Browsing by Subject "hiekka"

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  • 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.
  • Ryttäri, Terhi; Heiskala, Katri; Kekäläinen, Hannele; Koskela, Kasper; von Numers, Mikael; Rinkineva-Kantola, Leena; Syrjänen, Kimmo (Suomen ympäristökeskus, 2014)
    Ympäristöopas
    Hiekkarannat ja dyynit ovat lajirikkaita elinympäristöjä. Niillä elää lukuisia joukko kovakuoriaisia, luteita, perhosia, hämähäkkieläimiä, kasveja ja lintuja. Monet lajeista ovat nykyisin uhanalaisia. Hiekkarantoja, dyynejä ja niillä eläviä eliöitä uhkaavat muiden muassa Itämeren rehevöityminen, joka näkyy rannoilla levän kertymisenä ja umpeenkasvuna. Myös rakentaminen ja virkistyskäytöstä johtuva kuluminen heikentävät hiekkarantojen lajien elinmahdollisuuksia. Vieraslaji kurtturuusu leviää myös kovaa vauhtia etenkin Suomenlahden rannikolla. Tässä oppaassa kerrotaan hiekkarantojen ja dyynien monimuotoisesta elämästä. Itämeren tilan parantaminen on ensisijaista rantojen eliölajiston hyvinvoinnin kannalta. Meren elpyminen on kuitenkin hidasta ja sitä odotellessa meistä jokainen voi auttaa rantojen erikoistunutta eliölajistoa pienilläkin teoilla.
  • Stojiljkovic, Ana; Kauhaniemi, Mari; Kukkonen, Jaakko; Kupiainen, Kaarle; Karppinen, Ari; Denby, Bruce Rolstad; Kousa, Anu; Niemi, Jarkko V.; Ketzel, Matthias (Copernicus Publications, 2019)
    Atmospheric Chemistry and Physics
    We have numerically evaluated how effective selected potential measures would be for reducing the impact of road dust on ambient air particulate matter (PM10). The selected measures included a reduction of the use of studded tyres on light-duty vehicles and a reduction of the use of salt or sand for traction control. We have evaluated these measures for a street canyon located in central Helsinki for four years (2007–2009 and 2014). Air quality measurements were conducted in the street canyon for two years, 2009 and 2014. Two road dust emission models, NORTRIP (NOn-exhaust Road TRaffic Induced Particle emissions) and FORE (Forecasting Of Road dust Emissions), were applied in combination with the Operational Street Pollution Model (OSPM), a street canyon dispersion model, to compute the street increments of PM10 (i.e. the fraction of PM10 concentration originating from traffic emissions at the street level) within the street canyon. The predicted concentrations were compared with the air quality measurements. Both road dust emission models reproduced the seasonal variability of the PM10 concentrations fairly well but under-predicted the annual mean values. It was found that the largest reductions of concentrations could potentially be achieved by reducing the fraction of vehicles that use studded tyres. For instance, a 30 % decrease in the number of vehicles using studded tyres would result in an average decrease in the non-exhaust street increment of PM10 from 10 % to 22 %, depending on the model used and the year considered. Modelled contributions of traction sand and salt to the annual mean non-exhaust street increment of PM10 ranged from 4 % to 20 % for the traction sand and from 0.1 % to 4 % for the traction salt. The results presented here can be used to support the development of optimal strategies for reducing high springtime particulate matter concentrations originating from road dust. Short summary Nordic countries experience the deterioration of air quality in springtime due to high PM10 concentrations. Non-exhaust emissions from vehicular traffic are regarded as the most significant source of particulate air pollution during this time of year. The results from this study demonstrate the fact that changes in winter tyre types and adjustments to road maintenance could substantially reduce non-exhaust emissions.