Results 1 - 10 of 1848
Results 1 - 10 of 1848. Search took: 0.081 seconds
|Sort by: date | relevance|
[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] 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] 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] 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
[en] Possibly the most important aspect of performing maintenance of safety related equipment is maintaining the component's original design basis. Assuring that the repaired item will perform the same safety function within the original performance and equipment qualification parameters is commonly referred to as configuration control. Maintaining configuration control of a technologically current well documented item is easy. Unfortunately, this does not describe most safety related items requiring maintenance within the global nuclear industry. Items such as motors, transformers, metal clad switchgear (low and medium voltage circuit breakers), refrigeration compressors, and electronic components (i.e. circuit boards, power supplies, regulators, etc.) which routinely require repair have been in service for twenty plus years. As a result, finding replacement parts and or material to repair the items to the original condition is becoming more and more difficult. An added difficulty is the lack of original technical documentation available on the item which is being repaired. The lack of technical documentation makes it difficult to identify replacement material and parts when the original part or material is not available. The lack of documentation also makes it difficult to test the repaired item to make sure that the original configuration has been maintained after the repair. The presentation will discuss the details of repairing various items including motors, metal clad switchgear, refrigeration compressors and power supplies and the controls which are necessary to maintain the configuration of the original item. The discussion will include the Quality Assurance and engineering necessary to identify and evaluate replacement material and parts necessary to perform repairs on safety related equipment when the original material or part is not available. Examples of repairs which required different parts or materials than the original to be used in the repair will be given. The examples will provide a summary of the identification of the new part/material, the tests/inspections necessary on the new part/material, the documentation necessary to justify its use in the safety related repair in accordance with the guidelines of EPRI NP-6406, the justification to show that the items original environmental/seismic qualification (IEEE Std. 323 and IEEE Std. 344) is still valid and the verification and acceptance of the final repair configuration via dedication in accordance with guidelines of EPRI NP-5652. The examples will include the situation where little to no original technical documentation was available and the process which is necessary to assure configuration control in these instances. (author)
[en] A certificate has been obtained by SCC Environmental from the Quebec Ministry of Environment to demonstrate thermal phase separation (TPS) technology that separates contaminants from soils, sediments and sludges. The TPS process is a closed-loop, two-stage controlled thermal treatment and condensation and separation process, designed to remove chlorinated and non-chlorinated contaminants such as PCBs, PCP, PAH, chlorobenzenes, pesticides and insecticides from soils, sludges and sediments. During the process, organics from the soil are volatilized through indirect heat. The condensing gases are separated into oil, water and sludge fractions. The water is treated by sand filtration and activated carbon adsorption. Contaminants are sent to safe disposal. The tests will be conducted to verify the stability and reliability of the process. 1 tab., 2 figs
[en] The fate of hydrophobic organic compounds (HOCs) in soils and waters in a northern boreal catchment was explored through the development of a chemical fate model in a well-characterised catchment system dominated by two land types: forest and mire. Input was based solely on atmospheric deposition, dominated by accumulation in the winter snowpack. Release from soils was governed by the HOC concentration in soil, the soil organic carbon fraction and soil-water DOC content. The modelled export of selected HOCs in surface waters ranged between 11 and 250 ng day-1 during the snow covered period, compared to 200 and 9600 ng/d during snow-melt; highlighting the importance of the snow pack as a source of these chemicals. The predicted levels of HOCs in surface water were in reasonable agreement to a limited set of measured values, although the model tended to over predict concentrations of HOCs for the forested sub-catchment, by over an order of magnitude in the case of hexachlorobenzene and PCB 180. This possibly reflects both the heterogeneity of the forest soils and the complicated and changing hydrology experienced between the different seasons. - The fate of hydrophobic organic contaminants in a boreal forest catchment is connected to the flux of dissolved organic carbon and seasonal deposition.
[en] In an effort to support remedial investigations of abandoned septic tanks by US DOE, this report contains the results of chemical analyses of the contents of these abandoned tanks. Analytical data are presented for the following: volatile/TCLP volatile organics; semivolatile/TCLP semivolatile organics; PCB organics; total petroleum hydrocarbons; and total metals. The abandoned systems potentially received wastes or effluent from buildings which could have discharged non-domestic, petroleum hydrocarbons, hazardous, radioactive and/or mixed wastes. The 20 sites investigated are located on the Nevada Test Site
[en] The effect of polychlorinated biphenyls (PCBs) on Vero cell proliferation was investigated, with the attempts to assess the possible hormetic dose-response and to compare their structure-dependent toxicity. Both PCB congeners revealed low doses stimulation in our experiment. However, significant cytotoxicity was only observed in PCB 52 concentrations larger than 0.1 μg ml-1, while there was no significant inhibition in PCB 77-treated cells at concentrations selected. Furthermore, the time-dependent cytotoxic trends were different. The comparison between PCB 52 and PCB 77 indicated that the cytotoxic mechanisms involved in coplanar or non-coplanar PCB congener exposure were different, and this difference might be associated with individual genotoxicity and the release of contact inhibition, respectively.
[en] Turnaround time for this project was 60 days, as required in Reference 2. The analyses were to be performed using SW-846 procedures whenever possible to meet analytical requirements as a Resource Conservation Recovery Act (RCRA) protocol project. Except for the preparation and analyses of polychlorinated biphenyl hydrocarbons (PCB) and Nickel-63, which the program deleted as a required analyte for 222-S Laboratory, all preparative and analytical work was performed at the 222-S Laboratory. Quanterra Environmental Services of Earth City, Missouri, performed the PCB analyses. During work on this project, two events occurred nearly simultaneously, which negatively impacted the 60 day deliverable schedule: an analytical hold due to waste handling issues at the 222-S Laboratory, and the discovery of PCBs at concentrations of regulatory significance in the 105-N Basin samples. Due to findings of regulatory non-compliance by the Washington State, Department of Ecology, the 222-S Laboratory placed a temporary administrative hold on its analytical work until all waste handling, designation and segregation issues were resolved. During the hold of approximately three weeks, all analytical and waste.handling procedures were rewritten to comply with the legal regulations, and all staff were retrained in the designation, segregation and disposal of RCRA liquid and solid wastes