Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2000
Forfattere
Marianne Bechmann Johannes Deelstra Hans Olav Eggestad Bjørn Kløve P. Stålnacke Stine Vandsemb (permisjon) Lillian ØygardenSammendrag
Erosjon og næringsstofftap overvåkes i en rekke mindre nedbørfelter som representerer ulik jordbruksdrift, klima og jordsmonn i Norge. Overvåkingsprogammet ble satt i gang 1992, men en del av nedbørfeltene har målinger fra midten av 80-tallet. Erosjon og næringsstofftap er beregnet for agrohydrologiske år, 1. mai 1999 30. april 2000. Året 1999/2000 var preget av generelt høye nitrogentap i Grimestadbekken, Vasshaglona og Hotrankanalen (10-12 kg N/dekar), mens det for de øvrige feltene var mindre enn 5 kg N/dekar. I kornfeltene på Østlandet var nitrogentapet 2-5 kg/dekar, som er på nivå med middeltapene for hele måleperioden. I nedbørfelt med overveiende grasdyrking varierte nitrogentapene fra 1-5 kg/dekar, størst i nedbørfelt med størst husdyrtetthet. Svært store fosfortap ble registrert i Grimestadbekken (1220 g/dekar) og Vasshaglona (720 g/dekar) i 1999/00. I Hotrankanalen var fosfortapet 430 g/dekar. I kornfeltene i Akershus varierte fosfortapet 120-340 g/dekar, mens det på Hedmarken var 40 g/dekar. I nedbørfelter med overveiende grasdyrking ble det registret fosfortap på 30-500 g/dekar i 1999/00. Nedbørfeltet med myrjord ga de største tapene. I 1999/00 er det også målt svært høye jordtap i Grimestadbekken (730 kg/dekar) og Vasshaglona (140 kg/dekar). I Skuterud-, Mørdrebekken og Hotrankanalen var jordtapet ca 260 kg/dekar, mens det i Naurstadbekken og Vasshaglona lå jordtapene på ca 130 kg/dekar. Jordtapene fra Rømua var meget lave (60 kg/dekar) i 1999/00, sammenlignet med andre felt i tilsvarende områder. Kolstad-, Time- og Volbubekken hadde jordtap på ca 10 kg/dekar. Vannkvaliteten i jordbrukspåvirkede innsjøer er klassifisert i intervallet mindre god til meget dårlig.
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1999
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Forfattere
Bjørn KløveSammendrag
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Sammendrag
Five tracer experiments have been performed in a coarse-textured soil near the new main airport at Gardermoen, Norway. In two lysimeter walls, 30 and 40 measuring points form the basis for spatial moment calculations. Although experiments were performed under different meteorological conditions (autumn and snowmelt) and at two different sites, the ratios of centres of vertical mass over cumulative infiltration were of the same order of magnitude, indicating a gravity-dominated flow. Two-dimensional transport simulations with SUTRA (Voss, 1984), with a priori estimated input parameters and random fields of soil hydraulic properties revealed a relatively good agreement with the experimental results. Three possible sources of heterogeneity affecting the vertical displacement of solute during snowmelt were identified: variability of soil physical properties, soil surface elevations and variability of ground frost during the melting period. To obtain accurate predictions, soil heterogeneity was the most important factor to characterize for the coarse-textured soil under consideration.
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Forfattere
Helen FrenchSammendrag
Outline of the thesis Chapter 1 Introduction Chapter 2 was published in an international proceedings (French et al., 1994) at an early stage of this Ph.D work and describes the experimental field set-up at Gardermoen; instrumentation and installation procedures. As more installations have been included at the experimental site, the publication has been slightly modified to include these changes in the presented chapter. Chapter 3 evaluates the uncertainty of spatial moments calculations from a limited number of measuring points. This is done by theoretical simulations of flow and transport in a 2D model (SUTRA, Voss, 1984). Spatial moment calculations of a plume distribution based on 9000 nodes and a set up of 30 measuring points are compared and the situation for various degrees of heterogeneity of the permeability fields tested. A regular and an irregular set-up is examined. The simulations of this chapter are based on a groundwater level at 2.7 m depth which is similar to the monitored depth interval in the field (2.4 m deep). The simulations revealed that predictions of the vertical centres of mass were quite good. A larger difference between the depth of the monitored area and the depth to the groundwater, may inflict larger prediction errors of the vertical centres of mass. This point is not examined in chapter 3. An idea of what the prediction error of the vertical centre of mass might have been at the field site Moreppen, is provided from the simulation where the groundwater level is defined at the more realistic level of 4 m depth (Fig. 4, only one realisation is shown). Chapter 4 examines the heterogeneity of the snowmelt/drainage pattern at the field site and relates it to the local microtopography. The range of infiltration variation is quantified from melting plates and indirectly from breakthrough curves observed in the uppermost part of the monitoring zone. Chapter 5 compares numerical simulations of solute transport in a heterogeneous or homogeneous soil with field results performed during autumn rains and snowmelting conditions. Different combinations of heterogeneities, of infiltration and soil hydraulic conductivities are tested numerically and their relative importance is determined. Chapter 6 shows calculations of degradation rates and retardation factors on the basis of spatial moment analysis of field results. The plume evolution of a reactive and an inert chemical are compared, and the difference quantified by vertical centres of mass. Simulated development of concentration distribution is shown in figure 3. The use of average manganese concentrations as an indicator of degradation in the unsaturated zone is also evaluated.
Sammendrag
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