Norwegian Institute For Air Research

Lillestrom, Norway

Norwegian Institute For Air Research

Lillestrom, Norway

The Norwegian Institute for Air Research or NILU is one of the leading specialized scientific laboratories in Europe researching issues related to air pollution, climate change and health. NILU has a staff of scientists, engineers and technicians with specialized expertise for working on air pollution problems. The staff do more than two hundred projects annually for research councils, industries, international banks and local, national and international authorities and organizations. Its director since 2009 is Kari Nygaard. Wikipedia.

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Katsoyiannis A.,Norwegian Institute For Air Research | Breivik K.,Norwegian Institute For Air Research | Breivik K.,University of Oslo
Environmental Pollution | Year: 2014

Polycyclic Aromatic Hydrocarbons (PAHs) molecular diagnostic ratios (MDRs) are unitless concentration ratios of pair-PAHs with the same molecular weight (MW); MDRs have long been used as a tool for PAHs source identification purposes. In the present paper, the efficiency of the MDR methodology is evaluated through the use of a multimedia fate model, the calculation of characteristic travel distances (CTD) and the estimation of air concentrations for individual PAHs as a function of distance from an initial point source. The results show that PAHs with the same MW are sometimes characterized by substantially different CTDs and therefore their air concentrations and hence MDRs are predicted to change as the distance from the original source increases. From the assessed pair-PAHs, the biggest CTD difference is seen for Fluoranthene (107 km) vs. Pyrene (26 km). This study provides a strong indication that MDRs are of limited use as a source identification tool. © 2013 Elsevier Ltd. All rights reserved.

Prata A.J.,Norwegian Institute For Air Research | Prata A.T.,Monash University
Journal of Geophysical Research: Atmospheres | Year: 2012

Between 14 April and 25 May, 2010, Eyjafjallajökull volcano in Iceland erupted a large amount of fine grained ash. Dispersion models and satellite data were used to identify the location of the ash cloud, but accurate quantitative forecasts of the concentrations could not be made. By using multispectral satellite measurements from the Spin Enhanced Visible and Infrared Imager (SEVIRI), it is shown that quantitative estimates of the mass loadings (g m-2) can be made with a detection limit ∼0.2 g m-2, every 15 minutes. These data represent the most comprehensive coverage, in space and time, of the Eyjafjallajökull ash and its movement. A new ash concentration chart is proposed that removes the ambiguity inherent in assigning high concentrations to highly negative brightness temperature differences. Validation of satellite ash retrievals against measurements from aircraft, ground-based lidars, and air quality data is presented. The results show a mean bias of -47 g m-3 and standard deviation of ±154 g m -3. The satellite ash retrievals are sufficiently accurate for use with dispersion models to constrain ash concentration forecasts. Concentrations in the dense parts of the dispersing ash cloud occasionally exceeded 4 mg m -3 (∼3% of ash-affected pixels), and ash clouds with concentrations >2 mg m-3 covered large parts of European airspace on several occasions (∼50% of ash-affected pixels). The statistical analysis leads naturally to a logarithmic scale for assigning ash concentration limits. We suggest that a better approach is to utilize a dosage and illustrate this using a simple model of ash deposition on jet engines. © 2012 by the American Geophysical Union.

Schneider P.,Norwegian Institute For Air Research | Van Der A R.J.,Royal Netherlands Meteorological Institute
Journal of Geophysical Research: Atmospheres | Year: 2012

A global nine-year archive of monthly tropospheric NO2 data acquired by the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) instrument was analyzed with respect to trends between August 2002 and August 2011. In the past, similar studies relied on combining data from multiple sensors; however, the length of the SCIAMACHY data set now for the first time allows utilization of a consistent time series from just a single sensor for mapping NO2 trends at comparatively high horizontal resolution (0.25). This study provides an updated analysis of global patterns in NO2 trends and finds that previously reported decreases in tropospheric NO2 over Europe and the United States as well as strong increases over China and several megacities in Asia have continued in recent years. Positive trends of up to 4.05 (0.41) × 1015 molecules cm-2 yr-1 and up to 19.7 (1.9) % yr-1 were found over China, with the regional mean trend being 7.3 (3.1) % yr -1. The megacity with the most rapid relative increase was found to be Dhaka in Bangladesh. Subsequently focusing on Europe, the study further analyzes trends by country and finds significantly decreasing trends for seven countries ranging from -3.0 (1.6) % yr-1 to -4.5 (2.3) % yr -1. A comparison of the satellite data with station data indicates that the trends derived from both sources show substantial differences on the station scale, i.e., when comparing a station trend directly with the equivalent satellite-derived trend at the same location, but provide quite similar large-scale spatial patterns. Finally, the SCIAMACHY-derived NO2 trends are compared with equivalent trends in NO2 concentration computed using the Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP) model. The results show that the spatial patterns in trends computed from both data sources mostly agree in Central and Western Europe, whereas substantial differences are found in Eastern Europe.

Thompson R.L.,Norwegian Institute For Air Research | Stohl A.,Norwegian Institute For Air Research
Geoscientific Model Development | Year: 2014

We present a new modular Bayesian inversion framework, called FLEXINVERT, for estimating the surface fluxes of atmospheric trace species. FLEXINVERT can be applied to determine the spatio-temporal flux distribution of any species for which the atmospheric loss (if any) can be described as a linear process and can be used on continental to regional and even local scales with little or no modification. The relationship between changes in atmospheric mixing ratios and fluxes (the so-called source-receptor relationship) is described by a Lagrangian Particle Dispersion Model (LPDM) run in a backwards-in-time mode. In this study, we use FLEXPART but any LPDM could be used. The framework determines the fluxes on a nested grid of variable resolution, which is optimized based on the source-receptor relationships for the given observation network. Background mixing ratios are determined by coupling FLEXPART to the output of a global Eulerian model (or alternatively, from the observations themselves) and are also optionally optimized in the inversion. Spatial and temporal error correlations in the fluxes are taken into account using a simple model of exponential decay with space and time and, additionally, the aggregation error from the variable grid is accounted for. To demonstrate the use of FLEXINVERT, we present one case study in which methane fluxes are estimated in Europe in 2011 and compare the results to those of an independent inversion ensemble. © Author(s) 2014. CC Attribution 3.0 License.

Berger J.,Norwegian Institute For Air Research | Denby B.,Norwegian Institute For Air Research
Atmospheric Environment | Year: 2011

This paper concerns the development and evaluation of a new and generalised road dust emission model. Most of today's road dust emission models are based on local measurements and/or contain empirical emission factors that are specific for a given road environment. In this study, a more generalised road dust emission model is presented and evaluated. We have based the emissions on road, tyre and brake wear rates and used the mass balance concept to describe the build-up of road dust on the road surface and road shoulder. The model separates the emissions into a direct part and a resuspension part, and treats the road surface and road shoulder as two different sources. We tested the model under idealized conditions as well as on two datasets in and just outside of Oslo in Norway during the studded tyre season. We found that the model reproduced the observed increase in road dust emissions directly after drying of the road surface. The time scale for the build-up of road dust on the road surface is less than an hour for medium to heavy traffic density. The model performs well for temperatures above 0 °C and less well during colder periods. Since the model does not yet include salting as an additional mass source, underestimations are evident under dry periods with temperatures around 0 °C, under which salting occurs. The model overestimates the measured PM10 (particulate matter less than 10 μm in diameter) concentrations under heavy precipitation events since the model does not take the amount of precipitation into account. There is a strong sensitivity of the modelled emissions to the road surface conditions and the current parameterisations of the effect of precipitation, runoff and evaporation seem inadequate. © 2011.

Engelsen O.,Norwegian Institute For Air Research
Nutrients | Year: 2010

This paper reviews the main factors influencing the synthesis of vitamin D, with particular focus on ultraviolet radiation exposure. On the global level, the main source of vitamin D is the sun. The effect of solar radiation on vitamin D synthesis depends to some extent on the initial vitamin D levels. At moderate to high latitudes, diet becomes an increasingly important source of vitamin D due to decreased solar intensity and cold temperatures, which discourage skin exposure. During the mid-winter season, these factors result in decreased solar radiation exposure, hindering extensively the synthesis of vitamin D in these populations. © 2010 by the authors; licensee MDPI, Basel, Switzerland.

Kristiansen N.I.,Norwegian Institute For Air Research | Stohl A.,Norwegian Institute For Air Research | Wotawa G.,Central Institute for Meteorology and Geodynamics
Atmospheric Chemistry and Physics | Year: 2012

Caesium-137 (137Cs) and iodine-131 (131I) are radionuclides of particular concern during nuclear accidents, because they are emitted in large amounts and are of significant health impact. 137Cs and 131I attach to the ambient accumulation-mode (AM) aerosols and share their fate as the aerosols are removed from the atmosphere by scavenging within clouds, precipitation and dry deposition. Here, we estimate their removal times from the atmosphere using a unique high-precision global measurement data set collected over several months after the accident at the Fukushima Dai-ichi nuclear power plant in March 2011. The noble gas xenon-133 (133Xe), also released during the accident, served as a passive tracer of air mass transport for determining the removal times of 137Cs and 131I via the decrease in the measured ratios 137Cs/133Xe and 131I/133Xe over time. After correction for radioactive decay, the 137Cs/133Xe ratios reflect the removal of aerosols by wet and dry deposition, whereas the 131I/133Xe ratios are also influenced by aerosol production from gaseous 131I. We find removal times for 137Cs of 10.0-13.9 days and for 131I of 17.1-24.2 days during April and May 2011. The removal time of 131I is longer due to the aerosol production from gaseous 131I, thus the removal time for 137Cs serves as a better estimate for aerosol lifetime. The removal time of 131I is of interest for semi-volatile species. We discuss possible caveats (e.g. late emissions, resuspension) that can affect the results, and compare the 137Cs removal times with observation-based and modeled aerosol lifetimes. Our 137Cs removal time of 10.0 13.9 days should be representative of a "background" AM aerosol well mixed in the extratropical Northern Hemisphere troposphere. It is expected that the lifetime of this vertically mixed background aerosol is longer than the lifetime of fresh AM aerosols directly emitted from surface sources. However, the substantial difference to the mean lifetimes of AM aerosols obtained from aerosol models, typically in the range of 3-7 days, warrants further research on the cause of this discrepancy. Too short modeled AM aerosol lifetimes would have serious implications for air quality and climate model predictions. © 2012 Author(s).

Cassiani M.,Norwegian Institute For Air Research
Boundary-Layer Meteorology | Year: 2013

A new approach is proposed to predict concentration fluctuations in the framework of one-particle Lagrangian stochastic models. The approach is innovative since it allows the computation of concentration fluctuations in dispersing plumes using a Lagrangian one-particle model with micromixing but with no need for the simulating of background particles. The extension of the model for the treatment of chemically reactive plumes is also accomplished and allows the computation of plume-related chemical reactions in a Lagrangian one-particle framework separately from the background chemical reactions, accounting for the effect of concentration fluctuations on chemical reactions in a general, albeit approximate, manner. These characteristics should make the proposed approach an ideal tool for plume-in-grid calculations in chemistry transport models. The results are compared to the wind-tunnel experiments of Fackrell and Robins (J Fluid Mech, 117:1-26, 1982) for plume dispersion in a neutral boundary layer and to the measurements of Legg et al. (Boundary-Layer Meteorol, 35:277-302, 1986) for line source dispersion in and above a model canopy. Preliminary reacting plume simulations are also shown comparing the model with the experimental results of Brown and Bilger (J Fluid Mech, 312:373-407, 1996; Atmos Environ, 32:611-628, 1998) to demonstrate the feasibility of computing chemical reactions in the proposed framework. © 2012 Springer Science+Business Media B.V.

Stohl A.,Norwegian Institute For Air Research | Sodemann H.,Norwegian Institute For Air Research
Journal of Geophysical Research: Atmospheres | Year: 2010

We have developed a 5.5 year climatology of atmospheric transport into the Antarctic troposphere, which uses the same data set and methods as described in a recent study for the Arctic. This allows direct comparisons of transport properties for the two polar regions. The climatology is based on a simulation with the Lagrangian particle dispersion model FLEXPART, where the model atmosphere was globally filled with particles. Transport characteristics as well as emission sensitivities were derived from 6 hourly particle positions. We found that the probability for near-surface air to originate from the stratosphere on a time scale of 10 days is an order of magnitude higher near the South Pole than near the North Pole, a result of higher topography and descent that partly compensates for the flow of air down the Antarctic Plateau with the katabatic winds. The stratospheric influence is largest in fall, which is opposite to the seasonality in the Arctic. Stratospheric influence is much smaller over the shelf ice regions and in a band around Antarctica. The average time for which air near the surface has been exposed to continuous darkness in July (continuous light in January) is longest over the Ronne Ice Shelf and Ross Ice Shelf at∼11 days (20 days). We calculated how sensitive Antarctic air masses are to emission input up to 30 days before arriving in Antarctica if removal processes are ignored. The emission sensitivity shows strong meridional gradients and, as a result, is generally low over South America, Africa, and Australia. For a 10 day time scale, the largest emission sensitivities over these continents are 1-2 orders of magnitude smaller than over Eurasia for transport to the Arctic, showing that foreign continents have a much smaller potential to pollute the Antarctic than the Arctic troposphere. Emission sensitivities and derived black carbon (BC) source contributions over South America, Africa, and Australia are substantially (a factor 10 for Africa) larger in winter than in summer. In winter, biomass burning contributes more BC than anthropogenic sources. For typical aerosol lifetimes of 5-10 days, ship emissions south of 60°S account for half of the total BC concentrations in the lowest 1000 m of the atmosphere south of 70°S in December. The increasing number of tourists visiting Antarctica and fishing vessels operating close to Antarctica are, therefore, a matter of concern. Copyright © 2010 by the American Geophysical Union.

de Wit C.A.,University of Stockholm | Herzke D.,Norwegian Institute For Air Research | Vorkamp K.,National Environmental Research Institute of Denmark
Science of the Total Environment | Year: 2010

Polybrominated diphenyl ethers (PBDEs) containing two to 10 bromines are ubiquitous in the Arctic, in both abiotic and biotic samples. Hexabromocyclododecane (HBCD) is also ubiquitous in the Arctic, with the γ-HBCD isomer predominating in air, the α-HBCD isomer predominating in biota and similar concentrations of α-, β- and γ-HBCD found in marine sediments. Other brominated flame retardants (BFRs) found in some Arctic samples are polybrominated biphenyls (PBBs), tetrabromobisphenol A (TBBPA), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), hexabromobenzene (HxBBz), pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH). Temporal trends of tetra- to heptaBDEs and HBCD show increasing concentrations or a tendency to levelling off depending on the matrix (air, sediment, biota) and location, but no uniform picture for the Arctic emerges. BDE-209 concentrations are increasing in air. PBDEs and HBCD spatial trends in seabirds and marine mammals are similar to those seen previously for polychlorinated biphenyls (PCBs), with highest concentrations found in organisms from East Greenland and Svalbard. These trends indicate western Europe and eastern North America as important source regions of these compounds via long range atmospheric transport and ocean currents. Latitudinal trends showed lower concentrations and fluxes of PBDEs at higher latitudes. The tetra-hexaBDEs and α-HBCD biomagnify in Arctic food webs. Results for BDE-209 are more conflicting, showing either only low or no biomagnification potential. PBDE and HBCD concentrations are lower in terrestrial organisms and higher in marine top predators such as some killer whale populations in Alaska and glaucous gulls from the Barents Sea area. Higher concentrations are seen near populated areas indicating local sources. Findings of BTBPE, HxBBz, PBEB, PBT and TBECH in seabirds and/or marine mammals indicate that these compounds reach the Arctic, most probably by long range atmospheric transport and accumulate in higher trophic level organisms and that increasing use as PBDE replacements will lead to increasing concentrations. © 2009 Elsevier B.V.

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