خيارات البحث
النتائج 221 - 230 من 347
Reef degradation and coral biodiversity in Indonesia: effects of land-based pollution, destructive fishing practices and changes over time
1998
Edinger, E.N. | Jompa, J. | Limmon, G.V. | Widjatmoko, W. | Risk, M.J. (School of Geography and Geology, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada))
Thyroid hormones as biomarkers in grey seals
1998
Hall, A.J. | Green, N.J.L. | Jones, K.C. | Pomeroy, P.P. | Harwood, J. (Sea Mammal Research Unit, NERC, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife KY16 8LB (United Kingdom))
The environmental impact of shrimp aquaculture and the coastal pollution in Mexico
1998
Paez-Osuna, F. | Guerrero-Galvan, S.R. | Ruiz-Fernandez, A.C. (Estacion Mazatlan, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 811, Mazatlan 82000, Sinaloa (Mexico))
Mercury pollution and the Saimaa ringed seal (Phoca hispida saimensis)
1998
Hyvarinen, H. | Sipila, T. | Kunnasranta, M. | Koskela, J.T. (Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu (Finland))
Multitracer Study on Absorption of Radionuclides in Atmosphere-Plant Model System النص الكامل
1998
Shinonaga, Taeko | Ambe, Shizuko
The absorption of atmospheric radionuclides by soybean plants was experimentally studied using a radioactive multitracer consisting of radionuclides of Sc, Mn, Co, As, Se, Rb, Sr, Y, Eu, Gd, Yb, Hf, Re, and Ir. The soybean plants were cultivated in soil under no-rain conditions in a box containing air in which multitracer-absorbed cellulose particles were dispersed. The soil was covered with plastic film. After about one-month cultivation, the plants were harvested and washed with dilute HCl solution. The leaves, stems, and beans were subjected to γ-ray measurement. The radionuclides of As, Se, and Re were accumulated in the leaves, and those of Co, Se, and Rb were accumulated in the beans. Among them Se was accumulated to a large extent in the leaves and in the beans. Small amounts of the radionuclides of Co, Se, Rb and Re were found in the roots. Little absorption of these radionuclides into the soil occurred. These results indicate that various radionuclides in the atmosphere were absorbed through the soybean leaves and then transported to the seeds. These findings must be taken into consideration for a complete understanding of the system of uptake of radionuclides by the soybean plant.
اظهر المزيد [+] اقل [-]Effects of Alkalinity and External Sulphate and Phosphorus Load on Water Chemistry in Enclosures in an Eutrophic Shallow Lake النص الكامل
1998
Bellemakers, Martijn J. S. | Maessen, Mario
As a result of changes in hydrology, the former mesotrophic, shallow lake Naardermeer, has been eutrophicated during the last decades. To compensate for shortage of water, eutrophicated water with different chemical characteristics has been supplied. In order to determine the effects of alkalinity, acidity and external sulphate and phosphorus load on eutrophication processes, developments in water chemistry have been studied in enclosures. A decrease of the phosphorus load of the lake did not improve water quality on the short term. This observation was confirmed by this enclosure experiment. Reduction of alkalinity did improve water quality, particularly by reductions of turbidity and chlorophyll-a content. The significant increase in sulphate load in the water layer led to deterioriation of the water quality and an increased biomass of sessile algae by internal eutrophication, probably as a result of increased sulphate reduction in the sediment. Therefore, it seems that lowering of sulphate concentrations in the inlet water after the removal of phosphorus is necessary to improve the water chemistry. The best option, however, is to restore the former hydrological conditions after which the system will be fed only by seepage of groundwater poor in nutrients and sulphate.
اظهر المزيد [+] اقل [-]Bioaccumulation and Toxicity of Zinc in Spirogyra Fluviatilis Hilse (Chlorophyta) النص الكامل
1998
Saygideger, S.
The bioaccumulation and toxicity of zinc in Spirogyra fluviatilis Hilse, from two populations in the River Seyhan, Adana, Turkey, were examined in laboratory flowing-water channels. Plants were subjected to zinc concentrations ranging from 0 to 4.0 mg L⁻¹ at current velocities of 25–35 cm s⁻¹ for up to 3 h. There was little difference in zinc bioaccumulation between Spirogyra from the site showing mild organic pollution and that from the site subjected to considerable inputs from urban and motorway runoff. Uptake of zinc increased with increasing concentration in the test solution and was linear and proportional up to 0.5 mg L⁻¹. Cellular damage was evident in Spirogyra subjected to 0.5 mg L⁻¹ zinc, and increased with increasing zinc concentration.
اظهر المزيد [+] اقل [-]Anthropogenic Mercury Deposition to Arctic Lake Sediments النص الكامل
1998
Hermanson, Mark H.
The history of atmosheric mercury inputs to remote arctic regions can be measured in lake sediment cores using lead-210 chronology. In this investigation, total mercury deposition is measured in sediments from Imitavik and Annak Lakes on the Belcher Islands in southeastern Hudson Bay, an area in the southern Canadian Arctic with no history of local industrial or agricultural sources of contamination. Both lakes received background and atmospheric inputs of mercury while Annak also received mercury from raw domestic sewage from the Hamlet of Sanikiluaq, a growing Inuit community of about 550 established in the late 1960's. Results from Imitavik show that anthropogenic mercury inputs, apparently transported through the atmosphere, began to appear in the mid-eighteenth century, and continued to the 1990's. Annak had a similar mercury history until the late 1960's when disposal of domestic sewage led to increased sediment and contaminant accumulation. The high input of mercury to Annak confirms that Sanikiluaq residents are exposed to mercury through native food sources.
اظهر المزيد [+] اقل [-]Biological Elimination of Volatile Organic Compounds from Waste Gases in a Biofilter النص الكامل
1998
Wu, G. | Chabot, J. C. | Caron, J. J. | Heitz, M.
A great deal of research has been directed towards the problem of reduction and control of volatile organic compounds (VOCs). The aim of this research is to find a process that is both efficient and inexpensive in comparison with traditional air treatment technologies.Our biofilter (one stage system, 2 m in height) is an aerobic system for waste gases containing VOCs using the degradation properties of microbial flora (assorted cultures of Bacillus, Micrococcus, Acinetobacter and yeast). In this process, polluted gas diffuses across a filter bed into which a microbial culture has previously been introduced. Peat is the medium of choice for inoculation with microorganisms because of its adsorption and absorption properties, ability to retain moisture, and buffering capacity. Furthermore, the peat utilized is spherical in shape; thus, it is possible to avoid problems related to compacting.The objective of this study was to eliminate VOCs emitted from a rotogravure process. We were able to achieve promising results from biofiltration of two types of VOCs (a mixed solvent containing isopropyl acetate and 1-nitropropane, and the solvent: 1-nitropropane). The results obtained indicate that the elimination of nitropropane and the mixed solvent in the biofilter are considered to follow zero-order kinetics with reaction rate limitation and diffusion rate limitation, respectively.
اظهر المزيد [+] اقل [-]Use of Soft Data in a GIS to Improve Estimation of the Volume of Contaminated Soil النص الكامل
1998
Hendriks, L. A. M. | Leummens, H. | Stein, A. | de Bruijn, P.
In the practice of soil remediation, organoleptic observations such as the smell or the colour of contaminated soil play an important role when determining well-defined volumes of contaminated soil. A GIS is then used to combine quantitative measurements with such soft data. In this study general procedures concerning how to deal with this type of observations are presented. The procedures were applied to a former gas works site, which was contaminated with cyanide and polycyclic aromatic hydrocarbons in the Netherlands. The volume of contaminated soil was determined. Use of soft data reduced the uncertainty in the volume of contaminated soil with 4 to 16%.
اظهر المزيد [+] اقل [-]