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.
2005
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Hydraulics of subsurface flow filters (SSF) was studied by measurement of soil hydraulic conductivity (K) variation and performing tracer tests in two SSF filters consisting of 1-4 mm Ca rich sand (shell sand). Soil samples were carefully taken at several locations in Filter I. A tracer experiment was conducted in the undisturbed Filter II using KI. The measured K variability in Filter I was used to analyze the variations in tracer breakthrough. The spatial distribution of K was obtained by fitting a variogram to observed data and interpolation using Kriging. The tracer residence probability density function (PDF) was determined by modelling the tracer movement with a 3-D groundwater model. The observed and simulated tracer arrival was compared for cases with constant K, constant K and dispersion (D), and for spatially variable K and dispersion. The results show that groundwater models were well suited to simulate solute movement in the SSF system studied. An almost perfect fit to observed tracer PDF was obtained when variable K and dispersion was included in the model. This indicates that information on K variability and dispersion is important for studying solute movement in SSF constructed wetlands.
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Controlled experiments were carried out in a meso-scale sub-surface flow constructed sand filter treating municipal wastewater from a single household. The system consisted of a 50 cm high vertical flow column (pre-filter) with unsaturated flow and a 3 m long horizontal sub-surface flow unit (main filter) with saturated flow. Fluxes of nitrogen and carbon were analysed in four different operating conditions (low and high loading, with and without the pre-filter unit). Water samples were taken from the inlet, the outlet and within the sand filter at different depths and locations and analysed for water quality (Tot N, NO3-N, NH4-N, TOC, DOC, CODcr, BOD5, SS, pH and EC) and dissolved gas content (N2O, CH4 and CO2). Emissions of N2O, CH4 and CO2 were measured with the closed-chamber technique adjacent to water quality sampling points. The results show that pre-filtering in a vertical, unsaturated flow column changed the incoming ammonium to nitrate during low loading. During high loading part of the ammonium nitrified in the pre-filter was lost by denitrification. Within the horizontal main filter there were two pathways for the incoming nitrate: denitrification and dissimilatory nitrate reduction to ammonium (DNRA).
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The suitability of shell sand as a P sorbent has been tested both with laboratory batch experiments as well as in a sub-surface flow (SSF) meso-scale constructed sand filter treating municipal wastewater from a single household. The batch experiments suggest that retention of P in shell sand occurs both as sorption and precipitation. The soil-water ratio was found to be a crucial parameter when performing laboratory batch experiments. The maximum retention capacity was about 8000 and 800 mg P kg-1 sand, and the Kd was 33.7 and 82.9 L kg-1 for soil-water ratios of 5 g "75 mL and 50 g " 50 mL, re-spectively. The average total accumulated P concentration in samples from the SSF sand filter was 335 mg P kg-1. The Kd value based on [PO43-] and accumulated concentration of inorganic P in the SSF filter was 89.8 L kg-1. Thus the batch experiments overestimated the retention capacity of shell sand in real sand filter systems, however, a ratio of 50-50 gave a more reasonable estimate than a ratio of 5-75. The Kd value from batch samples with a ratio of 50-50 also gave a good estimate of the Kd value in the constructed sand filter. Ca-P was found to be the predominant form of P mineral in samples col-lected from the SSF sand filter. Some Al-P, loosely bounded P and occluded P were also present in the sand.
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Laboratory incubations with varying O2 and NO3 concentrations were performed with a range of filter materials used in constructed wetlands (CWs). The study included material sampled from functioning CWs as well as raw materials subjected to laboratory pre-incubation. 15N-tracer techniques were used to assess the rates of denitrification versus dissimilatory nitrate reduction to ammonium (DNRA), and the relative role of nitrification versus denitrification in producing N2O. The N2O/(N2+N2O) product ratio was assessed for the different materials. Sand, shell sand, and peat sustained high rates of denitrification. Raw light weight aggregates (LWA) had a very low rate, while in LWA sampled from a functioning CW, the rate was similar to the one found in the other materials. The N2O/(N2+N2O) ratio was very low for sand, shell sand and LWA from functioning CWs, but very high for raw LWA. The ratio was intermediate but variable for peat. The N2O produced by nitrification accounted for a significant percentage of the N2O accumulated during the incubation, but was dependent on the initial oxygen concentration. DNRA was significant only for shell sand taken from a functioning CW, suggesting that the establishment of active DNRA is a slower process than the establishment of a denitrifying flora.
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Oil transportation along the coastline of northern Norway has been one of the hottest topics discussed in the Barents Region for the recent two years. It is also an important issue of today"s political agenda and bilateral discussion between Norway and Russia. This Report is an extended and updated version of a similar report published back in 2003. The purpose of this new edition is to provide the reader with new and additional information. We believe this is of crucial importance as the organisation of the oil shipment through the Barents Sea is constantly changing. The new report presents the ongoing oil transportation activities in the Russian part of the Barents Region. Moreover, the report gives an overview of the existing reserves of hydrocarbons, oil production facilities, transportation routes (oil loading terminals, transshipment schemes, export routes) and transport systems (railways, waterways and pipelines), as well as some environmental aspects of the oil shipment (environmental policies and prevention systems). The authors also give their reflections and comments about oil transportation safety, and point out factors tat they believe are essential to achieve efficient oil spill protection inside the Russian Barents and further along the Norwegian coast. The report is prepared and published by Bioforsk Svanhovd (former Svanhovd Environmental Centre) with support from the Norwegian Barents Secretariat and the WWF Arctic Programmme. The report is also available in Russian.