| 1. |
- Shirokova, Liudmila S., et al.
(författare)
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Humic surface waters of frozen peat bogs (permafrost zone) are highly resistant to bio- and photodegradation
- 2019
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Ingår i: Biogeosciences. - : Nicolaus Copernicus University Press. - 1726-4170 .- 1726-4189. ; 16:12, s. 2511-2526
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to the large number of studies on humic waters from permafrost-free regions and oligotrophic waters from permafrost-bearing regions, the bio- and photolability of DOM from the humic surface waters of permafrost-bearing regions has not been thoroughly evaluated. Following standardized protocol, we measured biodegradation (at low, intermediate and high temperatures) and photodegradation (at one intermediate temperature) of DOM in surface waters along the hydrological continuum (depression -> stream -> thermokarst lake -> Pechora River) within a frozen peatland in European Russia. In all systems, within the experimental resolution of 5% to 10 %, there was no bio- or photodegradation of DOM over a 1-month incubation period. It is possible that the main cause of the lack of degradation is the dominance of allochthonous refractory (soil, peat) DOM in all waters studied. However, all surface waters were supersaturated with CO2. Thus, this study suggests that, rather than bio- and photodegradation of DOM in the water column, other factors such as peat pore-water DOM processing and respiration of sediments are the main drivers of elevated pCO(2) and CO2 emission in humic boreal waters of frozen peat bogs.
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| 2. |
- Vorobyev, Sergey N., et al.
(författare)
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Biogeochemistry of dissolved carbon, major, and trace elements during spring flood periods on the Ob River
- 2019
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Ingår i: Hydrological Processes. - : John Wiley & Sons. - 0885-6087 .- 1099-1085. ; 33:11, s. 1579-1594
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Tidskriftsartikel (refereegranskat)abstract
- Detailed knowledge of the flood period of Arctic rivers remains one of the few factors impeding rigorous prediction of the effect of climate change on carbon and related element fluxes from the land to the Arctic Ocean. In order to test the temporal and spatial variability of element concentration in the Ob River (western Siberia) water during flood period and to quantify the contribution of spring flood period to the annual element export, we sampled the main channel year round in 2014-2017 for dissolved C, major, and trace element concentrations. We revealed high stability (approximately <= 10% relative variation) of dissolved C, major, and trace element concentrations in the Ob River during spring flood period over a 1-km section of the river channel and over 3 days continuous monitoring (3-hr frequency). We identified two groups of elements with contrasting relationship to discharge: (a) DIC and soluble elements (Cl, SO4, Li, B, Na, Mg, Ca, P, V, Cr, Mn, As, Rb, Sr, Mo, Ba, W, and U) negatively correlated (p < 0.05) with discharge and exhibited minimal concentrations during spring flood and autumn high flow and (b) DOC and particle-reactive elements (Al, Fe, Ti, Y, Zr, Nb, Cs, REEs, Hf, Tl, Pb, and Th), some nutrients (K), and metalloids (Ge, Sb, and Te), positively correlated (p < 0.05) with discharge and showed the highest concentrations during spring flood. We attribute the decreased concentration of soluble elements with discharge to dilution by groundwater feeding and increased concentration of DOC and particle-reactive metals with discharge to leaching from surface soil, plant litter, and suspended particles. Overall, the present study provides first-order assessment of fluxes of major and trace elements in the middle course of the Ob River, reveals their high temporal and spatial stability, and characterizes the mechanism of river water chemical composition acquisition.
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| 3. |
- Serikova, Svetlana, 1989-
(författare)
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Carbon Emissions from Western Siberian Inland Waters
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inland waters (i.e. rivers, streams, lakes, ponds) emit carbon (C) into the atmosphere. The magnitude of global inland water C emission has been estimated to equal the global ocean C sink, thus making inland waters an important component of the global C cycle. Yet, the data used in estimating the magnitude of global inland water C emission lacks measurements of inland water C emissions from permafrost-affected regions in general and from Russia in particular, despite permafrost covering ~25% of the Northern Hemisphere and ~65% of Russia. This lack of data questions the accuracy of the current estimate of global inland water C emission and its predictive power in assessing changes in the global C cycle following permafrost thaw.In this thesis, we conducted detailed measurements of river and lake C emissions across ~1000 km permafrost gradient of Western Siberia (from permafrost-free to continuous permafrost zone) and assessed the magnitude of the total C emission from Western Siberian inland waters. We found that river and lake C emissions varied across the permafrost gradient with river C emissions being greatest in areas where permafrost is actively degrading, and lake C emissions being greatest in areas where permafrost is still intact. We also found that river and lake C emissions are likely driven by different factors with river C emissions being mainly controlled by temperature and hydrological conditions, whereas lake C emissions by sediment respiration and availability of recently thawed organic C. Further, we estimated the total C emission from Western Siberian inland waters to be greater than previously thought and exceeding the C export from this region to the Arctic Ocean. Such finding implies that a major part of the terrestrially-derived C is lost in Western Siberian inland waters, making this region a hotspot for inland water C emission following permafrost thaw. We also showed that apart from C emissions measurements across different inland water types and across the landscape, estimates of inland water surface areas are needed for accurate assessments of the total inland water C emission of any given region. Particularly, water surface areas of streams and ponds as well as inundated floodplains, especially in years of extreme flood events, are important for quantifying the total inland water C emission. Overall, this thesis presents new data related to C emissions from rivers and lakes in an area that undergoes rapid permafrost thaw, and urges to account for all inland water types and their respective water surface areas when attempting to achieve unbiased estimates of the inland water contribution to the atmospheric C budget.
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