| 1. |
- Grasset, Charlotte, et al.
(författare)
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An empirical model to predict methane production in inland water sediment from particular organic matter supply and reactivity
- 2021
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:10, s. 3643-3655
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Tidskriftsartikel (refereegranskat)abstract
- The highest CH4 production rates can be found in anoxic inland water surface sediments however no model quantifies CH4 production following fresh particular organic matter (POM) deposition on anoxic sediments. This limits our capability of modeling CH4 emissions from inland waters to the atmosphere. To generate such a model, we quantified how the POM supply rate and POM reactivity control CH4 production in anoxic surface sediment, by amending sediment at different frequencies with different quantities of aquatic and terrestrial POM. From the modeled CH4 production, we derived parameters related to the kinetics and the extent of CH4 production. We show that the extent of CH4 production can be well predicted by the quality (i.e., C/N ratio) and the quantity of POM supplied to an anoxic sediment. In particular, within the range of sedimentation rates that can be found in aquatic systems, we show that CH4 production increases linearly with the quantity of phytoplankton-derived and terrestrially derived POM. A high frequency of POM addition, which is a common situation in natural systems, resulted in higher peaks in CH4 production rates. This suggests that relationships derived from earlier incubation experiments that added POM only once, may result in underestimation of sediment CH4 production. Our results quantitatively couple CH4 production in anoxic surface sediment to POM sedimentation flux, and are therefore useful for the further development of mechanistic models of inland water CH4 emission.
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| 2. |
- Grasset, Charlotte, et al.
(författare)
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Can Soil Organic Carbon Fractions Be Used as Functional Indicators of Wetlands?
- 2017
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Ingår i: Wetlands (Wilmington, N.C.). - : Springer Science and Business Media LLC. - 0277-5212 .- 1943-6246. ; 37:6, s. 1195-1205
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Tidskriftsartikel (refereegranskat)abstract
- This work aimed to determine whether the organic carbon in wetland soils correlated with physico-chemical characteristics of wetlands (e.g. nutrient content, pH) and differentiated wetlands according to their plant community composition definied by the CORINE Biotope nomenclature. 96 wetlands were sampled in southeastern France, belonging to 14 CORINE habitats grouped into 3 CORINE hydrological categories: wet meadows, peatlands and aquatic wetlands. The total organic carbon content, the carbon content of humic fractions (humic acid (CHA), fulvic acid (CFA) and Chumin), and water extractable organic carbon were measured in samples collected in the upper 20 cm soil layer. These soil organic carbon fractions correlated with pH and soil nutrient content but differed slightly among the 14 CORINE habitats. In contrast, soil organic carbon fractions greatly differed among the 3 CORINE hydrological categories. The CFA/CHA ratio was significantly lower for wet meadows and peatlands and the proportion of CHumin was significantly higher for peatlands and aquatic wetlands. These soil organic carbon fractions inform on the hydrological status of wetlands and may consequently be used as functional indicator in addition to a plant-based classification as the CORINE Biotope nomenclature.
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| 3. |
- Grasset, Charlotte, et al.
(författare)
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Carbon allocation in aquatic plants with contrasting strategies : The role of habitat nutrient content
- 2015
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 26, s. 946-955
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Tidskriftsartikel (refereegranskat)abstract
- Questions: The link between the carbon composition of aquatic plants and (1) plant strategies and (2) habitat nutrient availability has received little attention. We tested whether three aquatic species belonging to the three adaptive strategies defined by Grime (ruderal, stress tolerant and competitive) had contrasting carbon allocation patterns, and if these patterns varied in the same way between populations distributed along a gradient of habitat nutrient content. Location: Wetlands in the northern Rhône River Basin, France. Methods: The three species were sampled in 17 wetlands along a gradient of nutrient content in the northern Rhône River Basin. In each population sampled, we measured plant water content, C/N ratio, structural compounds (lignin and structural polysaccharides) and storage compounds (free sugars and starch) in two seasons (spring and autumn 2012). Results: The stress-tolerant species had higher content of structural compounds than the competitive and ruderal species. The content of storage compounds was higher in the competitive and stress-tolerant species compared to the ruderal species. Allocation of carbon compounds varied with habitat nutrient content in different ways for the three species, suggesting contrasting plasticities, possibly linked to plant strategy. Conclusion: Plant strategies and habitat nutrient content are likely key drivers in plant carbon allocation and should be taken into account when studying interactions between habitat and plant quality.
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| 4. |
- Grasset, Charlotte, et al.
(författare)
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Carbon emission along a eutrophication gradient in temperate riverine wetlands : effect of primary productivity and plant community composition
- 2016
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 61, s. 1405-1420
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Tidskriftsartikel (refereegranskat)abstract
- Eutrophication increases primary productivity and favours the predominance of floating vegetation in wetlands. Carbon (C) fluxes in wetlands are strongly driven by primary productivity and can differ by vegetation type. However, to the best of our knowledge, the role of eutrophication in C fluxes has rarely been assessed. Consequently, we aimed to measure the seasonal variation in carbon dioxide (CO2) and methane (CH4) fluxes at six aquatic sites in four temperate wetlands, ranging along a gradient of sediment total phosphorus content, and determine whether C fluxes correlate with above-ground net primary productivity (ANPP) and plant community composition along this eutrophication gradient. Daytime CO2 emissions were significantly and negatively correlated with wetland net primary productivity as a result of the greater C fixation by photosynthesis during the peak of production. Conversely, CH4 emissions were significantly and positively correlated with wetland ANPP, possibly due to higher litter production and anaerobic decomposition. The highest CH4 emissions were observed above floating vegetation, which favoured hypoxic conditions in the water column. CH4 emissions including ebullition were higher above macroalgal belts than above vascular plants with floating leaves. CH4 emissions without ebullition (i.e. resulting from plant transport and diffusion) better correlated with the abundance of macroalgae than with the abundance of vascular plants with floating leaves. Our results suggest that eutrophication may greatly modify CO2 and CH4 emissions from wetlands through changes in vegetation type and productivity.
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| 5. |
- Grasset, Charlotte, et al.
(författare)
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Decreasing Photoreactivity and Concurrent Change in Dissolved Organic Matter Composition With Increasing Inland Water Residence Time
- 2024
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 38:3
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Tidskriftsartikel (refereegranskat)abstract
- Photochemical degradation of dissolved organic matter (DOM) has been the subject of numerous studies; however, its regulation along the inland water continuum is still unclear. We aimed to unravel the DOM photoreactivity and concurrent DOM compositional changes across 30 boreal aquatic ecosystems including peat waters, streams, rivers, and lakes distributed along a water residence time (WRT) gradient. Samples were subjected to a standardized exposure of simulated sunlight. We measured the apparent quantum yield (AQY), which corresponds to DOM photomineralization per photon absorbed, and the compositional change in DOM at bulk and individual compound levels in the original samples and after irradiation. AQY increased with the abundance of terrestrially derived DOM and decreased at higher WRT. Additionally, the photochemical changes in both DOM optical properties and molecular composition resembled changes along the natural boreal WRT gradient at low WRT (<3 years). Accordingly, mass spectrometry revealed that the abundance of photolabile and photoproduced molecules decreased with WRT along the boreal aquatic continuum. Our study highlights the tight link between DOM composition and DOM photodegradation. We suggest that photodegradation is an important driver of DOM composition change in waters with low WRT, where DOM is highly photoreactive.
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| 6. |
- Grasset, Charlotte, et al.
(författare)
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Hydrophilic Species Are the Most Biodegradable Components of Freshwater Dissolved Organic Matter
- 2023
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 57:36, s. 13463-13472
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Tidskriftsartikel (refereegranskat)abstract
- Aquatic dissolved organic matter (DOM) is a crucial component of the global carbon cycle, and the extent to which DOM escapes mineralization is important for the transport of organic carbon from the continents to the ocean. DOM persistence strongly depends on its molecular properties, but little is known about which specific properties cause the continuum in reactivity among different dissolved molecules. We investigated how DOM fractions, separated according to their hydrophobicity, differ in biodegradability across three different inland water systems. We found a strong negative relationship between hydrophobicity and biodegradability, consistent for the three systems. The most hydrophilic fraction was poorly recovered by solid-phase extraction (SPE) (3-28% DOC recovery) and was thus selectively missed by mass spectrometry analysis during SPE. The change in DOM composition after incubation was very low according to SPE-ESI (electrospray ionization)-mass spectrometry (14% change, while replicates had 11% change), revealing that this method is sub-optimal to assess DOM biodegradability, regardless of fraction hydrophobicity. Our results demonstrate that SPE-ESI mass spectrometry does not detect the most hydrophilic and most biodegradable species. Hence, they question our current understanding of the relationships between DOM biodegradability and its molecular composition, which is built on the use of this method.
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| 7. |
- Grasset, Charlotte, et al.
(författare)
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Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter
- 2018
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 63:4, s. 1488-1501
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Tidskriftsartikel (refereegranskat)abstract
- An important question in the context of climate change is to understand how CH4 production is regulated in anoxic sediments of lakes and reservoirs. The type of organic carbon (OC) present in lakes is a key factor controlling CH4 production at anoxic conditions, but the studies investigating the methanogenic potential of the main OC types are fragmented. We incubated different types of allochthonous OC (alloOC; terrestrial plant leaves) and autochthonous OC (autoOC; phytoplankton and two aquatic plants species) in an anoxic sediment during 130 d. We tested if (1) the supply of fresh alloOC and autoOC to an anoxic refractory sediment would fuel CH4 production and if (2) autoOC would decompose faster than alloOC. The addition of fresh OC greatly increased CH4 production and the δ13C-CH4 partitioning indicated that CH4 originated exclusively from the fresh OC. The large CH4 production in an anoxic sediment fueled by alloOC is a new finding which indicates that all systems with anoxic conditions and high sedimentation rates have the potential to be CH4 emitters. The autoOC decomposed faster than alloOC, but the total CH4 production was not higher for all autoOC types, one aquatic plant species having values as low as the terrestrial leaves, and the other one having values as high as phytoplankton. Our study is the first to report such variability, suggesting that the extent to which C fixed by aquatic plants is emitted as greenhouse gases or buried as OC in sediment could more generally differ between aquatic vegetation types.
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| 8. |
- Grasset, Charlotte, et al.
(författare)
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The CO2-equivalent balance of freshwater ecosystems is non-linearly related to productivity
- 2020
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Ingår i: Global Change Biology. - : John Wiley & Sons, Ltd. - 1354-1013 .- 1365-2486. ; 26:10, s. 5705-5715
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Tidskriftsartikel (refereegranskat)abstract
- Eutrophication of fresh waters results in increased CO2 uptake by primary production, but at the same time increased emissions of CH4 to the atmosphere. Given the contrasting effects of CO2 uptake and CH4 release, the net effect of eutrophication on the CO2-equivalent balance of fresh waters is not clear. We measured carbon fluxes (CO2 and CH4 diffusion, CH4 ebullition) and CH4 oxidation in 20 freshwater mesocosms with 10 different nutrient concentrations (total phosphorus range: mesotrophic 39 µg/L until hypereutrophic 939 µg/L) and planktivorous fish in half of them. We found that the CO2-equivalent balance had a U-shaped relationship with productivity, up to a threshold in hypereutrophic systems. CO2-equivalent sinks were confined to a narrow range of net ecosystem production (NEP) between 5 and 19 mmol O2 m?3 day?1. Our findings indicate that eutrophication can shift fresh waters from sources to sinks of CO2-equivalents due to enhanced CO2 uptake, but continued eutrophication enhances CH4 emission and transforms freshwater ecosystems to net sources of CO2-equivalents to the atmosphere. Nutrient enrichment but also planktivorous fish presence increased productivity, thereby regulating the resulting CO2-equivalent balance. Increasing planktivorous fish abundance, often concomitant with eutrophication, will consequently likely affect the CO2-equivalent balance of fresh waters.
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| 9. |
- Grasset, Charlotte, et al.
(författare)
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The transformation of macrophyte-derived organic matter to methane relates to plant water and nutrient contents
- 2019
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 64:4, s. 1737-1749
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Tidskriftsartikel (refereegranskat)abstract
- Macrophyte detritus is one of the main sources of organic carbon (OC) in inland waters, and it is potentially available for methane (CH4) production in anoxic bottom waters and sediments. However, the transformation of macrophyte‐derived OC into CH4 has not been studied systematically, thus its extent and relationship with macrophyte characteristics remains uncertain. We performed decomposition experiments of macrophyte detritus from 10 different species at anoxic conditions, in presence and absence of a freshwater sediment, in order to relate the extent and rate of CH4 production to the detritus water content, C/N and C/P ratios. A significant fraction of the macrophyte OC was transformed to CH4 (mean = 7.9%; range = 0–15.0%) during the 59‐d incubation, and the mean total C loss to CO2 and CH4 was 17.3% (range = 1.3–32.7%). The transformation efficiency of macrophyte OC to CH4 was significantly and positively related to the macrophyte water content, and negatively to its C/N and C/P ratios. The presence of sediment increased the transformation efficiency to CH4 from an average of 4.0% (without sediment) to 11.8%, possibly due to physicochemical conditions favorable for CH4 production (low redox potential, buffered pH) or because sediment particles facilitate biofilm formation. The relationship between macrophyte characteristics and CH4 production can be used by future studies to model CH4 emission in systems colonized by macrophytes. Furthermore, this study highlights that the extent to which macrophyte detritus is mixed with sediment also affects CH4 production.
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| 10. |
- Ho, Lionel, et al.
(författare)
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Assessing granular media filtration for the removal of chemical contaminants from wastewater
- 2011
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Ingår i: Water Research. - : Elsevier Ltd. - 0043-1354 .- 1879-2448. ; 45:11, s. 3461-3472
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Tidskriftsartikel (refereegranskat)abstract
- Granular media filtration was evaluated for the removal of a suite of chemical contaminants that can be found in wastewater. Laboratory- and pilot-scale sand and granular activated carbon (GAC) filters were trialled for their ability to remove atrazine, estrone (E1), 17α-ethynylestradiol (EE2), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR) and N-nitrosodiethylamine (NDEA). In general, sand filtration was ineffective in removing the contaminants from a tertiary treated wastewater, with the exception of E1 and EE2, where efficient removals were observed after approximately 150 d. Batch degradation experiments confirmed that the removal of E1 was through biological activity, with a pseudo-first-order degradation rate constant of 7.4 × 10-3 h-1. GAC filtration was initially able to effectively remove all contaminants; although removals decreased over time due to competition with other organics present in the water. The only exception was atrazine where removal remained consistently high throughout the experiment. Previously unreported differences were observed in the adsorption of the three nitrosamines, with the ease of removal following the trend, NDEA \textgreater NMOR \textgreater NDMA, consistent with their hydrophobic character. In most instances the removals from the pilot-scale filters were generally in agreement with the laboratory-scale filter, suggesting that there is potential in using laboratory-scale filters as monitoring tools to evaluate the performance of pilot- and possibly full-scale sand and GAC filters at wastewater treatment plants. © 2011 Elsevier Ltd.
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