578 resultados para Polychlorinated biphenyls (PCB)
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Continuous and comparable atmospheric monitoring programs to study the transport and occurrence of persistent organic pollutants (POPs) in the atmosphere of remote regions is essential to better understand the global movement of these chemicals and to evaluate the effectiveness of international control measures. Key results from four main Arctic research stations, Alert (Canada), Pallas (Finland), Storhofdi (Iceland) and Zeppelin (Svalbard/Norway), where long-term monitoring have been carried out since the early 1990s, are summarized. We have also included a discussion of main results from various Arctic satellite stations in Canada, Russia, US (Alaska) and Greenland which have been operational for shorter time periods. Using the Digital Filtration temporal trend development technique, it was found that while some POPs showed more or less consistent declines during the 1990s, this reduction is less apparent in recent years at some sites. In contrast, polybrominated diphenyl ethers (PBDEs) were still found to be increasing by 2005 at Alert with doubling times of 3.5 years in the case of deca-BDE. Levels and patterns of most POPs in Arctic air are also showing spatial variability, which is typically explained by differences in proximity to suspected key source regions and long-range atmospheric transport potentials. Furthermore, increase in worldwide usage of certain pesticides, e.g. chlorothalonil and quintozene, which are contaminated with hexachlorobenzene (HCB), may result in an increase in Arctic air concentration of HCB. The results combined also indicate that both temporal and spatial patterns of POPs in Arctic air may be affected by various processes driven by climate change, such as reduced ice cover, increasing seawater temperatures and an increase in biomass burning in boreal regions as exemplified by the data from the Zeppelin and Alert stations. Further research and continued air monitoring are needed to better understand these processes and its future impact on the Arctic environment.
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The Norwegian spring spawning (NSS) herring is an ecologically important fish stock in the Norwegian Sea, and with a catch volume exceeding one million tons a year it is also economically important and a valuable food source. In order to provide a baseline of the levels of contaminants in this fish stock, the levels of organohalogen compounds were determined in 800 individual herring sampled at 29 positions in the Norwegian Sea and off the coast of Norway. Due to seasonal migration, the herring were sampled where they were located during the different seasons. Concentrations of dioxins and dioxin-like PCBs, non-dioxin-like PCBs (PCB7) and PBDEs were determined in fillet samples of individual herring, and found to be relatively low, with means (min-max) of 0.77 (0.24-3.5) ngTEQ/kg wet weight (ww), 5.0 (1.4-24) µg/kg ww and 0.47 (0.091-3.1) µg/kg ww, respectively. The concentrations varied throughout the year due to the feeding- and spawning cycle: Starved, pre-spawning herring caught off the Norwegian coast in January-February had the highest levels and those caught in the Norwegian Sea in April-June, after further starvation and spawning, had the lowest levels. These results show that the concentrations of organohalogen compounds in NSS herring are relatively low and closely tied to their physiological condition, and that in the future regular monitoring of NSS herring should be made in the spawning areas off the Norwegian coast in late winter.
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Este PFC es un trabajo muy práctico, los objetivos fueron impuestos por el tutor, como parte del desarrollo de herramientas (software y hardware) que serán utilizados posteriormente a nivel de docencia e investigación. El PFC tiene dos áreas de trabajo, la principal y primera que se expone es la utilización de una herramienta de simulación térmica para caracterizar dispositivos semiconductores con disipador, la segunda es la expansión de una tarjeta de adquisición de datos con unas PCBs diseñadas, que no estaban disponibles comercialmente. Se ha probado y configurado “Autodesk 2013 Inventor Fusion” y “Autodesk 2013 Simulation and Multiphysics” para simulación térmica de dispositivos de alta potencia. Estas aplicaciones son respectivamente de diseño mecánico y simulación térmica, y la UPM dispone actualmente de licencia. En esta parte del proyecto se realizará un manual de utilización, para que se continúe con esta línea de trabajo en otros PFC. Además se han diseñado mecánicamente y simulado térmicamente diodos LED de alta potencia luminosa (High Brightness Lights Emitting Diodes, HB-LEDs), tanto blancos como del ultravioleta cercano (UVA). Las simulaciones térmicas son de varios tipos de LEDs que actualmente se están empleando y caracterizando térmicamente en Proyectos Fin de Carrera y una Tesis doctoral. En la segunda parte del PFC se diseñan y realizan unas placas de circuito impreso (PCB) cuya función es formar parte de sistemas de instrumentación de adquisición automática de datos basados en LabVIEW. Con esta instrumentación se pueden realizar ensayos de fiabilidad y de otro tipo a dispositivos y sistemas electrónicos. ABSTRACT. The PFC is a very practical work, the objectives were set by the tutor, as part of the development of tools (software and hardware) that will be used later at level of teaching and research. The PFC has two parts, the first one explains the use of a software tool about thermal simulation to characterize devices semiconductors with heatsink, and second one is the expansion of card data acquisition with a PCBs designed, which were not available commercially. It has been tested and configured "Autodesk 2013 Inventor Fusion" and "Autodesk 2013 Simulation Multiphysics” for thermal simulation of high power devices. These applications are respectively of mechanical design and thermal simulation, and the UPM has at present license. In this part of the project a manual of use will be realized, so that it is continued by this line of work in other PFC. Also they have been designed mechanically and simulated thermally LEDs light (High Brightness Lights Emitting Diodes , HB- LEDs) both white and ultraviolet. Thermal simulations are several types of LEDs are now being used in thermally characterizing in Thesis and PhD. In the second part of the PFC there are designed and realized circuit board (PCB) whose function is to be a part of instrumentation systems of automatic acquisition based on LabVIEW data. With this instrumentation can perform reliability testing and other electronic devices and systems.
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"This toxicological profile is prepared in accordance with guidelines developed by the Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA). The original guidelines were published in the Federal Register on April 17, 1987"--P. v.