The Influence of Ice-Resistant Coatings Characteristics to the Energy Efficiency of Ice-Going Ships

The main purpose of ice-resistant coatings designed for icebreakers and ice navigation ships is the ability to protect of the ship’s hull in the most severe operating conditions. The special coatings certified by the Classification Societies for ice abrasion can provide this protection. These coatings allow to reduce the required thickness of the ship’s hull and reduce the construction weight of the ships. On the other hand, these coatings must have a low friction coefficient, which reduce the frictional resistance of the hull on ice and fuel consumption, increase the service life of the ship and power plant, reduce CO2 emissions into the atmosphere and affect to the operational and economic efficiency of the ship. In this paper, we present the results of experimental tests of friction coefficient on ice for various types of ice-resistant coatings and analysis the influence of ice-resistant coatings characteristics to the energy efficiency of ice-going ships

Higher mass-independent isotope fractionation of methylmercury in the pelagic food web of Lake Baikal (Russia)

cited By 36International audienceMercury undergoes several transformations that influence its stable isotope composition during a number of environmental and biological processes. Measurements of Hg isotopic mass-dependent (MDF) and mass-independent fractionation (MIF) in food webs may therefore help to identify major sources and processes leading to significant bioaccumulation of methylmercury (MeHg). In this work, δ13C, δ15N, concentration of Hg species (MeHg, inorganic Hg), and stable isotopic composition of Hg were determined at different trophic levels of the remote and pristine Lake Baikal ecosystem. Muscle of seals and different fish as well as amphipods, zooplankton, and phytoplankton were specifically investigated. MDF during trophic transfer of MeHg leading to enrichment of heavier isotopes in the predators was clearly established by δ202Hg measurements in the pelagic prey-predator system (carnivorous sculpins and top-predator seals). Despite the low concentrations of Hg in the ecosystem, the pelagic food web reveals very high MIF Δ199Hg (3.15-6.65‰) in comparison to coastal fish (0.26-1.65‰) and most previous studies in aquatic organisms. Trophic transfer does not influence MIF signature since similar Δ199Hg was observed in sculpins (4.59 ± 0.55‰) and seal muscles (4.62 ± 0.60‰). The MIF is suggested to be mainly controlled by specific physical and biogeochemical characteristics of the water column. The higher level of MIF in pelagic fish of Lake Baikal is mainly due to the bioaccumulation of residual MeHg that is efficiently turned over and photodemethylated in deep oligotrophic and stationary (i.e., long residence time) freshwater columns. © 2012 American Chemical Society

Natural Hg isotopic composition of different Hg compounds in mammal tissues as a proxy for in vivo breakdown of toxic methylmercury

International audienceIn the last decade, specific attention has been paid to total mercury (HgT) stable isotopic composition, especially in natural samples such as aquatic organisms, due to its potential to track the cycle of this toxic element in the environment. Here, we investigated Hg Compound Specific stable Isotopic Composition (CSIC) of natural inorganic Hg (iHg) and methylmercury (MMHg) in various tissues of aquatic mammals (Beluga whale from the Arctic marine environment and seals from the freshwater lake Baikal, Russia). In seals' organs the variation in mass dependent fractionation (MDF, δ202Hg) for total Hg was significantly correlated to the respective fraction of iHg and MMHg compounds, with MMHg being enriched by ∼3‰ in heavier isotopes relative to iHg. On the other hand, we observe insignificant variation in Hg mass independent isotope fractionation (MIF, Δ199Hg) among iHg and MMHg in all organs for the same mammal species and MMHg in prey items. MIF signatures suggest that both MMHg and iHg in aquatic mammals have the same origin (i.e., MMHg from food), and are representative of Hg photochemistry in the water column of the mammal ecosystem. MDF signatures of Hg compounds indicate that MMHg is demethylated in vivo before being stored in the muscle, and the iHg formed is stored in the liver, and to a lesser extent in the kidney, before excretion. Thus, Hg CSIC analysis in mammals can be a powerful tool for tracing the metabolic response to Hg exposur