| 1. |
- Audet, J., et al.
(author)
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Forest streams are important sources for nitrous oxide emissions
- 2020
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In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26:2, s. 629-641
-
Journal article (peer-reviewed)abstract
- Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6±2.1 and 1.3±1.8µgN/L, respectively (mean±SD) despite higher total N (TN) concentrations in agricultural streams (1,520±1,640 vs. 780±600µgN/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low-order streams at the national scale revealed that ~1.8×109g N2O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800×109gCO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector. © 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd
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| 2. |
- Laudon, Hjalmar, et al.
(author)
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Consequences of rewetting and ditch cleaning on hydrology, water quality and greenhouse gas balance in a drained northern landscape
- 2023
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In: Scientific Reports. - 2045-2322. ; 13
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Journal article (peer-reviewed)abstract
- Drainage for forestry has created ~ 1 million km of artificial waterways in Sweden, making it one of the largest human-induced environmental disturbances in the country. These extensive modifications of both peatland and mineral soil dominated landscapes still carry largely unknown, but potentially enormous environmental legacy effects. However, the consequences of contemporary ditch management strategies, such as hydrological restoration via ditch blocking or enhancing forest drainage to promote biomass production via ditch cleaning, on water resources and greenhouse gas (GHG) fluxes are unclear. To close the gap between science and management, we have developed a unique field research platform to experimentally evaluate key environmental strategies for drained northern landscapes with the aim to avoid further environmental degeneration. The Trollberget Experimental Area (TEA) includes replicated and controlled treatments applied at the catchment scale based on a BACI approach (before-after and control-impact). The treatments represent the dominant ecosystem types impacted by ditching in Sweden and the boreal zone: (1) rewetting of a drained peatland, (2) ditch cleaning in productive upland forests and (3) leaving these ditches unmanaged. Here we describe the TEA platform, report initial results, suggest ways forward for how to best manage this historical large-scale alteration of the boreal landscape, as well as warn against applying these treatments broadly before more long-term results are reported.
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| 3. |
- Abbott, Benjamin, et al.
(author)
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Using multi-tracer inference to move beyond single-catchment ecohydrology
- 2016
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In: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 160, s. 19-42
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Journal article (peer-reviewed)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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| 4. |
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| 5. |
- Aldén, Marcus, et al.
(author)
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Applications of two-photon absorption for detection of CO in combustion gases
- 1984
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In: Applied Physics B. - 0946-2171. ; 33:4, s. 205-208
-
Journal article (peer-reviewed)abstract
- Laser-induced fluorescence has been used for detection of CO in different environments. The fluorescence light was obtained by using a two-photon transition between theX1?- and theB1?- electronical states around 230 nm. Cell measurements indicate a detection limit lower than 0.1 ppm. Measurements in a CH4/air flame and in a low pressure dc discharge were realized with a diode-array detector, which was used in an imaging mode, permitting single-shot CO distributions to be captured.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Audet, Joachim, et al.
(author)
-
Forest streams are important sources for nitrous oxide emissions - Nitrous oxide emissions from Swedish streams
- 2020
-
In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 26, s. 629-641
-
Journal article (peer-reviewed)abstract
- Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2O). N2O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2O concentrations of 1.6 +/- 2.1 and 1.3 +/- 1.8 mu g N/L, respectively (mean +/- SD) despite higher total N (TN) concentrations in agricultural streams (1,520 +/- 1,640 vs. 780 +/- 600 mu g N/L). Although clear patterns linking N2O concentrations and environmental variables were difficult to discern, the percent saturation of N2O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2O emissions. An estimate of the N2O emission from low-order streams at the national scale revealed that ~1.8 x 10(9) g N2O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2O sources in the landscape with 800 x 10(9) g CO2-eq emitted annually in Sweden, equivalent to 25% of the total N2O emissions from the Swedish agricultural sector.
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| 10. |
- Audet, Joachim, et al.
(author)
-
Nitrous oxide emissions from streams in a Swedish agricultural catchment
- 2017
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In: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 236, s. 295-303
-
Journal article (peer-reviewed)abstract
- Excess nitrogen fertiliser in agricultural soils might be leached to streams and converted to the greenhouse gas nitrous oxide (N2O). To assess the importance of N2O emissions from agricultural streams, concentration dynamics and emissions N2O emissions in streams were investigated in a 32 km2 lowland agricultural catchment located in Sweden. Dissolved N2O concentration was measured at nine occasions between December 2014 and August 2015 at nine stream stations. The stream stations represented sub-catchments with different land use characteristics with agricultural land use ranging from 0 to 63% of the area. Stream N2O percentage saturation ranged 40-2701% and showed large spatial and temporal variations. Statistical analysis using mixed models revealed that N2O concentration was significantly linked to nitrate concentration in the stream water, to the percentage arable land in the sub catchments as well as to the stream water discharge. Using two empirical equations to estimate the N2O emissions showed that streams were generally a source of N2O to the atmosphere (mean 108 and 175 mu g N m(-2) h(-1) with first and second equation). The catchment scale estimate of N2O stream emissions was compared to the estimate obtained using IPCC guidelines linking N fertilisation inputs and leaching to N2O emissions. The comparison suggested that N2O stream emission calculated using the IPCC methodology might be underestimated. A coarse estimate suggests that N2O stream emissions represent about 4% of the total N2O emissions from N-fertiliser at the catchment scale. Hence while streams covered only 0.1% of the catchment area they were of disproportionate importance as a source of N2O to the atmosphere.
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| 11. |
- Balathandayuthabani, Sivakiruthika, et al.
(author)
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Aquatic carbon fluxes in a hemiboreal catchment are predictable from landscape morphology, temperature, and runoff
- 2023
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In: Limnology and Oceanography Letters. - : Wiley. - 2378-2242. ; 8:2, s. 313-22
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Journal article (peer-reviewed)abstract
- Aquatic networks contribute greenhouse gases and lateral carbon (C) export from catchments. The magnitudes of these fluxes exceed the global land C sink but are uncertain. Resolving this uncertainty is important for understanding climate feedbacks. We quantified vertical methane (CH4) and carbon dioxide (CO2) emissions from lakes and streams, and lateral export of dissolved inorganic and organic carbon from a hemiboreal catchment for 3 yr. Lateral C fluxes dominated the total aquatic C flux. All aquatic C fluxes were disproportionately contributed from spatially restricted areas and/or short-term events. Hence, consideration of local and episodic variability is vital. Temperature and runoff were the main temporal drivers for lake and stream C emissions, respectively. Whole-catchment aquatic C emissions scaled linearly with these drivers within timeframes of stable land-cover. Hence, temperature and runoff increase across Northern Hemisphere humid areas from climate change may yield proportional increases in aquatic C fluxes.
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| 12. |
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| 13. |
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| 14. |
- Bansal, Sheel, et al.
(author)
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Practical Guide to Measuring Wetland Carbon Pools and Fluxes
- 2023
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In: Wetlands (Wilmington, N.C.). - : SPRINGER. - 0277-5212 .- 1943-6246. ; 43:8
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Research review (peer-reviewed)abstract
- Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions.
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| 15. |
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| 16. |
- Blom Kemdal, Anna, et al.
(author)
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Incels världsåskådning. Hur många Elliot Rodger finns på ett incelforum?
- 2024
-
Conference paper (pop. science, debate, etc.)abstract
- Skriftlig kommunikation från två typer av Reddit forum - Incels och Politics - jämfördes med varandra och med massmördaren Elliot Rodgers skriftliga manifest. Onlinespråk analyserades med LIWC (Linguistic Inquiry Word Count). Data analyserades med ROC-curve och AUC-curve. Linguistiska variabler som var respresentativa för en incel världsåskådning identifierades, en världsåskådning med socio-biologiska, pseudovetenskapliga teorier och negativa antaganden, uttryckta med ett tydligt stereotypiskt dehumaniserande språk, speciellt gällande kvinnor. Detta är i linje med tidigare studier av incels typiska lingvistiska och psykologiska begrepp. ICC (Intraclass correlation coefficient) användes för att undersöka likheter mellan incels, politics och Elliot Rodger. Det fanns stöd för en viss skillnad o absoluta skillnader mellan Incels och Elliot Rodger å ena sidan och Politics och Elliot Rodger å den andra. Incels visade likheter med Elliot Rodger och använde språk som tidigare forskning identifierat som riskbeteende, kopplat till ensamma våldsverkare. Resultaten är preliminära men visar att det finns behov av ytterligare forskning om incels språk och psykologi, för att medverka till att identifiera individer som riskerar att begå våldsamma brott.
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| 17. |
- Blom Kemdal, Anna, et al.
(author)
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The Incel World View : How many Incels are there on an incel forum?
- 2024
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Conference paper (pop. science, debate, etc.)abstract
- Skriftlig kommunikation från två typer av Reddit forum - Incels och Politics - jämfördes med varandra och med massmördaren Elliot Rodgers skriftliga manifest. Onlinespråk analyserades med LIWC (Linguistic Inquiry Word Count). Data analyserades med ROC-curve och AUC-curve. Linguistiska variabler som var respresentativa för en incel världsåskådning identifierades, en världsåskådning med socio-biologiska, pseudovetenskapliga teorier och negativa antaganden, uttryckta med ett tydligt stereotypiskt dehumaniserande språk, speciellt gällande kvinnor. Detta är i linje med tidigare studier av incels typiska lingvistiska och psykologiska begrepp. ICC (Intraclass correlation coefficient) användes för att undersöka likheter mellan incels, politics och Elliot Rodger. Det fanns stöd för en viss skillnad o absoluta skillnader mellan Incels och Elliot Rodger å ena sidan och Politics och Elliot Rodger å den andra. Incels visade likheter med Elliot Rodger och använde språk som tidigare forskning identifierat som riskbeteende, kopplat till ensamma våldsverkare. Resultaten är preliminära men visar att det finns behov av ytterligare forskning om incels språk och psykologi, för att medverka till att identifiera individer som riskerar att begå våldsamma brott.
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| 18. |
- Blom Kemdal, Anna, et al.
(author)
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The Incel World View : How Many Elliot Rodgers are there on an Incel Forum?
- 2024
-
Conference paper (other academic/artistic)abstract
- Skriftlig kommunikation från två typer av Reddit forum - Incels och Politics - jämfördes med varandra och med massmördaren Elliot Rodgers skriftliga manifest. Onlinespråk analyserades med LIWC (Linguistic Inquiry Word Count). Data analyserades med ROC-curve och AUC-curve. Linguistiska variabler som var respresentativa för en incel världsåskådning identifierades, en världsåskådning med socio-biologiska, pseudovetenskapliga teorier och negativa antaganden, uttryckta med ett tydligt stereotypiskt dehumaniserande språk, speciellt gällande kvinnor. Detta är i linje med tidigare studier av incels typiska lingvistiska och psykologiska begrepp. ICC (Intraclass correlation coefficient) användes för att undersöka likheter mellan incels, politics och Elliot Rodger. Det fanns stöd för en viss skillnad o absoluta skillnader mellan Incels och Elliot Rodger å ena sidan och Politics och Elliot Rodger å den andra. Incels visade likheter med Elliot Rodger och använde språk som tidigare forskning identifierat som riskbeteende, kopplat till ensamma våldsverkare. Resultaten är preliminära men visar att det finns behov av ytterligare forskning om incels språk och psykologi, för att medverka till att identifiera individer som riskerar att begå våldsamma brott.
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| 19. |
- Bravender, T., et al.
(author)
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Classification of Eating Disturbance in Children and Adolescents: Proposed Changes for the DSM-V
- 2010
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In: European Eating Disorders Review. - : Wiley. - 1072-4133 .- 1099-0968. ; 18:2, s. 79-89
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Journal article (peer-reviewed)abstract
- Childhood and adolescence are critical periods of neural development and physical growth. The malnutrition and related medical complications resulting from eating disorders such as anorexia nervosa (AN), bulimia nervosa (BN) and eating disorder not otherwise specified may have more severe and potentially more protracted consequences during youth than during other age periods. The consensus opinion of an international workgroup of experts on the diagnosis and treatment of child and adolescent eating disorders is that (a) lower and more developmentally sensitive threshold's of symptom seventy (e.g lower frequency of purging behaviours, significant deviations from growth curves as indicators of clinical seventy) be used as diagnostic boundaries for children and adolescents, (b) behavioural indicators of psychological features of eating disorders be considered even in the absence of direct self-report of such symptoms and (C) multiple informants (e.g parents) be used to ascertain symptom profiles. Collectively, these recommendations will permit earlier identification and intervention to prevent the exacerbation of eating disorder symptoms. Copyright (C) 2010 John Wiley & Sons, Ltd and Eating Disorders Association
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| 20. |
- Campeau, Audrey, et al.
(author)
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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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In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 23:12, s. 5523-5536
-
Journal article (peer-reviewed)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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| 21. |
- Campeau, Audrey, et al.
(author)
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Autumn destabilization of deep porewater CO2 store in a northern peatland driven by turbulent diffusion
- 2021
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)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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| 22. |
- Campeau, Audrey
(author)
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Carbon in Boreal Streams : Isotopic Tracing of Terrestrial Sources
- 2019
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Doctoral thesis (other academic/artistic)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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| 23. |
- Campeau, Audrey, et al.
(author)
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Current forest carbon fixation fuels stream CO 2 emissions
- 2019
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 10:1
-
Journal article (peer-reviewed)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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| 24. |
- Campeau, Audrey, et al.
(author)
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Multiple sources and sinks of dissolved inorganic carbon across Swedish streams, refocusing the lens of stable C isotopes
- 2017
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Journal article (peer-reviewed)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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| 25. |
- Campeau, Audrey, et al.
(author)
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Stable carbon isotopes reveal soil - stream DIC linkages in contrasting headwater catchments
- 2018
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In: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 123:1, s. 149-167
-
Journal article (peer-reviewed)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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| 26. |
- Chmiel, Hannah Elisa, 1983-, et al.
(author)
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The role of sediments in the carbon budget of a small boreal lake
- 2016
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In: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 61:5, s. 1814-1825
-
Journal article (peer-reviewed)abstract
- We investigated the role of lake sediments as carbon (C) source and sink in the annual C budget of a small (0.07 km2), shallow (mean depth 3.4 m), and humic lake (mean DOC concentration 17 mg L-1) in boreal Sweden. Organic carbon (OC) burial and mineralization in sediments were quantified from 210Pb-dated sediment and laboratory sediment incubation experiments, respectively, and upscaled to the entire basin and to one whole year, by using sediment thickness derived sub-bottom profiling, basin morphometry, and water column monitoring data of temperature and oxygen concentration. Furthermore, catchment C import, open water metabolism, photochemical mineralization as well as carbon dioxide (CO2) and methane (CH4) emissions to the atmosphere, were quantified to relate sediment processes to other lake C fluxes. We found that on a whole-basin and annual scale, sediment OC mineralization was three times larger than OC burial, and contributed about 16% to the annual CO2 emission from the lake to the atmosphere. Remaining contributions to the CO2 emission were attributed to water column metabolism (31%), photochemical mineralization (6%), and catchment imports via inlet streams and inflow of shallow groundwater (47%). We conclude that on an annual and whole-basin scale 1) sediment OC mineralization dominated over OC burial, 2) water column OC mineralization contributed more than sediments to lake CO2 emission, and 3) catchment import of C to the lake was greater than lake-internal C cycling.
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| 27. |
- Denfeld, Blaize A., et al.
(author)
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Temporal and spatial carbon dioxide concentration patterns in a small boreal lake in relation to ice cover dynamics
- 2015
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In: Boreal environment research. - 1239-6095 .- 1797-2469. ; 20:6, s. 679-692
-
Journal article (peer-reviewed)abstract
- Global carbon dioxide (CO2) emission estimates from inland waters commonly neglect the ice-cover season. To account for CO2 accumulation below ice and consequent emissions into the atmosphere at ice-melt we combined automatically-monitored and manually- sampled spatially-distributed CO2 concentration measurements from a small boreal ice-covered lake in Sweden. In early winter, CO2 accumulated continuously below ice, whereas, in late winter, CO2 concentrations remained rather constant. At ice-melt, two CO2 concentration peaks were recorded, the first one reflecting lateral CO2 transport within the upper water column, and the second one reflecting vertical CO2 transport from bottom waters. We estimated that 66%–85% of the total CO2 accumulated in the water below ice left the lake at ice-melt, while the remainder was stored in bottom waters. Our results imply that CO2 accumulation under ice and emissions at ice-melt are more dynamic than previously reported, and thus need to be more accurately integrated into annual CO2 emission estimates from inland waters.
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| 28. |
- Dinsmore, Kerry, et al.
(author)
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Contrasting CO2 concentration discharge dynamics in headwater streams : a multi-catchment comparison
- 2013
-
In: Journal of Geophysical Research-Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 118:2, s. 445-461
-
Journal article (peer-reviewed)abstract
- Aquatic CO2 concentrations are highly variable and strongly linked to discharge, but until recently, measurements have been largely restricted to low-frequency manual sampling. Using new in situ CO2 sensors, we present concurrent, high-frequency (<30 min resolution) CO2 concentration and discharge data collected from five catchments across Canada, UK, and Fennoscandinavia to explore concentration-discharge dynamics; we also consider the relative importance of high flows to lateral aquatic CO2 export. The catchments encompassed a wide range of mean CO2 concentrations (0.73–3.05 mg C L−1) and hydrological flow regimes from flashy peatland streams to muted outflows within a Finnish lake system. In three of the catchments, CO2 concentrations displayed clear bimodal distributions indicating distinct CO2 sources. Concentration-discharge relationships were not consistent across sites with three of the catchments displaying a negative relationship and two catchments displaying a positive relationship. When individual high flow events were considered, we found a strong correlation between both the average magnitude of the hydrological and CO2 response peaks, and the average response lag times. An analysis of lateral CO2 export showed that in three of the catchments, the top 30% of flow (i.e., flow that was exceeded only 30% of the time) had the greatest influence on total annual load. This indicates that an increase in precipitation extremes (greater high-flow contributions) may have a greater influence on the flushing of CO2 from soils to surface waters than a long-term increase in mean annual precipitation, assuming source limitation does not occur.
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| 29. |
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| 30. |
- Einarsdóttir, Karólina, et al.
(author)
-
High terrestrial carbon load via groundwater to a boreal lake dominated by surface water inflow
- 2017
-
In: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 122:1, s. 15-29
-
Journal article (peer-reviewed)abstract
- The input of dissolved organic and inorganic carbon (DOC and DIC) via direct groundwater seepage to boreal lakes is often assumed to be small in noncarbonaceous areas. However, measurements are rare. We estimated the terrestrial load of DOC, DIC, and methane (CH4) to a small boreal lake for the open water period, on the basis of measured concentrations of carbon species in near-shore groundwater wells and inlet streams, and measured area-specific discharge. The subcatchment directly draining into the lake via groundwater seepage contributed 18% to the total water input during the open water season. Compared to stream and lake water, near-shore groundwater concentrations of DOC were slightly elevated, and groundwater DIC and CH4concentrations were highly elevated. Consequently, direct groundwater seepage contributed 27% to the total DOC load, 64% to the total DIC load, and 96% to the total CH4 load from the catchment to the lake. Groundwater DIC import corresponded only to 5–8% of lake carbon dioxide (CO2) emission. In incubation experiments, we observed higher photochemical DOC loss rates in stream and groundwater samples (18–55% DOC loss upon 72 h UV-A exposure) than in lake water (15% DOC loss) and detected significant DOC flocculation in groundwater samples in both light and dark incubations (2–24% DOC loss). We conclude that even in regions where lake hydrology is dominated by surface water inflow via inlet streams, direct groundwater seepage can represent an important carbon source to boreal lakes, and groundwater DOC may be susceptible to in-lake removal via degradation and flocculation.
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| 31. |
- Ejhed, Helene, et al.
(author)
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Bruttobelastning på vatten av metaller från punktkällor och diffusa källor - slutrapport
- 2010
-
Reports (other academic/artistic)abstract
- Denna rapport omfattar redovisningar av beräkningar av bruttobelastning av metallerna Zn, Cd, Cu, Ni, Pb och Hg från diffusa källor och punktkällor geografiskt fördelat för hela Sverige. De diffusa källor som ingår är läckage från all markanvändning med klasserna: skog, hygge, övrig mark, fjäll, våtmark, vatten (öppen sjöyta) och tätort. Punktkällor som ingår är: samtliga i EMIR registrerade utsläpp till vatten och grundvatten gällande år 2007, kommunala reningsverk (KARV) utsläpp gällande år 2008 eller senast tillgängligt år, utsläpp enligt E-PRTR utgör en delmängd av EMIR utsläpp, nedlagda gruvdeponier (ej i EMIR) har sammanställts från länsstryrelse rapporter samt beräknade utsläpp från enskilda avlopp. Rapporten omfattar utförlig beskrivning av underlag till beräkningarna och svagheter i underlagen, diskussioner om skillnader mot uppmätt transport i flodmynningarna och förslag till vidareutveckling och förbättring av underlag. Resultaten för industrier, som presenteras nedan, avser samtliga punktkällor utom KARV och enskilda avlopp. Resultaten har tagits fram för internationell rapportering till EEA (Europeiska miljöbyrån) sammanställt per vattendistrikt. Det har varit uppenbart liksom i tidigare sammanställningar att det saknas dataunderlag för många källor och att osäkerheterna därför blir mycket stora i det sammanlagda resultatet. Rapporten inkluderar förslag till vidareutveckling och förbättring av underlag för att förbättra resultaten och inkludera, till exempel, avskiljning av metaller under transport från källan till havet.Modellerade bruttobelastningen har gett resultat som är av samma storleksordning som uppmätt transport i flodmynningarna, vilket innebär att de största källorna troligen finns inkluderade i datamaterialet. Det finns dock konstaterade mörkertal för ett flertal källor, varav avfallsdeponier, utlakning från båtbottenfärger, färg och rostskydd, utsläpp från icke-rapporterande verksamheter samt återcirkulation från sediment kan vara stora.Följande resultat i urval har beräknats i detta projekt:· För samtliga metaller står de diffusa källorna för merparten av den totala bruttobelastningen, för Cd, Cu och Hg mer än 80 % och för Pb och Ni mer än 90 %.· För Cd, Pb och Hg har läckage från skog och hygge samt depositionen på sjöyta beräknats vara de dominerande källorna.· För Hg är bidragen från övrig mark och dagvatten i tätort också betydande.· För Cu är skog och hygge den största källan, men övriga diffusa källor fördelas ungefär lika.· Ni har störst belastning från skog och hygge samt från jordbruksmark.· Zn har något lägre bidrag från diffusa källor, ca 77 % av totala bruttobelastningen relativt jämnt fördelat mellan de diffusa källorna.· 20 % av den totala bruttobelastningen av Zn har beräknats komma från industrier.· Av punktkällorna är industri den klart största källan till Cd och Pb (mer än 90 %) medan för Cu fördelas punktkällorna mer jämt mellan KARV och industri (cirka 30 respektive 60 %).Det finns skillnader mellan uppmätta transporter och beräknade resultat, både totalt och mellan de olika metallerna. Följande skillnader i urval har konstaterats:· Bruttobelastningen har beräknats vara generellt högre i förhållande till medelvärde av flodmynningstransporten i södra Sverige med några undantag, vilket kan bero på att metaller kan avskiljas vid transport från källorna till flodmynningarna (retention).· Bruttobelastningen har beräknats vara generellt låg i förhållande till medelvärde av flodmynningstransporten i norra Sverige, vilket kan bero på för låga beräknade läckagehalter.· Cu och Ni belastningarna har beräknats vara låga speciellt i norra Sverige, vilket kan bero på låga beräknade läckagehalter för markanvändningen skog, hygge och övrig mark eller på låga beräknade halter av jordbruksmark.Fördelning mellan bakgrund och antropogent har inte vara möjlig att beräkna med tillgängliga underlag i projektet. På grund av processer som kan äga rum i de antropogent påverkade markanvändningarna, jordbruksmark och skog samt hygge och påverkan av deposition av metaller och surt regn på samtlig markanvändning, så är den antropogena påverkan svår att tolka. Ytterligare utredning är nödvändig innan resultat kan presenteras för alla källor. Dock har samtliga punktkällor och diffus belastning från tätorter och väg samt deposition konstaterats domineras av antropogent ursprung i denna rapport.Förslag till vidareutveckling och förbättring av underlag:· Utredning av avvikelser jämfört med uppmätt transport.· Utveckling av beräkningar av retention för metaller.· Tillägg av saknade källor, till exempel Cu i båtbottenfärg.· Utredning av fördelning mellan antropogen belastning och bakgrund för de diffusa källorna till metaller.· Förbättring av underlagsmaterialet för läckagehalter (mätningar i jordbruks-, fjäll- och våtmarksområden) och deposition.
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| 32. |
- Eklöf, Karin, et al.
(author)
-
Brownification on hold : What traditional analyses miss in extended surface water records
- 2021
-
In: Water Research. - : Elsevier Ltd. - 0043-1354 .- 1879-2448. ; 203
-
Journal article (peer-reviewed)abstract
- Widespread increases in organic matter (OM) content of surface waters, as measured by color and organic carbon (OC), are a major issue for aquatic ecosystems. Long-term monitoring programs revealed the issue of “brownification”, with climate change, land cover changes and recovery from acidification all suspected to be major drivers or contributing factors. While many studies have focused on the impact and drivers, fewer have followed up on whether brownification is continuing. As time-series of OM data lengthen, conventional data-analysis approaches miss important information on when changes occur. To better identify temporal OM patterns during three decades (1990–2020) of systematic monitoring, we used generalized additive models to analyze 164 time-series from watercourses located across Sweden. Increases in OC that were widespread during 1990–2010 ceased a decade ago, and most color increases ceased 20 years ago. These findings highlight the need to reassess the understanding of brownification's spatial and temporal extent, as well as the tools used to analyze lengthening time series.
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| 33. |
- Eklöf, Karin, et al.
(author)
-
Effekter av dikesrensning och våtmarksrestaurering på kvicksilver i vatten
- 2024
-
Reports (other academic/artistic)abstract
- Dikning av våtmark i svenska skogsområden under de senaste 120 åren har bidragit till ökad skogsproduktion men också orsakat genomgripande förändringar i skogarnas omsättning och lagring av vatten. Med tiden ansamlas sediment och vegetation i dikena, och dikesrensning kan behövas för att upprätthålla en hög skogsproduktion. Åtgärden kan dock påverka markegenskaper och -processer, vattenkvalitet och kolbalans. Ökad avrinning av total-kvicksilver (THg) och biotillgängligt metylkvicksilver (MeHg) har pekats ut som en potentiell risk vid dikesrensning. En alternativ åtgärd för dikade områden är restaurering till mer naturliga våtmarksförhållanden. Från politiskt håll uppmuntras restaurering som en åtgärd mot översvämningar och torka, för att minska emission av växthusgaser och för att öka den biologiska mångfalden. Åtgärden, som i regel blötlägger torv, riskerar dock att öka den mikrobiella bildningen av MeHg. Mer ytliga flödesvägar i restaurerade våtmarker riskerar också att mobilisera kvicksilver (Hg) från markens övre lager. I ett experimentellt fältförsök med sex avrinningsområden och tre referensområden studerades effekter på THg och MeHg i dikesvatten, efter både dikesrensning och våtmarksrestaurering, upp till ca två år efter åtgärderna. Fältförsöket kompletterades med provtagning av THg och MeHg i rensade (n = 25; 1–4 år efter rensning) och orensade (n = 25) diken i en rumslig studie med en stor geografisk spridning. Dessutom utvärderades 15 sedimentationsdammar belägna nedströms dikesrensade områden med avseende på bildning av MeHg i dammarna. Slutligen i en litteraturstudie sammanställdes effekter av dikesrensning på skogsproduktion med syftet att väga dessa effekter mot effekter på THg och MeHg i vatten. Resultaten visar att dikesrensning inte ledde till några ökningar av THg och MeHg i avrinnande vatten. Tvärt om, minskade koncentrationen och exporten av THg och MeHg i vissa områden. Dikesrensning ledde inte heller till några tydliga ökningar av partikelbundet THg och MeHg. Risken att dikesrensning i avverkade områden kan leda till ökad mobilisering av MeHg från de avverkade områdena kunde inte påvisas genom hydrologisk modellering. Sedimentationsdammar, merparten relativt små, nedströms dikesrensade områden orsakade inga förhöjda halter av MeHg, varken i bottensediment eller i dikesvatten nedströms dammarna. Våtmarksrestaurering ledde till ökade koncentration och export av THg och MeHg i ett av de två restaurerade områdena. Sammanfattningsvis visar studierna i projektet att dikesrensning kan minska, och våtmarksrestaurering kan öka THg och MeHg i avrinnande vatten, men att det kan variera mellan områden. Det gäller åtminstone under de första åren efter åtgärderna som studierna avser. Dessa förändringar drivs troligtvis av en kombination av i) ändrade flödesvägar för vattnet och ii) förändrade redox-förhållanden i marken då grundvattenytan sänks (vid dikesrensning) respektive höjs (vid våtmarksrestaurering).
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| 34. |
- Erikshammar, Jarkko, et al.
(author)
-
Vendor managed inventory : a sawmills potential offering for builders merchants
- 2013
-
Reports (other academic/artistic)abstract
- Vendor managed inventory (VMI) is a frequently used method for and a widely discussed partnering initiatives for improving supply chain efficiency. VMI as a program has increased in popularity, especially in the grocery industry, where the supplier, reseller or distributor makes the main inventory replenishment decision for the consuming organization. The objective of implementing VMI programs is to decrease costs for inventory control and management, and create transparency; possibility to collaborative planning and replenishment and efficient consumer response. The theoretical framework presents the basics of VMI, what the effects are and what prerequisites for such a program demands. The theoretical framework is used for the model of analysis when analyzing the possibility to implement VMI from a sawmill perspective to one of their customer segments; builders merchants. This is a case study performed at a small and medium sized sawmill. The purpose of this study was to investigate the possibilities of theoretically implement VMI since the Swedish wood supply chain is in a need for new business models and services since the value refinement is too low. The current system for inventory management and replenishment is summarized and compared to a theoretical construction with VMI. The analysis shows total settlement days could increase with 50%. This has a positive effect on the net cash flow and the inventory turnover per year could almost double. Further does the relationship between Case Company and Builders merchant fulfill the requirements for implementing a VMI program, but there is reason to be aware of the potential pitfalls.
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| 35. |
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| 36. |
- Ewerlöf, Sofia, et al.
(author)
-
DN Debatt. ”Låt gräsklipparen stå – för naturens skull”
- 2023
-
In: Dagens nyheter (DN debatt). - 1101-2447.
-
Journal article (pop. science, debate, etc.)abstract
- In an era of species extinction and climate change, we should abandon the well-trimmed lawn and let gardens grow wilder, writes Anna Persson and other researchers and landscape architects on DN Debatt.
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| 37. |
- Gomez-Gener, L., et al.
(author)
-
Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions
- 2021
-
In: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 14, s. 289-294
-
Journal article (peer-reviewed)abstract
- Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27% (0.9 gC m(-2) d(-1)) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65-1.8 PgC yr(-1)) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20-0.55 PgC yr(-1). Failing to account for emission differences between day and night will lead to an underestimate of global CO2 emissions from rivers by up to 0.55 PgC yr(-1), according to analyses of high-frequency CO2 measurements.
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| 38. |
- Grace, Marcus, et al.
(author)
-
Student Decision-Making about a Globally Familiar Socioscientific Issue: The value of sharing and comparing views with international counterparts
- 2015
-
In: International Journal of Science Education. - : Informa UK Limited. - 0950-0693 .- 1464-5289. ; 37:11, s. 1855-1874
-
Journal article (peer-reviewed)abstract
- This paper focuses on the views of 16–17-year-old science students from England, Germany, Hong Kong and Sweden on whale hunting, and their perceptions of the views of their international counterparts. The students were all provided with the same decision-making task, discussed the issue in small groups and then presented their views on video, which were shared with their counterparts. The findings show that the decision-making task served to deepen and modify students’ views across all nationalities, and the students generally valued and learned from the sharing of views with students of the same age from around the world. However, an important discovery was that the German students’ opinions often ran counter to those from the other 3 locations, and the paper cautions against making broad-sweeping generalisations about students’ views on socioscientific issues.
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| 39. |
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| 40. |
- Gray, Marcus A, et al.
(author)
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Following one's heart: cardiac rhythms gate central initiation of sympathetic reflexes.
- 2009
-
In: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 29:6, s. 1817-25
-
Journal article (peer-reviewed)abstract
- Central nervous processing of environmental stimuli requires integration of sensory information with ongoing autonomic control of cardiovascular function. Rhythmic feedback of cardiac and baroreceptor activity contributes dynamically to homeostatic autonomic control. We examined how the processing of brief somatosensory stimuli is altered across the cardiac cycle to evoke differential changes in bodily state. Using functional magnetic resonance imaging of brain and noninvasive beat-to-beat cardiovascular monitoring, we show that stimuli presented before and during early cardiac systole elicited differential changes in neural activity within amygdala, anterior insula and pons, and engendered different effects on blood pressure. Stimulation delivered during early systole inhibited blood pressure increases. Individual differences in heart rate variability predicted magnitude of differential cardiac timing responses within periaqueductal gray, amygdala and insula. Our findings highlight integration of somatosensory and phasic baroreceptor information at cortical, limbic and brainstem levels, with relevance to mechanisms underlying pain control, hypertension and anxiety.
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| 41. |
- Guinea Barrientos, Héctor Estuardo, 1980-, et al.
(author)
-
Disaster management cooperation in central america : The case of rainfall-induced natural disasters
- 2015
-
In: Geografiska Annaler. Series A, Physical Geography. - : Wiley-Blackwell. - 0435-3676 .- 1468-0459. ; 97:1, s. 85-96
-
Journal article (peer-reviewed)abstract
- Rainfall-induced natural disasters rank first among all natural disasters in Central America. Due to the geographical conditions of the Central American region, it is common that two or more countries are struck by the same rainfall event, for example Hurricane Mitch in 1998 affected the entire Central American region, killing more than 18000 people. As a consequence, Central American countries have started to promote regional policies and programs that aim for better preparation and response to these events, including disaster management cooperation. However, cooperation poses several challenges that may hinder its goals. In order to analyse these challenges, we present analysis in this paper of the current policy and legal institutions as well as the main challenges that may hinder international disaster management cooperation in Central America.
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| 42. |
- Guinea Barrientos, Héctor Estuardo, 1980-
(author)
-
Institutional Aspects of Integrated Flood Management in Guatemala
- 2014
-
Doctoral thesis (other academic/artistic)abstract
- Floods are a recurrent natural disaster in Guatemala. Heavy and prolonged rainfall often results in floods that affect people’s life and property. Several institutions and policy instruments at local, national or transnational level address flood management.The purpose of this study is to provide useful insights of the institutional aspects of integrated flood management at local, national and transboundary level in Guatemala. Papers I and II, explore institutions at local level, paper III at national level, while paper IV addresses flood management institutions at transboundary level.This research found that for the local and national level, there are several institutions concerned with flood management. In contrast, at transboundary level, and especially for international rivers, flood management institutions are largely absent.At local level, the Local Councils for Development (COCODEs, the acronym in Spanish) are responsible for flood prevention and preparation. While some municipalities are active in flood prevention, response and recovery activities, their limited economic and technical resources restrict their scope of action. Local stakeholders such as COCODEs, farmers groups and other actors are largely neglected in the decision making process. The National Coordinator for Risk Reduction to Disasters (CONRED, Coordinadora Nacional para Reducción de Desastres), the Secretariat for Planning and Programming of the Presidency (SEGEPLAN, Secretaría de Planificación y Programación de la Presidencia), the Guatemalan Ministry of Infrastructure and other national institutions are in charge of planning and implementing flood management strategies, leaving public involvement of local actors mainly to public consultation. At the Central American level, the Coordination Centre for Natural Disasters Prevention in Central America (CEPREDENAC, Centro de Coordinación para la Prevención de Desastres Naturales en América Central), an institution part of the Central American Integration System (SICA by Spanish acronym), shall promote transboundary cooperation regarding disaster management, including flood management. However, transboundary flood management faces several challenges: territorial disputes and sovereignty issues over international rivers are significant obstacles to the implementation of integrated flood management programs.
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| 43. |
- Guseva, S., et al.
(author)
-
Variable Physical Drivers of Near-Surface Turbulence in a Regulated River
- 2021
-
In: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 57:11
-
Journal article (peer-reviewed)abstract
- Inland waters, such as lakes, reservoirs and rivers, are important sources of climate forcing trace gases. A key parameter that regulates the gas exchange between water and the atmosphere is the gas transfer velocity, which itself is controlled by near-surface turbulence in the water. While in lakes and reservoirs, near-surface turbulence is mainly driven by atmospheric forcing, in shallow rivers and streams it is generated by bottom friction of gravity-forced flow. Large rivers represent a transition between these two cases. Near-surface turbulence has rarely been measured in rivers and the drivers of turbulence have not been quantified. We analyzed continuous measurements of flow velocity and quantified turbulence as the rate of dissipation of turbulent kinetic energy over the ice-free season in a large regulated river in Northern Finland. Measured dissipation rates agreed with predictions from bulk parameters, including mean flow velocity, wind speed, surface heat flux, and with a one-dimensional numerical turbulence model. Values ranged from to . Atmospheric forcing or gravity was the dominant driver of near-surface turbulence for similar fraction of the time. Large variability in near-surface dissipation rate occurred at diel time scales, when the flow velocity was strongly affected by downstream dam operation. By combining scaling relations for boundary-layer turbulence at the river bed and at the air-water interface, we derived a simple model for estimating the relative contributions of wind speed and bottom friction of river flow as a function of depth.Plain Language SummaryInland water bodies such as lakes, reservoirs and rivers are an important source of climate forcing trace gases to the atmosphere. Gas exchange between water and the atmosphere is regulated by the gas transfer velocity and the concentration difference between the water surface and the atmosphere. The gas transfer velocity depends on near-surface turbulence, but robust formulations have not been developed for river systems. Their surface area is sufficiently large for meteorological forcing to cause turbulence, as in lakes and reservoirs, but turbulence generated from bed and internal friction of gravity-driven flows is also expected to contribute. Here we quantify near-surface turbulence using data from continuous air and water side measurements conducted over the ice-free season in a large subarctic regulated river in Finland. We find that turbulence, quantified as the dissipation rate of turbulent kinetic energy, is well described using equations for predicting turbulence from meteorological data for sufficiently high wind speeds whereas the contribution from bottom shear dominated at higher flow velocities. A one-dimensional river model successfully captured these processes. We provide a fundamental model for estimating the relative contributions of atmospheric forcing and bottom friction as a function of depth.
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| 44. |
- Gutiérrez Loza, Lucia, et al.
(author)
-
Air–sea CO2 exchange in the Baltic Sea—A sensitivity analysis of the gas transfer velocity
- 2021
-
In: Journal of Marine Systems. - : Elsevier. - 0924-7963 .- 1879-1573. ; 222
-
Journal article (peer-reviewed)abstract
- Air–sea gas fluxes are commonly estimated using wind-based parametrizations of the gas transfer velocity. However, neglecting gas exchange forcing mechanisms – other than wind speed – may lead to large uncertainties in the flux estimates and the carbon budgets, in particular, in heterogeneous environments such as marginal seas and coastal areas. In this study we investigated the impact of including relevant processes to the air–sea CO2 flux parametrization for the Baltic Sea. We used six parametrizations of the gas transfer velocity to evaluate the effect of precipitation, water-side convection, and surfactants on the net CO2 flux at regional and sub-regional scale. The differences both in the mean CO2 fluxes and the integrated net fluxes were small between the different cases. However, the implications on the seasonal variability were shown to be significant. The inter-annual and spatial variability were also found to be associated with the forcing mechanisms evaluated in the study. In addition to wind, water-side convection was the most relevant parameter controlling the air–sea gas exchange at seasonal and inter-annual scales. The effect of precipitation and surfactants seemed negligible in terms of the inter-annual variability. The effect of water-side convection and surfactants resulted in a reduction of the downward fluxes, while precipitation was the only parameter that resulted in an enhancement of the net uptake in the Baltic Sea.
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| 45. |
- Gutiérrez-Loza, Lucía, 1989-, et al.
(author)
-
Evaluating the effect of precipitation on air-sea CO2 exchange using eddy covariance measurements
-
Other publication (other academic/artistic)abstract
- The air-sea exchange of carbon dioxide (CO2) is modulated by processes controlling the physical and biogeochemical characteristics of the upper layer of the ocean. One such process is precipitation, which is known to alter the surface layer of the ocean via rain-induced turbulence, deposition of dissolved CO2, and through changes of the temperature, salinity, and chemical composition of the surface waters (i.e. dilution effects). Even though great advances have been made in the understanding of these mechanisms, and their impact on the regional and global air-sea CO2 fluxes from laboratory experiments and numerical models, the effect of rain and other types of precipitation has seldom been studied using field data. In this study, we use eddy covariance based measurements of air-sea CO2 flux along with in-situ precipitation data from the Östergarnsholm station in the central Baltic Sea, to evaluate the effect of precipitation on the gas exchange. The results show that most types of precipitation enhance the CO2 transport when the flux is positive, i.e. from the ocean to the atmosphere, in particular during high wind-speed conditions. Negative fluxes, on the other hand, are less affected by precipitation. Snow, and mixed precipitation of rain with snow, induce the greatest increase on the exchange rate, while smaller droplets like drizzle cause smaller enhancement. According to the results presented here, not only the impact of rain, but all types of precipitation, should be accounted for in the air-sea CO2 flux estimates, even in regions where precipitation rates are low. At high latitudes, accounting for these effects, in particular the effect of snow and other solid types of precipitations, might be essential to constrain regional CO2 flux estimates.
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| 46. |
- Gutiérrez Loza, Lucia, et al.
(author)
-
Measurement of air-sea methane fluxes in the Baltic Sea using the eddy covariance method
- 2019
-
In: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 7
-
Journal article (peer-reviewed)abstract
- Methane (CH4) is the second-most important greenhouse gas in the atmosphere having a significant effect on global climate. The ocean-particularly the coastal regions-have been recognized to be a net source of CH4, however, the constraints on temporal and spatial resolution of CH4 measurements have been the limiting factor to estimate the total oceanic contributions. In this study, the viability of micrometeorological methods for the analysis of CH4 fluxes in the marine environment was evaluated. We present 1 year of semi-continuous eddy covariance measurements of CH4 atmospheric dry mole fractions and air-sea CH4 flux densities at the Ostergarnsholm station at the east coast of the Gotland Island in the central Baltic Sea. The mean annual CH4 flux density was positive, indicating that the region off Gotland is a net source of CH4 to the atmosphere with monthly mean flux densities ranging between -0.1 and 36 nmol m(-2)s(-1). Both the air-water concentration gradient and the wind speed were found to be crucial parameters controlling the flux. The results were in good agreement with other measurements in the Baltic Sea reported in the MEMENTO database. Our results suggest that the eddy covariance technique is a useful tool for studying CH4 fluxes and improving the understanding of air-sea gas exchange processes with high-temporal resolution. Potentially, the high resolution of micrometeorological data can increase the understanding of the temporal variability and forcing processes of CH4 flux.
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| 47. |
- Gutiérrez-Loza, Lucía
(author)
-
Mechanisms controlling air-sea gas exchange in the Baltic Sea
- 2020
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Licentiate thesis (other academic/artistic)abstract
- Carbon plays a major role in physical and biogeochemical processes in the atmosphere, the biosphere, and the ocean. CO2 and CH4 are two of the most common carbon-containing compounds in the atmosphere, also recognized as major greenhouse gases. The exchange of CO2 and CH4 between the ocean and the atmosphere is an essential part of the global carbon cycle. The exchange is controlled by the air–sea concentration gradient and by the efficiency of the transfer processes. The lack of knowledge about the forcing mechanisms affecting the exchange of these climate-relevant gases is a major source of uncertainty in the estimation of the global oceanic contributions. Quantifying and understanding the air–sea exchange processes is essential to constrain the estimates and to improve our knowledge about the current and future climate. In this thesis, the mechanisms controlling the air–sea gas exchange in the Baltic Sea are investigated.The viability of micrometeorological techniques for CH4 monitoring in a coastal environment is evaluated. One year of semi-continuous measurements of air–sea CH4 fluxes using eddy covariance measurements suggests that the method is useful for CH4 flux estimations in marine environments. The measurements allow long-term monitoring at high frequency rates, thus, capturing the temporal variability of the flux. The region off Gotland is a net source of CH4, with both the air–sea concentration gradient and the wind as controlling mechanisms.A sensitivity analysis of the gas transfer velocity is performed to evaluate the effect of the forcing mechanisms controlling the air–sea CO2 exchange in the Baltic Sea. This analysis shows that the spatio-temporal variability of CO2 fluxes is strongly modulated by water-side convection, precipitation, and surfactants. The effect of these factors is relevant both at regional and global scales, as they are not included in the current budget estimates.
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| 48. |
- Gutiérrez-Loza, Lucía, 1989-
(author)
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On mechanisms controlling air-sea gas exchange
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Carbon is essential to the Earth’s system functioning, playing a major role in physical and biogeochemical processes in the atmosphere, the terrestrial biosphere, and the oceans. The concentration of carbon-based greenhouse gases in the atmosphere, such as carbon dioxide (CO2) and methane (CH4), has been increasing since the industrial era. Therefore, assessing the redistribution of these greenhouse gases between the Earth’s reservoirs has become essential for understanding the current climate system and modelling future climate scenarios.The oceans are a component of the global carbon cycle, and their role as sinks and sources of greenhouse gases has significant implications for the Earth’s climate. The gas exchange between the atmosphere and the ocean is driven by the concentration difference in these two reservoirs. However, the turbulent processes in the layers adjacent to the ocean surface control the efficiency of the transport.This thesis investigates mechanisms controlling the air–sea gas exchange using direct measurements of CO2 and CH4 fluxes from the Östergarnsholm station in the Central Baltic Sea. The gas exchange of both gases is found to have a strong variability at time scales from sub-hourly to inter-annual. The region is found to be a net source of CH4, with both the concentration gradient and wind as controlling mechanisms. In the case of the CO2 fluxes, the variability is strongly modulated by local processes such as sea spray and water-side convection, as well as precipitation. Interestingly, an asymmetric effect is observed, with these processes enhancing the upward transport of CO2 but not the downward flux. Furthermore, a model-based sensitivity analysis of the gas transfer velocity is performed to evaluate the effect of the forcing mechanisms on the air-sea gas exchange at a regional scale. The results show that water-side convection, precipitation, and surfactants strongly modulate the spatio-temporal variability of the CO2 fluxes in the Baltic Sea.
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| 49. |
- Gutiérrez Loza, Lucia, et al.
(author)
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On physical mechanisms enhancing air-sea CO2 exchange
- 2022
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In: Biogeosciences. - : European Geosciences Union (EGU). - 1726-4170 .- 1726-4189. ; 19:24, s. 5645-5665
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Journal article (peer-reviewed)abstract
- Reducing uncertainties in the air–sea CO2 flux calculations is one of the major challenges when addressing the oceanic contribution in the global carbon balance. In traditional models, the air–sea CO2 flux is estimated using expressions of the gas transfer velocity as a function of wind speed. However, other mechanisms affecting the variability in the flux at local and regional scales are still poorly understood. The uncertainties associated with the flux estimates become particularly large in heterogeneous environments such as coastal and marginal seas. Here, we investigated the air–sea CO2 exchange at a coastal site in the central Baltic Sea using nine years of eddy covariance measurements. Based on these observations we were able to capture the temporal variability of the air–sea CO2 flux and other parameters relevant for the gas exchange. Our results show that a wind-based model with similar pattern to those developed for larger basins and open sea condition can, on average, be a good approximation for k. However, in order to reduce the uncertainty associated to these averages and produce reliable short-term k estimates, additional physical processes must be considered. Using a normalized gas transfer velocity, we identified conditions associated to enhanced exchange (large k values). During high and intermediate wind speeds (above 6–8 m s−1),conditions on both sides of the air–water interface were found to be relevant for the gas exchange. Our findings further suggest that at such relatively high wind speeds, sea spray is an efficient mechanisms for air–sea CO2 exchange. During low wind speeds (<6 m s−1), water-side convection was found to be a relevant control mechanism. The effect of both sea spray and water-side convection on the gas exchange showed a clear seasonality with positive fluxes (winter conditions) being the most affected.
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| 50. |
- Haghighi, Mona, et al.
(author)
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A Comparison of Rule-based Analysis with Regression Methods in Understanding the Risk Factors for Study Withdrawal in a Pediatric Study
- 2016
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Journal article (peer-reviewed)abstract
- Regression models are extensively used in many epidemiological studies to understand the linkage between specific outcomes of interest and their risk factors. However, regression models in general examine the average effects of the risk factors and ignore subgroups with different risk profiles. As a result, interventions are often geared towards the average member of the population, without consideration of the special health needs of different subgroups within the population. This paper demonstrates the value of using rule-based analysis methods that can identify subgroups with heterogeneous risk profiles in a population without imposing assumptions on the subgroups or method. The rules define the risk pattern of subsets of individuals by not only considering the interactions between the risk factors but also their ranges. We compared the rule-based analysis results with the results from a logistic regression model in The Environmental Determinants of Diabetes in the Young (TEDDY) study. Both methods detected a similar suite of risk factors, but the rule-based analysis was superior at detecting multiple interactions between the risk factors that characterize the subgroups. A further investigation of the particular characteristics of each subgroup may detect the special health needs of the subgroup and lead to tailored interventions.
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