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1.
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2.
  • Cheung, Henry Lok Shan, et al. (författare)
  • Denitrification, anammox, and DNRA in oligotrophic continental shelf sediments
  • 2024
  • Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 69:3, s. 621-637
  • Tidskriftsartikel (refereegranskat)abstract
    • Continental shelf sediments are considered hotspots for nitrogen (N) removal. While most investigations have quantified denitrification in shelves receiving large amounts of anthropogenic nutrient supply, we lack insight into the key drivers of N removal on oligotrophic shelves. Here, we measured rates of N removal through denitrification and anammox by the revised-isotope pairing technique (r-IPT) along the Northeastern New Zealand shelf. Denitrification dominated total N2 production at depths between 30 and 128 m with average rates (± SE) ranging from 65 ± 28 to 284 ± 72 μmol N m−2 d−1. N2 production by anammox ranged from 3 ± 1 to 28 ± 11 μmol N m−2 d−1 and accounted for 2–19% of total N2 production. DNRA was negligible in these oligotrophic settings. Parallel microbial community analysis showed that both Proteobacteria and Planctomycetota were key taxa driving denitrification. Denitrification displayed a negative correlation with oxygen penetration depth, and a positive correlation with macrofauna abundance. Our denitrification rates were comparable to oligotrophic shelves from the Arctic, but were lower than those from nutrient-rich Pacific and Atlantic shelves. Based on our results and existing IPT measurements, the global shelf denitrification rate was reassessed to be 53.5 ± 8.1 Tg N yr−1, equivalent to 20 ± 2% of marine N removal. We suggest that previous estimates of global shelf N loss might have been overestimated due to sampling bias toward areas with high N loads in the Northern Hemisphere.
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3.
  • Sonesten, Lars (författare)
  • Miljöövervakningen av Sveriges sjöar och vattendrag : Representativiteten av den kontrollerande miljöövervakningen
  • 2013
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Samtliga ytvattenkategorier inom ett vattendistrikt ska omfattas av övervakningsprogram inklusive övervakningsnät för kontrollerande övervakning som upprättas enligt kap. 7 VFF. En översyn av hur representativt Sveriges kontrollerade övervakningsnät är har tidigare inte kunnat utföras på grund av omfattande kvalitetsbrister i länsstyrelserna och vattenmyndigheternas datasystem VISS (VattenInformationsSystem Sverige). Kvaliteten på informationen i VISS har under senare år genomgått en omfattande kvalitetssäkring, vilket har gett förutsättningarna för att nu kunna genomföra den sammanställning och översyn över den svenska miljöövervakningen av sjöar och vattendrag. Denna översyn har varit starkt önskad under flera år, då det finns ett stort behov av att se över och analysera hur ett representativt samordnat kontrollerande övervakningsprogram skulle kunna se ut. Översynen sker mot bakgrund av den samlade vatten övervakning som bedrivs i Sverige, bland annat för att optimera befintlig övervakning och att kunna förstärka den där brister har identifierats. Arbetet är också viktigt för att säkerställa att kommande rapporteringar såväl internationellt som nationellt blir så bra som möjligt.Uppdraget för projektet Representativ kontrollerande miljöövervakning (RepKöp) syftar till att ta fram ett förslag på hur ett representativt kontrollerande övervakningsprogram med avseende på (vattentyper), kvalitetsfaktorer och statusklasser bör se ut på nationell­ och distriktsnivå i Sverige. Förslaget tas fram mot bakgrund av den samlade vattenövervakningen som bedrivs i Sverige idag och mot bakgrund av vad behövs för att uppfylla vattendirektivets krav på kontrollerande övervakning av vattenförekomster.Resultaten från översynen är tänkta att dels fungera som underlag för att underlätta Havs­ och vattenmyndighetens och Vattenmyndigheternas arbete inför rapporteringen 2012, men framför allt ska projektet ge underlag för att ta fram optimerade övervakningsprogram för sjöar och vattendrag till en långsiktig plan med en första anhalt 2016. För att RepKÖP ska få praktisk betydelse i övervakningsSverige skall projektet resultera i ett underlag för framtida revision av befintliga övervakningsprogram för respektive distrikt.Arbetet inom RepKöp är uppdelat i flera delar, vilka tillsammans ska fungera som vägledning till:• Vattenförvaltningens arbete med kontrollerande övervakning• Upplägg av nationell och regional miljöövervakningMålgruppen för arbetet är i första hand:• Vattenmyndigheter• Länsstyrelserna• Naturvårdsverket• Havs­ och vattenmyndigheten• Datavärdar och utförare av miljöövervakningFöreliggande rapport är en sammanställning och analys av miljöövervakningen av svenska sjöar och vattendrag så som de beskrevs i VISS vid datauttaget för sjöar i oktober 2011 och vattendrag i maj 2012. Sammanställningen av informationen från VISS har initierat en hel del korrigeringar i systemet, men tyvärr har det inte av praktiska skäl varit möjligt att ta hänsyn till dessa i arbetet. Man skall vara medveten om att VISS är en levande databas som ständigt uppdateras och korrigeras, vilket gör att endast en ”ögonblicksbild” kan analyseras. Detta gör att när analysen är färdig har verkligheten med stor sannolikhet redan till viss del hunnit förändrats.
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4.
  • Roth, Florian, et al. (författare)
  • High spatiotemporal variability of methane concentrations challenges estimates of emissions across vegetated coastal ecosystems.
  • 2022
  • Ingår i: Global change biology. - : Wiley. - 1365-2486 .- 1354-1013. ; 28:14, s. 4308-4322
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal methane (CH4 ) emissions dominate the global ocean CH4 budget and can offset the "blue carbon" storage capacity of vegetated coastal ecosystems. However, current estimates lack systematic, high-resolution, and long-term data from these intrinsically heterogeneous environments, making coastal budgets sensitive to statistical assumptions and uncertainties. Using continuous CH4 concentrations, δ13 C-CH4 values, and CH4 sea-air fluxes across four seasons in three globally pervasive coastal habitats, we show that the CH4 distribution is spatially patchy over meter-scales and highly variable in time. Areas with mixed vegetation, macroalgae, and their surrounding sediments exhibited a spatiotemporal variability of surface water CH4 concentrations ranging two orders of magnitude (i.e., 6-460nM CH4 ) with habitat-specific seasonal and diurnal patterns. We observed (1) δ13 C-CH4 signatures that revealed habitat-specific CH4 production and consumption pathways, (2) daily peak concentration events that could change >100% within hours across all habitats, and (3) a high thermal sensitivity of the CH4 distribution signified by apparent activation energies of ~1eV that drove seasonal changes. Bootstrapping simulations show that scaling the CH4 distribution from few samples involves large errors, and that ~50 concentration samples per day are needed to resolve the scale and drivers of the natural variability and improve the certainty of flux calculations by up to 70%. Finally, we identify northern temperate coastal habitats with mixed vegetation and macroalgae as understudied but seasonally relevant atmospheric CH4 sources (i.e., releasing≥100μmol CH4 m-2 day-1 in summer). Due to the large spatial and temporal heterogeneity of coastal environments, high-resolution measurements will improve the reliability of CH4 estimates and confine the habitat-specific contribution to regional and global CH4 budgets.
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5.
  • Wang, Y. J., et al. (författare)
  • The formation of nitro-aromatic compounds under high NOx and anthropogenic VOC conditions in urban Beijing, China
  • 2019
  • Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:11, s. 7649-7665
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation in the urban atmosphere was little studied. In this work, we report an intensive field study of NACs in summer 2016 at an urban Beijing site, characterized by both high-NO(x)and anthropogenic VOC dominated conditions. We investigated the factors that influence NAC formation (e.g., NO2, VOC precursors, RH and photolysis) through quantification of eight NACs, along with major components in fine particulate matter, selected volatile organic compounds, and gases. The average total concentration of the quantified NACs was 6.63 ng m(-3), higher than those reported in other summertime studies (0.14-6.44 ng m(-3)). 4-Nitrophenol (4NP, 32.4 %) and 4-nitrocatechol (4NC, 28.5 %) were the top two most abundant NACs, followed by methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), and dimethyl-nitrophenol (DMNP). The oxidation of toluene and benzene in the presence of NOx was found to be a more dominant source of NACs than primary biomass burning emissions. The NO2 concentration level was found to be an important factor influencing the secondary formation of NACs. A transition from low- to high-NOx regimes coincided with a shift from organic- to inorganic-dominated oxidation products. The transition thresholds were NO2 similar to 20 ppb for daytime and NO2 similar to 25 ppb for nighttime conditions. Under low-NOx conditions, NACs increased with NO2, while the NO3 concentrations and (NO3-)/NACs ratios were lower, implying organic-dominated products. Under high-NOx conditions, NAC concentrations did not further increase with NO2, while the NO3- concentrations and (NO3-)/NACs ratios showed increasing trends, signaling a shift from organic- to inorganic-dominated products. Nighttime enhancements were observed for 3M4NC and 4M5NC, while daytime enhancements were noted for 4NP, 2M4NP, and DMNP, indicating different formation pathways for these two groups of NACs. Our analysis suggested that the aqueous-phase oxidation was likely the major formation pathway of 4M5NC and 3M5NC, while photo-oxidation of toluene and benzene in the presence of NO2 could be more important for the formation of nitrophenol and its derivatives. Using the (3M4NC+4M5NC) / 4NP ratios as an indicator of the relative contribution of aqueous-phase and gas-phase oxidation pathways to NAC formation, we observed that the relative contribution of aqueous-phase pathways increased at elevated ambient RH and remained constant at RH > 30 %. We also found that the concentrations of VOC precursors (e.g., toluene and benzene) and aerosol surface area acted as important factors in promoting NAC formation, and photolysis as an important loss pathway for nitrophenols.
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6.
  • Rämö, Robert, et al. (författare)
  • Sediment Remediation Using Activated Carbon: Effects of Sorbent Particle Size and Resuspension on Sequestration of Metals and Organic Contaminants.
  • 2022
  • Ingår i: Environmental toxicology and chemistry. - : Wiley. - 1552-8618 .- 0730-7268. ; 41:4, s. 1096-1110
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin-layer capping using activated carbon (AC) has been described as a cost-effective in situ sediment remediation method for organic contaminants. In this study, we compare the capping efficiency of powdered AC (PAC) against granular AC (GAC) using contaminated sediment from Oskarshamn harbor, Sweden. The effects of resuspension on contaminant retention and cap integrity were also studied. Intact sediment cores were collected from the outer harbor and brought to the laboratory. Three thin-layer caps, consisting of PAC or GAC mixed with clay, or clay only, were added to the sediment surface. Resuspension was created using a motor-driven paddle to simulate propeller wash from ship traffic. Passive samplers were placed in the sediment and in the water column to measure the sediment-to-water release of PAHs, PCBs, and metals. Our results show that a thin-layer cap with PAC reduced sediment-to-water fluxes of PCBs by 57 % under static conditions and 91 % under resuspension. Thin-layer capping with GAC was less effective than PAC, but reduced fluxes of high-molecular weight PAHs. Thin-layer capping with AC was less effective in retaining metals, except for Cd, which release was significantly reduced by PAC. Resuspension generally decreased water concentrations of dissolved cationic metals, perhaps due to sorption to suspended sediment particles. Sediment resuspension in treatments without capping increased fluxes of PCBs with log Kow > 7 and PAHs with log Kow 5 6, but resuspension reduced PCB and PAH fluxes through the PAC thin-layer cap. Overall, PAC performed better than GAC, but adverse effects on the benthic community and transport of PAC to non-target areas are drawbacks that favor the use of GAC. This article is protected by copyright. All rights reserved.© 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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7.
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9.
  • Baresel, Christian, et al. (författare)
  • Uncertainty-Accounting Environmental Policy and Management of Water Systems
  • 2007
  • Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:10, s. 3653–3659-
  • Tidskriftsartikel (refereegranskat)abstract
    • Environmental policies for water quality and ecosystemmanagement do not commonly require explicit stochasticaccounts of uncertainty and risk associated with thequantification and prediction of waterborne pollutant loadsand abatement effects. In this study, we formulate andinvestigate a possible environmental policy that does requirean explicit stochastic uncertainty account. We compareboth the environmental and economic resource allocationperformance of such an uncertainty-accounting environmentalpolicy with that of deterministic, risk-prone and riskaverseenvironmental policies under a range of differenthypothetical, yet still possible, scenarios. The comparisonindicates that a stochastic uncertainty-accountingpolicy may perform better than deterministic policies overa range of different scenarios. Even in the absence ofreliable site-specific data, reported literature values appearto be useful for such a stochastic account of uncertainty.
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10.
  • Drake, Henrik, 1979-, et al. (författare)
  • Ancient microbial activity in deep hydraulically conductive fracture zones within the Forsmark target area for deep geological nuclear waste disposal, Sweden
  • 2018
  • Ingår i: Geosciences. - : MDPI AG. - 2076-3263. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent studies reveal that organisms from all three domains of life—Archaea, Bacteria, and even Eukarya—can thrive under energy-poor, dark, and anoxic conditions at large depths in the fractured crystalline continental crust. There is a need for an increased understanding of the processes and lifeforms in this vast realm, for example, regarding the spatiotemporal extent and variability of the different processes in the crust. Here, we present a study that set out to detect signs of ancient microbial life in the Forsmark area—the target area for deep geological nuclear waste disposal in Sweden. Stable isotope compositions were determined with high spatial resolution analyses within mineral coatings, and mineralized remains of putative microorganisms were studied in several deep water-conducting fracture zones (down to 663 m depth), from which hydrochemical and gas data exist. Large isotopic variabilities of 13Ccalcite (?36.2 to +20.2‰V-PDB) and 34Spyrite (?11.7 to +37.8‰V-CDT) disclose discrete periods of methanogenesis, and potentially, anaerobic oxidation of methane and related microbial sulfate reduction at several depth intervals. Dominant calcite–water disequilibrium of 18O and 87Sr/86Sr precludes abundant recent precipitation. Instead, the mineral coatings largely reflect an ancient archive of episodic microbial processes in the fracture system, which, according to our microscale Rb–Sr dating of co-genetic adularia and calcite, date back to the mid-Paleozoic. Potential Quaternary precipitation exists mainly at ~400 m depth in one of the boreholes, where mineral–water compositions corresponded.
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11.
  • Sonesten, Lars (författare)
  • Deformiteter hos oligochaeter i Vänern
  • 2014
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Bottenlevande slamrörmaskar, oligochaeter, är känsliga miljöindikatorer i alla typerav vatten. I en retrospektiv studie har deformiteter hos oligochaeter från treolika nordliga Vänervikar jämförts under en period med minskad antropogen belastningmed avseende på näringsämnen och olika metaller. Stora mängder av miljöfarligaämnen finns dock lagrade i de sediment som oligochaeterna lever i.Resultaten från undersökningen visar på att de allra grövsta deformitetsformerna,dvs. groteskt förändrade ventrala borst, med tiden generellt sett har minskat i omfattning.Det finns däremot inga tecken på att lättare deformiteter har minskatnämnvärt annat än lokalt. Utöver de skador som noterades på ventrala borst vidtidigare undersökningar så noterades i denna undersökning även att deformiteterhos både dorsala och ventrala borst har tillkommit hos arten Potamothrix hammoniensisi samtliga tre fjärdar. Deformiteterna spänner mellan lättare och mergrava skador, där de lätta dominerar. Liknande skador hos dorsala borst har endastundantagsvis setts i tidigare material från Vänern.Även om förekomsten av de mest grava deformiteterna har minskat, så visar resultatenpå att de lättare skadorna inte har minskat noterbart under den undersöktaperioden annat än på vissa provplatser. Detta skulle kunna tyda på att oligochaeternafortfarande påverkas av upplagrade miljögifter i sedimenten.
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12.
  • Ritter, Camila, et al. (författare)
  • High-throughput metabarcoding reveals the effect of physicochemical soil properties on soil and litter biodiversity and community turnover across Amazonia.
  • 2018
  • Ingår i: PeerJ. - : PeerJ. - 2167-8359. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge on the globally outstanding Amazonian biodiversity and its environmental determinants stems almost exclusively from aboveground organisms, notably plants. In contrast, the environmental factors and habitat preferences that drive diversity patterns for micro-organisms in the ground remain elusive, despite the fact that micro-organisms constitute the overwhelming majority of life forms in any given location, in terms of both diversity and abundance. Here we address how the diversity and community turnover of operational taxonomic units (OTU) of organisms in soil and litter respond to soil physicochemical properties; whether OTU diversities and community composition in soil and litter are correlated with each other; and whether they respond in a similar way to soil properties.We used recently inferred OTUs from high-throughput metabarcoding of the 16S (prokaryotes) and 18S (eukaryotes) genes to estimate OTU diversity (OTU richness and effective number of OTUs) and community composition for prokaryotes and eukaryotes in soil and litter across four localities in Brazilian Amazonia. All analyses were run separately for prokaryote and eukaryote OTUs, and for each group using both presence-absence and abundance data. Combining these with novel data on soil chemical and physical properties, we identify abiotic correlates of soil and litter organism diversity and community structure using regression, ordination, and variance partitioning analysis.Soil organic carbon content was the strongest factor explaining OTU diversity (negative correlation) and pH was the strongest factor explaining community turnover for prokaryotes and eukaryotes in both soil and litter. We found significant effects also for other soil variables, including both chemical and physical properties. The correlation between OTU diversity in litter and in soil was non-significant for eukaryotes and weak for prokaryotes. The community compositions of both prokaryotes and eukaryotes were more separated among habitat types (terra-firme, várzea, igapó and campina) than between substrates (soil and litter).In spite of the limited sampling (four localities, 39 plots), our results provide a broad-scale view of the physical and chemical correlations of soil and litter biodiversity in a longitudinal transect across the world's largest rainforest. Our methods help to understand links between soil properties, OTU diversity patterns, and community composition and turnover. The lack of strong correlation between OTU diversity in litter and in soil suggests independence of diversity drives of these substrates and highlights the importance of including both measures in biodiversity assessments. Massive sequencing of soil and litter samples holds the potential to complement traditional biological inventories in advancing our understanding of the factors affecting tropical diversity.
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13.
  • Björk, Mats, 1960-, et al. (författare)
  • Methane emissions from macrophyte beach wrack on Baltic seashores
  • 2023
  • Ingår i: Ambio. - : Springer Nature. - 0044-7447 .- 1654-7209. ; 52:1, s. 171-181
  • Tidskriftsartikel (refereegranskat)abstract
    • Beach wrack of marine macrophytes is a natural component of many beaches. To test if such wrack emits the potent greenhouse gas methane, field measurements were made at different seasons on beach wrack depositions of different ages, exposure, and distance from the water. Methane emissions varied greatly, from 0 to 176 mg CH4-C m−2 day−1, with a clear positive correlation between emission and temperature. Dry wrack had lower emissions than wet. Using temperature data from 2016 to 2020, seasonal changes in fluxes were calculated for a natural wrack accumulation area. Such calculated average emissions were close to zero during winter, but peaked in summer, with very high emissions when daily temperatures exceeded 20 °C. We conclude that waterlogged beach wrack significantly contributes to greenhouse gas emissions and that emissions might drastically increase with increasing global temperatures. When beach wrack is collected into heaps away from the water, the emissions are however close to zero.
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14.
  • Oni, Stephen, et al. (författare)
  • Local- and landscape-scale impacts of clear-cuts and climate change on surface water dissolved organic carbon in boreal forests
  • 2015
  • Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953 .- 2169-8961. ; 120:11, s. 2402-2426
  • Tidskriftsartikel (refereegranskat)abstract
    • Forest harvesting and climate change may significantly increase concentrations and fluxes of dissolved organic carbon (DOC) in boreal surface waters. However, the likely magnitude of any effect will vary depending on the landscape-element type and spatial scale. We used a chain of hydrological, empirical, and process-based biogeochemical models coupled to an ensemble of downscaled Regional Climate Model experiments to develop scenario storylines for local- and landscape-scale effects of forest harvesting and climate change on surface water DOC concentrations and fluxes. Local-scale runoff, soil temperature, and DOC dynamics were simulated for a range of forest and wetland landscape-element types and at the larger landscape scale. The results indicated that climate change will likely lead to greater winter flows and earlier, smaller spring peaks. Both forest harvesting and climate change scenarios resulted in large increases in summer and autumn runoff and higher DOC fluxes. Forest harvesting effects were clearly apparent at local scales. While at the landscape scale, approximately 1 mg L−1 (or 10%) of the DOC in surface waters can be attributed to clear-cuts, both climate change and intensified forestry can each increase DOC concentrations by another 1 mg L−1 in the future, which is less than that seen in many waterbodies recovering from acidification. These effects of forestry and climate change on surface water DOC concentrations are additive at a landscape scale but not at the local scale, where a range of landscape-element specific responses were observed.
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15.
  • Kylander, Malin, 1977-, et al. (författare)
  • A novel geochemical approach to paleorecords of dust deposition and effective humidity: 8500 years of peat accumulation at Store Mosse (the "Great Bog") , Sweden )
  • 2013
  • Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 69, s. 69-82
  • Tidskriftsartikel (refereegranskat)abstract
    • Both bog surface wetness and atmospheric dust deposition are intricately linked to changes in the hydrological cycle and pairing these types of records at the same site provides complementary information. Here a peat core from Store Mosse in southern Sweden covering the last 8500 years was used to make a high-resolution paleoclimate reconstruction based on a combination of bog development, colourimetric humification and inorganic geochemistry data. The coupling of Principal Component Analysis with changepoint modelling allowed for precise linking of changes in bog surface wetness and dust deposition records.A long-term trend towards warm (and possibly wet) conditions starts ca 8150 cal yr BP and culminates with the most pronounced conditions from 6900 to 6600 cal yr BP. The most significant arid period at Store Mosse occurred between 6500 and 5600 cal yr BP during which dust deposition was significantly higher. Wetter conditions dominate from 5500 to 4980 cal yr BP as the transition from the Hypsithermal and into the Neoglacial is made. After a shift to drier conditions, humification enters a more stable period that lasts from 4525 until 3200 cal yr BP. It is during this time that the first possible anthropogenic dust signals occur at ca 4200 cal yr BP. From 3200 cal yr BP to present humification generally shows a long-term decline moving towards wetter conditions. The main exceptions are during the transition from the Neoglacial to Roman Warm Period which is registered as a significantly wetter period and two dry periods recorded 2365 to 2155 cal yr BP and 1275–1105 cal yr BP. In general, the observed changes agree well with regional records of effective humidity and temperature. The high temporal resolution of the Store Mosse record reveals that palaeoclimatic change over the last 8500 years in southern Sweden has had a complex and variable structure.
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16.
  • Capo, Eric, et al. (författare)
  • Oxygen-deficient water zones in the Baltic Sea promote uncharacterized Hg methylating microorganisms in underlying sediments
  • 2022
  • Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 67:1, s. 135-146
  • Tidskriftsartikel (refereegranskat)abstract
    • Human-induced expansion of oxygen-deficient zones can have dramatic impacts on marine systems and its resident biota. One example is the formation of the potent neurotoxic methylmercury (MeHg) that is mediated by microbial methylation of inorganic divalent Hg (HgII) under oxygen-deficient conditions. A negative consequence of the expansion of oxygen-deficient zones could be an increase in MeHg production due to shifts in microbial communities in favor of microorganisms methylating Hg. There is, however, limited knowledge about Hg-methylating microbes, i.e., those carrying hgc genes critical for mediating the process, from marine sediments. Here, we aim to study the presence of hgc genes and transcripts in metagenomes and metatranscriptomes from four surface sediments with contrasting concentrations of oxygen and sulfide in the Baltic Sea. We show that potential Hg methylators differed among sediments depending on redox conditions. Sediments with an oxygenated surface featured hgc-like genes and transcripts predominantly associated with uncultured Desulfobacterota (OalgD group) and Desulfobacterales (including Desulfobacula sp.) while sediments with a hypoxic-anoxic surface included hgc-carrying Verrucomicrobia, unclassified Desulfobacterales, Desulfatiglandales, and uncharacterized microbes. Our data suggest that the expansion of oxygen-deficient zones in marine systems may lead to a compositional change of Hg-methylating microbial groups in the sediments, where Hg methylators whose metabolism and biology have not yet been characterized will be promoted and expand.
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17.
  • Sobek, Anna, et al. (författare)
  • Organic matter degradation causes enrichment of organic pollutants in hadal sediments
  • 2023
  • Ingår i: Nature Communications. - 2041-1723. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • Burial of persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) in deep-sea sediments contributes to 60% of their historical emissions. Yet, empirical data on their occurrence in the deep-ocean is scarce. Estimates of the deep-ocean POP sink are therefore uncertain. Hadal trenches, representing the deepest part of the ocean, are hotspots for organic carbon burial and decomposition. POPs favorably partition to organic carbon, making trenches likely significant sinks for contaminants. Here we show that PCBs occur in both hadal (7720–8085 m) and non-hadal (2560–4050 m) sediment in the Atacama Trench. PCB concentrations normalized to sediment dry weight were similar across sites while those normalized to sediment organic carbon increased exponentially as the inert organic carbon fraction of the sediment increased in degraded hadal sediments. We suggest that the unique deposition dynamics and elevated turnover of organic carbon in hadal trenches increase POP concentrations in the deepest places on Earth.
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18.
  • Omstedt, Anders, 1949 (författare)
  • The Development of Climate Science of the Baltic Sea Region
  • 2017
  • Ingår i: Oxford Research Encyclopedia of Climate Science. - : Oxford University Press.
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • Dramatic climate changes have occurred in the Baltic Sea region caused by changes in orbital movement in the earth–sun system and the melting of the Fennoscandian Ice Sheet. Added to these longer-term changes, changes have occurred at all timescales, caused mainly by variations in large-scale atmospheric pressure systems due to competition between the meandering midlatitude low-pressure systems and highpressure systems. Here we follow the development of climate science of the Baltic Sea from when observations began in the 18th century to the early 21st century. The question of why the water level is sinking around the Baltic Sea coasts could not be answered until the ideas of postglacial uplift and the thermal history of the earth were better understood in the 19th century and periodic behavior in climate related time series attracted scientific interest. Herring and sardine fishing successes and failures have led to investigations of fishery and climate change and to the realization that fisheries themselves have strongly negative effects on the marine environment, calling for international assessment efforts. Scientists later introduced the concept of regime shifts when interpreting their data, attributing these to various causes. The increasing amount of anoxic deep water in the Baltic Sea and eutrophication have prompted debate about what is natural and what is anthropogenic, and the scientific outcome of these debates now forms the basis of international management efforts to reduce nutrient leakage from land. The observed increase in atmospheric CO and its effects on global warming have focused the climate debate on trends and generated a series of international and regional assessments and research programs that have greatly improved our understanding of climate and environmental changes, bolstering the efforts of earth system science, in which both climate and environmental factors are analyzed together.
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19.
  • Li, Jun, et al. (författare)
  • Hygroscopicity and Ice Nucleation Properties of Dust/Salt Mixtures Originating from the Source of East Asian Dust Storms
  • 2022
  • Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Dust storms are common meteorological events that occur frequently in the late spring and early summer in arid and semi-arid areas. The resulting lofted dust and salt mixtures can impact atmospheric chemistry and climate systems through the many pathways represented by aerosol-cloud-climate interactions. In this study, dust/salt samples were collected from important sources of the East Asian dust storm, including the Badain Jaran Desert, the Tengger Desert and the Ulan Buh Desert in northwestern China. Ion chromatography (IC) measurements were performed to determine the concentrations of cations and anions. The ionic concentrations, pH and dissolvable fractions of sand samples show a positive correlation, indicating that the dissolved content is rich in alkaline ions. A positive matrix factorization (PMF) receptor model was employed to analyze the IC results, and from the PMF solutions non-obvious connections to local geography emerge. The results of hygroscopic experiments of sand samples which were measured by a vapor sorption analyzer indicate that the hygroscopicity may be related to the soluble content of samples, and the observed hygroscopic behavior can be well described by a thermodynamic model. The morphology of individual particles was chemically mapped by the synchrotron-based scanning transmission X-ray microscopy, and needle-shaped CaCO3 particles were observed to adhere to more irregular high K-containing particles. Moreover, a continuous flow diffusion chamber was used to investigate the ice nucleation abilities of typical salts, with both homogeneous freezing and deposition nucleation being observed. The results indicate that the salts primarily act as cloud condensation nuclei but can also act as ice nucleating particles at low temperatures.
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20.
  • Broman, Elias, 1985-, et al. (författare)
  • Biotic interactions between benthic infauna and aerobic methanotrophs mediate methane fluxes from coastal sediments
  • 2024
  • Ingår i: The ISME journal. - 1751-7370 .- 1751-7362. ; 18:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal ecosystems dominate oceanic methane (CH4) emissions. However, there is limited knowledge about how biotic interactions between infauna and aerobic methanotrophs (i.e. CH4 oxidizing bacteria) drive the spatial-temporal dynamics of these emissions. Here, we investigated the role of meio- and macrofauna in mediating CH4 sediment-water fluxes and aerobic methanotrophic activity that can oxidize significant portions of CH4. We show that macrofauna increases CH4 fluxes by enhancing vertical solute transport through bioturbation, but this effect is somewhat offset by high meiofauna abundance. The increase in CH4 flux reduces CH4 pore-water availability, resulting in lower abundance and activity of aerobic methanotrophs, an effect that counterbalances the potential stimulation of these bacteria by higher oxygen flux to the sediment via bioturbation. These findings indicate that a larger than previously thought portion of CH4 emissions from coastal ecosystems is due to faunal activity and multiple complex interactions with methanotrophs.
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21.
  • Katrantsiotis, Christos, et al. (författare)
  • Seasonal variability in temperature trends and atmospheric circulation systems during the Eemian (Last Interglacial) based on n-alkanes hydrogen isotopes from Northern Finland
  • 2021
  • Ingår i: Quaternary Science Reviews. - Amsterdam : Elsevier. - 0277-3791 .- 1873-457X. ; 273, s. 107250-107250
  • Tidskriftsartikel (refereegranskat)abstract
    • The Last Interglacial warm period, the Eemian (ca. 130-116 thousand years ago), serves as a reference for projected future climate in a warmer world. However, there is a limited understanding of the seasonal characteristics of interglacial climate dynamics, especially in high latitude regions. In this study, we aimto provide new insights into seasonal trends in temperature and moisture source location, linked to shifts in atmospheric circulation patterns, for northern Fennoscandia during the Eemian. Our study is based on the distribution and stable hydrogen isotope composition (dD) of n-alkanes in a lake sediment sequence from the Sokli paleolake in NE Finland, placed in a multi-proxy framework. The dD values of predominantly macrophyte-derived mid-chain n-alkanes are interpreted to reflect lake water dD variability influenced by winter precipitation dD (dDprec), ice cover duration and deuterium (D)-depleted meltwater. The dD values of terrestrial plant-derived long-chain n-alkanes primarily reflect soil water dD variability modulated by summer dDprec and by the evaporative enrichment of soil and leaf water. The dDprec variability in our study area is mostly attributed to the temperature effect and the moisture source location linked to the relative dominance between D-depleted continental and polar air masses and Denriched North Atlantic air masses. The biomarker signal further corroborates earlier diatom-based studies and pollen-inferred January and July temperature reconstructions from the same sediment sequence. Three phases of climatic changes can be identified that generally follow the secular variationsin seasonal insolation: (i) an early warming trend succeeded by a period of strong seasonality (ii) a midoptimum phase with gradually decreased seasonality and cooler summers, and (iii) a late climatic instability with a cooling trend. Superimposed on this trend, two abrupt cooling events occur in the early and late Eemian. The Sokli dD variability is generally in good agreement with other North Atlantic and Siberian records, reflecting major changes in the atmospheric circulation patterns during the Eemian as a response to orbital and oceanic forcings.
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22.
  • Andrén, Elinor, et al. (författare)
  • Holocene climate and environmental change in north-eastern Kamchatka (Russian Far East), inferred from a multi-proxy study of lake sediments
  • 2015
  • Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 134, s. 41-54
  • Tidskriftsartikel (refereegranskat)abstract
    • A sediment record from a small lake in the north-eastern part of the Kamchatka Peninsula has been investigated in a multi-proxy study to gain knowledge of Holocene climatic and environmental change. Pollen, diatoms, chironomids and selected geochemical parameters were analysed and the sediment record was dated with radiocarbon. The study shows Holocene changes in the terrestrial vegetation as well as responses of the lake ecosystem to catchment maturity and multiple stressors, such as climate change and volcanic eruptions. Climate change is the major driving force resulting in the recorded environmental changes in the lake, although recurrent tephra deposition events also contributed. The sediment record has an age at the base of about 10,000 cal yrs BP, and during the first 400 years the climate was cold and the lake exhibited extensive ice-cover during winter and relatively low primary production. Soils in the catchment were poor with shrub alder and birches dominatingthe vegetation surrounding the lake. At about 9600–8900 cal yrs BP the climate was cold and moist, and strong seasonal wind stress resulted in reduced ice-cover and increased primary production. After ca. 8900 cal yrs BP the forest density increased around the lake, runoff decreased in a generally drier climate resulting in decreasedprimary production in the lake until ca. 7000 cal yrs BP. This generally dry climate was interrupted by a brief climatic perturbation, possibly attributed to the 8.2 ka event, indicating increasingly windy conditions with thick snow cover, reduced ice-cover and slightly elevated primary production in the lake. The diatom record shows maximum thermal stratification at ca. 6300–5800 cal yrs BP and indicates together with the geochemical proxies a dry and slightly warmer climate resulting in a high productive lake. The most remarkably change in the catchment vegetation occurred at ca. 4200 cal yrs BP in the form of a conspicuous increase in Siberian dwarf pine (Pinus pumila), indicating a shift to a cooler climate with a thicker and more long-lasting snow cover. Thisvegetational change was accompanied by marked shifts in the diatom and chironomid stratigraphies, which are also indicative of colder climate and more extensive ice-cover.
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23.
  • Lutz, Anna, 1986, et al. (författare)
  • Gas to Particle Partitioning of Organic Acids in the Boreal Atmosphere
  • 2019
  • Ingår i: Acs Earth and Space Chemistry. - : American Chemical Society (ACS). - 2472-3452. ; 3:7, s. 1279-1287
  • Tidskriftsartikel (refereegranskat)abstract
    • Gas to particle partitioning of carboxylic acids was investigated using a high-resolution chemical ionization time-of-flight mass spectrometer (HR-CI-ToF-MS) with the filter inlet for gases and aerosol (FIGAERO). Specifically, the partitioning coefficients of 640 components with unique molecular composition were calculated from an assumed linear relationship between [particle]/[gas] versus the mass of the organic fraction (M-org) according to Raoult's law, i.e., equilibrium phase partitioning. We demonstrate that, using the full data set, most of the compounds do not follow a linear relationship. This is especially the case for low- and high-molecular-weight species. Using a subset of the data, with concurrent low sulfate ambient observations ([SO42- < 0.4 mu g m(-3)), the relationship improved significantly and K-i could be derived from the slope of a linear regression to the data. The 100 species with the highest R-2 (>= 0.7) of this regression are presented. The restrictions during high sulfate conditions can be explained by changes in either the equilibrium conditions (e.g., the activity coeffient, gamma(i)) or uptake kinetics (mass transfer limitation). This study demonstrates that partitioning of compounds in the complex ambient atmosphere follows ideal Raoult's law for some limited conditions and stresses the need for studies also in more polluted environments.
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24.
  • Alvarez, Belinda, et al. (författare)
  • Assessing the potential of sponges (Porifera) as indicators of ocean dissolved Si concentrations
  • 2017
  • Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 4
  • Tidskriftsartikel (refereegranskat)abstract
    • We explore the distribution of sponges along dissolved silica (dSi) concentration gradients to test whether sponge assemblages are related to dSi and to assess the validity of fossil sponges as a palaeoecological tool for inferring dSi concentrations of the past oceans. We extracted sponge records from the publically available Global Biodiversity Information Facility (GBIF) database and linked these records with ocean physiochemical data to evaluate if there is any correspondence between dSi concentrations of the waters sponges inhabit and their distribution. Over 320,000 records of Porifera were available, of which 62,360 met strict quality control criteria. Our analyses was limited to the taxonomic levels of family, order and class. Because dSi concentration is correlated with depth in the modern ocean, we also explored sponge taxa distributions as a function of depth. We observe that while some sponge taxa appear to have dSi preferences (e.g., class Hexactinellida occurs mostly at high dSi), the overall distribution of sponge orders and families along dSi gradients is not sufficiently differentiated to unambiguously relate dSi concentrations to sponge taxa assemblages. We also observe that sponge taxa tend to be similarly distributed along a depth gradient. In other words, both dSi and/or another variable that depth is a surrogate for, may play a role in controlling sponge spatial distribution and the challenge is to distinguish between the two. We conclude that inferences about palaeo-dSi concentrations drawn from the abundance of sponges in the stratigraphic records must be treated cautiously as these animals are adapted to a great range of dSi conditions and likely other underlying variables that are related to depth. Our analysis provides a quantification of the dSi ranges of common sponge taxa, expands on previous knowledge related to their bathymetry preferences and suggest that sponge taxa assemblages are not related to particular dSi conditions.
  •  
25.
  • Li, J., et al. (författare)
  • Hygroscopicity of Fresh and Aged Salt Mixtures from Saline Lakes
  • 2021
  • Ingår i: Atmosphere. - : MDPI AG. - 2073-4433. ; 12:9
  • Tidskriftsartikel (refereegranskat)abstract
    • The high hygroscopicity of salt aerosol particles makes the particles active in aerosol and cloud formations. Inland saline lakes are an important and dynamic source of salt aerosol. The salt particles can be mixed with mineral dust and transported over long distances. During transportation, these particles participate in atmospheric heterogeneous chemistry and further impact the climate and air quality on a global scale. Despite their importance and potential, relatively little research has been done on saline lake salt mixtures from atmospheric perspectives. In this study, we use experimental and model methods to evaluate the hygroscopic properties of saline lake brines, fresh salt aerosol particles, and aged salt aerosol particles. Both original samples and literature data are investigated. The original brine samples are collected from six salt lakes in Shanxi and Qinghai provinces in China. The ionic compositions of the brines are determined and the hygroscopicity measurements are performed on crystallized brines. The experimental results agree well with theoretical deliquescence relative humidity (DRH) values estimated by a thermodynamic model. The correlations between DRHs of different salt components and the correlations between DRHs and ionic concentrations are presented and discussed. Positive matrix factorization (PMF) analysis is performed on the ionic concentrations data and the hygroscopicity results, and the solutions are interpreted and discussed. The fresh and aged salt aerosol particles are analyzed in the same way as the brines, and the comparison shows that the aged salt aerosol particles completely alter their hygroscopic property, i.e., transferring from MgCl2- governed to NH4NO3- governed.
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26.
  • Zilius, Mindaugas, et al. (författare)
  • Spatiotemporal patterns of N2 fixation in coastal waters derived from rate measurements and remote sensing
  • 2021
  • Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 18, s. 1857-1871
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal lagoons are important sites for nitrogen (N) removal via sediment burial and denitrification. Blooms of heterocystous cyanobacteria may diminish N retention as dinitrogen (N2) fixation offsets atmospheric losses via denitrification. We measured N2 fixation in the Curonian Lagoon, Europe's largest coastal lagoon, to better understand the factors controlling N2 fixation in the context of seasonal changes in phytoplankton community composition and external N inputs. Temporal patterns in N2 fixation were primarily determined by the abundance of heterocystous cyanobacteria, mainly Aphanizomenon flos-aquae, which became abundant after the decline in riverine nitrate inputs associated with snowmelt. Heterocystous cyanobacteria dominated the summer phytoplankton community resulting in strong correlations between chlorophyll a (Chl a) and N2 fixation. We used regression models relating N2 fixation to Chl a, along with remote-sensing-based estimates of Chl a to derive lagoon-scale estimates of N2 fixation. N2 fixation by pelagic cyanobacteria was found to be a significant component of the lagoon's N budget based on comparisons to previously derived fluxes associated with riverine inputs, sediment-water exchange, and losses via denitrification. To our knowledge, this is the first study to derive ecosystem-scale estimates of N2 fixation by combining remote sensing of Chl a with empirical models relating N2 fixation rates to Chl a.
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27.
  • Maskenskaya, Olga M., et al. (författare)
  • Source and character of syntaxial hydrothermal calcite veins in Paleoproterozoic crystalline rocks revealed by fine-scale investigations
  • 2014
  • Ingår i: Geofluids. - : Wiley. - 1468-8115 .- 1468-8123. ; 14:4, s. 495-511
  • Tidskriftsartikel (refereegranskat)abstract
    • Calcite veins in Paleoproterozoic granitoids on the Baltic Shield are the focus of this study. These veins are distinguished by their monomineralic character, unusual thickness and closeness to Neoproterozoic dolerite dykes and therefore have drawn attention. The aim of this study was to define the source of these veins and to unravel their isotopic and chemical nature by carrying out fine-scale studies. Seven calcite veins covering a depth interval of 50-420m below the ground surface and composed of breccias or crack-sealed fillings typically expressing syntaxial growth were sampled and analysed for a variety of physicochemical variables: homogenization temperature (T-h) and salinity of fluid inclusions, and stable isotopes (Sr-87/Sr-86, C-13/C-12, O-18/O-16), trace-element concentrations (Fe, Mn, Mg, Sr, rare earth elements) and cathodoluminescence (CL) of the solid phase. The fluid-inclusion data show that the calcites were precipitated mainly from relatively low-temperature (T-h=73-106 degrees C) brines (13.4-24.5wt.% CaCl2), and the Sr-87/Sr-86 is more radiogenic than expected for Rb-poor minerals precipitated from Neoproterozoic fluids. These features, together with the distribution of C-13 and O-18 values, provide evidence that the calcite veins are not genetic with the nearby Neoproterozoic dolerite dykes, but are of Paleozoic age and were precipitated from warm brines expressing a rather large variability in salinity. Whereas the isotopic and chemical variables express rather constant average values among the individual veins, they vary considerably on fine-scale across individual veins. This has implications for understanding processes causing calcite-rich veins to form and capture trace metals in crystalline bedrock settings.
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28.
  • Arellano, Santiago, 1981 (författare)
  • Studies of Volcanic Plumes with Remote Spectroscopic Sensing Techniques -DOAS and FTIR measurements on volcanoes of the Network for Observation of Volcanic and Atmospheric Change-
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Volcanism is a rich geodynamical process, closely linked to the origin and ongoing evolution of the lithosphere, atmosphere, hydrosphere and biosphere. Humans have benefited from the resources provided by volcanoes but also been threatened by the dangers of volcanic eruptions, which accurate prediction remains elusive. This is partly due to the inherent complexity of volcanic systems and partly because of the difficulty of conducting key observations to characterize them. In particular, since the segregation and escape of magmatic volatiles are essential mechanisms behind volcanic eruptions, monitoring the intensity and composition of the resulting emissions in the atmosphere is essential to characterize the state of volcanic activity; however, their direct measurement is not always feasible.Remote spectroscopic sensing, whereby gas species can be quantified by their spectral signatures in electromagnetic radiation gathered at a prudent distance from the plume, offers the possibility to conduct reliable and sustainable monitoring of volcanic emissions. To expand the remote sensing capabilities of volcanological observatories the Network for Observation of Volcanic and Atmospheric Change (NOVAC) was established in 2005. The central theme of this thesis is the acquisition, analysis and interpretation of measurements of volcanic gas emissions on volcanoes of NOVAC. Measurements of the mass flow rate of SO2 and the molar ratios of SO2 against BrO and HCl were obtained by scanning-Differential Optical Absorption Spectroscopy (DOAS) of scattered solar ultraviolet radiation and by Fourier-Transform Spectroscopy (FTIR) of direct solar infrared radiation. The uncertainty of the measurements is characterized and methods for combining observations from different sensors implemented. Statistical and physical models of degassing are proposed for selected volcanoes of the network. The resulting time-series of emission on 16 volcanoes is one of the more detailed compilations of volcanic degassing in the last decade, particularly from passive emissions which are difficult to detect from satellite platforms. This work aims at advancing our knowledge of volcanic eruptions for a better mitigation of their risks.
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29.
  • Weis, Franz A., et al. (författare)
  • Magmatic water contents determined through clinopyroxene : Examples from the Western Canary Islands, Spain
  • 2015
  • Ingår i: Geochemistry Geophysics Geosystems. - 1525-2027. ; 16:7, s. 2127-2146
  • Tidskriftsartikel (refereegranskat)abstract
    • Water is a key parameter in magma genesis, magma evolution, and resulting eruption styles, because it controls the density, the viscosity, as well as the melting and crystallization behavior of a melt. The parental water content of a magma is usually measured through melt inclusions in minerals such as olivine, a method which may be hampered, however, by the lack of melt inclusions suitable for analysis, or postentrapment changes in their water content. An alternative way to reconstruct the water content of a magma is to use nominally anhydrous minerals (NAMs), such as pyroxene, which take up low concentrations of hydrogen as a function of the magma's water content. During magma degassing and eruption, however, NAMs may dehydrate. We therefore tested a method to reconstruct the water contents of dehydrated clinopyroxene phenocrysts from the Western Canary islands (n=28) through rehydration experiments followed by infrared and Mossbauer spectroscopy. Employing currently available crystal/melt partitioning data, the results of the experiments were used to calculate parental water contents of 0.710.07 to 1.490.15 wt % H2O for Western Canary magmas during clinopyroxene crystallization at upper mantle conditions. This H2O range is in agreement with calculated water contents using plagioclase-liquid-hygrometry, and with previously published data for mafic lavas from the Canary Islands and comparable ocean island systems elsewhere. Utilizing NAMs in combination with hydrogen treatment can therefore serve as a proxy for pre-eruptive H2O contents, which we anticipate becoming a useful method applicable to mafic rocks where pyroxene is the main phenocryst phase.
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30.
  • Bobrowski, Nicole, et al. (författare)
  • Multi-component gas emission measurements of the active lava lake of Nyiragongo, DR Congo
  • 2017
  • Ingår i: Journal of African Earth Sciences. - : Elsevier BV. - 1879-1956 .- 1464-343X. ; 134, s. 856-865
  • Tidskriftsartikel (refereegranskat)abstract
    • Between 2007 and 2011 four measurement campaigns (June 2007, July 2010, June 2011, and December 2011) were carried out at the crater rim of Nyiragongo volcano, DR Congo. Nyiragongo is one of the most active volcanoes in Africa. The ground-based remote sensing technique Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which uses scattered sunlight, the in-situ Multi-Component Gas Analyzer System (Multi-GAS) and alkaline impregnated filter were simultaneously applied during all field trips. The bromine monoxide to sulfur dioxide (BrO/SO2) and carbon dioxide to sulfur dioxide (CO2/SO2) molar ratios were determined, among other ratios. During the different field trips variations of the level of the lava lake up to several tens of meters were observed during intervals of the order of minutes up to days and also between the years. The measured gas ratios presented covariations with the lava lake level changes. BrO/SO2 ratios and CO2/SO2 ratios showed similar behavior. Annual CO2/SO2 and BrO/SO2 average values are generally positively correlated. In June 2011 increased BrO/SO2 as well as increased CO2/SO2 ratios have been observed before a sudden decrease of the lava lake. Overall the Cl/S ratio, determined by filter-pack sampling, shows an increasing trend with time, which is accompanied by a decreasing sulfur dioxide flux, the later measured nearly continuously by automated MAX-DOAS instruments since 2004. Mean gas emission fluxes of CO2, Cl and ‘minimum-BrO’ fluxes are calculated using their ratio to SO2. The first two show an increase with time, in contrast to the SO2 fluxes. A simple conceptual model is proposed which can explain in particular the June 2011 data, but as well our entire data set. The proposed model takes up the idea of convective magma cells inside the conduit and the possible temporary interruption of part of the cycling. We propose than two alternatives to explain the observed gas emission variation: 1. It is assumed that the diffuse and fumarolic degassing could have significant influence on measured gas composition. The measured gas composition might rather represent a gas mixture of plume, diffuse and fumarolic degassing than only representing the volcanic plume. 2. It is proposed that the interruption of the convection has taken place in the upper part of the conduit and deep degassing of CO2 and bromine initially continues while mixing already with gas emissions from an ageing source, which is characterized by an already diminishing sulfur content. These complex process but as well as the gas mixing of different sources, could explain general features of our dataset, but can unfortunately neither be confirmed nor disproven by the data available today.
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31.
  • Bidleman, Terry, et al. (författare)
  • Chapter 2: Properties, sources, global fate and transport
  • 2013
  • Ingår i: Canadian Arctic Contaminants Assessment Report III 2013. - Ottawa : Northern Contaminants Program, Aboriginal Affairs and Northern Development Canada. - 9781100546520 ; , s. 19-146
  • Bokkapitel (refereegranskat)abstract
    • Part II of the second Canadian Arctic Contaminants Assessment Report (CACAR-II) began with a section on “Physicochemical Properties of Persistent Organic Pollutants”, which identified key physicochemical (pchem) properties, provided the rationale for their measurement or prediction and tabulated literature citations for chemicals that are of concern to the NCP (Bidleman et al. 2003). The section also discussed temperature dependence of pchem properties and their applications to describing partitioning in the physical environment.There is, and will continue to be, emphasis on predictive approaches to screening chemicals for persistence, bioaccumulation and toxic (PB&T)properties, as well as long-range atmospheric transport (LRAT) potential (Brown and Wania 2008, Czub et al. 2008, Fenner et al. 2005, Gouin andWania 2007, Howard and Muir 2010, Klasmeier et al. 2006, Matthies et al. 2009, Muir and Howard 2006). This has created the need for determining pchem properties of new and emerging chemicals of concern.Predicting gas exchange cycles of legacy persistent organic pollutants (POPs) and new and emerging chemicals of concern places a high demand on the accuracy of pchem properties, particularly the air/water partition coefficient, KAW. Hexachlorocyclohexanes (HCHs) in Arctic Ocean surface waters are close to air-water equilibrium, with excursions toward net volatilization or deposition that vary with location and season (Hargrave et al. 1993, Jantunen et al. 2008a, Lohmann et al. 2009, Su et al. 2006, Wong et al. 2011) while hexachlorobenzene (HCB) (Lohmann et al. 2009, Su et al. 2006, Wong et al. 2011) and some current use pesticides (CUPs) (Wong et al. 2011) are undergoing net deposition. The predicted Arctic Contamination Potential (ACP) for persistent organic chemicals is strongly influenced by ice cover due to its effect on air-water gas exchange (Meyer and Wania 2007).Many advances have taken place and numerous papers have been published since CACAR-II, which present new measurements and predictions of pchem properties. This section does not attempt to provide a comprehensive review of the field, or to compile pchem properties from the many studies. The approach taken is to highlight the reports which are most relevant to polar science, particularly in areas of improving reliability of pchem properties for POPs, improving experimental techniques and comparing predictive methods. The section ends with a discussion of polyparameter linear free energy relationships (pp-LFERs), which goes beyond partitioning descriptions based on single pchem properties by taking into account specific chemical interactions that can take place in airsurface and water-surface exchange processes. A detailed list of chemical names and nomenclature are provided in the Glossary.
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32.
  • Kreuger, Jenny, et al. (författare)
  • Modelling pesticide transport in a shallow groundwater catchment using tritium and helium-3 data
  • 2014
  • Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927. ; 50, s. 231-239
  • Tidskriftsartikel (refereegranskat)abstract
    • Using tritium and helium-3 data for calibration, a 2-D transport model was set up to explain the occurrence of bentazone, dichlorprop, glyphosate, isoproturon, MCPA and metamitron in a small groundwater catchment in southern Sweden. The model was parameterised with site-specific degradation and sorption data to enable transport simulations. Local climatological data and a 21-year record of agricultural pesticide use within the study area were used as boundary conditions. Model output was evaluated against a 7-year long pesticide monitoring data-series from two monitoring wells within the study area. The model successfully predicts observed breakthrough of bentazone, dichlorprop, isoproturon and MCPA. However, it fails to simulate observed occurrences of glyphosate and metamitron. Glyphosate and metamitron exhibit relatively high sorption potential, and their occurrence is suggested to be the result of non-equilibrium preferential flow paths which the model cannot reproduce due the conceptualisation of the system as homogenous and isotropic. The results indicate a promising methodological approach applicable to groundwater contamination risk assessment, and demonstrate the potential for transport model calibration by means of tritium and helium-3 data. Main constraints of the study relate to the relatively simple system conceptualisation, indicating a need for further consideration of physical and chemical heterogeneity. (C) 2014 Elsevier Ltd. All rights reserved.
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33.
  • Quintana, Isabel, et al. (författare)
  • Växtplankton
  • 2015
  • Ingår i: Vänern: Årsskrift 2015. ; 91, s. 36-39
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
  •  
34.
  • Ranta, E., et al. (författare)
  • Fluid-rock reactions in the 1.3Ga siderite carbonatite of the GrOnnedal-ika alkaline complex, Southwest Greenland
  • 2018
  • Ingår i: Contributions to Mineralogy and Petrology. - : Springer Science and Business Media LLC. - 0010-7999 .- 1432-0967. ; 173:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Petrogenetic studies of carbonatites are challenging, because carbonatite mineral assemblages and mineral chemistry typically reflect both variable pressure-temperature conditions during crystallization and fluid-rock interaction caused by magmatic-hydrothermal fluids. However, this complexity results in recognizable alteration textures and trace-element signatures in the mineral archive that can be used to reconstruct the magmatic evolution and fluid-rock interaction history of carbonatites. We present new LA-ICP-MS trace-element data for magnetite, calcite, siderite, and ankerite-dolomite-kutnohorite from the iron-rich carbonatites of the 1.3Ga GrOnnedal-ika alkaline complex, Southwest Greenland. We use these data, in combination with detailed cathodoluminescence imaging, to identify magmatic and secondary geochemical fingerprints preserved in these minerals. The chemical and textural gradients show that a 55m-thick basaltic dike that crosscuts the carbonatite intrusion has acted as the pathway for hydrothermal fluids enriched in F and CO2, which have caused mobilization of the LREEs, Nb, Ta, Ba, Sr, Mn, and P. These fluids reacted with and altered the composition of the surrounding carbonatites up to a distance of 40m from the dike contact and caused formation of magnetite through oxidation of siderite. Our results can be used for discrimination between primary magmatic minerals and later alteration-related assemblages in carbonatites in general, which can lead to a better understanding of how these rare rocks are formed. Our data provide evidence that siderite-bearing ferrocarbonatites can form during late stages of calciocarbonatitic magma evolution.
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35.
  • Ledesma, Jose, et al. (författare)
  • Aquatic DOC export from subarctic Atlantic blanket bog in Norway is controlled by seasalt deposition, temperature and precipitation
  • 2016
  • Ingår i: Biogeochemistry. - : Springer Science and Business Media LLC. - 0168-2563 .- 1573-515X. ; 127, s. 305-321
  • Tidskriftsartikel (refereegranskat)abstract
    • Comprehensive and credible peatland carbon budgets, needed for global carbon accounting, must include lateral aquatic organic carbon export. Here, we quantify aquatic dissolved organic carbon (DOC) export for an Atlantic bog in subarctic Norway, the Andøya peatland, and test for sensitivity to climatic drivers. Hydrology, DOC concentrations and DOC export were simulated for 2000–2013 using the process-based catchment model Integrated Catchments model for Carbon(INCA-C), calibrated to site-specific water chemistry and hydrology (2011–2014) using readily-available data on temperature, precipitation and seasalt deposition. Measured streamwater DOC declined under seasalt episodes and was strongly positively related to temperature. Model calibrations successfully reproduced the water balance, variation in runoff (R2=0.67; Nash–Sutcliffe model efficiency NS=0.67) and DOC concentrations (R2=0.85; NS=0.84). The most sensitive model parameters related to temperature-sensitivity of DOC production and DOC (de)sorption sensitivity to seasalts. Model uncertainty related to parameter space was similar to interannual variation in DOC export. Mean annual modelled DOC export was 7.2±0.7g C m−2 year−1, roughly 35% of the net land–atmospheric CO2 exchange at Andøya from 2009 to 2012 (estimated elsewhere). Current and antecedent mean temperature and precipitation were strong drivers of seasonal modelled DOC export, implying that warmer and wetter summers will lead to more DOC export. Evaluation of similar climate impacts on net peatland carbon accumulation requires additional exploration of the climate-sensitivity of land–atmosphere fluxes of CO2 and methane. Process-based models are valuable tools to account for lateral DOC exports in carbon balances of northern peatlands, especially where long-term monitoring data are lacking.
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36.
  • Soerensen, Anne L., et al. (författare)
  • Deciphering the Role of Water Column Redoxclines on Methylmercury Cycling Using Speciation Modeling and Observations From the Baltic Sea
  • 2018
  • Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 32:10, s. 1498-1513
  • Tidskriftsartikel (refereegranskat)abstract
    • Oxygen-depleted areas are spreading in coastal and offshore waters worldwide, but the implication for production and bioaccumulation of neurotoxic methylmercury (MeHg) is uncertain. We combined observations from six cruises in the Baltic Sea with speciation modeling and incubation experiments to gain insights into mercury (Hg) dynamics in oxygen depleted systems. We then developed a conceptual model describing the main drivers of Hg speciation, fluxes, and transformations in water columns with steep redox gradients. MeHg concentrations were 2-6 and 30-55 times higher in hypoxic and anoxic than in normoxic water, respectively, while only 1-3 and 1-2 times higher for total Hg (THg). We systematically detected divalent inorganic Hg (Hg-II) methylation in anoxic water but rarely in other waters. In anoxic water, high concentrations of dissolved sulfide cause formation of dissolved species of Hg-II: HgS2H(aq)- and Hg (SH)(2)(0)((aq)). This prolongs the lifetime and increases the reservoir of Hg-II readily available for methylation, driving the high MeHg concentrations in anoxic zones. In the hypoxic zone and at the hypoxic-anoxic interface, Hg concentrations, partitioning, and speciation are all highly dynamic due to processes linked to the iron and sulfur cycles. This causes a large variability in bioavailability of Hg, and thereby MeHg concentrations, in these zones. We find that zooplankton in the summertime are exposed to 2-6 times higher MeHg concentrations in hypoxic than in normoxic water. The current spread of hypoxic zones in coastal systems worldwide could thus cause an increase in the MeHg exposure of food webs.
  •  
37.
  • Kylander, Malin E., et al. (författare)
  • Potentials and problems of building detailed dust records using peat archives : An example from Store Mosse (the "Great Bog"), Sweden
  • 2016
  • Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533 .- 0046-564X. ; 190, s. 156-174
  • Tidskriftsartikel (refereegranskat)abstract
    • Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the "Great Bog"), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385-5300 cal yr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE- rich phosphate minerals over time. These clays are likely transported from a long-distance source (< 100 km). While dust deposition was reduced during the second event (5300-4370 cal yr BP), this is the most distinct in terms of its source character with [Eu/Eu*] UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380- 2200 cal yr BP) and fourth (1275-1080 cal yr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much shorter in duration, which in combination with evidence of their local and regional character, may explain why they have not been seen elsewhere. 
  •  
38.
  • Linderholm, Johan, 1963-, et al. (författare)
  • Ørlandet Iron Age settlement pattern development: Geoarchaeology (geochemistry and soil micromorphology) and plant macrofossils
  • 2019
  • Ingår i: Environment and Settlement: Ørland 600 BC–AD 1250. - : Nordic Open Access Scholarly Publishing (NOASP). - 9788202664831 - 9788202595319 ; , s. 107-134
  • Bokkapitel (refereegranskat)abstract
    • Macrofossil and geoarchaeological data from a variety of contexts and periods at Vik can provide either in situ or proxyinformation on the human – environment interactions at the site through time. The aim of this paper is to discuss settlementactivity patterns through time and space, with special emphasis on agriculture and animal husbandry strategies. The calcareousshell bank deposits at the site led to a reduction of the amount of analysed citric soluble phosphate and are apparentlyalso linked to very poor macrofossil preservation. The analysis shows that farming in the pre-Roman Iron Age involvedanimal management and manuring of fields where naked and hulled barley were cultivated. Stock was kept in the long houses.There are also indications that animals grazed along the shore. In the Roman Iron Age there is no clear evidence of keepinglivestock indoors; byre residues were instead found in house-associated waste heaps, where chemical data indicate thatdung was left to ferment. Near-house Roman Iron Age waste deposits were also characterised by latrine and fish processingwaste, as well as by high temperature artisan residues – fuel ash and iron working materials. Analysis of soil chemical samplesindicates an increase and intensification of occupation over time during the pre-Roman Iron Age and the Roman Iron Age.Viking-medieval features were also a remarkable source for monitoring latrine, byre and industrial waste, including the secondaryuse of water holes and wells that supplied water to both people and animals.
  •  
39.
  • Iburg, Sven, et al. (författare)
  • Organic Contaminant Mixture Significantly Changes Microbenthic Community Structure and Increases the Expression of PAH Degradation Genes
  • 2020
  • Ingår i: Frontiers in Environmental Science. - : Frontiers Media SA. - 2296-665X. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • © Copyright © 2020 Iburg, Nybom, Bonaglia, Karlson, Sobek and Nascimento. Studying the effects of chemical contaminants on the structure and function of microbial and meiofauna communities have traditionally focused on specific effects of single contaminants on single species. This has left the complex interactions between mixtures of contaminants and its non-specific toxicity effects on the functions and structure of sediment microbial communities mostly overlooked. In order to improve our insights on such questions, we performed an experiment where Baltic Sea sediments were spiked with an ecologically relevant mixture of seven organic contaminants below specific toxicity levels and used 16S and 18S rRNA metabarcoding from RNA extracts to monitor changes in active microbial and meiofauna diversity and community structure in the spiked treatment compared to controls. In addition, we investigated the effects of exposure to this contaminant mixture on potential nitrification rates and on the expression of key-genes in the microbial nitrification and PAH degradation pathways with qPCR. There were significant differences in both eukaryotic and microbial community structures in sediments spiked with a mixture of organic contaminants. Nematoda showed a significant increase in overall relative abundance to the added contaminants (5.5 ± 1.1% higher in spiked), particularly taxa of the genus Leptolaimus (increased from 10.2 ± 5.4% in the controls to 32.5 ± 10.2% in the spiked treatment). Conversely, a significant decrease in relative abundance from 18.2 ± 5.6% in control to 7 ± 3.4% in of the genus Paraplectana was also detected. Additionally, while the abundance of active PAH degraders was significantly higher in spiked sediments than in the controls, no significant effect of our organic mixture was found on nitrification rates or the expression of AmoA (bacterial ammonia oxidizer gene). Our data indicate that mixtures of organic contaminants can have significant effects on microbenthic community structure even when its individual components are present at concentrations below its specific toxicity. In addition, we suggest that eRNA-based metabarcoding can offer important insights in microbenthic community structure and activities, and further empathizes the potential of meiofauna as bio-indicators of chemical contamination in benthic ecosystems.
  •  
40.
  • Sonesten, Lars (författare)
  • Vattenkvaliteten i Storvänern
  • 2015
  • Ingår i: Vänern: Årsskrift 2015. ; 91, s. 33-35
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
  •  
41.
  • Vajda, Vivi, et al. (författare)
  • Geochemical Fingerprints of Ginkgoales Across the Triassic-Jurassic Boundary of Greenland
  • 2021
  • Ingår i: International journal of plant sciences. - Chicago : University of Chicago Press. - 1058-5893 .- 1537-5315. ; 182:7, s. 649-662
  • Tidskriftsartikel (refereegranskat)abstract
    • Premise of research. Geochemical fingerprinting of fossil plants is a relatively new research field complementing morphological analyses and providing information for paleoenvironmental interpretations. Ginkgoales contains a single extant species but was diverse through the Mesozoic and is an excellent target for biochemical analyses.Methodology. Cuticles derived from fresh and fallen autumn leaves of extant Ginkgo biloba and seven fossil gink- goalean leaf taxa, one seed fern taxon, and two taxa with bennettitalean affinity were analyzed by infrared (IR) microspec- troscopy at the D7 beamline in the MAX IV synchrotron laboratory, Sweden. The fossil material derives from Triassic and Jurassic successions of Greenland. Spectral data sets were compared and evaluated by hierarchical cluster analysis (HCA) and principal component analysis performed on vector-normalized, first-derivative IR absorption spectra.Pivotal results. The IR absorption spectra of the fossil leaves all reveal signatures that clearly indicate the pres- ence of organic compounds. Spectra of the extant G. biloba leaves reveal the presence of aliphatic chains, aromatic and ester carbonyl functional groups from polymer cutin and other waxy compounds, and polysaccharides. Inter- estingly, both the extant autumn leaves and the fossil specimens reveal the presence of carboxyl/ketone molecules, suggesting that chemical alterations during the initial stages of decomposition are preserved through fossilization. Two major subclusters were identified through HCA of the fossil spectra.Conclusions. Consistent chemical IR signatures, specific for each fossil taxon are present in cuticles, and suf- ficient molecular content is preserved in key regions to reflect the plants’ original chemical signatures. The alter- ations of the organic compounds are initiated as soon as the leaves are shed, with loss of proteins and increased ester and carboxyl/ketone compound production in the fallen leaves. We further show that the groupings of taxa reflect a combination of phylogeny and environmental conditions related to the end-Triassic event.
  •  
42.
  • Konn, Cécile, 1981- (författare)
  • Origin of organic compounds in fluids from ultramafic-hosted hydrothermal vents of the Mid-Atlantic Ridge
  • 2009
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Natural gas, primarily methane (CH4), is produced in substantial amounts in ultramafic-hosted hydrothermal systems. These systems could also generate oil (heavier hydrocarbons) and the first building blocks of life (prebiotic molecules). In the presence of iron bearing minerals, serpentinisation reactions generate H2. Subsequently, CH4 could be synthesised by Fischer-Tropsch Type (FTT) reaction (4H2 + CO2 → CH4 + 2H2O) which is an abiotic process. This has lead to the idea of abiotic formation of larger organic molecules. Both thermodynamics and laboratory work support this idea, yet field data have been lacking. This study focuses on determining the organic content of fluids from ultramafic-hosted hydrothermal systems from the Mid-Atlantic Ridge (MAR) and the origin of the compounds. Fluids were collected from the Lost City, Rainbow, Ashadze and Logatchev vent fields during the EXOMAR (2005), SERPENTINE (2007), MoMARDREAMnaut (2007) and MOMAR08-Leg2 (2008) cruises conducted by IFREMER, France. A SBSE-TD-GC-MS technique was developed and used to extract, concentrate, separate and identify compounds in the fluids. Hydrothermally derived compounds appeared to consist mainly of hydrocarbons and O-bearing molecules. In addition, some amino acids were detected in the fluids by ULPC-ESI-QToF-MS but their origin will need to be determined. The organic content of the Rainbow fluids did not show intra field variability unlike differences could be noted over the years. In order to address the question of the source of the molecules, compound specific carbon isotopic analyses were carried out and completed with a bacterial (Pyrococcus abyssi) hydrothermal degradation experiment. The δ13C data fall in the range of -40 to -30‰ (vs. V-PDB), but individual δ13C values preclude the identification of a biogenic or abiogenic origin of the compounds. The degradation experiment, however, suggests an abiogenic origin of a portion of saturated hydrocarbons whereas carboxylic acids would be biogenic, and aromatic compounds would be thermogenic.
  •  
43.
  • Eveborn, David, 1978-, et al. (författare)
  • Phosphorus in soil treatment systems : accumulation and mobility
  • 2014
  • Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 64, s. 42-52
  • Tidskriftsartikel (refereegranskat)abstract
    • In several western countries, septic tanks with subsequent soil treatment systems (STS) are a common treatment technique for domestic wastewater in rural areas. However the suitability of STS (especially relatively close to surface waters) can be questioned since the discharge of phosphorus (P) from such effluents is not well known. In this study, six STS in Sweden (11 to 28 years old) were investigated by means of batch and column experiments on samples taken from the unsaturated subsoil beneath the distribution pipes. At all sites the wastewater had clearly influenced the soil. This was observed through decreased pH, increased amounts of oxalate extractable metals and altered P sorption properties. The amount of accumulated P in the STS (defined as the amount of total P in the STS samples minus the amount of total P in unused soil samples) were found to be between 0.32 and 0.87 kg m-3, which in most cases was just a small fraction of the estimated P load (< 30%). Column studies revealed that remarkably high P concentrations (up to 6 mg L-1) were leached from the material when deionized water was applied. However, the response to deionized water varied between the sites. The affinity for P in the soils was well correlated to the amount of oxalate-extractable aluminium (as evidenced by a strong relationship between oxalate-extractable Al and oxalate-extractable P) and generally soils with high content of oxalate extractable Al was also less vulnerable to P leakage.
  •  
44.
  • Roldin, Pontus, et al. (författare)
  • The role of highly oxygenated organic molecules in the Boreal aerosol-cloud-climate system
  • 2019
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10, s. 1-15
  • Tidskriftsartikel (refereegranskat)abstract
    • Over Boreal regions, monoterpenes emitted from the forest are the main precursors for secondary organic aerosol (SOA) formation and the primary driver of the growth of new aerosol particles to climatically important cloud condensation nuclei (CCN). Autoxidation of monoterpenes leads to rapid formation of Highly Oxygenated organic Molecules (HOM). We have developed the first model with near-explicit representation of atmospheric new particle formation (NPF) and HOM formation. The model can reproduce the observed NPF, HOM gas-phase composition and SOA formation over the Boreal forest. During the spring, HOM SOA formation increases the CCN concentration by ~10 % and causes a direct aerosol radiative forcing of −0.10 W/m2. In contrast, NPF reduces the number of CCN at updraft velocities < 0.2 m/s, and causes a direct aerosol radiative forcing of +0.15 W/m2. Hence, while HOM SOA contributes to climate cooling, NPF can result in climate warming over the Boreal forest.
  •  
45.
  • Erlandsson, M., et al. (författare)
  • Spatial and temporal variations of base cation release from chemical weathering on a hillslope scale
  • 2016
  • Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 441, s. 1-13
  • Tidskriftsartikel (refereegranskat)abstract
    • Cation release rates to catchment runoff from chemical weathering were assessed using an integrated catchment model that included the soil's unsaturated, saturated and riparian zones. In-situ mineral dissolution rates were calculated in these zones as a function of pH, aluminum and dissolved organic carbon (DOC) concentrations along a hillslope in Northern Sweden where soil water was monitored over nine years. Three independent sets of mineral dissolution equations of varying complexity were used: PROFILE, Transition-State Theory (TST), and the Palandri & Kharaka database. Normalization of the rate-coefficients was necessary to compare the equations, as published rate-coefficients gave base cation release rates differing by several orders of magnitude. After normalizing the TST- and Palandri & Kharaka-rate coefficients to match the base cation release rates calculated from the PROFILE-equations, calculated Ca2 + and Mg2 + release rates are consistent with mass balance calculations, whereas those of Na+ and K+ are overestimated. Our calculations further indicate that a significant proportion of base cations are released from the organic soils in the near-stream zone, in part due to its finer texture. Of the three sets of rate equations, the base cation release rates calculated from the normalized TST-equations were more variable than those calculated using the other two sets of equations, both spatially and temporally, due to its higher sensitivity to pH. In contrast, the normalized Palandri & Kharaka-equations were more sensitive to variations in soil temperature.
  •  
46.
  • Winterdahl, Mattias, et al. (författare)
  • Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites
  • 2011
  • Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:8, s. 920-930
  • Tidskriftsartikel (refereegranskat)abstract
    • Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at GAyenrdsjon increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20-62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.
  •  
47.
  • Bidleman, Terry, 1942-, et al. (författare)
  • A review of halogenated natural products in Arctic, Subarctic and Nordic ecosystems
  • 2019
  • Ingår i: Emerging Contaminants. - : Elsevier. - 2405-6650 .- 2405-6642. ; 5, s. 89-115
  • Tidskriftsartikel (refereegranskat)abstract
    • Halogenated natural products (HNPs) are organic compounds containing bromine, chlorine, iodine, andrarely fluorine. HNPs comprise many classes of compounds, ranging in complexity from halocarbons tohigher molecular weight compounds, which often contain oxygen and/or nitrogen atoms in addition tohalogens. Many HNPs are biosynthesized by marine bacteria, macroalgae, phytoplankton, tunicates,corals, worms, sponges and other invertebrates. This paper reviews HNPs in Arctic, Subarctic and Nordicecosystems and is based on sections of Chapter 2.16 in the Arctic Monitoring and Assessment Program(AMAP) assessment Chemicals of Emerging Arctic Concern (AMAP, 2017) which deal with the highermolecular weight HNPs. Material is updated and expanded to include more Nordic examples. Much ofthe chapter is devoted to “bromophenolic” HNPs, viz bromophenols (BPs) and transformation productsbromoanisoles (BAs), hydroxylated and methoxylated bromodiphenyl ethers (OH-BDEs, MeO-BDEs) andpolybrominated dibenzo-p-dioxins (PBDDs), since these HNPs are most frequently reported. Othersdiscussed are 2,20-dimethoxy-3,30,5,50-tetrabromobiphenyl (2,20-dimethoxy-BB80), polyhalogenated 10-methyl-1,20-bipyrroles (PMBPs), polyhalogenated 1,10-dimethyl-2,20-bipyrroles (PDBPs), polyhalogenatedN-methylpyrroles (PMPs), polyhalogenated N-methylindoles (PMIs), bromoheptyl- and bromooctylpyrroles, (1R,2S,4R,5R,10E)-2-bromo-1-bromomethyl-1,4-dichloro-5-(20-chloroethenyl)-5-methylcyclohexane (mixed halogenated compound MHC-1), polybrominated hexahydroxanthene derivatives(PBHDs) and polyhalogenated carbazoles (PHCs). Aspects of HNPs covered are physicochemicalproperties, sources and production, transformation processes, concentrations and trends in the physicalenvironment and biota (marine and freshwater). Toxic properties of some HNPs and a discussion of howclimate change might affect HNPs production and distribution are also included. The review concludeswith a summary of research needs to better understand the role of HNPs as “chemicals of emergingArctic concern”.
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48.
  •  
49.
  • Chan, Phoebe, et al. (författare)
  • Freshening of the Alaska Coastal Current recorded by coralline algal Ba/Ca ratios
  • 2011
  • Ingår i: Journal of Geophysical Research-Biogeosciences. - 0148-0227. ; 116
  • Tidskriftsartikel (refereegranskat)abstract
    • Arctic Ocean freshening can exert a controlling influence on global climate, triggering strong feedbacks on ocean-atmospheric processes and affecting the global cycling of the world's oceans. Glacier-fed ocean currents such as the Alaska Coastal Current are important sources of freshwater for the Bering Sea shelf, and may also influence the Arctic Ocean freshwater budget. Instrumental data indicate a multiyear freshening episode of the Alaska Coastal Current in the early 21st century. It is uncertain whether this freshening is part of natural multidecadal climate variability or a unique feature of anthropogenically induced warming. In order to answer this, a better understanding of past variations in the Alaska Coastal Current is needed. However, continuous long-term high-resolution observations of the Alaska Coastal Current have only been available for the last 2 decades. In this study, specimens of the long-lived crustose coralline alga Clathromorphum nereostratum were collected within the pathway of the Alaska Coastal Current and utilized as archives of past temperature and salinity. Results indicate that coralline algal Mg/Ca ratios provide a 60 year record of sea surface temperatures and track changes of the Pacific Decadal Oscillation, a pattern of decadal-to-multidecadal ocean-atmosphere climate variability centered over the North Pacific. Algal Ba/Ca ratios (used as indicators of coastal freshwater runoff) are inversely correlated to instrumentally measured Alaska Coastal Current salinity and record the period of freshening from 2001 to 2006. Similar multiyear freshening events are not evident in the earlier portion of the 60 year Ba/Ca record. This suggests that the 21st century freshening of the Alaska Coastal Current is a unique feature related to increasing glacial melt and precipitation on mainland Alaska.
  •  
50.
  • Gamboa, G., et al. (författare)
  • Mg/Ca ratios in coralline algae record northwest Atlantic temperature variations and North Atlantic Oscillation relationships
  • 2010
  • Ingår i: Journal of Geophysical Research-Oceans. - 0148-0227. ; 115
  • Tidskriftsartikel (refereegranskat)abstract
    • [1] Climate variability in the North Atlantic has been linked in part to the North Atlantic Oscillation (NAO). The NAO influences marine ecosystems in the northwestern Atlantic and transport variability of the cold Labrador Current. Understanding historic patterns of NAO variability requires long-term and high-resolution climate records that are not available from instrumental data. Here we present the first century-scale proxy record of sea surface temperature (SST) variability from the Newfoundland shelf, a region from which other annual-resolution shallow marine proxies are unavailable. The 116 year record was obtained from three sites along the eastern Newfoundland shelf using laser ablation inductively coupled mass spectrometry-determined Mg/Ca ratios in the crustose coralline alga Clathromorphum compactum. The alga is characterized by a high Mg-calcite skeleton exhibiting annual growth increments and a century-scale lifespan. Results indicate positive correlations between interannual variations in Mg/Ca ratios and both station-based and gridded instrumental SST. In addition, the record shows high spatial correlations to SST across the Newfoundland shelf and the Gulf of St. Lawrence. Before 1950 the Mg/Ca proxy record reveals significant departures from gridded temperature records. While the Newfoundland shelf is generally considered a region of negative correlations to the NAO, the algal time series as well as a recent modeling study suggest a variable negative relationship with the NAO which is strongest after similar to 1960 and before the mid-1930s.
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