Sökning: "rivers"

Visar resultat 41 - 45 av 208 avhandlingar innehållade ordet rivers.

1. 41. Impact of hydropower regulation on river water geochemistry and hyporheic exchange

   Författare :Dmytro Siergieiev; Hjalmar Laudon; Luleå tekniska universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; regulated river; hyporheic zone; hydraulic conductivity; clogging layer; Applied Geology; Tillämpad geologi;

   Sammanfattning : Hydropower regulation of rivers exhibits a threat to the riverine ecosystems. Fragmentation of flow, landscape disturbances, and water retention are key features of regulated catchments, resulting in reduced floods and geochemical tr¬ansport, non-natural water level fluctuations, and thus disturbed exchange between the river and the aquifer. LÄS MER

3. 42. Distribution, Sources and Environmental Pathways of Radioactive 129I in Fresh and Saline Water in the Baltic Region

   Författare :Abdulaziz Kekli; Ala Aldahan; Xiaolin Hou; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Earth sciences; 129I; iodine; environment; precipitation; river; Baltic Sea; radioactivity; Geovetenskap; Earth sciences; Geovetenskap;

   Sammanfattning : This thesis deals with distribution, sources and pathways of radioactive 129I (T1/2=15.6 My) in 54 rivers covering the Baltic region, precipitation (rain and snow) from southern, central and northern Sweden, and saline water from three depth profiles in the Baltic Sea and a surface water transect from the Baltic to the Kattegat. LÄS MER

4. 43. Utilization of terrestrially derived dissolved organic nitrogen by aquatic bacteria

   Författare :Ramunas Stepanauskas; Biologiska institutionen; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; amino acids; spring flood; UV radiation; estuarine mixing; microbial loop; bacterial bioassays; marine eutrophication; bioavailability; Dissolved organic nitrogen; DON; extracellular aminopeptidase; Baltic Sea; Hydrobiology; marine biology; aquatic ecology; limnology; Marinbiologi; limnologi; akvatisk ekologi;

   Sammanfattning : I investigated the bacterial utilization of terrestrially derived dissolved organic nitrogen (DON) in aquatic ecosystems, and assessed the potential role of river-born DON in marine eutrophication. To determine the bioavailability of DON, I developed a bioassay employing N-limited bacterial regrowth cultures, which were calibrated with additions of inorganic nitrogen. LÄS MER

5. 44. Properties of humic substances from groundwater and surface waters

   Författare :Catharina Pettersson; Linköpings universitet; []
   Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; INTERDISCIPLINARY RESEARCH AREAS; TVÄRVETENSKAPLIGA FORSKNINGSOMRÅDEN;

   Sammanfattning : Humic substances play an important role in the environment. The aim of this thesis is to enhance the understanding of the behaviour of humic substances in natural waters and their importance for mobilizatiou/immobilization, redistribution, bioavailability and removal of metals and organic pollutants from aqueous systems. LÄS MER

7. 45. Attraction channel as entrance to fishways

   Författare :Elianne Wassvik; Luleå tekniska universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Strömningslära; Fluid Mechanics;

   Sammanfattning : The utilization of rivers for hydropower production leads to problems for fish migration. Migratory fish that swim upstream for reproduction need to overcome obstructions to reach their spawning grounds. On their way upstream they follow high water velocities. LÄS MER