Browsing by Subject "sedimentaatio"

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  • Näkki, Pinja; Setälä, Outi; Lehtiniemi, Maiju (2019)
    Marine Pollution Bulletin 119 (1): 255-261
    Microplastics (MPs) are observed to be present on the seafloor ranging from coastal areas to deep seas. Because bioturbation alters the distribution of natural particles on inhabited soft bottoms, a mesocosm experiment with common benthic invertebrates was conducted to study their effect on the distribution of secondary MPs (different-sized pieces of fishing line < 1 mm). During the study period of three weeks, the benthic community increased MP concentration in the depth of 1.7-5.1 cm in the sediment. The experiment revealed a clear vertical gradient in MP distribution with their abundance being highest in the uppermost parts of the sediment and decreasing with depth. The Baltic clam Macoma balthica was the only study animal that ingested MPs. This study highlights the need to further examine the vertical distribution of MPs in natural sediments to reliably assess their abundance on the seafloor as well as their potential impacts on benthic communities.
  • Marttila, H.; Tammela, S.; Mustonen, K.-R.; Louhi, P.; Muotka, Timo; Mykrä, Heikki; Klove, B. (IWA Publishing, 2019)
    Hydrology Research 1 June 2019; 50 (3): 878–885
    We conducted a series of tracer test experiments in 12 outdoor semi-natural flumes to assess the effects of variable flow conditions and sand addition on hyporheic zone conditions in gravel beds, mimicking conditions in headwater streams under sediment pressure. Two tracer methods were applied in each experiment: 2–5 tracer-pulse tests were conducted in all flumes and pulses were monitored at three distances downstream of the flume inlet (0 m, 5 m and 10 m, at bed surface), and in pipes installed into the gravel bed at 5 m and 10 m distances. The tracer breakthrough curves (total of 120 tracer injections) were then analysed with a one-dimensional solute transport model (OTIS) and compared with data from the gravel pipes in point-dilution pulse tests. Sand addition had a strong negative effect on horizontal fluxes (qh), whereas the fraction of the median travel time due to transient storage (F200) was determined more by flow conditions. These results suggest that even small additions of sand can modify the hyporheic zone exchange in gravel beds, thus making headwater streams with low sediment transport capacity particularly vulnerable to sediments transported into the stream from catchment land use activities.
  • Lehtoranta, Jouni (Finnish Environment Institute, 2003)
    Monographs of the Boreal Environment Research 24
    One of the main threats facing the Baltic Sea is eutrophication due to an excess supply of nutrients. In the Gulf of Finland, primary productivity and biomasses of autotrophic and heterotrophic organisms are among the highest in the Baltic. The high biomasses are attributed mainly to the eutrophying effects of the large land-derived nutrient inflow from St. Petersburg and via the River Neva. The role of sediment phosphorus (P) in eutrophication is, however, poorly understood in the Gulf. The aim of this study was to obtain information on the regional levels of sediment P and to specify the pools of P. Efforts were also made to define the sediment retention ability of P along the estuarine gradient, to establish the factors that affect the benthic fl ux of P and to assess whether sulphur (S) is a significant factor in sediment P cycling. On the basis of the results it was possible to quantify and consider the ecological implications of the benthic flux of P.The sediments of the Gulf are rich in organic matter, nitrogen (N) and P. A large portion of the mobile pool of P in these sediments consists of iron (Fe)-bound P, which is released when Fe(III) oxides are reduced under anoxic conditions. The increase in the sediment organic matter concentration along the estuarine gradient seems to impair the sediments’ ability to retain P. The highest benthic P efflux was measured in summer and the lowest in winter. The decrease in the near-bottom oxygen concentration in summer may favour anaerobic sulphate reduction followed by iron sulphide (FeS) formation close to the sediment- water interface. In the sediment, the key role in preventing P from entering the water is played by the binding ability of P related to diffusing Fe. In the brackish Baltic Sea, in contrast to most lake systems, the diffusion of Fe may be inactivated by FeS formation. Thus, high effluxes of P to oxic water were measured on bottoms where black sediment indicating the presence of FeS extended to the surface of the sediment.The P released from the sediments of the Gulf itself may largely explain the high P concentrations and low N:P ratios in near-bottom waters in summer and, after autumn mixing, in the entire water column. However, the input of P from the main Baltic basin may also lead to an increase in P concentrations in the Gulf. The high release rates of P measured – rather than denitrification – largely explain the N limitation of the primary production. A relationship seems to exist between the increase in near-bottom salinity and the weakening of the sediment oxidation state of the Gulf since 1996. The inflow of saline water to the Gulf strengthens density stratification, thus favouring the release of P to water. Therefore, the variations in hydrological factors may produce a marked between-year variation in the benthic P efflux and counteract the reduction in the external P load. The ability of sediment to retain P could most likely be promoted by decreasing the sedimentation of labile organic matter on the bottom. Organic matter sedimentation could be lowered by cutting the amount of bioavailable N and P from an anthropogenic sources.
  • Heiskanen, Anna-Stiina (Finnish Environment Institute, 1998)
    Monographs of the Boreal Environment Research 8
  • Heikkilä, Raimo (Finnish Environment Institute, 1999)
    Monographs of the Boreal Environment Research 15
  • Turunen, Jarno; Marttila, Hannu; Kämäri, Maria; Saari, Markus; Heikkinen, Kaisa; Postila, Heini; Koljonen, Saija (Suomen ympäristökeskus, 2019)
    Suomen ympäristökeskuksen raportteja 46/2019
    Valuma-alueiden eroosio ja vedessä kulkeutuvan kiintoaineen sedimentaatio ovat luonnollisia prosesseja virtavesissä. Ne ylläpitävät virtavesien elinympäristöjen monimuotoisuutta. Ihmistoiminta, erityisesti maankäyttö, on kuitenkin merkittävästi lisännyt eroosiota ja hienon kiintoaineksen määrää virtavesissä, millä on lukuisia haitallisia vaikutuksia virtavesien ekosysteemeihin. Tässä kirjallisuuskatsauksessa kuvataan virtavesien luontaisen sekä ihmistoiminnan muuttaman kiintoaineen eroosion ja sedimentaation merkitystä virtavesissä. Katsauksessa käsitellään liiallisen kiintoainekuormituksen ja sedimentaation vaikutuksia virtavesien perustuotantoon ja vesikasvillisuuteen, pohjaeläimiin, kaloihin sekä mikrobeihin ja hajotusprosesseihin. Lisäksi käsitellään kiintoainekuormituksen ja sedimentaation arvioinnin ja vesienhoidon kannalta keskeisiä seuranta-, vesiensuojelu- ja kunnostusmenetelmiä sekä tutkimustarpeita.
  • Asamoah, Benjamin O.; Salmi, Pauliina; Räty, Jukka; Ryymin, Kalle; Talvitie, Julia; Karjalainen, Anna K.; Kukkonen, Jussi V. K.; Roussey, Matthieu; Peiponen, Kai-Erik (MDPI, 2021)
    Polymers 13: 6
    The abundance of microplastics (MPs) in the atmosphere, on land, and especially in water bodies is well acknowledged. In this study, we establish an optical method based on three different techniques, namely, specular reflection to probe the medium, transmission spectroscopy measurements for the detection and identification, and a speckle pattern for monitoring the sedimentation of MPs filtrated from wastewater sludge and suspended in ethanol. We used first Raman measurements to estimate the presence and types of different MPs in wastewater sludge samples. We also used microscopy to identify the shapes of the main MPs. This allowed us to create a teaching set of samples to be characterized with our optical method. With the developed method, we clearly show that MPs from common plastics, such as polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polyethylene (PE), are present in wastewater sludge and can be identified. Additionally, the results also indicate that the density of the plastics, which influences the sedimentation, is an essential parameter to consider in optical detection of microplastics in complex natural environments. All of the methods are in good agreement, thus validating the optics-based solution.
  • Ojanen, Titta (Vesihallitus. National Board of Waters, 1979)
    Vesientutkimuslaitoksen julkaisuja 34, 74-87
    Tuusulanjärven typpi- ja fosforitase.
  • Kämäri, Maria; Alho, Petteri; Veijalainen, Noora; Aaltonen, Juha; Huokuna, Mikko; Lotsari, Eliisa (2015)
    Hydrological Processes 29(22): 4738–4755
    A large number of rivers are frozen annually and the river ice cover has an influence on the geomorphological processes. These processes in cohesive sediment rivers are not fully understood. Therefore, this paper demonstrates the impact of river ice cover on sediment transport, i.e. turbidity, suspended sediment loads and erosion potential, compared with a river with ice-free flow conditions. The present sediment transportation conditions during the annual cycle are analysed, and the implications of climate change on wintertime geomorphological processes are estimated. A one-dimensional hydrodynamic model has been applied to the Kokemäenjoki River in SW Finland. The shear stress forces directed to the river bed are simulated with present and projected hydro-climatic conditions. The results of shear stress simulations indicate that a thermally formed smooth ice cover diminishes river bed erosion, compared with an ice-free river with similar discharges. Based on long-term field data, the river ice cover reduces turbidity statistically significantly. Furthermore, suspended sediment concentrations measured in ice-free and ice-covered river water reveal a diminishing effect of ice cover on riverine sediment load. The hydrodynamic simulations suggest that the influence of rippled ice cover on shear stress is varying. Climate change is projected to increase the winter discharges by 27–77 % on average by 2070–2099. Thus, the increasing winter discharges and possible diminishing ice cover periods both increase the erosion potential of the river bed. Hence, the wintertime sediment load of the river is expected to become larger in the future.
  • Kankaanpää, Harri (Finnish Institute of Marine Research, 1997)
    Monographs of the Boreal Environment Research 6
  • Taipalinen, Irmeli (Vesihallitus. National Board of Waters, 1980)
    Vesientutkimuslaitoksen julkaisuja 39, 37-45
    Ruoppaustöiden vaikutuksista veden laatuun Kallavedessä