water properties, including Hg loads, created for the Mackenzie drainage system. The mixing model will be used to simulate future riverine Hg transfer rates to the Beaufort Sea under varying scenarios of Hg release from the different terrestrial reservoirs, such as permafrost soils. The study design, methods, and preliminary findings will be presented.
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| 18. |
- Zdanowicz, Christian, 1966-, et al.
(författare)
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Mercury inputs to the Mackenzie River and the Beaufort Sea: : Future impacts of permafrost thaw
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies highlighted the existence of a large reservoir of mercury (Hg) stored in frozen soils and peat of the circum-Arctic, and evidence is accumulating that this Hg is being released by permafrost thaw to streams and lakes in the northern Yukon and Northweest Territories. This raises the question whether such releases will increase the net export of Hg by large Arctic rivers to marginal seas of the Arctic Ocean, and thus potentially negating some of the long-term environmental benefits of Hg emissions reductions under the UN Minamata convention. In 2018 we initiated a Swedish-Canadian research project to investigate the sources of Hg entering the Mackenzie River, using an approach that combines measurements of multiple water quality parameters, including isotopes of Hg and carbon (dissolved and particulate). We carried out a sampling survey across the Mackenzie River Basin (MRB) in the summer of 2018, and will extend this with additional sampling in 2019. We will present our initial findings from this study, with a focus on the implications for climate change on the cycling of terrestrial Hg between the MRB and Beaufort Sea.
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| 19. |
- Åkerblom, Staffan, et al.
(författare)
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Spatial and temporal variations in riverine mercury in the Mackenzie River Basin, Canada, from community-based water quality monitoring data.
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 853
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Tidskriftsartikel (refereegranskat)abstract
- Arctic rivers deliver~40 t yr−1 of mercury (Hg) to the Arctic Ocean, ~6%of which is from the Mackenzie River Basin(MRB), a region warming at ~3 times the mean hemispheric rate. How this will affect Hg transfer to ecosystems of theBeaufort Sea is a worrying issue. To help address this question, we analyzed >500 measurements ofHg and other waterproperties from 22 rivers collected in 2012–2018 by communities of the MRB. This new dataset provides a more comprehensiveview of riverine Hg variations across the basin than was previously available. We find that rivers issuedfrom mountains in the western MRB contribute the largest share of Hg in the Mackenzie River, 60–95 % of it beingcarried as fine suspended solids and probably sourced from riverbank erosion and thaw slumps. In contrast, lowlandrivers of the central and eastern MRB contribute larger shares of dissolved Hg (up to 78 %), likely from recent atmosphericdeposition through precipitation. Using load modelling constrained by the new water quality dataset, we estimatethat the three largest western tributaries (Liard, Peel and Arctic Red rivers) of the Mackenzie contribute 60 % ofthe annual MRB THg export and DHg export to the Beaufort Sea during freshet, as well as 51 % of DHg export, whilesupplying 60% of freshet discharge. Load modelling also reveals a sustained decline in DHg loads of ~13 kg yr−1 between2001 and 2016 in the lower Mackenzie River, which likely reflect a decreasing trend in atmospheric Hg depositionover most of northwestern Canada during this period. This study highlights the value of community-based waterquality monitoring in helping to support assessments of riverine Hg in theMRB in support of the Minamata Conventionon Mercury.
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