Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Geokemi) "

Sökning: hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Geokemi)

Sortera/gruppera träfflistan
  • 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)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.
  • 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. - 0899-5362. ; 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.
  • 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 Verlag (Germany). - 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.
  • Sonesten, Lars (författare)
  • Miljöövervakning av Sveriges sjöar och vattendrag : representativiteten av den kontrollerande miljöövervakningen
  • 2013
  • Rapport (övrigt vetenskapligt)abstract
    • Rapporten presenterar en sammanställning och analys av miljöövervakningen i svenska sjöar och vattendrag 2011-2012. Rapporten ger en sammanställning av pågående övervakningsprogram och hur stationer och parametrar fördelar sig i sjöar och vattendrag. Rapporten utgör en grund för det fortsatta arbetet med övervakningsprogrammens syfte och hur man skall kunna utforma optimerade och kostnadseffektiva övervakningsprogram för förvaltningssyfte. Resultaten från projektets olika delar skall användas inom den pågående revideringen av den nationella och regionala miljöövervakningen.
  • 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.
  • 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.
  • 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. - 1680-7316. ; 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.
  • Barrientos, Natalia, 1985- (författare)
  • Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios Implications for bottom water palaeothermometry
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • <p>Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.</p><p>The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (<em>Elphidium clavatum</em>, <em>Nonionella labradorica</em>, <em>Cassidulina neoteretis</em>, <em>Oridorsalis tener</em>, <em>Cibicidoides wuellerstorfi</em> and <em>Quinqueloculina arctica</em>). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for <em>E. clavatum</em>, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).</p><p>The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker <em>Oden</em> to the East Siberian Arctic Ocean.</p>
  • Sonesten, Lars (författare)
  • Miljöövervakningen i sjöar och vattendrag kartlagd
  • 2014
  • Ingår i: Sötvatten 2014: om miljötillståndet i Sveriges sjöar, vattendrag och grundvatten. - Havs- och vattenmyndigheten. - 978-91-87025-63-1 ; s. 8-12
  • Bokkapitel (övrigt vetenskapligt)
Skapa referenser, mejla, bekava och länka
fritt online (465)
Typ av publikation
tidskriftsartikel (1409)
konferensbidrag (286)
rapport (129)
doktorsavhandling (95)
licentiatavhandling (66)
annan publikation (61)
visa fler...
bokkapitel (36)
forskningsöversikt (11)
samlingsverk (redaktörskap) (5)
bok (4)
proceedings (redaktörskap) (1)
visa färre...
Typ av innehåll
refereegranskat (1540)
övrigt vetenskapligt (790)
populärvet., debatt m.m. (40)
Öhlander, Björn (239)
Ingri, Johan, (154)
Hålenius, Ulf, (102)
Lundberg, Angela (99)
Alakangas, Lena, (84)
Widerlund, Anders, (78)
visa fler...
Rodushkin, Ilya, (74)
Maurice, Christian, (69)
Gustafsson, Jon Pett ... (56)
Baxter, Douglas (52)
Zack, Thomas, 1968-, (48)
Whitehouse, Martin J ... (47)
Engström, Emma, (45)
Romer, Rolf L., (43)
Bosi, Ferdinando, (40)
Sonesten, Lars (39)
Löfgren, Stefan, (35)
Rodushkin, Ilia, (35)
Pasero, Marco, (35)
Skogby, Henrik (33)
Malinovskiy, Dmitry (30)
Aiglsperger, Thomas, (27)
Hatert, Frédéric, (27)
Mäkitalo, Maria, (26)
Gustafsson, Örjan, (24)
Boström, Kurt (24)
Pontér, Christer (24)
Andersson, Per (23)
Åström, Mats E., (23)
Land, Magnus (23)
Holmström, Henning, (23)
Andersson, Per S., (22)
Mills, Stuart J., (22)
Köhler, Stephan, (21)
Ecke, Frauke (21)
Huser, Brian, (21)
Siergieiev, Dmytro, (20)
Whitehouse, Martin, (20)
Ask, Maria, (18)
Troll, Valentin R., (18)
Sjöstedt, Carin, (18)
Kaasalainen, Hanna, (18)
Nason, Peter, (17)
Berggren Kleja, Dan, (17)
Bonaglia, Stefano, (17)
Laudon, Hjalmar (16)
Troll, Valentin, (16)
Jia, Yu, (16)
Persson, Ingmar (15)
Bishop, Kevin (15)
visa färre...
Luleå tekniska universitet (958)
Sveriges Lantbruksuniversitet (226)
Naturhistoriska riksmuseet (204)
Göteborgs universitet (124)
Uppsala universitet (123)
Stockholms universitet (114)
visa fler...
Lunds universitet (99)
Kungliga Tekniska Högskolan (85)
Chalmers tekniska högskola (65)
Umeå universitet (45)
Linnéuniversitetet (27)
Linköpings universitet (23)
Örebro universitet (17)
Naturvårdsverket (4)
RISE (4)
Högskolan Väst (1)
Karolinska Institutet (1)
visa färre...
Engelska (1924)
Svenska (130)
Italienska (2)
Odefinierat språk (1)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (2103)
Teknik (111)
Lantbruksvetenskap (79)
Medicin och hälsovetenskap (6)
Samhällsvetenskap (6)
Humaniora (6)


pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy