Results 1 - 10 of 2000
Results 1 - 10 of 2000. Search took: 0.024 seconds
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[en] The present study contributed towards establishing the status of a tropical and a moderate latitude marine ecosystem in terms of the concentration of anthropogenic, lipid associated, cyclic, halogenated hydrocarbons in surface sediments and benthic macroinvertebrates. Samples were obtained from the coastal region and the continental slope of Kenya (Indian Ocean), the Dutch coastal region and the continental shelf of the North Sea, and a bay area of Curacao (Netherlands Antilles, Caribbean). In surface sediments (Kenya), congeners CB28, CB52, CB101, CB118, CB153, CB138 and CB180, and the pesticides alpha-HCH and gamma-HCH, dieldrin, endrin and members of the DDT family were not identified, except in the estuarine zone of the Sabaki River. In North Sea surface sediment, the characteristics PCB pattern was always determined, and concentrations were particularly enhanced in sediment from the river mouths. Also, alpha-HCH, p,p'-DDD and p,p'-DDE were quantified in most samples. Regarding benthic invertebrates, CBs and p,p'-DDE were quantified. Some samples showed particularly enhanced levels in bivalve molluscs and certain penaeid prawns the Kenyan coastal region. The high levels present in the digestive (pyloric caeca) and reproductive (gonad) organs of seastar from the North Sea confirmed distinct concentration gradients. Sponges and tunicates from the bay area of Curacao accumulated CBs and p,p'-DDE, but not at very high concentrations. (author). 23 refs, 2 figs, 7 tabs
[en] For reasons of precautionary health care, materials containing PCBs are removed from buildings. The paper gives an introductory description of these materials, mentions the legal boundary conditions, and discusses the principles of and practical experience in PCB decontamination of buildings as well as necessary protection measures. (orig.)
[de]Aus Gruenden der Gesundheitsvorsorge werden PCB-haltige Materialien aus Gebaeuden entfernt. In diesem Beitrag werden neben einer einfuehrenden Stoffbeschreibung und den rechtlichen Rahmenbedingungen die Grundsaetze und Praxiserfahrungen der PCB-Gebaeudesanierung sowie die erforderlichen Schutzmassnahmen eroertert. (orig.)
[en] Within the framework of the Bavarian soil cadastre, 260 soils from 90 sites throughout Bavaria were sampled for organic pollutants between 1986 and mid-1989. From the material class of the polychlorinated biphenyls (PCB), first results were introduced. The PCB total concentrations depend very strongly on soil utilization. Forest sites occupy a special position. The comparison of agricultural and forest soils with regard to pollutant concentrations is possible only with volume specific concentrations and/or a site-specific material balance. (orig.)
[de]Im Rahmen des Bodenkatasters Bayern wurden in den Jahren von 1986 bis Mitte 1989 landesweit 260 Bodenproben von 90 Standorten auf organische Problemstoffe untersucht. Aus der Stoffklasse der polychlorierten Biphenyle (PCB) wurden erste Ergebnisse vorgestellt. Die PCB-Gesamtgehalte haengen sehr stark von der Bodennutzung ab. Forstwirtschaftlich genutzte Standorte nehmen dabei eine Sonderstellung ein. Der Vergleich von landwirtschaftlich und forstwirtschaftlich genutzten Boeden hinsichtlich ihrer Problemstoffbelastung ist nur mit volumenspezifischen Konzentrationen bzw. einer standortsbezogenen Stoffbilanzierung moeglich. (orig.)
[en] The relationship was studied between the relative mobility of a group of 19 chlorophenols in different buffers modified by eight kinds of different organic additives in capillary zone electrophoresis and a set of 10 molecular descriptors calculated by semi-empirical quantum chemical method PM3 implemented in HyperChem. Using multiple linear regression (MLR), we obtained an empirical function which included five descriptors. The performance of radial basis function neural network (RBFNN) was evaluated and proved better than MLR
[en] Population models can be used to place observed toxic effects into an assessment of the impacts on population-level endpoints, which are generally considered to provide greater ecological insight and relevance. We used an individual-based model of mink to evaluate the population-level effects of exposure to polychlorinated biphenyls (PCBs) and the impact that different remediation strategies had on mink population endpoints (population size and extinction risk). Our simulations indicated that the initial population size had a strong impact on mink population dynamics. In addition, mink populations were extremely responsive to clean-up scenarios that were initiated soon after the contamination event. In fact, the rate of PCB clean-up did not have as strong a positive effect on mink as did the initiation of clean-up (start time). We show that population-level approaches can be used to understand adverse effects of contamination and to also explore the potential benefits of various remediation strategies. - Highlights: → We used an individual-based model of mink to evaluate population-level impacts of PCB contamination. → The model was also used to explore the population responses to different PCB remediation strategies. → Population size had a large impact on whether mink populations persisted or went extinct. → Starting remediation sooner had a stronger positive effect on mink populations than did the rate of PCB clean-up. → Individual-based models are useful in understanding effects of contamination and different remediation strategies. - An individual-based model of mink showed strong population-level effects of PCB contamination and provided insight into optimal PCB remediation strategies.
[en] Wild forest animals are used as biological indicators for pollutant loads in ecological research. Advantages and disadvantages of animal biological indicators for monitoring the heavy metal contamination are discussed. It is shown which mammal species are especially suitable and which factors must be considered in the selection of investigation material, the analysis and the interpretation of the results. (orig.)
[de]Freilebende Wildtiere werden in der oekologischen Forschung als Bioindikatoren fuer die Belastung mit Umweltschadstoffen eingesetzt. Es werden in der nachfolgenden Arbeit Vor- und Nachteile tierischer Bioindikatoren fuer die Erfassung der Schwermetallkontamination diskutiert. Es wird gezeigt, welche Saeugetierarten besonders geeignet sind und welche Faktoren bei der Auswahl des Untersuchungsmaterials, der Analyse und der Intrpretation der Ergebnisse beruecksichtigt werden muessen. (orig.)
[en] In high speed PCB design, microstirp lines were used to control the impedance, however, the discontinuous microstrip line can cause signal integrity problems. In this paper, we use the transmission line theory to study the characteristics of microstrip lines. Research results indicate that the discontinuity such as truncation, gap and size change result in the problems such as radiation, reflection, delay and ground bounce. We change the discontinuities to distributed parameter circuits, analysed the steady-state response and transient response and the phase delay. The transient response cause radiation and voltage jump.
[en] A new chemiselective method of synthesis of 2,4,6-triiodoaniline and 2,4-diiodoaniline by reaction between aniline and potassium dichloroiodate in HCl solution was suggested. Subsequent desamination of 2,4,6-triiodoaniline results in 1,3,5-triiodobenzene with a high yield
[ru]Предложен новый хемоселективный метод синтеза 2,4,6-трииоданилина и 2,4-дииоданилина реакций анилина с дихлориодатом калия в растворе HCl. Последующее дезаминирование 2,4,6-трииоданилина приводит к 1,3,5-трииодбензолу с хорошим выходом
[en] Several studies of environmental samples indicate that the levels of many persistent organic pollutants (POPs) are increasing in Africa, but few studies have been conducted in humans. Simultaneously, many African countries are experiencing a rapid economic growth and implementing information and communication technologies (ICT). These changes have generated high amounts of electronic waste (e-waste) that have not been adequately managed. We tested the hypothesis that the current levels of two main classes of POPs in Western and Central African countries are affected by the degree of socioeconomic development. We measured the levels of 36 POPs in the serum of recent immigrants (N = 575) who came from 19 Sub-Saharan countries to the Canary Islands (Spain). We performed statistical analyses on their anthropometric and socioeconomic data. High median levels of POPs were found in the overall sample, with differences among the countries. Organochlorine pesticide (OCP) and polychlorinated biphenyl (PCB) levels increased with age. People from low-income countries had significantly higher OCP levels and much lower PCB levels than those from high-income countries. We found a significant association between the implementation of ICT and PCB contamination. Immigrants from the countries with a high volume of imports of second-hand electronic equipment had higher PCB levels. The economic development of Africa and the e-waste generation have directly affected the levels of POPs. The POP legacies of these African populations most likely are due to the inappropriate management of the POPs' residues. - Highlights: • Higher levels of organochlorine pesticides in Africans from low-income countries • Higher levels of PCBs in Africans from high-income countries • Levels of PCBs are significantly higher in people from West Africa. • Significant association between implementation of ICT and PCB contamination • High volume of second-hand electronic equipment is associated with high PCB levels