Browsing by Subject "happi"

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  • Heiskanen, Juha; Laitinen, Jukka (Suomen metsätieteellinen seura, 1992)
  • Kylä-Harakka, Tellervo (Vesihallitus. National Board of Waters, 1979)
    Vesientutkimuslaitoksen julkaisuja 34, 52-59
    Streeter-Phelps-mallin soveltaminen Äänekosken vesireitille.
  • Laaksonen, Reino; Malin, Väinö (Vesihallitus. National Board of Waters, 1982)
    Vesientutkimuslaitoksen julkaisuja 49, 54-57
    Suomen järvien kriittisistä happipitoisuuksista
  • Lehtoranta, Jouni; Bendtsen, Jørgen; Lännergren, Christer; Saarijärvi, Erkki; Lindström, Magnus; Pitkänen, Heikki (Elsevier BV, 2022)
    Ecological Engineering
    We studied the effects of pumping surface water down through the pycnocline (i.e. artificial ventilation) on hydrodynamics, oxygen concentrations, hydrogen sulfide, and nutrients in two anoxic coastal basins (Lännerstasundet and Sandöfjärden). In addition, in a corresponding laboratory aquarium experiment, pumping of less saline surface water entrained dense bottom water with a mixing ratio of 6.8 and illustrated dispersal below the pycnocline. Oxygen saturation increased from 0 to 20%; oxygen penetrated poorly into the sediment of the aquarium. In the salinity-stratified Lännerstasundet basin, ventilation also oxidized the anoxic bottom water. The ventilation removed hydrogen sulfide and decreased the sub-pycnocline water pools of phosphorus and ammonium, which was not observed in a neighboring reference basin. The summertime ventilation warmed and made the sub-pycnocline water less saline. In the autumn, the inflows of cooled water from the surroundings with equal or higher salinity promoted its sinking in the relatively warm ventilated basin. The inflows maintained oxygen concentrations between 4 and 8 mg L−1 for months after the ventilation ended. In contrast to Lännerstasundet, ventilation did not prevent formation of anoxia and release of nutrients in the temperature-stratified Sandöfjärden. Here, the ventilation capacity was less than that in Lännerstasundet and ventilation expanded the sub-thermocline bottom area, warmed the bottom sediments, and probably displaced oxic water from the experimental area. The ventilation did not promote density conditions for inflows and no marked inflow-induced oxidation was observed after midsummer. We conclude that a significant amount of anoxic water was entrained into the ascending plume which reduced the oxygen content below the pycnocline ventilation in aquarium experiment. Additionally, summertime ventilation may improve the status of the salinity-stratified basins for further oxidation. The improvement occurs due to autumn cooling and favorable basin topography, which promote inflows of oxic water with larger density and thereby, renewal of bottom water in the pumped basin. The semi-enclosed and temperature-stratified basin cannot form such favorable density conditions for inflows and thus ventilation is less efficient.
  • Suutari, Sonja (Helsingin yliopisto, 2019)
    Propionibacterium freudenreichii is a common bacterium used in food industry. Despite of its wide use it has not been extensively studied yet. P. freudenreichii is usually considered as an anaerobe although it carries all the genes required for aerobic respiration in its genome. In my study, I examined the effect of oxygen on cell physiology and metabolism of P. freudenreichii. Cells were grown in bioreactors under anaerobic and microaerobic conditions as well as using a two-step cultivation with first an anaerobic and then a microaerobic phase. The partial pressure of oxygen was 0 kPa in anaerobic conditions and 4 kPa in microaerobic conditions. The growth rates and amount of ATP were studied, the metabolic activity of the cells was analysed, production of acetic, pyruvic, lactic and propionic acid was examined and finally I studied the expression of the atpA and recA genes. According to the results, P. freudenreichii grows with about two times shorter generation time in microaerobic conditions than in anaerobic conditions. The cells were metabolically most active in exponential phase when conditions were microaerobic. The amount of ATP was found to be rather static under the conditions used. Propionic acid was produced in anaerobic conditions but when conditions switched to microaerobic, its concentration diminished. Pyruvic acid was found to accumulate in microaerobic conditions. The atpA gene was expressed more efficiently in microaerobic conditions than in anaerobic conditions. P. freudenreichii probably utilizes reversible Wood-Werkman -fermentation route to produce ATP by oxidative phosphorylation when oxygen serves as an electron acceptor. Substrate-level phosphorylation did not increase in microaerobic conditions. The growth rate of P. freudenreichii and the final cell densities it reaches can be increased by cultivation in microaerobic conditions instead of anaerobic conditions.
  • Kerminen, Sakari; Halmekoski, Matti (Valtion painatuskeskus, 1967)
    Valtakunnansuunnittelutoimiston julkaisusarja B ; 10
  • Kettunen, Ilpo (Vesihallitus. National Board of Waters, 1979)
    Vesientutkimuslaitoksen julkaisuja 34, 47-51
    Veden laadun horisontaaliset erot jätevesien pilaamalla vesialueella Saimaalla.
  • Arppe, Laura (University of Helsinki, 2009)
    Publications of the Department of Geology. D.
  • Kylä-Harakka, Tellervo (Vesihallitus, 1979)
    Vesihallitus. Tiedotus 169
  • Unknown author (Vesihallitus, 1974)
    Vesihallitus. Tiedotus 59
  • Länsirinne, Tapani (University of Helsinki, 1988)
  • Korhonen, Kaija; Mäkinen, Irma; Näykki, Teemu; Järvinen, Olli; Tervonen, Keijo; Ilmakunnas, Markku (Suomen ympäristökeskus, 2006)
    Suomen ympäristökeskuksen raportteja 17/2006
  • Kämäräinen, Antti (Helsingfors universitet, 2014)
    Street trees are an important part of a comfortable urban environment. Their beneficial effects in the built environment have been documented in a number of ways around the world. In urban environment tree roots are often grown in limited volumes of soil and competing for space with artificial construction materials and technical structures. Low oxygen concentrations in urban soils are considered as one of the major growth limiting factors, particularly under street pavements. The terrestrial growth conditions are difficult to alter in urban environment. By improving below-ground conditions, tree well-being and sustainability can be significantly increased. Increased ensign of growing conditions and the awareness of the value of urban trees have contributed to the creation of landscaping applications such as structural soil. This study compared gas concentrations in the air of structural and conventional soils, used in roadside tree plantings in the City of Helsinki. Soil air samples were collected during growing seasons 2012 and 2013. Proportions of nitrogen, oxygen, carbon dioxide and methane in soil air were determined by a gas chromatograph. CO?-fluxes were used to evaluate the effect of the soil surfacing material to ground ventilation. Structural soil contained more oxygen in all depths compared to conventional tree soil. A strong correlation existed between oxygen and carbon dioxide concentrations. It seems that cobblestone coating with wide seams does not impair the ground ventilation compared to soil covered with cast-iron grate. Atmospheric growth conditions were more favorable in the structural soil; however the oxygen concentrations in conventional soil were also high.
  • Pitkänen, Heikki (Vesihallitus, 1979)
    Vesihallitus. Tiedotus 175
  • Åberg, Gunnar (University of Helsinki, 1960)
  • Laaksonen, Reino (Vesihallitus, 1974)
    Vesientutkimuslaitoksen julkaisuja 9
    Engl. summary: On the factors structure of water quality