Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2009
Abstract
No abstract has been registered
Abstract
Due to the exponential increase in production and marketing of engineered nanomaterials, concerns are raised about their inevitable spreading in the environment. Soils, with their high proportion of solid phase, are likely to constitute the major ultimate sink for engineered nanoparticles (ENPs). Regrettably, data are scarce on the potential environmental risks of ENPs on soil ecosystems. The main reason for this key knowledge gap was the lack of methodologies able to trace the ENPs in complex environmental matrices like soils, which already contain a high background of natural nanoparticles (e.g. clays, organic matter, iron oxides). Using neutron activation as a tracer technique enabled us to overcome this hurdle: neutron activated ENPs can readily be quantified by gamma spectrometry, in all kind of samples, including living organisms. Here we examined the uptake and excretion kinetics of cobalt (Co-NPs, APS 3.9 ± 0.8 nm) and silver nanoparticles (Ag-NPs, APS 20.2 ± 2.5 nm) in the earthworm Eisenia fetida, as well as their internal distribution within worms. We compared the uptake, retention time and internal ditribution of Co-NPs and Ag-NPs with those of soluble salts of cobalt and silver. Earthworms were fed over a 28d period with horse manure contaminated with either neutron activated Co-NPs and Ag-NPs, or Co and Ag salts spiked with the radiotracers 60Co and 110mAg. Accumulation and excretion kinetics were assessed by gamma spectrometry on living earthworms along a three month period for silver treatments and a five month period for cobalt treatments. The patterns of accumulation were highly different for cobalt and silver. The concentration ratios [(Bq/g worm) / (Bq/g food)] after 28d uptake were 0.93 ± 0.36 and 2.02 ± 0.65 for Co-NP and Co2+, respectively, while corresponding values for Ag-NPs and Ag+ were 0.015 ± 0.016 and 0.054 ± 0.024, respectively. Almost all absorbed Co-NPs and Co2+ remained within the worms four months after transfer to clean soil, while Ag concentration ratios fell to almost zero within a few days. We investigated futher the distribution of Co-NPs and Co2+ in worms bodies by coupling autoradiography images of worm transects and gamma spectrometry on individual organs. The body wall, mainly composed of muscular fibers, and the reproductive organs (e.g. spermathecae and seminal vesicles) accumulated lower amounts of cobalt than the digestive tract. By far, the highest accumulation was found in the blood, namely in the pseudo-hearts.
Abstract
One of the major concerns regarding use of velvet bentgrass in Scandinavia is whether current cultivars are sufficiently tolerant to frost. In 2008-09 the four velvet bentgrass (VB, Agrostis canina L.) cultivars Avalon, Greenwich, Legendary, and Villa, and the creeping bentgrass (CB, Agrostis stolonifera L.) cultivar Penn A-4 (control) were established from seed in 7.5x10x10 cm pots filled with a USGA-spec. sand containing 0.5% (w/w) organic matter. The following four treatments representing different phases of cold acclimation were compared: (i) nonacclimated (NA) plants maintained at 18 °C/12 °C (day/night) and 16 h photoperiod (150 μmol/m/s); (ii) plants acclimated at 2 °C and 16 h photoperiod (250 μmol/m/s) for 2 wk (A2); (iii) plants acclimated as ii plus 2 wk of sub-zero acclimation in darkness at -2 °C (A2+SZA2); and (iv) naturally acclimated plants under outdoor (field) conditions in November -December (FA). Freezing tolerance was assessed visually as percent of pot surface covered with healthy turf after 26 days of recovery in the greenhouse. To examine the relationship between physiological changes under cold acclimation and freezing tolerance, crowns of VB and CB were harvested for carbohydrate (CHO) analysis after each hardening treatment. Results showed that FA plants survived all freezing treatments (plant coverage more than 90 %). A2+SZA2 plants had better survival after freezing to -9 °C, -12 °C and -15 °C as compared with A2 plants. Differences in freezing tolerance between VB and CB were not significant. NA plants survived none of freezing temperatures. The predominant CHO in VB and CB crowns were sucrose and fructans. Compared with NA plants, A2 plants had significantly higher concentrations of fructose, sucrose and fructan. Exposure to -2 ºC in darkness (A2+SZA2) had no further effect on these concentrations. Natural hardening (FA) resulted in total carbohydrate and fructan concentrations significantly lower than for plants exposed to artificial acclimation.
Abstract
Mechanical strength properties are the most important feature of wood in constructions. In decaying wood strength loss can precede mass loss. Hence, both in laboratory and outdoor applications non-destructive measurement methods for early decay detection are in demand. The aim of this study was to evaluate the applicability of ultrasonic pulse propagation as a tool for decay detection in different laboratory setups. A dynamic MOE (MOEdyn) strength test device based on measurement of ultrasonic pulse propagation was used for non-destructive strength evaluation in different exposure situations for Scots pine sapwood. Two different test setups were used. In the first test MOEdyn was measured above fibre saturation. A range of different wood protection treatments were tested according to the terrestrial microcosms (TMC) test, a modified ENV 807. Three different soil types were used: forest soil dominated by white rot, Simlångsdalen test field soil dominated by brown rot and compost soil characterised by a mixture of bacteria and soft rot. Before strength testing the samples were water saturated and MOEdyn was measured above the fibre saturation point at time intervals (0, 8, 16, 24, 32 and 40 weeks) using ultrasound. Comparisons of strength loss were performed between treatments in the different soil types, and strength loss was also compared with mass loss. In the second test MOEdyn were measured below fibre saturation. Ultrasound measurements were performed on 0.5 m pine logs sampled from five trees from the same stand in central Southern Norway. Logs from two of the trees had varying amounts of discoloration due to an incipient attack by the white rot fungus Phlebiopsis gigantea during storage. Amount of visible discoloration had effect on MOEdyn values from measurements on log ends. Transversal measurement of MOEdyn was not successful. In a subsequent water uptake test, logs with discoloration absorbed substantially more water than the rest of the sample. The conclusion of this study was that the use of ultrasonic MOE is applicable as an evaluation tool in early decay detection.
Authors
Belachew Asalf Tadesse Håvard Eikemo Andrew Dobson Anne-Marte Tronsmo Cecilie Hagen David M. Gadoury Robert C Seem Arne StensvandAbstract
Several non-chemical control agents are now registered and available for control of powdery mildews. However, there is little or no information about their efficacy against strawberry powdery mildew, caused by Podosphera aphanis. Trials were conducted to compare the performance of non-chemical control agents to chemical fungicides under laboratory, greenhouse and high plastic tunnel conditions. The treatments included: AQ10 (active ingredient is Ampelomyces quisqualis, a hyperparasite on powdery mildew), AQ10 + Silwet Gold (organosilicon adjuvant, enhances distribution and wetting), Vacciplant (active ingredient is laminarin, an extract from brown algae), JMS Stylet oil (mineral oil), Rape seed oil + detergent, Thiovit (wettable sulphur), Topas 100 EC (penconazole) + Candit (kresoximmethyl) and water as control. In the greenhouse, one quarter of the recommended dose was used either daily in one experiment or three times per week in another. In the field, half of recommended rates were applied twice weekly. Both in the greenhouse and tunnel experiments, the chemical control Topas + Candit and AQ10 + Silwet Gold significantly reduced disease severity. AQ10,Vacciplant and Thiovit were moderately effective when applied daily in the greenhouse trial, but not significantly different from the water control when applied three time per week in the greenhouse and twice a week in the tunnel experiment. In the plastic tunnel, the JMS stylet oil and Rape seed oil + detergent treatments caused severe phytotoxic reaction (necrosis). AQ10 used alone had the poorest performance in the tunnel. This indicated that the spreader either enhances the effect of AQ10 and/or the spreader itself had an effect. In laboratory experiments with powdery mildew grown on strawberry leaflets in Petri dishes, spore germination after treatments with water, Stylet oil, Candit and Thiovit were 74, 53, 8 and 7%, respectively. The effect of Thiovit found in the laboratory was not reflected in the greenhouse and plastic tunnel trials. We will further explore the protectant, curative and eradicative effects of the compounds included here.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Daniel P. Rasse Karin Knoth de Zarruk Line Tau StrandAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Denitrification is a key ecosystem process which is essential to avoid massive enrichment of nitrate in surface and ground water. A rather narrow group of bacteria are able to carry out denitrification, and they are known to be sensitive to environmentally toxic pollutants like e.g. heavy metals. Since these microorganisms carry out a key ecosystem function, they are strong candidates for testing and monitoring environmental effects of toxic substances likely to reach the soil environment. We conducted a series of experiments where either a pure strain of a denitrifying bacterium (Paracoccus denitrificans) or intact soil microbial communities containing indigenous denitrifiers were subjected to different types of silver nanoparticles (average particle size 20 and 1 nm) at a wide range of concentrations. The results showed that the smallest particles were far more toxic than the larger ones on a mass basis and completely killed off denitrifying bacteria in vitro at concentrations as low as 100 ppb. When soil was present, this concentration had no effect on respiration and even the far more sensitive process of denitrification, measured as production of the gases NO, N2O and N2, was unaffected. Results from experiments that are under way will also be presented. Here threshold levels for inhibition of denitrification by P. denitrificans and intact microbial communities are established for the two types of silver nanoparticles and where toxicity is compared when expressed on a mass basis vs. a surface area basis. Also the sensitivity of the different steps in the denitrification process will be compared and related to corresponding data for dissolved metals. The perspectives for using denitrification impediment as a way to assess ecotoxicity at a functional level will be discussed.