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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Frogner-Kockum, Paul, et al.
(författare)
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CoGas-projektet : Utveckling av en provtagningsmetod för att mätaföroreningstransport med gasflöden från fiberbankar
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I CoGas projektet utvecklades en fältutrustning och en metod som möjliggör in-situ provtagning av gas från fiberbankar. Detta för att kunna kvantifiera utsläpp av växthusgaser och medföljande halvflyktiga föroreningar (kvicksilver (Hg) och persistenta organiska miljögifter (POP)) samt gasmedierad partikelresuspension. En övergripande målsättning är att kunna bidra med kunskap om hur olika typer av föroreningar transporteras och sprids från fiberbankar. Den nya provtagningsutrustningen användes vid tre fiberbankar i Västernorrland (Väja, Sandviken och Köpmanholmen) där både passiv och forcerad gasprovtagning testades. Vid passiv provtagning mättes det naturliga gasflödet under en längre tid för att mäta mängden växthusgaser och partiklar som sprids under naturliga förhållanden. Det gick dock inte att detektera POPs i gasen som samlades in med den passiva provtagningen. För att kunna extrahera större volymer gas per tidsenhet och för att kunna analysera halten Hg i gasen utvecklades en forcerad provtagningsmetod. Järnstänger monterades därför under provtagaren vilka penetrerade sedimentytan och skapade artificiella transportgångar. Studien visade att andelen metangas vid in-situ provtagning (52–76 %) överensstämde relativt väl med de halter som tidigare uppmätts i laboratoriestudier (56 %; Lehoux et al, 2021). Våra resultat indikerar dock att de sammanlagda utsläppen av växthusgaser (CO2-ekvivalenter) från fiberbankar är i storleksordningen 52 000 – 170 000 ton/år, en uppskattning som är 25–70 gånger lägre än tidigare uppskattat av Lehoux et al. (2021). Att det blir så pass stor skillnad bedöms bero på att man i den tidigare beräkningen baserad på en laboratoriestudie (Lehoux et al., 2021) inte tog hänsyn till att den biologiskt aktiva zonen för metanogener i fiberbankarna bara utgör de översta decimetrarna av fiberbankarna (Regnell et al, 2014). Genom att ta med hela fiberbanksmassan i sina beräkningar (Lehoux et al., 2021) fick de en kraftig överskattad uppskattning av växthusgasutsläppet från Sveriges fiberbankar. Fiberbankarna i Sverige bedöms dock ändå stå för betydande utsläpp av växthusgaser, motsvarande ca 10–30 % av utsläppen från Sveriges avfallsdeponier. Kvicksilverhalterna (Hg) var i genomsnitt 1,6 ng/m3 i Väja, 6,0 ng/m3 i Sandviken och 19 ng/m3 i Köpmanholmen. Hg(0)-halten i gasfasen vid Köpmanholmen är ca 15 gånger högre än bakgrundshalterna i luft (1,3 ng/m3, IVL 2023). Av analyserade POPs kunde endast hexaklorbensen (HCB) detekteras, vilket antas bero på att HCB är mer volatilt än de övriga. HCB- halterna i den insamlade gasen var i genomsnitt 2,7 ng/m3, (n = 5) vid Väja och 8,5 ng/m3, (n = 6) vid Köpmanholmen, vilket är ca 100–200 gånger högre än de HCB-halter som påträffas i bakgrundsluft (Bidleman et al., 2017). För både HCB och Hg följer halten i gasen halten i sedimentet. Fluxet av HCB och Hg i gasfas från fiberbankarna kan uppskattas utifrån föroreningskoncentrationen i gasen (provtagen med den forcerade metoden) och gasflödet (provtaget med den passiva metoden). Givet att det genomsnittliga gasflödet i de lyckade provtagningarna är representativt uppskattas HCB-flux för de båda fiberbankarna vid ostörda förhållanden till i genomsnitt 3,2 ng/m2/år (1,5 ng/m2/år för Väja och 4,7 ng/m2/år för Köpmanholmen). Det genomsnittliga Hg-fluxet beräknades vid ostörda förhållanden till 0,4 ng/m2/år vid Väja, 1,5 ng/m2/år vid Sandviken och 4,6 ng/m2/år vid Köpmanholmen. Föroreningsfluxet i gasfas bedöms därmed vara relativt begränsat vid naturliga förhållanden. Den gasmedierade partikelspridningen varierade mellan 17–49 mg/m2/dag för Väja och Sandviken men var högre i Köpmanholmen (> 200 mg/m2/dag vid båda provtagningstillfällena). Partiklarnas föroreningsinnehåll har inte kunnat analyseras inom ramen för projektet men vid fysisk störning av fiberbankssediment bedöms betydligt större mängder HCB och Hg, i både gasfas och bundet till partiklar, kunna frigöras, åtminstone under en kort tid. Detta behöver beaktas vid riskbedömning och val av åtgärder av förorenade fiberbankar.
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| 4. |
- Li, Chuxian, et al.
(författare)
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Mercury deposition and redox transformation processes in peatland constrained by mercury stable isotopes
- 2023
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Peatland vegetation takes up mercury (Hg) from the atmosphere, typically contributing to net production and export of neurotoxic methyl-Hg to downstream ecosystems. Chemical reduction processes can slow down methyl-Hg production by releasing Hg from peat back to the atmosphere. The extent of these processes remains, however, unclear. Here we present results from a comprehensive study covering concentrations and isotopic signatures of Hg in an open boreal peatland system to identify post-depositional Hg redox transformation processes. Isotope mass balances suggest photoreduction of HgII is the predominant process by which 30% of annually deposited Hg is emitted back to the atmosphere. Isotopic analyses indicate that above the water table, dark abiotic oxidation decreases peat soil gaseous Hg0 concentrations. Below the water table, supersaturation of gaseous Hg is likely created more by direct photoreduction of rainfall rather than by reduction and release of Hg from the peat soil. Identification and quantification of these light-driven and dark redox processes advance our understanding of the fate of Hg in peatlands, including the potential for mobilization and methylation of HgII.
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| 5. |
- Noumonvi, Koffi Dodji, et al.
(författare)
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The Kulbäcksliden research infrastructure : a unique setting for northern peatland studies
- 2023
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Ingår i: Frontiers in Earth Science. - : Frontiers Media S.A.. - 2296-6463. ; 11
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Forskningsöversikt (refereegranskat)abstract
- Boreal peatlands represent a biogeochemically unique and diverse environment in high-latitude landscape. They represent a long-term globally significant sink for carbon dioxide and a source of methane, hence playing an important role in regulating the global climate. There is an increasing interest in deciphering peatland biogeochemical processes to improve our understanding of how anthropogenic and climate change effects regulate the peatland biogeochemistry and greenhouse gas balances. At present, most studies investigating land-atmosphere exchanges of peatland ecosystems are commonly based on single-tower setups, which require the assumption of homogeneous conditions during upscaling to the landscape. However, the spatial organization of peatland complexes might feature large heterogeneity due to its varying underlying topography and vegetation composition. Little is known about how well single site studies represent the spatial variations of biogeochemical processes across entire peatland complexes. The recently established Kulbäcksliden Research Infrastructure (KRI) includes five peatland study sites located less than 3 km apart, thus providing a unique opportunity to explore the spatial variation in ecosystem-scale processes across a typical boreal peatland complex. All KRI sites are equipped with eddy covariance flux towers combined with installations for detailed monitoring of biotic and abiotic variables, as well as catchment-scale hydrology and hydrochemistry. Here, we review studies that were conducted in the Kulbäcksliden area and provide a description of the site characteristics as well as the instrumentation available at the KRI. We highlight the value of long-term infrastructures with ecosystem-scale and replicated experimental sites to advance our understanding of peatland biogeochemistry, hydrology, ecology, and its feedbacks on the environment and climate system.
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| 6. |
- Peng, Haijun, et al.
(författare)
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Climatic controls on the dynamic lateral expansion of northern peatlands and its potential implication for the 'anomalous' atmospheric CH4 rise since the mid-Holocene
- 2024
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 908
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the dynamic changes in peatland area during the Holocene is essential for unraveling the connections between northern peatland development and global carbon budgets. However, studies investigating the centennial to millennial -scale process of peatland expansion and its climate and environmental drivers are still limited. In this study, we present a reconstruction of the peatland area and lateral peatland expansion rate of a peatland complex in northern Sweden since the mid -Holocene, based on Ground Penetrating Radar measurements of peat thickness supported by radiocarbon (14C) dates from four peat cores. Based on this analysis, lateral expansion of the peatland followed a northwest -southeast directionality, constrained by the undulating post-glacial topography. The areal extent of peat has increased non -linearly since the mid -Holocene, and the peatland lateral expansion rate has generally been on the rise, with intensified expansion occurring after around 3500 cal yr BP. Abrupt declines in lateral expansion rates were synchronized with the decreases in total solar irradiance superimposed on the millennial ice -rafted debris events in the northern high latitudes. Supported by the temporal evolution of peatland extent in four other Fennoscandian peatlands, it appears that the northern peatland areal extent during the early to middle Holocene was much smaller compared to previous empirical model reconstructions based on basal age compilations. Interestingly, our reconstruction shows the increments of peat area since the mid -Holocene coincide with the rise in atmospheric CH4 concentration, and that abrupt variations in atmospheric CH4 on decadal to centennial timescales could be synchronized with peatland lateral expansion rates. Based on our analysis we put forward the hypothesis that lateral expansion of northern peatlands is a significant driver of dynamics in the late Holocene atmospheric CH4 budget. We strongly urge for more empirical data to quantify lateral expansion rates and test such hypotheses.
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| 7. |
- Peng, Haijun, et al.
(författare)
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Environmental Controls on Multi-Scale Dynamics of Net Carbon Dioxide Exchange From an Alpine Peatland on the Eastern Qinghai-Tibet Plateau
- 2022
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands are characterized by their large carbon storage capacity and play an essential role in the global carbon cycle. However, the future of the carbon stored in peatland ecosystems under a changing climate remains unclear. In this study, based on the eddy covariance technique, we investigated the net ecosystem CO2 exchange (NEE) and its controlling factors of the Hongyuan peatland, which is a part of the Ruoergai peatland on the eastern Qinghai-Tibet Plateau (QTP). Our results show that the Hongyuan alpine peatland was a CO2 sink with an annual NEE of -226.61 and -185.35 g C m(-2) in 2014 and 2015, respectively. While, the non-growing season NEE was 53.35 and 75.08 g C m(-2) in 2014 and 2015, suggesting that non-growing seasons carbon emissions should not be neglected. Clear diurnal variation in NEE was observed during the observation period, with the maximum CO2 uptake appearing at 12:30 (Beijing time, UTC+8). The Q(10) value of the non-growing season in 2014 and 2015 was significantly higher than that in the growing season, which suggested that the CO2 flux in the non-growing season was more sensitive to warming than that in the growing season. We investigated the multi-scale temporal variations in NEE during the growing season using wavelet analysis. On daily timescales, photosynthetically active radiation was the primary driver of NEE. Seasonal variation in NEE was mainly driven by soil temperature. The amount of precipitation was more responsible for annual variation of NEE. The increasing number of precipitation event was associated with increasing annual carbon uptake. This study highlights the need for continuous eddy covariance measurements and time series analysis approaches to deepen our understanding of the temporal variability in NEE and multi-scale correlation between NEE and environmental factors.
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| 8. |
- Peng, Haijun, et al.
(författare)
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Methane Emissions Offset Net Carbon Dioxide Uptake From an Alpine Peatland on the Eastern Qinghai-Tibetan Plateau
- 2021
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Ingår i: Journal of geophysical research. Atmospheres. - 2169-897X .- 2169-8996. ; 126
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands store large amounts of carbon (C) and actively exchange greenhouse gases (GHGs) with the atmosphere, thus significantly affecting global C cycle and climate. Large uncertainty exists in C and GHG estimates of the alpine peatlands on Qinghai-Tibetan Plateau (QTP), as direct measurements of CO2 and CH4 fluxes are scarce in this region. In this study, we provided 32-month CO2 and CH4 fluxes measured using the eddy covariance (EC) technique in a typical alpine peatland on the eastern QTP to estimate the net C and CO2 equivalent (CO2-eq) fluxes and investigate their environmental controls. Our results showed that the mean annual CO2 and CH4 fluxes were -68 +/- 8 g CO2-C m(-2) yr(-1) and 35 +/- 0.3 g CH4-C m(-2) yr(-1), respectively. While considering the traditional and sustained global warming potentials of CH4 over the 100-year timescale, the peatland acted as a net CO2-eq source (1,059 +/- 30 and 1,853 +/- 31 g CO2-eq m(-2) yr(-1), respectively). The net CO2-eq emissions during the non-growing seasons contributed to over 40% of the annual CO2-eq budgets. We further found that net CO2-eq flux was primarily influenced by global radiation and soil temperature variations. This study was the first assessment to quantify the net CO2-eq flux of the alpine peatland in the QTP region using EC measurements. Our study highlights that CH4 emissions from the alpine peatlands can largely offset the net cooling effect of CO2 uptake and future climate changes such as global warming might further enhance their potential warming effect.
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| 9. |
- Peng, Haijun
(författare)
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Temporal variations of carbon and water fluxes in a subtropical mangrove forest: Insights from a decade-long eddy covariance measurement
- 2023
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 343
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Tidskriftsartikel (refereegranskat)abstract
- Mangroves, highly efficient ecosystems in sequestering CO2, are strongly impacted by climate change. The lack of long-term observation in mangroves hinders the evaluation of seasonal and inter-annual variability in carbon and water fluxes and their responses to various environmental drivers. In this study, we measured net ecosystem CO2 exchange and evapotranspiration between the atmosphere and subtropical mangroves using the eddy covariance technique over a decade (2010-2019) in southern China. This mangrove forest acted as a strong CO2 sink, with annual net ecosystem production (NEP) ranging from 622.5 to 832.8 g C m(-2) year(-1). The annual evapotranspiration (ET) varied between 934.6 and 1004.9 mm year(-1). During the study period, ET consistently remained higher in the wet season (May to October) compared to the dry season, while NEP did not exhibit consistent seasonal variation. Path analysis indicated that during the dry season, NEP was primarily influenced by global solar radiation and vapor pressure deficit. However, in the wet season, NEP was regulated by a combination of global solar radiation, vapor pressure deficit, air temperature, and tidal inundation time. Additionally, the promoting effect of global solar radiation on NEP decreased in the wet season, while the inhibitory influences of higher temperature and vapor pressure deficit on NEP intensified during the period. Unlike NEP, the dominant factors affecting ET (global solar radiation, air temperature, and vapor pressure deficit) and their intensities remained relatively consistent during both seasons. Furthermore, the relative importance of global solar radiation on NEP and ET increased over the decade, while the influence of tidal inundation time diminished. This study not only improves the understanding of the response of subtropical mangroves to climate change but also provides a valuable benchmark dataset to validate the interannual variability of mangrove carbon and water fluxes estimated from the models.
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