| 11. |
- Einarsdóttir, Karólina, 1980-
(författare)
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Mire Aeration & Particles Experiment : Dataset from the study: Particles and aeration at mire-stream interfaces cause selective removal and modification of dissolved organic matter. Article accepted by AGU-JGR-Biogeosciences
- 2020
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Annan publikationabstract
- The dataset contains physio-chemical data from an experiment that aimed to answer how aeration of anoxic mire water, and suspended particles, may impacts dissolved organic matter in both quality and quantity. The experimental data gives idea how physio-chemical parameters may change upon aeration, e.g., at soil-water interfaces or when anoxic mire water merges into a stream and the water is mixed with the atmosphere. In addition, the importance of suspended particles that are found in the mire water was also examined. The dataset comprises measured concentrations of dissolved organic carbon (DOC), inorganic carbon (IC), particulate organic carbon (POC) and particulate nitrogen (PN), dissolved iron (DFe, divided in ferrous (Fe (II)) and ferric (Fe(III)) forms), dissolved oxygen, temperature, chemical composition of DOM (intensity of formulas CHO) divided in three fractions depending on hydrophobicity, and intensity of absorbance of 254nm. The study was conducted in September 2017 and the samples come from a sloping mire that drains into small headwater-stream and is located in a boreal forest of Mid-Sweden. The samples were anoxic and sampled for all parameters in a nitrogen aired glovebox prior the experiment start, half of the samples were aerated, and half of the aerated and half of the anoxic samples contained particles from the mire while the other half was filtered through GF/F filter. After aeration, samples for DFe species and IC were taken from aerated samples. Oxygen was monitored the whole time. The experiment went on for five days and then all parameters were measured again.
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| 12. |
- Einarsdóttir, Karólina, 1980-, et al.
(författare)
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Particles and Aeration at Mire-Stream Interfaces Cause Selective Removal and Modification of Dissolved Organic Matter
- 2020
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 125:12
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands are dominant sources of dissolved organic matter (DOM) to boreal inland waters and play important roles in the aquatic carbon cycle. Yet before peat-derived DOM enters aquatic networks, it needs to pass through peat-stream interfaces that are often characterized by transitions from anoxic or hypoxic to oxic conditions. Aeration at these interfaces may trigger processes that impact the DOM pool, and its fate downstream. Here we experimentally assessed how the aeration of iron- and organic-rich mire-waters influences biodegradation, particle-formation, and modification of DOM. In addition, we investigated how suspended peat-derived particles from mires may influence these processes. We found that within 5 days of aeration, 20% of the DOM transformed into particulate organic matter (POM). This removal was likely due to combination of mechanisms including coprecipitation with oxidized iron, aggregation, and DOM-adsorption onto peat-derived particles. Peat-derived particles promoted microbial activity, but biodegradation was a minor loss mechanism of DOM removal. Interestingly, microbial respiration accounted for only half of the oxygen loss, suggesting substantial nonrespiratory oxygen consumption. The differences observed in DOM characteristics between anoxic and aerated treatments suggest that hydrophilic, aromatic DOM coprecipitated with iron oxides in aerated samples, and the corresponding C:N analysis of generated POM revealed that these organic species were nitrogen-poor. Meanwhile, POM formed via adsorption onto peat-derived particles generated from nonaromatic DOM and more nitrogen-rich species. Hence, selective removal of DOM, dissolved iron, and thus oxygen may be important and overlooked processes in mire-dominated headwater systems.
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| 13. |
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| 14. |
- Evans, Chris D., et al.
(författare)
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Variability in organic carbon reactivity across lake residence time and trophic gradients
- 2017
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Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 10:11, s. 832-835
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Tidskriftsartikel (refereegranskat)abstract
- The transport of dissolved organic carbon from land to ocean is a large dynamic component of the global carbon cycle. Inland waters are hotspots for organic matter turnover, via both biological and photochemical processes, and mediate carbon transfer between land, oceans and atmosphere. However, predicting dissolved organic carbon reactivity remains problematic. Here we present in situ dissolved organic carbon budget data from 82 predominantly European and North American water bodies with varying nutrient concentrations and water residence times ranging from one week to 700 years. We find that trophic status strongly regulates whether water bodies act as net dissolved organic carbon sources or sinks, and that rates of both dissolved organic carbon production and consumption can be predicted from water residence time. Our results suggest a dominant role of rapid light-driven removal in water bodies with a short water residence time, whereas in water bodies with longer residence times, slower biotic production and consumption processes are dominant and counterbalance one another. Eutrophication caused lakes to transition from sinks to sources of dissolved organic carbon. We conclude that rates and locations of dissolved organic carbon processing and associated CO2 emissions in inland waters may be misrepresented in global carbon budgets if temporal and spatial reactivity gradients are not accounted for.
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| 15. |
- Groeneveld, Marloes, et al.
(författare)
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Effects of adsorption to glacial suspended sediment and phototransformations on the bioavailability of dissolved organic matter from a thawing palsa mire
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The thawing of permafrost leads to increased export of organic matter that was previously stored within frozen peatland soils into aquatic ecosystems. Since this organic matter is reactive to microbial and photochemical processes, permafrost thaw is expected to cause increased production of greenhouse gases. Simultaneously, warming also results in glacial melt, and glacial runoff streams often contain high loads of suspended sediment. As these minerogenic particles are transported downstream the aquatic continuum, they can eventually mix with water containing high concentrations of organic matter freshly released from thawing permafrost and act as an adsorbent. We compared the effects of adsorption of dissolved organic matter (DOM) to glacial suspended sediment to that of photodegradation, which is another major process affecting the fate of DOM in high latitude aquatic ecosystems. Specifically, we determined the composition and bioavailability of DOM from a surface water draining from a thawing peat plateau in northern Sweden. We used optical measurements and mass spectrometry to evaluate changes in DOM composition and modelled degradation kinetics during a three-month incubation to determine bioavailability. Exposure to light increased organic matter bioavailability, whereas pre-treatment by adsorption to mineral particles slightly decreased bioavailability compared to the control if the particle-associated organic matter was removed from the water. These findings contribute to a better overall understanding of the influence of adsorption to mineral particles, photoreactivity, and microbial degradation in subarctic aquatic ecosystems.
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| 16. |
- Groeneveld, Marloes M.
(författare)
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Adsorption of dissolved organic matter in aquatic ecosystems : Effects on composition and reactivity
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inland waters receive organic matter from terrestrial ecosystems and in situ production. In transit from land to the ocean, dissolved organic carbon (DOC) may be mineralised to inorganic forms (CO2 and CH4) by microbial degradation and photodegradation. It may also transition from dissolved into particulate phase, and be transferred to the sediment and buried. One way in which this can happen is by adsorption of dissolved organic matter (DOM) to mineral particles. This process is rarely studied in inland waters, since suspended particles are often in short supply. However, there are scenarios under which high particle concentrations occur, and in those cases, adsorption may have a substantial effect on DOM composition and reactivity. The overall aim of this thesis was to investigate the potential for DOM adsorption to inorganic particles and the resulting effect on DOM composition, as well as its biological reactivity. Three studies within this thesis focus on different types of surfaces waters in the boreal landscape of Sweden, and one study focuses on coastal moorland streams in the United Kingdom. Adsorption experiments were conducted under controlled laboratory conditions using batch experiments. DOM quality was studied based on bulk optical properties, and composition was examined by high resolution mass spectrometry. Adsorption experiments using a commercially available reference clay (containing substantial amounts of aluminium and iron oxides) as the adsorbent show a widespread potential for DOM in inland water to adsorb to mineral particles. The extent of DOM adsorption in the experiments was regulated by two factors: 1) DOM composition, since compounds with a terrestrial signature were selectively adsorbed, and 2) water chemistry, as adsorption was impaired by pH>7 and higher concentrations of base cations. These general patterns were observed across surface waters with contrasting DOC concentrations, DOM composition and water chemistry parameters, and across spatial and temporal scales. In contrast, adsorption to suspended sediment derived from a glacial stream resulted in the removal of ‘protein-like’ DOM that is produced in situ, rather than terrestrially derived DOM. Hence, the mineralogy of particles may determine which DOM fraction is adsorbed. Experiments examining microbial degradation indicated that the effect of adsorption on the bioavailability of the remaining DOM depends on which DOM fraction is removed by the different adsorbents. This thesis shows that adsorption to mineral particles in aquatic ecosystems is a highly relevant biogeochemical process that has the potential to alter DOM composition and thereby affect its biological reactivity.
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| 17. |
- Groeneveld, Marloes M., et al.
(författare)
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Seasonally variable interactions between dissolved organic matter and mineral particles in an agricultural river
- 2023
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Ingår i: Aquatic Sciences. - : Springer Nature. - 1015-1621 .- 1420-9055. ; 85
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Tidskriftsartikel (refereegranskat)abstract
- Streams and rivers form an important link in the global carbon cycle by transporting and transforming large amounts of carbon imported from terrestrial ecosystems to the oceans. Since streams in agricultural areas often experience increased concentrations of suspended mineral particles from soil erosion, they are important sites where dissolved organic carbon (DOC) may be adsorbed to particles and retained in the sediment. As the extent of adsorption varies with the molecular composition of dissolved organic matter (DOM), which is seasonally variable, we expect also the fraction of organic material that adsorbs to mineral particles to fluctuate over time. We sampled the agriculturally impacted River Fyrisån (Sweden) monthly during 1 year, and measured DOC concentration and DOM composition based on several optical properties. At each sampling occasion, we estimated the potential for adsorption by exposing the samples to a reference clay. The potential for adsorption was greatest when riverine DOM had the most terrestrial character, as this fraction of the DOM pool was selectively adsorbed to clay surfaces. The extent of adsorption was negatively related to the concentration of base cations, most notably calcium. We suggest that the observed relationships between the potential for adsorption, DOM composition and base cations are linked by discharge. A bioavailability test at one sampling occasion suggested that DOM remaining after exposure to clay particles was more biodegradable. This implies that adsorption may alter the degradation potential of DOM remaining in solution, which could have far reaching effects on the fate of organic carbon.
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| 18. |
- Groeneveld, Marloes M., et al.
(författare)
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Selective Adsorption of Terrestrial Dissolved Organic Matter to Inorganic Surfaces Along a Boreal Inland Water Continuum
- 2020
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Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 125:3
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Tidskriftsartikel (refereegranskat)abstract
- Different processes contribute to the loss or transformation of dissolved organic matter (DOM) and change DOM concentration and composition systematically along the inland water continuum. Substantial efforts have been made to estimate the importance of microbial and photochemical degradation for DOM concentration and composition and, to some extent, also DOM losses by flocculation, whereas the significance of DOM adsorption to inorganic surfaces has received less attention. Hence, knowledge on the possible extent of adsorption, its effect on DOM loads and composition and on where along the aquatic continuum it might be important, is currently limited or lacking altogether. Here we experimentally determine DOM adsorption onto mineral particles in freshwater ecosystems covering a water residence time gradient in boreal landscape Sweden. We hypothesized that adsorption would gradually decrease with increasing water residence time but actually found that DOM is highly susceptible to adsorption throughout the aquatic continuum. Mass spectrometry and fluorescence analysis on DOM suggest that freshly produced aquatic DOM is less susceptible to adsorption than more terrestrial material. Moreover, the percentage DOM adsorbed in the experiments greatly exceeds the actual adsorption taking place in boreal inland waters across all studied systems. These results illustrate the potential impact of mineral erosion, for example, as a result of agriculture, mining or forestry practices, on the availability, transport, and composition of organic carbon in inland waters.
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| 19. |
- Groeneveld, Marloes M., et al.
(författare)
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The influence of pH on dissolved organic matter fluorescence in inland waters
- 2022
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Ingår i: Analytical Methods. - : Royal Society of Chemistry. - 1759-9660 .- 1759-9679. ; 14:13, s. 1351-1360
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence is an easily available analytical technique used to assess the optical characteristics of dissolved organic matter (DOM). Despite widespread use, there has been some confusion about how robust fluorescence spectroscopy is to differences in solution pH. Here we assess fluorescence characteristics of three natural water samples and one commercially available standard (Nordic Reservoir) by modifying the pH across a range from 3.5 to 9.0 at 0.5 pH increments. We used two statistical approaches to assess if fluorescence intensity shifted significantly across this pH range. We identified that humic-like and protein-like fluorescence was largely stable within the pH range of 5.5 to 7.5, which represents 80% of Swedish lakes and streams. Likewise, we found that the three commonly used fluorescence indices were robust across the full pH range tested with the exception of the humification index, which had a narrower range of stability. The commerical humic substance sample was highly unstable with changes to pH in the regions of protein-like fluorescence being particularly sensitive. One of our conclusions is that differences in fluorescence intensity in the pH range of 5.5 to 7.5, typical for most inland waters, are generally minor. We recommend adjusting the pH when samples fall outside this region and to be especially careful in interpreting results from commercial humic substances.
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| 20. |
- Guillemette, Francois, et al.
(författare)
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Preferential sequestration of terrestrial organic matter in boreal lake sediments
- 2017
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : AMER GEOPHYSICAL UNION. - 2169-8953 .- 2169-8961. ; 122:4, s. 863-874
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Tidskriftsartikel (refereegranskat)abstract
- The molecular composition and origin has recently been demonstrated to play a critical role in the persistence of organic matter in lake water, but it is unclear to what degree chemical attributes and sources may also control settling and burial of organic matter in lake sediments. Here we compared the annual contribution of allochthonous and autochthonous sources to the organic matter settling in the water column and present in the sediments of 12 boreal lakes. We used the fluorescence properties and elemental composition of the organic matter to trace its origin and found a consistent pattern of increasing contribution of terrestrial compounds in the sediments as compared to the settling matter, with an annual average allochthony of similar to 87% and similar to 57%, respectively. Seasonal data revealed a predominance of in-lake-produced compounds sinking in the water column in summer. Yet only a slight concurrent decrease in the contribution of terrestrial C to lake sediments was observed during the same period, and sediment allochthony increased again to high levels in autumn. Our results reveal a preferential preservation of allochthonous matter in the sediments and highlight the role of lakes as sequesters of organic carbon primarily originating from the surrounding landscape.
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