خيارات البحث
النتائج 231 - 240 من 333
Bioaccumulation and Toxicity of Zinc in Spirogyra Fluviatilis Hilse (Chlorophyta)
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 [-]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))
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))
Effects of nesting yellow-legged gulls (Larus cachinnans pallas) on the heavy metal content of soils in the Cies Islands (Galicia, North-West Spain)
1998
Perez, X.L.O. (Departamento de Edafoloxia e Quimica Agricola, Facliltade de Bioloxia, 15 706 Santiago de Compostela (Spain))
Environmental contaminants in tissues of a neonate St Lawrence beluga whale (Delphinapterus leucas)
1998
Gauthier, J.M. | Pelletier, E. | Brochu, C. | Moore, S. | Metcalfe, C.D. | Beland, P. (Trent University, Environmental and Resources Studies Program, Peterborough, Ontario K9J 7B8 (Canada))
UK national marine analytical quality control scheme: the assessment of performance in the determination of organochlorines in water, 1992-1996
1998
Law, R.J. | Dobson, J.E. (The Centre for Environment, Fisheries and Aquaculture Science, CEFAS Burnham Laboratory, Burnham-on-Crouch, Essex CMO 8HA (United Kingdom))
An Emissions Inventory for Regional Atmospheric Modeling of Mercury
1998
Pai, Prasad | Heisler, S. (Steven) | Joshi, Aruna
Estimates of mercury emissions from individual sources and source categories are needed to understand relationships between the emissions and resulting deposition and to evaluate possible approaches to reducing those emissions. We have developed geographically-resolved estimates of annual average mercury emission rates from current anthropogenic sources in the 48 contiguous United States. These estimates were made by applying emission factors to individual facility operating data and to county-wide source activity levels. We apportioned the emissions to an Eulerian modeling grid system using point source coordinates and the fractions of county areas in each grid cell. Point sources account for about 89% of the 48-state total mercury emissions of 146.4 Mg/yr. Most of the emissions in the inventory are from combustion of mercury-containing fossil fuels and municipal waste, located primarily in the mid-Atlantic and Great Lakes states as well as in the Southeast. The major uncertainties in the emission estimates are caused by uncertainties in the emission factors used to develop the estimates. This uncertainty is likely a result of variability in the mercury content of the combusted materials and in the removal of mercury by air pollution control devices. The greatest research need to reduce uncertainties in mercury emission estimates is additional measurements to improve emission factors.
اظهر المزيد [+] اقل [-]Arsenic in Human and Cow's Milk: a Reflection of Environmental Pollution
1998
Ulman, Cevval | Gezer, Semra | Anal, Özden | Töre, I Ruhi | Kirca, Üzeyir
Arsenic, an environmental pollutant, is present in minute but invariable amounts in food, drinking water and ambient air. Izmir is founded on a land of long extinct volcanoes, with vast areas of lava ground suitable for agriculture. It is located at close vicinity to high thermal activity, e.g., hot springs and thermal baths. In the present study, total arsenic level in breast milk was assessed in randomly chosen 35 lactating women of different socioeconomic levels who live downtown in Izmir and in milk of 36 cows grazing on shoulder grass of highways with heavy traffic. Total arsenic was assessed on an atomic absorption spectrophotometer (AA-680 Shimadzu). Mean (± SEM) arsenic was found to be 4.219 ± 0.079 µg L⁻¹ in breast milk, and 4.932 ± 0.38 µg L⁻¹ in cow's milk. Conclusion: in Izmir, arsenic contamination of breast milk was not found so as to be considered noxious for suckling infants, whereas was found relatively higher in cow's milk. It would be prudent to remember breast and cow's milk arsenic contamination in breast fed or milk fed babies living in areas with higher thermal activity or in regions where ground water is with high arsenic content.
اظهر المزيد [+] اقل [-]Influence of pH and Zinc Concentration on Cadmium Sorption in Acid, Sandy Soils
1998
Wilkins, B. J. | Brummel, N. | Loch, J. P. G.
Batch adsorption experiments were carried out with samples from an A-, Bh- and C-horizon of contaminated sandy soil of podzolic character from the Kempen region at the Dutch-Belgian border. Cadmium sorption was studied on 3 soil samples at 3 different pH-levels (3.6, 4.3 and soil buffered pH) and 3 different additions of zinc (0–40 mg l⁻¹).Adsorption of cadmium by acid sandy soils can be fitted by a Freundlich adsorption isotherm. Although zinc competes with cadmium for the sorption sites, we observe a two to three times stronger competition effect of the proton cation, which is explained by the chemical properties of both ions. The cadmium adsorption coefficient KF decreases considerably by an increase of the proton activity used in the sorption experiments. Organic matter content explains for a large part the variation of KF of te three soil samples. Desorption data do not fit the proposed regression model for adssorption. Not all the cadmium, intitially present in the polluted soil, will fylly desorb reversibly. Thus, part of the cadmium may be irreversible bound.
اظهر المزيد [+] اقل [-]California sea lion (Zalophus californianus) populations and SIGMA DDT contamination
1998
O'Shea, T.J. | Brownell, R.L. Jr. (US Geological Survey, Biological Resources Division, Midcontinent Ecological Science Center, 4512 McMurry Avenue, Fort Collins, Colorado 80525-3400 (USA))