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.
2002
Forfattere
Trond MæhlumSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Rapporten presenterer en laboratoriemetode for bestemmelse av effekter på frysing og tining på aggregatstabilitet. Steg for steg prosedyrer for de ulike delene av behandlingen er beskrevet i detalj. Behandlingen omfatter uttak av jord, sikting av jord til ønsket aggregatstørrelse, pakking av jord i sylindre, innstilling av vanninnhold i prøvene, fryse-tine behandling under kontrollerte forhold, og stabilitetstester med regnsimulator og våtsikteapparat.
Forfattere
Johannes DeelstraSammendrag
Summary: The report describes the erosion problems in Sub-Basin III, Managua, Nicaragua and proposes measures to alleviate these. Soil loss in the upper part of the catchment causes serious sedimentation in the downstream reaches of the open water courses, resulting in a reduced discharge capacity for water. This in its turn leads to flooding of urban areas during high rainfall periods and under extreme events can lead to closure of the international airport. In addition does the soil loss from agricultural land contribute in the ongoing deterioration of the water quality of Lake Managua while at the same time leading to a decrease in soil fertility and production capacity. An assessment is made of the present soil loss from agricultural land in the Subcuenca III and recommendations are proposed concerning soil conservation measures. Soil loss has been calculated using the Universal Soil Loss Equation (USLE). Very high figures for soil loss were obtained and the question has been raised whether these were realistic. However, the calculations were seriously hampered due to the lack of input data while at the same time were no data were available for validation.. Therefore, also proposals are given for a measurement programme to improve data availability and to be able to verify calculated soil loss. The report is the original to the report " Estudio Agrohidrológico" which is part of the "Estudio Agroecologico y de Drenaje Pluvial de la Subcuenca III de la Cuenca Sur del Lago de Managua" (Agro-Ecological and Rainwater Drainage Study of Sub-Basin III of the Southern Basin of Lake Managua).
Forfattere
Ole Martin Eklo Olav Lode Randi Bolli Reidun Aspmo Gunnhild Riise Tore Krogstad Brit Salbu Johannes DeelstraSammendrag
Det er ikke registrert sammendrag
Forfattere
Johannes DeelstraSammendrag
Summary: The report describes the erosion problems in Subcuenca III, Managua, Nicaragua and proposes measures to alleviate these. Soil loss in the upper part of the catchment causes serious sedimentation in the downstream reaches of the open water courses, resulting in a reduced discharge capacity for water. This in its turn leads to flooding of urban areas during high rainfall periods and under extreme events can lead to closure of the international airport. In addition does the soil loss from agricultural land contribute in the ongoing deterioration of the water quality of Lake Managua while at the same time leading to a decrease in soil fertility and production capacity. An assessment is made of the present soil loss from agricultural land in the Subcuenca III and recommendations are proposed concerning soil conservation measures. Soil loss has been calculated using the Universal Soil Loss Equation (USLE). Very high figures for soil loss were obtained and the question has been raised whether these were realistic. However, the calculations were seriously hampered due to the lack of input data while at the same time were no data were available for validation.. Therefore, also proposals are given for a measurement programme to improve data availability and to be able to verify calculated soil loss. The report is translated from the original "Agro-hydrological study of Subcuenca III, Managua, Nicaragua." which is part of the "Estudio Agroecologico y de Drenaje Pluvial de la Subcuenca III de la Cuenca Sur del Lago de Managua
Sammendrag
Summary: In Norway there exist a very limited number of studies on soil variability within soil map units. The main purpose of this study has been to provide information on and describe the variability in soil hydraulic properties and soil water content of a silty clay loam of South-eastern Norway. Measurements of soil hydraulic properties were carried out along a 50 meter transect during summer 2000. The measurements included: 1) laboratory saturated hydraulic conductivity (Kls), measured on 100 cm3 cores, 2) infiltration rate (q(h)), measured with tension infiltrometer at matric potentials h = -15, -6 and -3 cm, and 3) soil surface water content, measured in the top 5 cm of the soil with a TDR probe. Field saturated and near saturated hydraulic conductivity (Kfs and Kf(h)) were estimated from the infiltration rates. Variability in hydraulic conductivity was moderate to high along the transect, with coefficients of variation (CV) ranging from 79 for K(-15) to 224 % for K(-6). The sample distribution was approximately lognormal. Kls varied from 1.0 to 341 cm/h, with an arithmetic mean (AM) of 46 cm/h. Kfs was less than Kls, ranging from 0.27 to 63 cm/h, with AM = 13 cm/h. Spatial correlation of all variables was examined by computing variograms. Kls showed some degree of spatial correlation, with a effective ranges of approximately 7 meters. The nugget variance was rather high compared to the sill, indicating a large random component related to small-scale variability and measurement errors. Field hydraulic conductivity generally showed no clear sign of spatial correlation, except for Kf(-6)6,15, which had a range of 9.6 m. Soil water content was measured at six dates during the growing season. The spatial patterns varied from time to time. Where spatial correlation existed, effective ranges varied from 4.3 to 7.4 meters. As with Kls, the variation appeared to be dominated by a random component. From these results it was concluded that 1) at this scale of investigation, hydraulic conductivity exhibits a large degree of random variation related to soil heterogeneity and sample volume, 2) the most appropriate approach for modelling water flow and solute transport using these data would be to use the probability density function of the attributes, and 3) spatial trends and scale should be considered when planning the experimental design to assure that the sampling scheme encompasses a complete picture of the processes under investigation.
Sammendrag
Concentrations and fluxes of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), together with pools of carbon and nitrogen in the soil and biomass, were determined along north-south and east-west transects across Norway, Sweden and Finland. The data were analysed statistically and modelled using the mechanistic model DyDOC.Concentrations of DOC and DON were greatest in the O horizon and decreased downwards in the soil. The highest production of dissolved organic matter appears to take place in the O horizon and any contribution from thoroughfall is probably small. A pronounced seasonal effect with peak DOC concentrations in late summer/early autumn may be due to a seasonal (largely temperature) effect on DOC production.The effect of acidic precipitation upon DOC concentrations and fluxes was unclear. DOC in the O horizon was mostly of recent origin, while DOC in the B horizon appeared to include some older material, possibly desorbed from the soil. A positive correlation was found with electrical conductivity and a negative correlation with pH in DOC concentrations from the O horizon.A lack of correlation between DOC concentrations and temperature is probably due to a time lag between peak temperatures and peak DOC concentrations. Modelling of DOC concentrations and fluxes using DyDOC gave rasonable results, suggesting that it might be possible to use DyDOC as a general tool for modelling and forecasting DOC concentrations and fluxes in Nordic forest ecosytems.Scenario analysis using DyDOC suggested that increased temperature without increased litter input might result in increased production of CO2 rather than DOC. An increase in both temperature and litter input would lead to increased DOC concentrations, with possible implications for drinking water quality. Increased precipitation will lead to increased fluxes of DOC.
Forfattere
Nicholas ClarkeSammendrag
In natural waters, total organic carbon (TOC) is the sum of particulate and dissolved organic carbon. Dissolved organic carbon (DOC) is operationally defined, usually as organic carbon that passes through a 0.45 µm filter. Cellulose acetate or nitrate filters should not be used for this purpose due to contamination or adsorption problems. Glass fibre filters are preferable. Although the discussion below concerns DOC, much of it applies to TOC as well. Organic carbon is most often determined after oxidation to CO2 using combustion, an oxidant such as persulphate, UV or other high-energy radiation, or a combination of some of these. If only UV radiation with oxygen as oxidant is used, low DOC values may be obtained in the presence of humic substances. A variety of methods are used for detection, including infrared spectrometry, titration and flame ionization detection after reduction to methane. Always follow the instrument manufacturer’s instructions. For determination of dissolved organic carbon, dissolved inorganic carbon must be either removed by purging the acidified (for example with phosphoric acid) sample with a gas which is free from CO2 and organic compounds, or determined and subtracted from the total dissolved carbon. If acidification followed by purging is used, care should be taken as volatile organic compounds may also be lost. After acidification, remove CO2 by blowing a stream of pure carbon-free inert gas through the system for at least 5 minutes. Carbon is ubiquitous in nature, so reagents, water, and glassware cannot be completely cleaned of it. Method interferences (positive bias) may be caused by contaminants in the carrier gas, dilution water, reagents, glassware, or other sample processing hardware (for example a homogenization device). All of these materials must be routinely demonstrated to be free from interference under the conditions of analysis by running reagent blanks. Plastic bottles can bleed carbon into water samples, especially when they are new, or when they are used for low-level samples (less than 200 ppb C). Any new bottles (especially plastic) should ideally be filled with clean water for a period of several days or boiled in water for a few hours before use. The use of high purity or purified reagents and gases helps to minimise interference problems. It is very important to use ultra-pure water with a carbon filter or boiled distilled water just before preparing stock and standard solutions, in order to remove dissolved CO2. The stock solution should not be kept too long (about one week). For most DOC instruments a correction for DOC (due to dissolved CO2) in the dilution water used for calibration standards is necessary, especially for standards below 10 ppm C. The carbon in the blank should only be subtracted from standards and not from samples. For calibration, standard solutions are most often potassium hydrogen phthalate for total dissolved carbon and sodium bicarbonate for dissolved inorganic carbon. The DOC concentration should be within the working range of the calibration. If necessary the sample can be diluted. Sample DOC below about 50 ppb C can be affected by atmospheric exposure. In these cases, sampling bottles should be kept closed when possible, and autosampler vials should be equipped with septa for needle piercing by the autosampler.
Forfattere
Nicholas ClarkeSammendrag
Within ICP Forests, the question has arisen whether it is necessary to determine DOC or TOC in deposition. There are several possible reasons for doing so, which can be summarised under two headings: quality control and process studies.