Technical Note: The air quality modeling system Polyphemus

International audiencePolyphemus is an air quality modeling platform which aims at covering the scope and the abilities of modern air quality systems. It deals with applications from local scale to continental scale, using two Gaussian models and two Eulerian models. It manages passive tracers, radioactive decay, photochemistry and aerosol dynamics. The structure of the system includes four independent levels with data management, physical parameterizations, numerical solvers and high-level methods such as data assimilation. This enables sensitivity and uncertainty analysis, primarily through multimodel approaches. On top of the models, drivers implement advanced methods such as model coupling or data assimilation

Retinoid-Induced Expression and Activity of an Immediate Early Tumor Suppressor Gene in Vascular Smooth Muscle Cells

Retinoids are used clinically to treat a number of hyper-proliferative disorders and have been shown in experimental animals to attenuate vascular occlusive diseases, presumably through nuclear receptors bound to retinoic acid response elements (RARE) located in target genes. Here, we show that natural or synthetic retinoids rapidly induce mRNA and protein expression of a specific isoform of A-Kinase Anchoring Protein 12 (AKAP12β) in cultured smooth muscle cells (SMC) as well as the intact vessel wall. Expression kinetics and actinomycin D studies indicate Akap12β is a retinoid-induced, immediate-early gene. Akap12β promoter analyses reveal a conserved RARE mildly induced with atRA in a region that exhibits hyper-acetylation. Immunofluorescence microscopy and protein kinase A (PKA) regulatory subunit overlay assays in SMC suggest a physical association between AKAP12β and PKA following retinoid treatment. Consistent with its designation as a tumor suppressor, inducible expression of AKAP12β attenuates SMC growth in vitro. Further, immunohistochemistry studies establish marked decreases in AKAP12 expression in experimentally-injured vessels of mice as well as atheromatous lesions in humans. Collectively, these results demonstrate a novel role for retinoids in the induction of an AKAP tumor suppressor that blocks vascular SMC growth thus providing new molecular insight into how retiniods may exert their anti-proliferative effects in the injured vessel wall

Development and Validation of a 3D Chemistry-Transport Model, POLAIR 3D, by Comparison with Data from ESQUIF Campaign

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Fukushima Daiichi–derived radionuclides in the atmosphere, transport and deposition in Japan A review

International audienceThe Fukushima Daiichi Nuclear Power Plant accident of March 11 2011 led to a significant release of radionuclides in the environment. More than 99% of the release activity in the atmosphere was due to highly volatile radionuclides such as I, Te, Cs, Xe, Kr. Fairly quickly after the accident, the main release events had been identified and their consequences roughly assessed. Most releases were dispersed over the Pacific Ocean whereas about 20% was dispersed over the Japan main highland causing areas of significant deposit. Since then, the understanding of the different episodes has been greatly enhanced. It is appropriate to review what happened in terms of releases into the atmosphere, transport, and deposition of radionuclides on the Japanese territory. We describe here, the current state of understanding of the release phase of the accident and the means used to achieve it. Numerous radiological measurements taken in the Japanese environment enabled the scientists to substantially reconstruct the four main sequences of contamination, to identify the probable trajectories of the radioactive plumes, and to link them with precipitation data to explain the areas of deposition. The measurements were supplemented by modelling techniques. The most significant progress come from the quantification of the atmospheric releases, the improvement of meteorological data to better take into account the influence of the complex orography on the plumes trajectories and the modelling of deposition processes. Notwithstanding more realistic simulations, progress is still to be made to accurately estimate people exposure due to the release phase of the FDNPP accident. An important result is that the bulk of the deposition was mostly generated at the beginning of the precipitation, by light rain in less than one hour. The scavenging of plume transported in altitude generates high deposition zones. Therefore, they do not necessarily match the zones within which inhalation exposure to the radioactive plumes was the largest. © 2018 Elsevier Lt

The IRSN’s earliest assessments of the Fukushima accident's consequences for the terrestrial environment in Japan

In 2011 the IRSN conducted several assessments of atmospheric radioactive releases due to the Fukushima Daiichi NPP accident (March 11, 2011) and of their impact on Japan’s terrestrial environment. They were based on the IRSN’s emergency management tools and on the abundant information and technical data gradually published in Japan. According to these assessments, the main release phase lasted from March 12 to 25, 2011 and impacted Japanese land in two events, the first on 15 and 16 March, in which the main radioactive deposits were formed, and the second from March 20 to 23, which was less significant. The highest amounts of radioactive deposits were found in an area extending upwards of several tens of kilometers northwest of the plant. Lower amounts were discontinuously scattered in an area extending up to over 250 km away. Initially composed mainly of short-lived radionuclides, the deposits’ activity sharply decreased in the subsequent weeks. Since the summer of 2011, cesium-134 and cesium-137 have become the residual deposits’ main components. According to IRSN estimates, in the absence of protection, the doses due to exposure to the radioactive plume during the atmospheric release phase may have been potentially higher for people who remained in coastal areas up to several tens of kilometers north and south of the damaged plant. Thereafter, people living up to 50 km northwest of the plant, outside the 20-km emergency evacuation zone, were potentially most vulnerable to residual radioactive deposits over time