Found 10000 publications. Showing page 349 of 400:
Modeling the Dynamic Behavior of Radiocesium in Grazing Reindeer
Radiocesium contamination in Norwegian reindeer and the factors influencing contamination levels have been studied for more than 50 years, providing significant amounts of data. Monitoring contamination in reindeer is of utmost importance for reindeer husbandry and herders in Norway and will need to be studied for many years because of the persistent contamination levels due to the 1986 Chernobyl fallout. This paper presents a novel dynamic model that takes advantage of the large data sets that have been collected for reindeer monitoring to estimate 137Cs in reindeer meat at any given time. The model has been validated using detailed 137Cs data from one of the herds most affected by the fallout. The model basis includes detailed 137Cs soil data from aerial surveys, GPS-based knowledge of reindeer migration, and local soil-to-vegetation 137Cs transfer information. The validation exercise shows that the model satisfactorily predicts both short- and long-term changes in 137Cs concentrations in reindeer meat and suggests that the model will be a useful tool in estimating seasonal changes and evaluating possible remedial actions in case of a future fallout event.
2022
Hazard identification and safety assessment of the huge variety of nanomaterials (NMs), calls for robust and validated toxicity screening tests in combination with cheminformatics approaches to identify factors that can drive toxicity. Cytotoxicity and genotoxicity of seventeen JRC repository NMs, derived from titanium dioxide, zinc oxide, silver and silica, were tested in vitro using human lung alveolar epithelial cells A549. Cytotoxicity was assessed with the AlamarBlue (AB) and colony forming efficiency (CFE) assays, and genotoxicity by the enzyme-linked version of the comet assay. Nanoparticle tracking analysis (NTA) was used to measure size of the NMs in stock and in cell culture medium at different time points. Categorization and ranking of cytotoxic and genotoxic potential were performed (EU-NanoREG2 project approach). Descriptors for prediction of NMs toxicity were identified by quantitative structure-activity relationship (QSAR) analysis. Our results showed that ZnO NMs (NM-110 and NM-111), and Ag NMs (NM-300K and NM-302) were cytotoxic, while the TiO2 and SiO2 NMs were non-cytotoxic. Regarding genotoxicity, TiO2 NM-100, ZnO NM-110, SiO2 NM-203 and Ag NM-300K were categorized as positive. Cheminformatics modeling identified electron properties and overall chemical reactivity as important descriptors for cytotoxic potential, HOMO-LUMO energy parameter, ionization potential, pristine size for the NMs´ genotoxic potential, and presence of surface coating as descriptor for induction of DNA oxidized base lesions.
2022
We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, “Nanoparticle Populations” of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles.
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Mercury isotope evidence for Arctic summertime re-emission of mercury from the cryosphere
During Arctic springtime, halogen radicals oxidize atmospheric elemental mercury (Hg0), which deposits to the cryosphere. This is followed by a summertime atmospheric Hg0 peak that is thought to result mostly from terrestrial Hg inputs to the Arctic Ocean, followed by photoreduction and emission to air. The large terrestrial Hg contribution to the Arctic Ocean and global atmosphere has raised concern over the potential release of permafrost Hg, via rivers and coastal erosion, with Arctic warming. Here we investigate Hg isotope variability of Arctic atmospheric, marine, and terrestrial Hg. We observe highly characteristic Hg isotope signatures during the summertime peak that reflect re-emission of Hg deposited to the cryosphere during spring. Air mass back trajectories support a cryospheric Hg emission source but no major terrestrial source. This implies that terrestrial Hg inputs to the Arctic Ocean remain in the marine ecosystem, without substantial loss to the global atmosphere, but with possible effects on food webs.
2022
The assessment of long-range transport potential (LRTP) is enshrined in several frameworks for chemical regulation such as the Stockholm Convention. Screening for LRTP is commonly done with the OECD Pov and LRTP Screening Tool employing two metrics, characteristic travel distance (CTD) and transfer efficiency (TE). Here we introduce a set of three alternative metrics and implement them in the Tool’s model. Each metric is expressed as a fraction of the emissions in a source region. The three metrics quantify the extent to which the chemical (i) reaches a remote region (dispersion, ϕ1), (ii) is transferred to surface media in the remote region (transfer, ϕ2), and (iii) accumulates in these surface media (accumulation, ϕ3). In contrast to CTD and TE, the emissions fractions metrics can integrate transport via water and air, enabling comprehensive LRTP assessment. Furthermore, since there is a coherent relationship between the three metrics, the new approach provides quantitative mechanistic insight into different phenomena determining LRTP. Finally, the accumulation metric, ϕ3, allows assessment of LRTP in the context of the Stockholm Convention, where the ability of a chemical to elicit adverse effects in surface media is decisive. We conclude that the emission fractions approach has the potential to reduce the risk of false positives/negatives in LRTP assessments.
2022
Monitoring of the atmospheric ozone layer and natural ultraviolet radiation. Annual report 2021.
This report summarizes the results from the Norwegian monitoring programme on stratospheric ozone and UV radiation measurements. The ozone layer has been measured at three locations since 1979: In Oslo/Kjeller, Tromsø/Andøya and Ny-Ålesund. The UV-measurements started in 1995. The results show that there was a significant decrease in stratospheric ozone above Norway between 1979 and 1997. After that, the ozone layer stabilized at a level ~2% below pre-1980 level. The year 2021 was characterized by low total ozone values in June and July, whereas “normal” ozone values were measured during winter and spring.
NILU
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Svalbard is a remote and scarcely populated Arctic archipelago and is considered to be mostly influenced by long-range-transported air pollution. However, there are also local emission sources such as coal and diesel power plants, snowmobiles and ships, but their influence on the background concentrations of trace gases has not been thoroughly assessed. This study is based on data of tropospheric ozone (O3) and nitrogen oxides (NOx) collected in three main Svalbard settlements in spring 2017. In addition to these ground-based observations and radiosonde and O3 sonde soundings, ERA5 reanalysis and BrO satellite data have been applied in order to distinguish the impact of local and synoptic-scale conditions on the NOx and O3 chemistry. The measurement campaign was divided into several sub-periods based on the prevailing large-scale weather regimes. The local wind direction at the stations depended on the large-scale conditions but was modified due to complex topography. The NOx concentration showed weak correlation for the different stations and depended strongly on the wind direction and atmospheric stability. Conversely, the O3 concentration was highly correlated among the different measurement sites and was controlled by the long-range atmospheric transport to Svalbard. Lagrangian backward trajectories have been used to examine the origin and path of the air masses during the campaign.
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Northern Fulmars (Fulmarus glacialis) are a pelagic seabird species distributed at northern and polar latitudes. They are often used as an indicator of plastic pollution in the North Sea region, but data are lacking from higher latitudes, especially when it comes to chicks. Here, we investigated amounts of ingested plastic and their characteristics in fulmar chicks from the Faroe Islands. Plastic particles (≥1 mm) in chicks of two age classes were searched using a digestion method with KOH. In addition, to evaluate if additive tissue burden reflects plastic ingestion, we measured liver tissue concentrations of two pollutant classes associated with plastic materials: polybrominated diphenyl ethers (PBDEs) and several dechloranes, using gas chromatography with high-resolution mass spectrometry. The most common shape was hard fragment (81%) and the most common polymer was polyethylene (73%). Plastic contamination did not differ between either age class, and we found no correlation between neither the amount and mass of plastic particles and the concentration of additives. After comparison with previous studies on adult fulmars, we do not recommend using chicks for biomonitoring adults because chicks seem to ingest more plastics than adults.
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Assessment of heavy metal and POP pollution on global, regional and national scales
Meteorological Synthesizing Centre - East (MSC-E)
2022