Change search
Refine search result
3456789 251 - 300 of 742
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 251.
    Gärdebo, Johan
    et al.
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, History of Science, Technology and Environment.
    Marzecova, A.
    Knowles, S. G.
    The orbital technosphere: The provision of meaning and matter by satellites2017In: The Anthropocene Review, ISSN 2053-0196, E-ISSN 2053-020X, Vol. 4, no 1, p. 44-52Article in journal (Refereed)
    Abstract [en]

    With a new ‘technosphere’ concept, Peter Haff offers a provocative reconceptualization of technology in Anthropocene, not as derivative consequence of human activity, but as a new ‘quasi-autonomous’ sphere of the environment that conditions human survival within the Earth System. Paying attention to the expansion of the orbital satellites in outer space, this paper suggests that technosphere analysis needs to conceptualize specific histories of the planetary-scale technology while considering how these technologies provide the epistemological basis and limitations for the technosphere. Satellites enhance the capacity of the technosphere as a system and provide systemic knowledge that is the basis for the meaning of the technosphere concept. Yet, this expansion is rooted in the contingencies of earthly geopolitics and the continual breakdown of technology – in this instance as a space debris layer formed in orbit around Earth that endangers the technosphere itself.

  • 252.
    Gålfalk, Magnus
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Karlson, Martin
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Centre for Climate Science and Policy Research, CSPR.
    Crill, Patrick
    Stockholm Univ, Sweden.
    Bousquet, Philippe
    LSCE, France.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Technical note: A simple approach for efficient collection of field reference data for calibrating remote sensing mapping of northern wetlands2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 5, p. 1549-1557Article in journal (Refereed)
    Abstract [en]

    The calibration and validation of remote sensing land cover products are highly dependent on accurate field reference data, which are costly and practically challenging to collect. We describe an optical method for collection of field reference data that is a fast, cost-efficient, and robust alternative to field surveys and UAV imaging. A lightweight, waterproof, remote-controlled RGB camera (GoPro HERO4 Silver, GoPro Inc.) was used to take wide-angle images from 3.1 to 4.5 m in altitude using an extendable monopod, as well as representative near-ground (amp;lt; 1 m) images to identify spectral and structural features that correspond to various land covers in present lighting conditions. A semi-automatic classification was made based on six surface types (graminoids, water, shrubs, dry moss, wet moss, and rock). The method enables collection of detailed field reference data, which is critical in many remote sensing applications, such as satellite-based wetland mapping. The method uses common non-expensive equipment, does not require special skills or training, and is facilitated by a step-by-step manual that is included in the Supplement. Over time a global ground cover database can be built that can be used as reference data for studies of non-forested wetlands from satellites such as Sentinel 1 and 2 (10 m pixel size).

  • 253.
    Hall, Adrian M.
    et al.
    University of St Andrews, Scotland, UK.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glacial and periglacial buzzsaws: fitting mechanisms to metaphors2014In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 81, no 2, p. 189-192Article in journal (Refereed)
    Abstract [en]

    The buzzsaw hypothesis refers to the potential for glacial and periglacial processes to rapidly denude mountains at and above glacier Equilibrium Line Altitudes (ELAs), irrespective of uplift rates, rock type or pre-existing topography. Here the appropriateness of the buzzsaw metaphor is examined alongside questions of the links between glacial erosion and ELAs, and whether the glacial system can produce low-relief surfaces or limit summit heights. Plateau fragments in mountains on both active orogens and passive margins that have been cited as products of glacial and periglacial buzzsaw erosion instead generally represent dissected remnants of largely inherited, pre-glacial relief. Summit heights may correlate with ELAs but no causal link need be implied as summit erosion rates are low, cirque headwalls may not directly abut summits and, on passive margins, cirques are cut into pre-existing mountain topography. Any simple links between ELAs and glacial erosion break down on passive margins due to topographic forcing of ice-sheet growth, and to the km-scale vertical swaths through which ELAs have shifted through the Quaternary. Glaciers destroy rather than create low-relief rock surfaces through the innate tendency for ice flow to be faster, thicker and warmer along valleys. The glacial buzzsaw cuts down.

  • 254.
    Hallström, Ellinor
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Payment for Ecosystem Services (PES) and Water Resource Management of the tropical mountain ecosystem páramo: A case study in the northern parts of Ecuador2017Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Latin America has pioneered the concept of Payment for Ecosystem Services (PES) as a strategy to improve the management of ecosystem services. Ecuador is not an exception, where many PES schemes have been implemented to protect the tropical mountain ecosystem “páramo” and the water resources these areas are generating for downstream societies. A successful PES scheme needs to achieve both targeted bio-physical objectives and at the same time benefit local conditions while not risking to sacrifice the local demand for ecosystem services. This balance is explored here in a case study focusing on the Río Grande watershed in the highlands in the northern parts of Ecuador by exemplifying community participation in the public PES scheme Socio Bosque (PSB) starting in 2009. The water resource distribution (precipitation, discharge, actual evapotranspiration and potential evapotranspiration) in the watershed was evaluated over the last decades. The local perception of the PSB and its impacts on local and regional water resources were also studied and characterized. The results showed that the annual discharge in the Río Grande watershed has decreased significantly from 1967-2014 and that the annual discharge was significantly lower between 1997-2015 compared to 1979-1997. Since precipitation did not decrease significantly during this period, the changes of the annual discharge are more likely depended on factors controlling the seasonal distribution of discharge and evapotranspiration in the watershed. For example, large scale land use changes coupled with a significantly warmer climate in the region could be a possible driver. Of course, this would not exclude other important factors such as changes in water demand and the supply of freshwater from the Río Grande watershed to downstream societies. The results of this case study showed that it is likely too early to see any impacts in the water balance components as a direct response to the implemented PSB scheme. Clearly, this motivates a need for continued evaluation of the local perception and the water resources to ensure that the need and demand for ecosystem services in a long-term perspective are maintained.

  • 255. Han, X.
    et al.
    Fraenz, M.
    Dubinin, E.
    Wei, Y.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wan, W.
    He, M.
    Rong, Z. J.
    Chai, L.
    Zhong, J.
    Li, K.
    Barabash, S.
    Discrepancy between ionopause and photoelectron boundary determined from Mars Express measurements2014In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, no 23, p. 8221-8227Article in journal (Refereed)
    Abstract [en]

    The Martian ionosphere directly interacts with the solar wind due to lack of a significant intrinsic magnetic field, and an interface is formed in between. The interface is usually recognized by two kinds of indicators: the ionopause identified from ionospheric density profiles and the photoelectron boundary (PEB) determined from the electron energy spectrum at higher energies. However, the difference between them remains unclear. We have determined the locations of crossings of the ionopause and PEB from Mars Express observations during 2005-2013 and found that the average position of the PEB appears to be similar to 200km higher than that of the ionopause, which corresponds to 10(3)cm(-3) in the electron density profile. The discrepancy can be explained by cross-field transport of photoelectrons.

  • 256.
    Han, Zhiyong
    et al.
    Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing 210023, Jiangsu, Peoples R China..
    Li, Xusheng
    Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing 210023, Jiangsu, Peoples R China..
    Yi, Shuangwen
    Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing 210023, Jiangsu, Peoples R China..
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Chen, Yingyong
    Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing 210023, Jiangsu, Peoples R China..
    Wang, Xiaoyong
    Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing 210023, Jiangsu, Peoples R China..
    Lu, Huayu
    Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing 210023, Jiangsu, Peoples R China..
    Extreme monsoon aridity episodes recorded in South China during Heinrich Events2015In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 440, p. 467-474Article in journal (Refereed)
    Abstract [en]

    Geological records of climate change since the last glaciation in South China, a core area of the East Asian monsoon, are key to understanding secular variation in the monsoon system. However, with the exception of the speleothems, records from this area with independent age control are few. We investigated aeolian sand deposition on a sand hill on the shore of Poyang Lake in South China and reconstructed the chronological sequence of aeolian deposition using Optically Stimulated Luminescence (OSL) dating. Without exception, all aeolian sediments were deposited within seven periods that generally match the timing of Heinrich events and other cold periods in Greenland. We argue that aeolian sand accumulation in this region is most likely forced by extreme aridity driven by weakening of the summer monsoon, while the characteristics of this deposition are influenced by winter monsoon intensity. The monsoon shifts revealed here suggest a possible link between North Atlantic cooling and summer monsoon strength in South China, and support the intensities of cooling phases recorded in Greenland ice cores.

  • 257.
    Hanley, John
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Caballero, Rodrigo
    Stockholm University, Faculty of Science, Department of Meteorology .
    The role of large-scale atmospheric flow and Rossby wave breaking in the evolution of extreme windstorms over Europe2012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, p. L21708-Article in journal (Refereed)
    Abstract [en]

    We investigate the relationship between large-scale atmospheric flow and the evolution of the most extreme windstorms affecting Western Continental Europe. The 25 most destructive Western Continental European wind storms are selected from a 43-year climatology. 22 of these storms are grouped as having a similar trajectory and evolution. We show that these storms typically occur during particularly strong and persistent positive NAO anomalies which peak approximately 2 days before the storms' peak intensity; the NAO pattern then shifts eastward to a position over the European continent when the storms strike Europe. A temporal composite of potential temperature on the 2-PVU surface suggests that this NAO shift is the result of simultaneous cyclonic and anticyclonic wave breaking penetrating further to the east than during a typical high-NAO event. This creates an extremely intense, zonally-orientated jet over the North Atlantic whose baroclinicity favours explosive intensification of storms while steering them into Western Continental Europe.

  • 258.
    Hannerz, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Lotsch, Alexander
    Assessment of remotely sensed and statistical inventories of African agricultural fields2008In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, International Journal of Remote Sensing, Vol. 29, no 13, p. 3787-3804Article in journal (Refereed)
    Abstract [en]

    This paper critically examines different sources of remotely sensed and statistical inventories of African agricultural fields. Substantial discrepancies are found across alternative sources of information in both the extent and location of agricultural fields. In one-third of the countries, the difference between lowest and highest field extent estimate exceeds 25% of the total country area, and the maximum difference at the continental level is 2.6 million km2. Much of the disagreement between land-cover maps arises from areas of low cropping density. These inconsistencies have important implications when using these data directly, e.g. for the assessment of land cover changes, or indirectly in economic or physical models, and indicate a need to explicitly quantify uncertainties arising from the limitations in land-cover data. They also highlight the need for development of regional land information systems for baseline development and informed policy decisions.

  • 259. Harden, Jennifer W.
    et al.
    Koven, Charles D.
    Ping, Chien-Lu
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    McGuire, A. David
    Camill, Phillip
    Jorgenson, Torre
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Michaelson, Gary J.
    O'Donnell, Jonathan A.
    Schuur, Edward A. G.
    Tarnocai, Charles
    Johnson, Kristopher
    Grosse, Guido
    Field information links permafrost carbon to physical vulnerabilities of thawing2012In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 39, p. L15704-Article in journal (Refereed)
    Abstract [en]

    Deep soil profiles containing permafrost (Gelisols) were characterized for organic carbon (C) and total nitrogen (N) stocks to 3 m depths. Using the Community Climate System Model (CCSM4) we calculate cumulative distributions of active layer thickness (ALT) under current and future climates. The difference in cumulative ALT distributions over time was multiplied by C and N contents of soil horizons in Gelisol suborders to calculate newly thawed C and N. Thawing ranged from 147 PgC with 10 PgN by 2050 (representative concentration pathway RCP scenario 4.5) to 436 PgC with 29 PgN by 2100 (RCP 8.5). Organic horizons that thaw are vulnerable to combustion, and all horizon types are vulnerable to shifts in hydrology and decomposition. The rates and extent of such losses are unknown and can be further constrained by linking field and modelling approaches. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems. Citation: Harden, J. W., et al. (2012), Field information links permafrost carbon to physical vulnerabilities of thawing, Geophys. Res. Lett., 39, L15704, doi: 10.1029/2012GL051958.

  • 260.
    Hargelius, Malcolm
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Hansbokorrelationens tillförlitlighet för kommersiella syften2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Geotechnicans in Sweden and rest of Scandinavia have a wide experience of stability calculations in cohesive soils. The two main parameters for this type of calculations are the undrained shear strength and the preconsolidation pressure. The most common methods in Sweden to determine the undrained shear strength in field is the vane shear strength test and CPT-test, in laboratories the fall cone test is well used. To determine the preconsolidation pressure CRS-analyses are well used. For more accurate measurements the odeometer tests are more suitable. However this method is both expensive and time-consuming form of analysis from a commercial aspect. Therefore is different correlation equations used as a compliment in these different stability evaluations. 

    This research will focus on the empirical Hansbo Correlation and its relation to results from commercial surveys. The commercial data come from Atkins Sverige’s project data base. The results after comparing Hansbo correlation with the commercial data showed on a significant divergence, which indicate a great unsureness of the Hansbo correlation. As a result of this contingency it is of importance to take cautiousness in the use of empirical correlations in stability calculations. 

  • 261.
    Hargelius, Malcolm
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Modellering och analys av grundvattenflödet i en byggnads grundläggning2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Most of Sweden’s older buildings constructed in clay rich areas are founded on wood poles. The poles are used to build the constructions in areas with soils without satisfying stability, such e.g. clay soils, where the poles are used as the “stable ground” where the building are founded upon. One of the problems with wood poles are that to prevent the wood from rotting the poles must be covered with water, to make an oxygen free environment. The problems start first when the water levels start to decrease due to dewatering or if the water is contaminated with bacteria from e.g. leaky sewer pipes. The contamination leads to decomposing of the wood, which affect the stability of the poles negatively. To prevent the leaky aquifers many houses, have water supply by wells where water is added to the aquifer to keep the water at stable levels.

    In Uppsala, Sweden an apartment building founded on wood poles have this problems with a contaminated and leaky aquifer. The reason to the contamination was an old sewer pipe that start leaking due to subsidence of the clay below the house. The dewatering of the aquifer was detected in 2016 when the water supply to the aquifer increased from 10th of cubic meters per year to 10th of cubic meters per day.

    In an attempt to find out what the reason to the high discharge from the aquifer a groundwater model was constructed to modelling the groundwater flows below the building. To modeling this problem the software Groundwater Modeling System (GMS) and MODFLOW was used. By construct a 3D grid of cells in the same dimensions as the building divided in to three different layers it was possible to simulating the groundwater flow through the aquifer.

    The way we did it was by knowing that as part of the foundation there was “channels” filled with gavel above the poles. The hypothesis was that the water was flowing through this high hydraulic conductivity “gravel channels” and there for we used the model to performed calculations of the hydraulic conductivity in the channels and the areas around the channels. The results told us that there were high conductivity zones in the south west part of the building. After the calculation of the conductivity, a test was performed, where the water supply where turned off and the decrease of the water levels was measured.

    By using this calculated hydraulic conductivity and the observed levels from the water supply test we let the model calculate the change of water level during the whole-time series. The results told us that there was a possible groundwater flow to the sought west and that some sort of threshold in the channel prevented the water to sink below a curtain limit of 7.65 meter.

  • 262.
    Harrie, Lars
    et al.
    Lund University.
    Larsson, Karin
    Lund University.
    Tenenbaum, David
    Lund University.
    Horemuz, Milan
    Royal Institute of Technology (KTH).
    Ridefelt, Hanna
    National mapping and land registration authority, Gävle, Sweden.
    Lysell, Gunnar
    National mapping and land registration authority, Gävle, Sweden.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Sahlin, Eva A.U.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Adelsköld, Göran
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Högström, Mats
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Lagerstedt, Jakob
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Some strategic national initiatives for the Swedish education in the geodata field2014In: Connecting a Digital Europe through Location and Place: Selected best short papers and posters of the AGILE 2014 Conference, 3‐6 June 2014, Castellón, Spain / [ed] Joaquin Huerta, Sven Schade, Carlos Granell, AGILE Digital Editions , 2014Conference paper (Refereed)
    Abstract [en]

    This paper describes national cooperation in Sweden launched by its universities and authorities, aimed at improving geodata education. These initiatives have been focused upon providing common access to geodata, the production of teaching materials in Swedish and organizing annual meetings for teachers. We argue that this type of cooperation is vital to providing high quality education for a poorly recognized subject in a country with a relatively small population.

  • 263. Harrison, John A.
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Beusen, Arthur H. W.
    Conley, Daniel J.
    McCrackin, Michelle L.
    Global importance, patterns, and controls of dissolved silica retention in lakes and reservoirs2012In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 26, no 2, p. n/a-n/aArticle in journal (Refereed)
    Abstract [en]

    Lentic water bodies (lakes and reservoirs) offer favorable conditions for silica (SiO2) burial in sediments. Recent global estimates suggest that (1) lentic SiO2 trapping is a globally important SiO2 flux, and (2) through reservoir construction, humans have dramatically altered river dissolved SiO2 (DSi) transport and coastal DSi delivery. However, regional to global scale patterns and controls of DSi removal in lentic systems are poorly constrained. Here we use 27 published lake and reservoir DSi budgets to develop insights into patterns and controls of lentic DSi retention and to develop a new, spatially explicit, global model of lentic DSi removal called SiRReLa (Silica Retention in Reservoirs and Lakes). In our analysis, lentic DSi removal (kg SiO2 yr−1) was significantly and positively related to DSi loading (P < 0.0001; r2 = 0.98), and DSi removal efficiency was significantly and positively related to water residence time (P < 0.0001; r2 = 0.68). In addition, DSi settling rates were, on average, 6.5-fold higher in eutrophic systems than in non-eutrophic systems (median settling velocities: 11.1 and 1.7 m yr−1 for eutrophic and non-eutrophic systems, respectively; P < 0.01). SiRReLa, which incorporates these insights, performed quite well in predicting both total DSi removal (kg SiO2 yr−1; Nash Sutcliffe Efficiency (N.S.E) = 0.88) and DSi removal efficiency (% Si removed; N.S.E. = 0.75), with no detectable bias in the model. Global application of SiRReLa confirms that lentic systems are important sinks for DSi, removing 89.1 Tg DSi yr−1 from watersheds globally, roughly 19–38% of all DSi inputs to surface waters. Small lakes and reservoirs (<50 km2) were critical in the analysis, retaining 81% (72 Tg DSi yr−1) of the globally retained total. Furthermore, although reservoirs occupy just 6% of the global lentic surface area, they retained approximately 35% of the total DSi removed by lentic systems. Regional hot spots for lentic DSi removal were identified and imply that lentic systems can remove the vast majority of DSi across a large fraction of Earth's land surface. Finally, a sensitivity analysis indicates that future improvements in DSi trapping and transport models should focus on improving estimates of DSi input to surface waters.

  • 264.
    Hartman, Steven
    Mid Sweden University, Faculty of Human Sciences, Department of Humanities.
    Unpacking the Black Box: the need for Integrated Environmental Humanities (IEH)2015Other (Other (popular science, discussion, etc.))
    Abstract [en]

    The circumstances that have given rise to the Anthropocene concept require that we reassess our assumptions about human agency and human effects on the earth system. Human activities, and thus human choices, clearly lie at the root of the great environmental predicament of our age, which is not primarily an ecological crisis, though its ramifications are far reaching within ecological systems. Rather, it is a crisis of culture. If the humanities "are a unique repository of knowledge and insight into the rich diversity of the human experience" from which we learn to make sense of our "responses, motivations and actions" in the face of challenges, then it is risky to omit humanities knowledge from scientific assessment and consultation processes informing environmental policy.

    The complete article is available for free viewing on the Future Earth site: bit.ly/1QoHPeC .

  • 265. He, Hongxing
    et al.
    Jansson, Per-Erik
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Svensson, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Bjorklund, Jesper
    Tarvainen, Lasse
    Klemedtsson, Leif
    Kasimir, Asa
    Forests on drained agricultural peatland are potentially large sources of greenhouse gases - insights from a full rotation period simulation2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 8, p. 2305-2318Article in journal (Refereed)
    Abstract [en]

    The CoupModel was used to simulate a Norway spruce forest on fertile drained peat over 60 years, from planting in 1951 until 2011, describing abiotic, biotic and greenhouse gas (GHG) emissions (CO2 and N2O). By calibrating the model against tree ring data a "vegetation fitted" model was obtained by which we were able to describe the fluxes and controlling factors over the 60 years. We discuss some conceptual issues relevant to improving the model in order to better understand peat soil simulations. However, the present model was able to describe the most important ecosystem dynamics such as the plant biomass development and GHG emissions. The GHG fluxes are composed of two important quantities, the spruce forest carbon (C) uptake, 413 g C m(-2) yr(-1) and the decomposition of peat soil, 399 g C m(-2) yr(-1) . N2O emissions contribute to the GHG emissions by up to 0.7 g N m(-2) yr(-1), corresponding to 76 g C m(-2) yr(-1) . The 60-year old spruce forest has an accumulated biomass of 16.0 kg C m(-2) (corresponding to 60 kg CO2 m(-2)). However, over this period, 26.4 kg C m(-2) (97 kg CO2 eq m(-2)) has been added to the atmosphere, as both CO2 and N2O originating from the peat soil and, indirectly, from forest thinning products, which we assume have a short lifetime. We conclude that after harvest at an age of 80 years, most of the stored biomass carbon is liable to be released, the system having captured C only temporarily and with a cost of disappeared peat, adding CO2 to the atmosphere.

  • 266.
    Hedayati, Maryeh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Sharma, Prabhakar
    Nalanda Univ, Sch Ecol & Environm Studies, Nalanda 803116, Bihar, India.
    Katyal, Deeksha
    Guru Gobind Singh Indraprastha Univ, Sch Environm Management, New Delhi, India.
    Fagerlund, Fritjof
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Transport and retention of carbon-based engineered and natural nanoparticles through saturated porous media2016In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 18, no 3, article id 57Article in journal (Refereed)
    Abstract [en]

    Carbon-based engineered nanoparticles have been widely used due to their small size and unique physical and chemical properties. At the same time, the toxic effects of these nanoparticles on human and fish cells have also been observed; therefore, their release and distribution into the surface and subsurface environment is a subject of concern. The aim of this research is to evaluate and compare the transports and retentions of two types of engineered nanoparticles (multiwalled carbon nanotubes and C-60) and the natural carbon nanoparticles collected from a fire accident. Several laboratory experiments were conducted to observe the transport behavior of nanoparticles through a column packed with silica sand. The column experiments were intended to monitor the effect of ionic strength on transport of nanoparticles as a function of their shapes. It was observed that the mobilities of both types of engineered nanoparticles were reduced with the increasing ionic strength from 1.34 to 60 mM. However, at ionic strengths up to 10.89 mM, spherical nanoparticles were more mobile than cylindrical nanoparticles, but the mobility of the cylindrical nanoparticles became significantly higher than spherical nanoparticles at the ionic strength of 60 mM. In comparison with natural fire-born nanoparticles, both types of engineered nanoparticles were much less mobile under the selected experimental condition in this study. Furthermore, inverse modeling was used to calculate parameters such as attachment efficiency, the longitudinal dispersivity, and capacity of the solid phase for the attachment of nanoparticles. The results indicate that the combination of the shape and the solution chemistry of the NPs are responsible for the transport and the retention of nanoparticles in natural environment; however, fire-burned nanoparticles can be highly mobile at the natural groundwater chemistry.

  • 267.
    Hedmark, Mia
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Inventering och sammanställning av publikationer inom geovetenskaplig didaktik2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a general definition of science education and earth science education.An inventory has been conducted of published material during the years 2011-2013, withthe start in 2013 and working backwards for international publications and with no timelimits in time for Swedish publications. Different databases were used during April 2013 forthe inventory.The thesis organizes and analyses published material in earth science education in a tablewith a following discussion.The purpose with the inventory was to investigate the amount and content ofprevious year’s publications in earth science education. Concept inventories were foundto be the most common subject of the found material, followed by virtual field studies. Thelargest amount of publications was published in North America. Only one publication wasfound in Sweden.

  • 268.
    Heingård, Miriam
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    The Function of FoxB During Limb Development and Axis Formation in the Spider Parasteatoda tepidariorum2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Arthropods are the most diverse and speciose group of animals on the planet. A key factor in their success is the adaptation of various appendages to new functions and environments, resulting in radically different morphologies. To understand this diversity, it is important to study the underlying genetic mechanisms. However, the gene regulatory networks governing the development of limbs are relatively poorly understood in many arthropods. The FoxB gene is known to have a conserved expression pattern in all arthropods hitherto investigated. It is expressed along the ventral ectoderm of all appendages, indicative of a function in ventral limb patterning. In this study, I conducted a functional analysis of FoxB in the house spider Parasteatoda tepidariorum by means of parental RNA interference. The knockdown of FoxB resulted in severe phenotypes of arrested development and inability to form proper germ bands, hypothesized to be the consequence of FoxB working antagonisitcally to dpp, a gene crucial for dorsal field formation and axial symmetry in Parasteatoda. Embryos depleted of FoxB had abnormal limbs characterized by an L-shaped morphology, likely caused by an absence or alteration of ventral limb morphology. I also present evidence that FoxB is likely upstream of the ventrally expressed genes wingless and H15-2 and probably a repressor of the dorsal limb marker optomotor-blind. Furthermore, I show for the first time that FoxB is expressed ventrally in Drosophila imaginal leg discs and in the antennal disc. The present study demonstrates the conserved ventral limb expression of FoxB in arthropods, and evidence for a role in limb patterning in spiders. FoxB appears to be an excellent candidate gene for studying ventral limb development in arthropods, and has potential to be the focus of future studies investigating this topic.

    The full text will be freely available from 2019-12-31 12:00
  • 269.
    Helanow, Christian
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Effects of numerical implementations of the impenetrability condition on non-linear Stokes flow: applications to ice dynamicsManuscript (preprint) (Other academic)
    Abstract [en]

    The basal sliding of glaciers and ice sheets can constitute a large part of the total observed ice velocity, in particular in dynamically active areas. It is therefore important to accurately represent this process in numerical models. The condition that the sliding velocity should be tangential to the bed is realized by imposing an impenetrability condition at the base. We study the, in glaciological literature used, numerical implementations of the impenetrability condition for non-linear Stokes flow with Navier's slip on the boundary. Using the finite element method, we enforce impenetrability by: a local rotation of the coordinate system (strong method), a Lagrange multiplier method enforcing zero average flow across each facet (weak method) and an approximative method that uses the pressure variable as a Lagrange multiplier for both incompressibility and impenetrability. An analysis of the latter shows that it relaxes the incompressibility constraint, but enforces impenetrability approximately if the pressure is close to the normal component of the stress at the bed. Comparing the methods numerically using a method of manufactured solutions unexpectedly leads to similar convergence results. However, we find that, for more realistic cases, in areas of high sliding or varying topography the velocity field simulated by the approximative method differs from that of the other methods by approx. 1% (two dimensional flow) and  > 5% when compared to the strong method (three-dimensional flow). In this study the strong method, which is the most commonly used in numerical ice sheet models, emerges as the preferred method due to its stable properties (compared to the weak method in three dimensions) and ability to well enforce the impenetrability condition.

  • 270.
    Helanow, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ahlkrona, Josefin
    Galerkin Least-Squares Stabilization in Ice Sheet Modeling - Accuracy, Robustness, and Comparison to other TechniquesManuscript (preprint) (Other academic)
    Abstract [en]

    We investigate the accuracy and robustness of one of the most common methods used in glaciology for the discretization of the p-Stokes equations: equal order finite elements with Galerkin Least-Squares (GLS) stabilization. Furthermore we compare the results to other stabilized methods. We find that the vertical velocity component is more sensitive to the choice of GLS stabilization parameter than horizontal velocity. Additionally, the accuracy of the vertical velocity component is especially important since errors in this component can cause ice surface instabilities and propagate into future ice volume predictions. If the element cell size is set to the minimum edge length and the stabilization parameter is allowed to vary non-linearly with viscosity, the GLS stabilization parameter found in literature is a good choice on simple domains. However, near ice margins the standard parameter choice may result in significant oscillations in the vertical component of the surface velocity. For these cases, other stabilization techniques, such as the interior penalty method, result in better accuracy and are less sensitive to the choice of the stabilization parameter. During this work we also discovered that the manufactured solutions often used to evaluate errors in glaciology are not reliable due to high artificial surface forces at singularities. We perform our numerical experiments in both FEniCS and Elmer/Ice.

  • 271.
    Hell, Benjamin
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gridding heterogeneous bathymetric data sets with stacked continuous curvature splines in tension2011In: Marine Geophysical Researches, ISSN 0025-3235, E-ISSN 1573-0581, Vol. 32, no 4, p. 493-501Article in journal (Refereed)
    Abstract [en]

    Gridding heterogeneous bathymetric data sets for the compilation of Digital bathymetric models (DBMs), poses specific problems when there are extreme variations in source data density. This requires gridding routines capable of subsampling high-resolution source data while preserving as much as possible of the small details, at the same time as interpolating in areas with sparse data without generating gridding artifacts. A frequently used gridding method generalizes bicubic spline interpolation and is known as continuous curvature splines in tension. This method is further enhanced in this article in order to specifically handle heterogeneous bathymetric source data. Our method constructs the final grid through stacking several surfaces of different resolutions, each generated using the splines in tension algorithm. With this approach, the gridding resolution is locally adjusted to the density of the source data set: Areas with high-resolution data are gridded at higher resolution than areas with sparse source data. In comparison with some of the most widely used gridding methods, our approach yields superior DBMs based on heterogeneous bathymetric data sets with regard to preserving small bathymetric details in the high-resolution source data, while minimizing interpolation artifacts in the sparsely data constrained regions. Common problems such as artifacts from ship tracklines are suppressed. Even if our stacked continuous curvature splines in tension gridding algorithm has been specifically designed to construct DBMs from heterogeneous bathymetric source data, it may be used to compile regular grids from other geoscientific measurements.

  • 272.
    Hellqvist, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Kvartärgeologi och landskapsanalys2011Report (Other academic)
    Abstract [sv]

    Landskapsanalysen runt utgrävningen i Nibble baseras framför allt på en jordartsgeologisk detaljkartläggning. För annan typ av information kring landskapets förändring och utveckling, har använts tidigare undersökningar i områdets närhet eller i denna del av Uppland och Västmanland. Anledningen till detta arbetssätt är flera. Dels är landskapsutvecklingen i många delar mycket likartad i regionen, dels har mycket av den paleoekologiska insatsen koncentrerats på detaljstudier av anläggningar och närmiljön i Nibble och dels har kunskapen om jordarterna och deras karaktär i detalj för ytan ganska stor betydelse för förståelsen av ytorna på utgrävningsplatsen samt även anläggningarnas karaktär och utseende. Bland annat förekom mycket diskussioner om vissa anläggningar och karaktären på områdets moränavsättningar.

    Den jordartsgeologiska detaljkartläggningen är en presentation av i första hand jordartsgeologin i området runt Nibble, ca 4 km väster om Enköping. Karteringen baseras främst på undersökning i fält, provtagning och grundläggande jordartsanalys i samband med den arkeologiska slutundersökningen i maj t.o.m. oktober 2007. I samband med den geologiska kartläggningen, har det tagits ett antal jordartsprover i utgrävningsområdet (se nedan). Syftet är bl.a. att göra själva jordartsklassificeringen mer komplett och därmed stärka den detaljerade kartläggningen. Ett annat syfte är att ge en möjlighet till tolkning av markanvändningen i området och hur man utnyttjat marken för odling och hur detta återspeglas i de kulturlager som finns kvar idag.

    Till detta kommer även uppgifter från litteraturstudier, men då platsen och området runt Nibble inte ingått i några tidigare undersökningar eller speciella studier, så finns det inte några tidigare detaljstudier eller undersökningar att tillgå. Den jordartsgeologiska karteringen (Möller, 1985) som Sveriges Geologiska Undersökning (SGU) genomfört i området är naturligtvis ett viktigt komplement i sammanhanget och uppgifter från den används som jämförelsematerial till de resultat som framkommit i samband med kartläggningen av Nibble 2007. I de sammanhangen refereras till uppgifter på kartbladet Enköping SV och är därför mer karakteristika och specifika drag för jordartgeologin kopplade till en radie om > 5 km runt Nibble. Till detta kommer en del referenser från bl.a. Enköpingstrakten, där det framför allt finns undersökningar kring Enköpingsåsen.

                          Nibble ligger på många sätt i relativt klassisk kvartärgeologisk mark med tanke på att hela Mälardalsregionen varit föremål för stort intresse och undersökningar under lång tid. Detta har även möjliggjorts eftersom det är en expansiv region med mycket samhällen och återkommande arbeten med infrastruktur. I områdena tunt Enköping finns stora slättområden, uppbyggda av framför allt finsediment som lera, vilket ger speciella förutsättningar för det arkeologiska utgrävningsarbetet och bevarandeförhållanden. Det undersökta området har helt legat under havsytan efter senaste istidens avslutning (Weichsel) och sedimentation av finsediment har skett i akvatisk miljö. Därför domineras jordartsgeologin till stora delar av glaciala postglaciala leror.

  • 273.
    Hellqvist, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Moränkällan2011Report (Other academic)
    Abstract [sv]

    Under utgrävningarna i Nibble så framkom ett för arkeologiska utgrävningar ovanligt fynd i form av en naturlig källa. Sannolikt har likartade bildningar hittats i samband med utgrävningar tidigare, men att kunna klassificera en sådan bildning redan i samband med slutundersökningens tidiga skede och att kunna klassificera vilken typ av källa det rör sig om är nog mycket unikt. Källor är normalt klassificerade utifrån det hydrogeologiska sammanhang och den miljö de är bildade i och om man, som sker i samband med en arkeologisk utgrävning, skalar av markskiktet så kan det naturligtvis bli svårt att urskilja att det faktiskt rör sig om en källa. Fördelen med källan i Nibble är att utflödet för vattnet i marken skedde vid en ansamling av stora block och därför ”skyddades” detta från att på något sätt förstöras i samband med avbaning av markskiktet i samband med utgrävningen eller annan tidigare markanvändning.

    I naturen avslöjas källor ofta genom ett utflöde i marken som via markens fuktighet och växtlighet. Källor har spelat stor roll i kulturhistorien och det vi idag kan se på platser som tydliga källor är ofta utbyggda och arrangerade av människor som har ramat in, skyddat eller på något sätt markerat utflödet bl.a. för att i olika syften kunna utnyttja källans vatten som ofta håller mycket hög kvalitet. Den sista fasen i denna kulturhistoriska utveckling var utvecklandet av brunnsdrickning som förekommit från åtminstone 1600-talet och fram till 1900-talet. Flera av Sveriges kända sådana platser har idag gett namn åt kolsyrat vatten på flaska, som exempelvis Loka brunn och Ramlösa brunn. Vissa har med tiden övergått i mer moderniserade s.k. ”spa-anläggningar” som exempelvis Sätra brunn.

    Med tanke på källans vatten och det fenomen då vattnet kommer fram ur marken, så kan man lätt tänka sig att källan måste ha varit föremål för människors förundran och kanske tro långt tillbaka i tiden. Betydelsen och värdet av källor har dock förändrats genom historien, både i tro och också kult. I de förkristna källor som kan ge en vägledning, de isländska berättelserna genom poetiska Eddan, så berättas att källorna var förutsättningen för världen och om källorna sinade så skulle världen gå under. Även det omtalade trädet Yggdrasil fick sitt vatten från tre källor. Uppfattningen om världens undergång kommer via germansk tradition och spåras tillbaka till indoeuropeisk mytologi (Hult, 2006).

    En tidigare vanlig uppfattning kring källor och dess vatten var att de hade en helande förmåga och även kunde hjälpa försvagade och sjuka kroppar. Man trodde även på källans mystiska krafter. Källor och källvatten kom att få en stark ställning i den katolska kyrkan och även i Sverige finns exempel på helgonkällor och ännu vanligare är källor som benämns trefaldighets- och midsommarkällor. Dessa källor har varit en viktig del i trefaldighetsfirande, ibland även valborgsmässofirande och liknande. Denna tradition anses av en del ha sina rötter i vad som kallats ”hednisk källkult” med ett ursprung i förhistorisk tid.

    Traditioner kring vissa källor har en kulturhistorisk bakgrund i tron kring källorna som går tillbaka till medeltiden och bl.a. den katolska kyrkan i Sverige. Under reformationen förändrades synen på källorna och 1544 förbjöds svenskarna att dricka hälsa från trefaldighetskällorna. I det protestantiska Sverige kom seden att dricka källa att kallas för katolsk vidskepelse (Hult, 2006). Sedan dess har mycket hänt i synen på källorna fram till modern tid och idag är seder kring källor mer att betrakta som pittoreska traditionsinslag där människor får möjlighet att samlas.

    Till all denna tro och kult ska man naturligtvis tillägga, att källor i stor utsträckning fungerat som källa för vatten – både på landsbygden och i städer. Möjligheten att använda dessa platser för att få tillgång till friskt och bra vatten som strömmar ut ur marken, utan att man behöver ta upp detta själv, har naturligtvis använts flitigt när det är möjligt.

  • 274.
    Hellqvist, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Reconstructing environment and human impact during 1500 years of mining activity around FalunCopper mine, Sweden, through a multidisciplinary approach2013In: Environmental and Archaeological Science Conference: AEA & UKAS 2013 Cardiff University 11th-14th April 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Mining impact on the surrounding environment is one of the most severe human activities. The time the mining has been lasting is usually proportional to and increases the impact on the surrounding environment. In the interdisciplinary project presented in this paper, ”Falun above from Falun under”, is the earliest history from around 1300-1500 BP studied together with the increasing environmental impact of growing mining activity around Falun Copper mine. The environmental and cultural development is followed forward until the mine is lastly abandoned in 1992.

    The projects aim is to study the area unbiased and explore previous reference as well as initiating new investigations. The project use the British project ”Great Yarmouth Archaeological map project” as a model. Falun Copper mine have a central and in time long part in Sweden and was 2001 established as a UNESCO World Heritage and is therefore in some parts rather well studied –primarily in archaeology, earth science and history. Within the project today is several methods used and under development: sedimentological mapping, reconstruction and analysis; insect and pollen analysis; dendrochronology; GIS; archive material and previous archaeological and geotechnical reports etc. There are also studies connected to preservation (World Heritage) and environmental history pedagogy and didactics.

  • 275.
    Hellqvist, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Johansson, Jenny
    Almgren, Elisabeth
    Traustadottir, Ragnheidur
    Environmental and climatic changes during the late Holocene in Hjaltadalur, Skagafjörður, northern Iceland, interpreted from peat core analyses and pollen identification2016In: Theme B - Landscape Historical Ecology and Climate Change: B1 Land-use and Anthropogenic Land-cover Change over the Holocene - Information of Value for Climate and Environmental Research, 2016Conference paper (Refereed)
    Abstract [en]

    A landscape analysis based on a combination of several proxies including pollen analysis, loss on ignition, radiocarbon dating, sediment analysis and tephra analysis was undertaken on samples from Hjaltadalur, northern Iceland. The central settlement in the valley, Hólar, is an important site that was once the religious and cultural centre of northern Iceland. Sampling was done in wetlands and one mire (Viðvik) was chosen as the main study site for sampling and analyses. The results provide useful information and insights into temperature fluctuations and climatic development during the late Holocene. In the pollen record there is a transition from a warm and dry forest-like landscape to a cooler, more humid, open landscape during the last 5000 years, with a marked shift from a warm and dry to a cool and humid climate around 2500 years ago. Human activities are reflected by a distinct peak in the Compositae-pollen curve in the uppermost sequence of the sediment core that is indicative of the settlement period during the years AD 870-930. The climatic transition, which contributed to a reduction of the birch population, started before human settlement and the Landnám period (AD 870-930) and thus implies that humans were not solely responsible for the birch decline and the transition of the landscape from forest-like conditions to a more open environment, although the subsequent Viking Age and later settlements continued the afforestation trend.

  • 276.
    Hellqvist, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Lundqvist, Jennie
    Hedmark, Mia
    Developing Earth Science education research2014In: 31st Nordic Geological Winter Meeting. Lund, Sweden, January 8-10 2014. Scientific program: Outreach and Education: Reaching out with WOW to the many, Lund: Geologiska Föreningen , 2014, p. 167-167Conference paper (Refereed)
    Abstract [en]

    This paper presents an attempt to build up research within the field earth science education, presenting results from interview studies on the student’s experience of participation to Earth science (1st year earth science students), inventory on previous research, interviews of primary school pupils and a public survey of knowledge in earth science. In Sweden, there is almost no research on Earth science education, the field within science education concerning Earth Science. In both European and international perspective this is in opposite to Physics, Computer science, Chemistry and Biology. Also in an international perspective the published research on Earth science education is very low, with one exceptional exception in North America where there is a lot of research in science education of different subjects. The largest number of publications is, therefore, also published in North America. The subjects of highest interest in previous earth science education research are on questions about misconceptions, concept inventories and field related education, where virtual field studies is of special interest.

    In the attempt to build up research, focus is primarily on education and teaching in university studies, but pre-university studies (primary & secondary school; upper secondary school) and the public knowledge on Earth science are also of interest. The studies focus on: experience of participation (i.e. identity); managing difficult and/or advanced questions; misconceptions; education in particular fields, especially field studies and laboratory work. Methodological the research is mainly performed through quantitative and qualitative data analysis, case study research and phenomenographic approaches.

  • 277.
    Henderiks, Jorijntje
    Stockholm University.
    Coccolithophore size rules — Reconstructing ancient cell geometry and cellular calcite quota from fossil coccoliths2008In: Marine Micropaleontology, ISSN 0377-8398, E-ISSN 1872-6186, Vol. 67, no 1-2, p. 143-154Article in journal (Refereed)
  • 278.
    Henderiks, Jorijntje
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Size of marine phytoplankton: Why does it matter?2011Conference paper (Other academic)
    Abstract [en]

    Marine phytoplankton, such as diatoms and coccolithophores, constitute the base of the marine food chain and are a fundamental component in biogeochemical cycles. The overall ecological success of marine phytoplankton, but also its taxonomic diversity and size distribution, determines the efficiency by which fixed carbon is transferred to higher trophic levels and into the deep ocean- and sedimentary carbon reservoirs. In recent years, several hypotheses have been invoked to explain distinct macroevolutionary decreases in the cell size of phytoplankton during the Cenozoic. Global, long-term cooling has been cast a major role in driving these cell size decreases. Despite overall correspondence between long-term trends, however, it's becoming more and more clear that not all phytoplankton dance to the same tune. The latter is particularly evident when looking at different coccolithophore lineages. Here, I will review the state-of-the-art and highlight some open avenues that are worth exploring.

  • 279.
    Henderiks, Jorijntje
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Hannisdal, Bjarte
    Centre for Geobiology, Dept. of Earth Sciences, University of Bergen, N.
    Liow, Lee Hsiang
    CEES, Dept. of Biology, University of Oslo, N.
    Calcifying phytoplankton biomass and CO2: A striking balance2010Conference paper (Other academic)
  • 280.
    Henderiks, Jorijntje
    et al.
    Stockholm University.
    Pagani, Mark
    Coccolithophore cell size and the Paleogene decline in atmospheric CO22008In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 269, no 3-4, p. 576-584Article in journal (Refereed)
  • 281.
    Henderiks, Jorijntje
    et al.
    Stockholm University.
    Pagani, Mark
    Refining ancient carbon dioxide estimates: Significance of coccolithophore cell size for alkenone-based pCO2 records2007In: Paleoceanography, ISSN 0883-8305, E-ISSN 1944-9186, Vol. 22, no 3, p. PA3202-Article in journal (Refereed)
  • 282.
    Henderiks, Jorijntje
    et al.
    Stockholm University.
    Rickaby, Rosalind E. M.
    Dept. of Earth Sciences, Oxford University, UK.
    A coccolithophore concept for constraining the Cenozoic carbon cycle2007In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 4, no 3, p. 323-329Article in journal (Refereed)
  • 283.
    Herbert, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Seasonal variations in the composition of mine drainage-contaminated groundwater in Dalarna, Sweden2006In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 90, no 3, p. 197-214Article in journal (Refereed)
    Abstract [en]

    Groundwater down-gradient from a mine rock dump in Dalarna, Sweden was sampled from the onset of snowmelt runoff (April) until October in order to investigate seasonal variations in groundwater composition. The results demonstrate that considerable variation in solute concentration (Al, Cu, Fe, SO42-, Zn) and acidity occurs in groundwater; the greatest change in solute concentrations occurs during the melting of the snow cover, when sulfide oxidation products are flushed from the rock dump. During this period, groundwater flow is concentrated near the soil surface with an estimated velocity of 1 m/day. Groundwater acidity varied by a factor of four closest to the rock dump during the sampling period, but these variations were attenuated with distance from the rock dump. Over a distance of 145 in, groundwater pH increases from 2.5 to 4.0 and acidity decreases from 3-13 to 0.8-1.1 meq/L, which is the combined effect of ferric iron precipitation and aluminosilicate weathering. As a result of flushing from the upper soil horizons, peaks in total organic carbon and ammonium concentrations in groundwater are observed at the end of snowmelt. In soils impacted by acidic surface runoff, the sequential extraction of C horizon soils indicates the accumulation of Cu in well-crystallized iron oxyhydroxides in the upper C horizon, while Cu, Fe, Ni and Zn accumulate in a well-crystallized iron oxyhydroxide hardpan that has formed 2.5m below the ground surface. Surface complexation modeling demonstrates that SO42- and Cu adsorb to the abundant iron oxyhydroxides at pH < 4, while Zn adsorption in this pH range is minimal.

  • 284.
    Holmgren, Bror
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Soil organic carbon pools of the Torneträsk catchment area: The importance of soil depth and stone and boulder content for carbon inventories in formerly glaciated subarctic soils2013Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    High latitude soils are estimated to store a considerable part of the global pool of soil organic carbon (SOC). Studies of global and regional SOC pools have estimated total inventories in northern Sweden’s subarctic region to fall within 10-50 kg m-2. However, correction factors for stone and boulder content of soils are often overlooked in SOC-studies and soil profiles are commonly normalized to a depth of 1 m, which can result in substantial overestimates of the SOC pool if a large part of the soil volume is occupied by stones/boulders or if the soil depth is shallower than 1 m. This study was performed to quantify SOC in soils of the Torneträsk catchment area using detailed measures of soil depth and stone/boulder contents. Two non-destructive sampling methods, ground penetrating radar (GPR) and rod penetration, were used to measure soil depth and stone and boulder content in the catchment area. Results show that average soil depth (n = 52344) varied between 0.95 – 2.14 m depending on elevation and the average mire depth was 0.63 m. Stone and boulder content of the soil was estimated to 49 – 68 % depending on elevation. The results were added to existing carbon and soil density data from the Torneträsk catchment area and total SOC inventories were calculated to 6.8 – 13.1 kg m-2. The results of this study indicate that previous studies on regional and global scale may have overestimated the SOC pools in the subarctic regions of northern Sweden.

  • 285.
    Holmgren, Bror
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Tracing the source of colourless carbon in an arctic lake on SW Greenland: Insights of organic matter origin from hydrogen isotope analyses of samples prepared using steam equilibration2016Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Lakes play an important role in the global carbon (C) cycle as they process carbon from terrestrial (allochthonous) and within lake (autochthonous) sources and may store C over long periods of time. Some arctic lakes contain high concentrations of dissolved organic carbon (DOC) that does not absorb light and thus remains colourless. The origin of this DOC remains unknown, but the sediment of these lakes have been suggested to accumulate primarily autochthonous (algal) C. I developed an experimental chamber for hydrogen (H) isotope pre-treatments and applied a novel H isotope tracing approach to determine the origin of the DOC and sediment C of a lake on SW Greenland known to contain colourless DOC. I hypothesized that autochthonous C was the prime source of DOC and sediment C, in line with previous theories. Analyses of algae and soil samples from the catchment revealed that local allochthonous and autochthonous C sources had a δ2H composition of -139 ‰ and -209 ‰, respectively. In contrast to my hypothesis, the analysed DOC had a mean δ2H isotopic composition of -147 ‰ indicating a dominance (ca 80-90 %) of allochthonous C. Similarly, the sediment had a mean δ2H isotopic composition of -155 ‰, suggesting that about 84 % of the C accumulating in the sediment was derived from terrestrial sources. The terrestrial origin was supported by field observations of high DOC seepage water (up to 70 mg L-1) with uncharacteristically low light absorption values entering the lake during high precipitation events. My results indicate that terrestrial processes are fundamental C sources for arctic lakes, even in regions with very low precipitation.

  • 286.
    Horemuz, Milan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Geodesy (closed 20110301).
    Gajdamiwicz, Krzysztof
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Geodesy (closed 20110301).
    Integration of digital camera with INS2005Conference paper (Refereed)
  • 287.
    Hossain, Mohammed
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Sustainable Arsenic Mitigation A Strategy for Scaling-up Safe Water Access: A Strategy for Scaling-up Safe Water Access2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In rural Bangladesh, the drinking water supply is mostly dependent upon manually operated hand pumped tubewells, installed by the local community. The presence of natural arsenic (As) in groundwater and its wide scale occurrence has drastically reduced the safe water access across the country and put tens of millions of people under health risk. Despite significant progress in understanding the source and distribution of As and its mobilization through sediment-water interactions, there has been limited success in mitigation since the problem was discovered in the country’s water supply in 1993. This study evaluated the viability of other kinds of alternative safe drinking water options and found tubewells are the most suitable due to simplicity and technical suitability, a wide acceptance by society and above all low cost for installation, operation and maintenance. During planning and decision making in the process of tubewell installation, depth of the tubewell is a key parameter as it is related to groundwater quality and cost of installation. The shallow wells (usually < 80m) are mostly at risk of As contamination. One mitigation option are deep wells drilled countrywide to depths of around 250 m. Compared to safe water demand, the number of deep wells is still very low, as the installation cost is beyond affordability of the local community, especially for the poor and disadvantaged section of the society. Using depth-specific piezometers (n=82) installed in 15 locations spread over the 410 km2 area of Matlab (an As-hot spot) in southeastern Bangladesh, groundwater monitoring was done over a 3 year period (pre- and post-monsoon for 2009-2011 period). Measurements were performed for hydrogeological characterization of shallow, intermediate deep and deep aquifer systems to determine the possibility of targeting safe aquifers at different depths as the source of a sustainable drinking water supply. In all monitoring piezometers, As was found consistently within a narrow band of oscillation probably due to seasonal effects. Hydrogeochemically, high-As shallow groundwaters derived from black sands are associated with elevated DOC, HCO3, Fe, NH4-N and PO4-P and with a relatively low concentration of Mn and SO4. Opposite to this, shallow aquifers composed of red and off-white sediments providing As-safe groundwater are associated with low DOC, HCO3, Fe, NH4-N and PO4-P and relatively higher Mn and SO4. Groundwaters sampled from intermediate deep and deep piezometers which were found to be low in As, are characterized by much lower DOC, HCO3, NH4-N and PO4-P compared to the shallow aquifers. Shallow groundwaters are mostly Ca-Mg-HCO3 type and intermediate deep and deep aquifers’ groundwaters are mostly Na-Ca-Mg-Cl-HCO3 to Na-Cl-HCO3 type.

    A sediment color tool was also developed on the basis of local driller’s color perception of sediments (Black, White, Off-white and Red), As concentration of tubewell waters and respective color of aquifer sediments. A total of 2240 sediment samples were collected at intervals of 1.5 m up to a depth of 100 m from all 15 nest locations. All samples were assigned with a Munsell color and code, which eventually led to identify 60 color varieties. The process continued in order to narrow the color choices to four as perceived and used by the local drillers for identification of the targeted As-safe aquifers. Munsell color codes assigned to these sediments render them distinctive from each other which reduces the risk for misinterpretation of the sediment colors. During the process of color grouping, a participatory approach was considered taking the opinions of local drillers, technicians, and geologists into account. In addition to the monitoring wells installed in the piezometer nests, results from 87 other existing drinking water supply tubewells were also considered for this study. A total of 39 wells installed in red sands at shallow depths producing As-safe water providing strong evidence that red sediments are associated with As-safe water. Average and median values were found to be less than the WHO guideline value of 10 μg/L. Observations for off-white sediments were also quite similar. Targeting off-white sands could be limited due to uncertainty of proper identification of color, specifically when day-light is a factor. Elevated Mn in red and off-white sands is a concern in the safe water issue and emphasizes the necessity of a better understanding of the health impact of Mn. White sediments in shallow aquifers are relatively uncommon and seemed to be less important for well installations. Arsenic concentrations in more than 90% of the shallow wells installed in black sands are high with an average of 239 μg/L from 66 wells installed in black sediments. It is thereby recommended that black sands in shallow aquifers must be avoided. This sediment color tool shows the potential for enhancing the ability of local tubewell drillers for the installation of As-safe shallow drinking water tubewells.

    Considering the long-term goal of the drinking water safety plan to provide As-safe and low-Mn drinking water supply, this study also pioneered hydrogeological exploration of the intermediate deep aquifer (IDA) through drilling up to a depth of 120 m. Clusters of tubewells installed through site optimization around the monitoring piezometer showed a similar hydrochemical buffer and proved IDA as a potential source for As-safe and low-Mn groundwater. Bangladesh drinking water standard for As (50 µg/L) was exceeded in only 3 wells (1%) and 240 wells (99%) were found to be safe. More than 91% (n=222) of the wells were found to comply with the WHO guideline value of 10 µg/L. For Mn, 89% (n=217) of the wells show the concentration within or below the previous WHO guideline value of 0.4 mg/L, with a mean and median value of 0.18 and 0.07 mg/L respectively. The aquifer explored in the Matlab area shows a clear pattern of low As and low Mn. The availability of similar sand aquifers elsewhere at this depth range could be a new horizon for tapping safe drinking water at about half the cost of deep tubewell installation.

    All findings made this study a comprehensive approach and strategy for replication towards As mitigation and scaling-up safe water access in other areas of Bangladesh and elsewhere having a similar hydrogeological environment.

  • 288.
    Hotchkiss, E. R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hall, R. O., Jr.
    Sponseller, R. A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Butman, D.
    Klaminder, J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Laudon, H.
    Rosvall, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Karlsson, J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Sources of and processes controlling CO2 emissions change with the size of streams and rivers2015In: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 8, no 9, p. 696-699Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide (CO2) evasion from streams and rivers to the atmosphere represents a substantial flux in the global carbon cycle(1-3). The proportions of CO2 emitted from streams and rivers that come from terrestrially derived CO2 or from CO2 produced within freshwater ecosystems through aquatic metabolism are not well quantified. Here we estimated CO2 emissions from running waters in the contiguous United States, based on freshwater chemical and physical characteristics and modelled gas transfer velocities at 1463 United States Geological Survey monitoring sites. We then assessed CO2 production from aquatic metabolism, compiled from previously published measurements of net ecosystem production from 187 streams and rivers across the contiguous United States. We find that CO2 produced by aquatic metabolism contributes about 28% of CO2 evasion from streams and rivers with flows between 0.0001 and 19,000 m(3) s(-1). We mathematically modelled CO2 flux from groundwater into running waters along a stream-river continuum to evaluate the relationship between stream size and CO2 source. Terrestrially derived CO2 dominates emissions from small streams, and the percentage of CO2 emissions from aquatic metabolism increases with stream size. We suggest that the relative role of rivers as conduits for terrestrial CO2 efflux and as reactors mineralizing terrestrial organic carbon is a function of their size and connectivity with landscapes.

  • 289.
    Hotchkiss, Erin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Program in Ecology and Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA.
    Hall, R. O., Jr.
    Baker, M. A.
    Rosi-Marshall, E. J.
    Tank, J. L.
    Modeling priming effects on microbial consumption of dissolved organic carbon in rivers2014In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 119, no 5, p. 982-995Article in journal (Refereed)
    Abstract [en]

    Rivers receive and process large quantities of terrestrial dissolved organic carbon (DOC). Biologically available (unstable) DOC leached from primary producers may stimulate (i.e., prime) the consumption of more stable terrestrially derived DOC by heterotrophic microbes. We measured microbial DOC consumption (i.e., decay rates) from contrasting C sources in 10 rivers in the western and Midwestern United States using short-term bioassays of river water, soil and algal leachates, glucose, and commercial humate. We added inorganic nutrients (ammonium and phosphorus) to a subset of bioassays. We also amended a subset of river, soil, and commercial humate bioassays with glucose or algal leachates to test the hypothesis that unstable DOC primes consumption of more stable DOC. We used prior measurements of source-specific DOC bioavailability, linked with a Bayesian process model, to estimate means and posterior probability distributions for source-specific DOC decay rates in multisource bioassays. Modeled priming effects ranged from a -130 to +370% change in more stable DOC decay when incubated with unstable DOC. Glucose increased modeled river DOC decay by an average of 87% among all rivers. Glucose and algal leachates increased soil leachate and commercial humate decay by an average of 25% above background rates. Inorganic nutrient additions did not have consistent effects on DOC decay, likely because most of the study rivers had high ambient background nutrients. Our results demonstrate that the priming effect can augment DOC decay in rivers. In addition, Bayesian models can be used to estimate mechanisms driving aquatic ecosystem processes that are difficult to measure directly.

  • 290. Huayu, Lu
    et al.
    Stevens, Thomas
    Centre for the Environment, University of Oxford, UK .
    Shuangwen, Yi
    Xuefeng, Sun
    An erosional hiatus in Chinese loess sequences revealed by closely spaced optical dating2006In: Chinese Science Bulletin, ISSN 1001-6538, E-ISSN 1861-9541, Vol. 51, no 18, p. 2253-2259Article in journal (Refereed)
  • 291.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Virtanen, Tarmo
    University of Helsinki.
    Kaverin, Dmitry
    Komi Science Centre.
    Pastukhov, Alexander
    Komi Science Centre.
    Rivkin, Felix
    Institute FSUE Fundamentprojekt.
    Marchenko, Sergey
    University of Alaska Fairbanks.
    Romanovsky, Vladimir
    University of Alaska Fairbanks.
    High‐resolution mapping of ecosystem carbon storageand potential effects of permafrost thaw in periglacialterrain, European Russian Arctic2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116Article in journal (Refereed)
    Abstract [en]

    This study describes detailed partitioning of phytomass carbon (C) and soil organiccarbon (SOC) for four study areas in discontinuous permafrost terrain, Northeast EuropeanRussia. The mean aboveground phytomass C storage is 0.7 kg C m−2. Estimated landscapeSOC storage in the four areas varies between 34.5 and 47.0 kg C m−2 with LCC (landcover classification) upscaling and 32.5–49.0 kg C m−2 with soil map upscaling. A nestedupscaling approach using a Landsat thematic mapper land cover classification for thesurrounding region provides estimates within 5 ± 5% of the local high‐resolutionestimates. Permafrost peat plateaus hold the majority of total and frozen SOC, especially inthe more southern study areas. Burying of SOC through cryoturbation of O‐ or A‐horizonscontributes between 1% and 16% (mean 5%) of total landscape SOC. The effect ofactive layer deepening and thermokarst expansion on SOC remobilization is modeled forone of the four areas. The active layer thickness dynamics from 1980 to 2099 is modeledusing a transient spatially distributed permafrost model and lateral expansion of peatplateau thermokarst lakes is simulated using geographic information system analyses.Active layer deepening is expected to increase the proportion of SOC affected by seasonalthawing from 29% to 58%. A lateral expansion of 30 m would increase the amount ofSOC stored in thermokarst lakes/fens from 2% to 22% of all SOC. By the end of thiscentury, active layer deepening will likely affect more SOC than thermokarst expansion,but the SOC stores vulnerable to thermokarst are less decomposed.

  • 292. Hunt, Allen G.
    et al.
    Stefano, Manzoni
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Networks on Networks: The physics of geobiology and geochemistry2015Book (Other academic)
    Abstract [en]

    This book presents research into the physical rules that can underlie the behaviour of biota, as well as the geochemistry of soil development. It addresses both nutrient and water transport limitations of processes from chemical weathering to vascular plant growth. It attempts to bring order to the question of the extent to which soils can facilitate plant growth, and what limitations on plant sizes, metabolism, occurrence and correlations can be formulated thereby.

  • 293. Hwang, K. -J
    et al.
    Sibeck, D. G.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Choi, E.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.;Univ Space Res Assoc, Ctr Res & Explorat Space Sci & Technol, Greenbelt, MD USA..
    Chen, L. -J
    Ergun, R. E.
    Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA..
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Giles, B. L.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Pollock, C. J.
    Denali Sci LLC, Healy, AK USA..
    Gershman, D.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dorelli, J. C.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Avanov, L.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Paterson, W. R.
    NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA USA..
    Strangeway, R. J.
    Torbert, R. B.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Magnetospheric Multiscale mission observations of the outer electron diffusion region2017In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 5, p. 2049-2059Article in journal (Refereed)
    Abstract [en]

    This paper presents Magnetospheric Multiscale mission (MMS) observations of the exhaust region in the vicinity of the central reconnection site in Earth's magnetopause current sheet. High-time-resolution measurements of field and particle distributions enable us to explore the fine structure of the diffusion region near the X line. Ions are decoupled from the magnetic field throughout the entire current sheet crossing. Electron jets flow downstream from the X line at speeds greater than the ExB drift velocity. At/around the magnetospheric separatrix, large-amplitude electric fields containing field-aligned components accelerate electrons along the magnetic field toward the X line. Near the neutral sheet, crescent-shaped electron distributions appear coincident with (1) an out-of-plane electric field whose polarity is opposite to that of the reconnection electric field and (2) the energy transfer from bulk kinetic to field energy. The observations indicate that MMS passed through the edge of an elongated electron diffusion region (EDR) or the outer EDR in the exhaust region.

  • 294.
    Hylander, Lars D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Lindvall, Anders
    Foundation for Metal Biology, Öfre Slottsgatan 16A, S-753 12 Uppsala, Sweden.
    Gahnberg, Lars
    Public Dental Health Service, County of Uppsala, Ulleråkersvägen 21, S-750 17 Uppsala, Sweden.
    High mercury emissions from dental clinics despite amalgam separators2006In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 362, no 1-3, p. 74-84Article in journal (Refereed)
    Abstract [en]

    Mercury (Hg) as amalgam has been used as a dental filling material for more than 150 years. Thereby, dentists and their patients have been directly exposed to Hg, and the public and the environment indirectly exposed via Hg emissions from incinerators and Hg in waste water from households and dental clinics. Due to the toxic properties of Hg and bioaccumulation in biota of Hg emitted via dental clinic waste water, amalgam separators were introduced in Sweden in the 1980s. Although these amalgam separators in the certification process are required to remove at least 95% of incoming Hg in a standardized laboratory test, their efficiency in practical use has not been properly investigated. Here we present actual Hg emissions via waste water from 12 dental clinics equipped with the same type of amalgam separator based on sedimentation. All waste water was collected for four consecutive working days, initially at ordinary operating conditions and a second time after a thorough revision and cleaning of the discharge system. The results indicate that mercury emissions from dental clinics can be reduced by an improved design of the discharge system, a sensible use of high pressure water cleaning, and regular maintenance, including replacement of amalgam separators and filters at certain intervals. The study also indicates that banning Hg in dentistry is the one long-term way to stop Hg emissions from dental amalgam.

  • 295.
    Håkanson, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Andersson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Uppsala Centre for Sustainable Development, CSD Uppsala, The Baltic University Programme.
    Rydén, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Uppsala Centre for Sustainable Development, CSD Uppsala, The Baltic University Programme.
    4. The Baltic Sea Basin: Nature, History, and Economy2003In: Environmental Science: Understanding, protecting and managing the environment in the Baltic Sea Region / [ed] Lars Rydén, Pawel Migula and Magnus Andersson, Uppsala: Baltic University Press , 2003, 1, p. 92-119Chapter in book (Other (popular science, discussion, etc.))
  • 296. Höglund, Lars Olof
    et al.
    Herbert Jr., Roger
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Air and Water Science. Luft- och vattenlära.
    MiMi – Performance Assessment main report: Report from the MISTRA research program Mitigation of the environmental impact from mining waste (MiMi)2004Book (Other scientific)
  • 297.
    Höök, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Global Energy Systems.
    Depletion rate analysis of fields and regions: a methodological foundation2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 121, no 4, p. 95-108Article in journal (Refereed)
    Abstract [en]

    This paper presents a comprehensive mathematical framework for depletion rate analysis and ties it to the physics of depletion. Theory was compared with empirical data from 1036 fields and a number of regions. Strong agreement between theory and practice was found, indicating that the framework is plausible. Both single fields and entire regions exhibit similar depletion rate patterns, showing the generality of the approach. The maximum depletion rates for fields were found to be well described by a Weibull distribution.

    Depletion rates were also found to strongly correlate with decline rates. In particular, the depletion rate at peak was shown to be useful for predicting the future decline rate. Studies of regions indicate that a depletion rate of remaining recoverable resources in the range of 2–3% is consistent with historical experience. This agrees well with earlier “peak oil” forecasts and indicates that they rest on a solid scientific ground. 

  • 298.
    Höök, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Global Energy Systems.
    Future coal production outlooks in the IPCC Emission Scenarios: Are they plausible?2011In: Energy and Environment, ISSN 0958-305X, E-ISSN 2048-4070, Vol. 22, no 7, p. 837-858Article in journal (Refereed)
    Abstract [en]

    Anthropogenic climate change caused by CO2 emissions is strongly linked to the future energy production, specifically coal. The Special Report on Emission Scenarios (SRES) contains 40 scenarios for future fossil fuel production and is used by the IPCC to assess future climate change. This study examines the SRES coal production outlooks. Fundamental assumptions regarding coal availability and production in SRES was also compared with recent studies on reasonable future production outlooks. It was found that SRES puts unreasonable expectation on just a few countries. Is it reasonable to expect that China, already accounting for 46% of the global output, would increase their production by a factor of 8 over the next 90 years, as implied by certain SRES scenarios? It is concluded that SRES is underpinned by a paradigm of perpetual growth and technological optimism as well as old and outdated resource estimates. This has resulted in overoptimistic production outlooks.

  • 299.
    Höök, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Natural Resources and Sustainable Development.
    Mapping Chinese Supply2018In: Nature Energy, ISSN 0028-212X, E-ISSN 2213-0217, Vol. 3, no 3, p. 166-167Article in journal (Other academic)
    Abstract [en]

    Documenting the emissions and net energy of a crude supply could be essential to meeting national emission and energy security targets. Using data from hundreds of fields worldwide, a well-to-refinery study presents a high-granularity profile of China’s crude oil supply in terms of emissions and energy return on input.

    The full text will be freely available from 2018-08-27 08:56
  • 300.
    Höök, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Global Energy Systems.
    Dean, Fantazzini
    Moscow State University.
    André, Angelantoni
    Post Peak Living.
    Simon, Snowden
    University of Liverpool.
    Coal-to-Liquids: viability as a peak oil mitigation strategy2012In: Twenty Ninth Annual International Pittsburgh Coal Conference, 2012Conference paper (Refereed)
    Abstract [en]

    Converting coal to a liquid, commonly known as coal-to-liquids (CTL), can supply liquid fuels and has been successfully used in several countries, particularly in South Africa. However, it has not become a major contributor to the global oil supply. Increasing awareness of the scarcity of oil and rising oil prices has increased the interest in coal liquefaction. This paper surveys CTL technology, economics and environmental performance. Understanding the fundamental aspects of coal liquefaction technologies is vital for planning and policy-making since future CTL production will be integrated in a much larger global energy and liquid fuel production system.

    The economic analysis shows that many CTL studies assume conditions that are optimistic at best. In addition, the strong risk for a CTL plant to become a financial black hole is highlighted. This helps to explain why China has recently slowed down the development of its CTL program.

    The technical analysis investigates the coal consumption of CTL. Generally, a yield of between 1–2 barrels/ton coal can be achieved while the technical limit seems to be 3 barrels/ton coal. This puts a strict limit on future CTL capacity imposed by future coal production, regardless of other factors such as economic viability, emissions or environmental concern. For example, assuming that 10% of world coal production can be diverted to CTL, the contribution to the liquid fuel supply will be limited to only a few million barrels per day (Mb/d). This prevents CTL from becoming a viable mitigation plan for liquid fuel shortage on a global scale.

    However, it is still possible for individual nations to derive a significant share of their fuel supply from CTL but those nations must also have access to equally significant coal production capacity. It is unrealistic to claim that CTL provides a feasible solution to liquid fuels shortages created by peak oil. At best, it can be only a minor contributor and must be combined with other strategies to ensure future liquid fuel supply.

3456789 251 - 300 of 742
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf