| 1. |
- Barros, Nathan, et al.
(författare)
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Carbon emission from hydroelectric reservoirs linked to reservoir age and latitude
- 2011
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Ingår i: Nature Geoscience. - : Nature Publishing Group. - 1752-0894 .- 1752-0908. ; 4:9, s. 593-596
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Tidskriftsartikel (refereegranskat)abstract
- Hydroelectric reservoirs cover an area of 3.4 x 10(5) km(2) and comprise about 20% of all reservoirs. In addition, they contain large stores of formerly terrestrial organic carbon. Significant amounts of greenhouse gases are emitted(2), especially in the early years following reservoir creation, but the global extent of these emissions is poorly known. Previous estimates of emissions from all types of reservoir indicate that these human-made systems emit 321 Tg of carbon per year (ref. 4). Here we assess the emissions of carbon dioxide and methane from hydroelectric reservoirs, on the basis of data from 85 globally distributed hydroelectric reservoirs that account for 20% of the global area of these systems. We relate the emissions to reservoir age, location biome, morphometric features and chemical status. We estimate that hydroelectric reservoirs emit about 48 Tg C as CO(2) and 3 Tg C as CH(4), corresponding to 4% of global carbon emissions from inland waters. Our estimates are smaller than previous estimates on the basis of more limited data. Carbon emissions are correlated to reservoir age and latitude, with the highest emission rates from the tropical Amazon region. We conclude that future emissions will be highly dependent on the geographic location of new hydroelectric reservoirs.
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| 2. |
- Bastviken, David, et al.
(författare)
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Freshwater Methane Emissions Offset the Continental Carbon Sink
- 2011
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 331:6013, s. 50-50
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Tidskriftsartikel (refereegranskat)abstract
- Inland waters (lakes, reservoirs, streams, and rivers) are often substantial methane (CH4) sources in the terrestrial landscape. They are, however, not yet well integrated in global greenhouse gas (GHG) budgets. Data from 474 freshwater ecosystems and the most recent global water area estimates indicate that freshwaters emit at least 103 teragrams of CH4 year−1, corresponding to 0.65 petagrams of C as carbon dioxide (CO2) equivalents year−1, offsetting 25% of the estimated land carbon sink. Thus, the continental GHG sink may be considerably overestimated, and freshwaters need to be recognized as important in the global carbon cycle.
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| 3. |
- Fischer, Helmut, et al.
(författare)
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Microbial leaf degraders in boreal streams : bringing together stochastic and deterministic regulators of community composition
- 2009
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 54:11, s. 2276-2289
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Tidskriftsartikel (refereegranskat)abstract
- Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream. 2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within-streams, although communities differed more strongly between streams. 3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition. 4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in-stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.
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| 4. |
- Groeneveld, Marloes M., et al.
(författare)
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Photochemical mineralisation in a boreal brown water lake: considerable temporal variability and minor contribution to carbon dioxide production
- 2016
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Ingår i: Biogeosciences. - : COPERNICUS GESELLSCHAFT MBH. - 1726-4170 .- 1726-4189. ; 13:13, s. 3931-3943
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Tidskriftsartikel (refereegranskat)abstract
- Sunlight induces photochemical mineralisation of chromophoric dissolved organic matter (CDOM) to dissolved inorganic carbon (DIC) in inland waters, resulting in carbon dioxide (CO2) emissions to the atmosphere. Photochemical rate modelling is used to determine sunlight-induced CO2 emissions on large spatial and temporal scales. A sensitive model parameter is the wavelength-specific photochemical CDOM reactivity, the apparent quantum yield (AQY). However, the temporal variability of AQY spectra within inland waters remains poorly constrained. Here, we studied a boreal brown water lake in Sweden. We measured AQY spectra for photochemical DIC production monthly between June and November 2014 and parameterised a photochemical rate model. The total AQY between 280 and 600 nm increased about 3-fold during the open-water period, likely due to a high rainfall event with consecutive mixing in autumn that increased availability of highly photoreactive CDOM. However, the variability in AQY spectra over time was much smaller than previously reported variability in AQY spectra between lakes. Yet, using either the AQY spectrum from the least or from the most photoreactive water sample resulted in a 5-fold difference in simulated annual DIC photoproduction (2012-2014), with 2.0 +/- 0.1 and 10.3 +/- 0.7 g C m(-2) yr(-1), respectively. This corresponded to 1 and 8% of the mean CO2 emissions measured from this lake. We conclude that (1) it may be recommendable to conduct repeated AQY measurements throughout the season for more accurate simulation of annual photochemical DIC production in lakes and (2), in agreement with previous studies, direct CDOM photomineralisation makes only a minor contribution to mean CO2 emissions from Swedish brown water lakes.
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| 5. |
- Gudasz, Cristian, et al.
(författare)
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Constrained microbial processing of allochthonous organic carbon in boreal lake sediments
- 2012
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 57:1, s. 163-175
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Tidskriftsartikel (refereegranskat)abstract
- We investigated sediment bacterial metabolism in eight lakes with different inputs of allochthonous and autochthonous organic carbon in south-central Sweden. Sediment bacterial production, mineralization and biomass were measured on a seasonal basis and along a lake depth gradient together with different water and sediment characteristics. Sediment bacterial metabolism was primarily controlled by temperature but also regulated by organic carbon quality/origin. Metabolism was positively correlated to measures of autochthonous influence on the sediment organic carbon, but did not show a similar increase with increasing input of allochthonous organic carbon. Hence, in contrast to what is currently known for the water column, increasing amounts of terrestrial organic carbon do not result in enhanced sediment bacterial metabolism. Meio- and macrobenthic invertebrate biomass were at most weakly correlated to bacterial metabolism and biomass, suggesting limited control of sediment bacteria by grazing. We suggest that the bacterial metabolism in boreal lake sediments is constrained by low temperatures and by the recalcitrant nature of the dominant organic carbon, resulting in sediments being an effective sink of organic carbon.
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| 6. |
- Gudasz, Cristian, et al.
(författare)
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Temperature-controlled organic carbon mineralization in lake sediments
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 466:7305, s. 478-481
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands, soils and the ocean floor are well-recognized as sites of organic carbonaccumulation andrepresentimportant global carbon sinks(1,2). Although the annual burial of organic carbon in lakes and reservoirs exceeds that of ocean sediments(3), these inland waters are components of the global carbon cycle that receive only limited attention(4-6). Of the organic carbon that is being deposited onto the sediments, a certain proportion will be mineralized and the remainder will be buried over geological timescales. Here we assess the relationship between sediment organic carbon mineralization and temperature in a cross-system survey of boreal lakes in Sweden, and with input froma compilation of published data from awide range of lakes that differ with respect to climate, productivity and organic carbon source. We find that the mineralization of organic carbon in lake sediments exhibits a strongly positive relationship with temperature, which suggests that warmer water temperatures lead to more mineralization and less organic carbon burial. Assuming that future organic carbon delivery to the lake sediments will be similar to that under present-day conditions, we estimate that temperature increases following the latest scenarios presented by the Intergovernmental Panel on Climate Change(7) could result in a 4-27 per cent (0.9-6.4 Tg Cyr(-1)) decrease in annual organic carbon burial in boreal lakes.
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| 7. |
- Gudasz, Cristian, et al.
(författare)
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Temperature sensitivity of organic carbon mineralization in contrasting lake sediments
- 2015
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 120:7, s. 1215-1225
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Tidskriftsartikel (refereegranskat)abstract
- Temperature alone explains a great amount of variation in sediment organic carbon (OC) mineralization. Studies on decomposition of soil OC suggest that (1) temperature sensitivity differs between the fast and slowly decomposition OC and (2) over time, decreasing soil respiration is coupled with increase in temperature sensitivity. In lakes, autochthonous and allochthonous OC sources are generally regarded as fast and slowly decomposing OC, respectively. Lake sediments with different contributions of allochthonous and autochthonous components, however, showed similar temperature sensitivity in short-term incubation experiments. Whether the mineralization of OC in lake sediments dominated by allochthonous or autochthonous OC has different temperature sensitivity in the longer term has not been addressed. We incubated sediments from two boreal lakes that had contrasting OC origin (allochthonous versus autochthonous), and OC characteristics (C/N ratios of 21 and 10) at 1, 3, 5, 8, 13, and 21 degrees C for five months. Compared to soil and litter mineralization, sediment OC mineralization rates were low in spite of low apparent activation energy (E-a). The fraction of the total OC pool that was lost during five months varied between 0.4 and 14.8%. We estimate that the sediment OC pool not becoming long-term preserved was degraded with average apparent turnover times between 3 and 32years. While OC mineralization was strongly dependent on temperature as well as on OC composition and origin, temperature sensitivity was similar across lakes and over time. We suggest that the temperature sensitivity of OC mineralization in lake sediments is similar across systems within the relevant seasonal scales of OC supply and degradation.
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| 8. |
- 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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| 9. |
- Jansen, Joachim, 1989-, et al.
(författare)
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Global increase in methane production under future warming of lake bottom waters
- 2022
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 28:18, s. 5427-5440
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Tidskriftsartikel (refereegranskat)abstract
- Lakes are significant emitters of methane to the atmosphere, and thus are important components of the global methane budget. Methane is typically produced in lake sediments, with the rate of methane production being strongly temperature dependent. Local and regional studies highlight the risk of increasing methane production under future climate change, but a global estimate is not currently available. Here, we project changes in global lake bottom temperatures and sediment methane production rates from 1901 to 2099. By the end of the 21st century, lake bottom temperatures are projected to increase globally, by an average of 0.86-2.60 degrees C under Representative Concentration Pathways (RCPs) 2.6-8.5, with greater warming projected at lower latitudes. This future warming of bottom waters will likely result in an increase in methane production rates of 13%-40% by the end of the century, with many low-latitude lakes experiencing an increase of up to 17 times the historical (1970-1999) global average under RCP 8.5. The projected increase in methane production will likely lead to higher emissions from lakes, although the exact magnitude of the emission increase requires more detailed regional studies.
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| 10. |
- Lavonen, Elin, et al.
(författare)
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Selective Chlorination of Natural Organic Matter: Identification of Previously Unknown Disinfection Byproducts
- 2013
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Ingår i: Environmental Science and Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 47:5, s. 2264-2271
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Tidskriftsartikel (refereegranskat)abstract
- Natural organic matter (NOM) serve as precursors for disinfection byproducts (DBPs) in drinking water production making NOM removal essential in predisinfection treatment processes. We identified molecular formulas of chlorinated DBPs after chlorination and chloramination in four Swedish surface water treatment plants (WTPs) using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Chlorine-containing formulas were detected before and after disinfection and were therefore classified to identify DBPs. In total, 499 DBPs were detected, of which 230 have not been reported earlier. The byproducts had, as a group, significantly lower ratio of hydrogen to carbon (H/C) and significantly higher average carbon oxidation state (Cos), double bond equivalents per carbon (DBE/C) and ratio of oxygen to carbon (O/C) compared to Cl-containing components present before disinfection and CHO formulas in samples taken both before and after disinfection. Electrophilic substitution, the proposed most significant reaction pathway for chlorination of NOM, results in carbon oxidation and decreased H/C while O/C and DBE/C is left unchanged. Because the identified DBPs had significantly higher DBE/C and O/C than the CHO formulas we concluded that chlorination of NOM during disinfection is selective toward components with relatively high double bond equivalency and number of oxygen atoms per carbon. Furthermore, choice of disinfectant, dose, and predisinfection treatment at the different WTPs resulted in distinct patterns in the occurrence of DBP formulas.
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