Articles avec #radionucleides - chimiques - nanoparticules...
Author: David Shukman, BBC News, 18 March 2015
Rising above the scene of the world’s worst nuclear accident is the spectacular sight of the largest moveable structure ever created on land.
The complex of nuclear power plants at Chernobyl has dominated this corner of northwest Ukraine for decades but the new construction towers over it all.
The project is to build what is called a New Safe Confinement – in effect, a giant cover, a kind of dome, to fit over the building that houses the reactor that exploded on 26 April, 1986.
The radiation immediately above the reactor is still far too intense for the new enclosure to be built exactly where it is needed – anyone working there can only stay very briefly.
So adjacent land has been cleared and then decontaminated – a massive task in itself – to allow the new structure to be assembled before being manoeuvred into position.
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Un rapport à lire ici du Centre d’expertise en analyse environnementale du Québec (CEAEQ). Le CEAEQ est une agence québécoise (Canada) du ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques qui fournit des services spécialisés touchant différents aspects de l'analyse environnementale (analyses de laboratoire, accréditation, études écotoxicologiques et études de terrain).
A publication in the Proceedings of the National Academy of Sciences of the United States of America (published ahead of print December 29, 2014, doi:10.1073/pnas.1412814112)
Authors: John N. Smith (a), Robin M. Brown (b), William J. Williams (b), Marie Robert (b), Richard Nelson (a), and S. Bradley Moran (c)
(a) Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS, Canada B2Y 4A2;
(b) Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, BC, Canada V8L 4B2; and
(c) Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882-1197
Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved December 2, 2014 (received for review July 28, 2014)
To whom correspondence should be addressed. Email: email@example.com.
The radionuclide results in this report represent the first systematic study, to our knowledge, of the arrival of the Fukushima radioactivity signal in continental waters off North America. The present time series results are critical to an understanding of the circulation of Fukushima tracers in the eastern North Pacific and to the tuning and validation of ocean circulation models that are being used to predict the future evolution of this signal. They are also important for informing the public of the magnitude of the Fukushima radioactivity signal in North American continental waters and enabling a science-based assessment of the significance of its potential effects on human health and the environment.
The large discharge of radioactivity into the northwest Pacific Ocean from the 2011 Fukushima Dai-ichi nuclear reactor accident has generated considerable concern about the spread of this material across the ocean to North America. We report here the first systematic study to our knowledge of the transport of the Fukushima marine radioactivity signal to the eastern North Pacific. Time series measurements of 134Cs and137Cs in seawater revealed the initial arrival of the Fukushima signal by ocean current transport at a location 1,500 km west of British Columbia, Canada, in June 2012, about 1.3 y after the accident. By June 2013, the Fukushima signal had spread onto the Canadian continental shelf, and by February 2014, it had increased to a value of 2 Bq/m3 throughout the upper 150 m of the water column, resulting in an overall doubling of the fallout background from atmospheric nuclear weapons tests. Ocean circulation model estimates that are in reasonable agreement with our measured values indicate that future total levels of 137Cs (Fukushima-derived plus fallout 137Cs) off the North American coast will likely attain maximum values in the 3–5 Bq/m3 range by 2015–2016 before declining to levels closer to the fallout background of about 1 Bq/m3 by 2021. The increase in 137Cs levels in the eastern North Pacific from Fukushima inputs will probably return eastern North Pacific concentrations to the fallout levels that prevailed during the 1980s but does not represent a threat to human health or the environment.
Freely available online through the PNAS open access option here
Abstract: Accidental release of nuclides into the ocean is causing health risks to marine organisms and humans. All life forms are susceptible to gamma radiation with a high variation, depending on various physical factors such as dose, mode, and time of exposure and various biological factors such as species, vitality, age, and gender. Differences in sensitivity of gamma radiation are also associated with different efficiencies of mechanisms related to protection and repair systems. Gamma radiation may also affect various other integration levels: from gene, protein, cells and organs, population, and communities, disturbing the energy flow of food webs that will ultimately affect the structure and functioning of ecosystems. Depending on exposure levels, gamma radiation induces damages on growth and reproduction in various organisms such as zooplankton, benthos, and fish in aquatic ecosystems. In this paper, harmful effects of gamma-irradiated aquatic organisms are described and the potential of marine copepods in assessing the risk of gamma radiation is discussed with respect to physiological adverse effects that even affect the ecosystem level.
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