Fant 9850 publikasjoner. Viser side 322 av 394:
2020
2020
2020
2020
Atmospheric turbulence and in particular its effect on tracer dispersion may be measured by cameras sensitive to the absorption of ultraviolet (UV) sunlight by sulfur dioxide (SO2), a gas that can be considered a passive tracer over short transport distances. We present a method to simulate UV camera measurements of SO2 with a 3D Monte Carlo radiative transfer model which takes input from a large eddy simulation (LES) of a SO2 plume released from a point source. From the simulated images the apparent absorbance and various plume density statistics (centre-line position, meandering, absolute and relative dispersion, and skewness) were calculated. These were compared with corresponding quantities obtained directly from the LES. Mean differences of centre-line position, absolute and relative dispersions, and skewness between the simulated images and the LES were generally found to be smaller than or about the voxel resolution of the LES. Furthermore, sensitivity studies were made to quantify how changes in solar azimuth and zenith angles, aerosol loading (background and in plume), and surface albedo impact the UV camera image plume statistics. Changing the values of these parameters within realistic limits has negligible effects on the centre-line position, meandering, absolute and relative dispersions, and skewness of the SO2 plume. Thus, we demonstrate that UV camera images of SO2 plumes may be used to derive plume statistics of relevance for the study of atmospheric turbulent dispersion.
2020
2020
2020
2020
2020
The geographic distribution of NO2-concentrations in air in the area around E16 Arna – Vågsbotn (Bergen) was mapped by
NILU after request by Statens vegvesen. Measurements were carried out with passive air samplers at 10 sites in the area
Gaupås-Kalsås-Blinde. The project was carried out in winter (28. January – 24. March 2020) in an area which often is subject to inversion conditions in wintertime.
The winter 2019-2020 proved to be a mild winter, no inversion conditions were registered. The NO2-concentration was highest in the first week and decreased gradually every week. During the two last weeks, traffic was reduced as a consequence of pandemia measures. The average concentration at the most polluted site over the entire measurement period was 22.9 μg/m3. Comparison of results from the measurement area with observations from monitoring stations in Bergen showed that the NO2-level close to E16 was as high as at traffic stations in Bergen.
NILU
2020
Equinor Mongstad. Spredningsberegninger av utslipp til luft.
NILU has performed dispersion calculations for emissions of NOx, SOx and particles to air from Mongstad refinery north of Bergen on the west coast of Norway. Hourly mean concentrations have been calculated using the Gaussian model CONCX. All hourly mean values are below Norwegian threshold values. Regional model calculations using the WRF-EMEP model system, show low values of NOx, SOx and particles in the vicinity of the Mongstad refinery. All calculated values are below Norwegian threshold values. Deposition calculations show that 12 % of nitrogen, 17 % of sulphur and 18 % of PM10 from Mongstad are deposited within the innermost model grid (105 x 105 km2). As an additional study, the components lead, mercury, chromium, PCB7, cadmium and arsenic have been assessed. The contribution from Mongstad refinery is small.
NILU
2020
2020
2020
Regionalized environmental impacts of construction machinery
PURPOSE:
This study aims to establish a regionalized environmental impact assessment of construction machinery equipped with diesel engines certified by the European emission standard Stage V, and operated in cold climatic zones in Europe.
METHOD:
The study quantifies potential environmental impacts associated with construction machinery over the entire lifecycle, from extraction of materials to the end-of-life. For the operation phase, a meso-level emission accounting method is applied to quantify tailpipe emissions for certain subcategories of construction machinery. This is achieved by determining the operational efficiency of each machine in terms of effective hours. The quantified emission data are then adjusted based on engine deterioration models to estimate the rate of increase in emissions throughout the lifetime of each machine. Finally, the CML impact assessment method is applied to inventory data to quantify potential environmental impacts.
RESULTS:
The study shows that tailpipe emissions, which largely depend on an engine’s fuel consumption, had the largest contribution to environmental impacts in most impact categories. At the same time, there was a positive correlation between the operation weight and the impacts of the machinery. Also, machinery with similar operation weight had relatively similar impact patterns due to similar driving factors and dependencies. In addition, network, sensitivity, and uncertainty analyses were performed to quantify the source of impacts and validate the robustness of the study. Results of the sensitivity analysis showed that the responsiveness of the studied systems is very sensitive to changes in the amount of fuel consumption. In addition, the uncertainty results showed that the domain of uncertainty increased as the operation weight subcategory of machinery increased.
CONCLUSION:
This study extends previous work on the life cycle assessment (LCA) of construction machinery, and the methodology developed provides a basis for future extension and improvement in this field. The use of effective hours as the unit of operational efficiency helps to resolve uncertainties linked to lifetime and annual operation hours. Also, the obtained results can be of use for decision support and for assessing the impacts of transition from fossil fuels to alternative fuel types.
2020
2020