خيارات البحث
النتائج 261 - 270 من 373
THE state of pollution levels of karachi harbour and adjoining coastal water النص الكامل
1997
Akhtar, Waseem | Ali, Iqbal | Zaidi, S. S. H. | Jilani, Seema
A study was carried out recently to determine the pollution level of waters in the Karachi harbour and adjoining backwaters. Nine locations were selected, four in the backwaters, two on the seaside, and three in the main navigable channel. Four of these locations were deliberately selected to coincide with those of a previous study conducted in 1982 by Pakistan Council of Scientific and Industrial Research (PCSIR) so that the values for the concentration of different pollutants could be compared. Analysis was conducted for pH, bicarbonates, Total Solids, Volatile matter in Total Solids, Chlorides, Sulphates, Calcium, Magnesium, Sodium and Potassium.The results indicate that the composition of sea water as far as the concentration of above constituents is concerned has not changed much since the time of the PCSIR study, viz 1982, except that the organic matter concentration has increased. The reasons for this increase in organic loading and its possible impact are discussed in this paper.
اظهر المزيد [+] اقل [-]Pigment changes in norway spruce induced by dust pollution النص الكامل
1997
MANDRE, MALLE | TUULMETS, LIIVI
The influence of alkaline dust pollution (pH of water solution of dust 12.3–12.7) from a cement plant (Kunda town, Estonia) on chlorophylls and carotenoids of the needles of 60–80 year old Norway spruce was studied on sample plots established at different distances from the emission source. The highest sensitivity to dust impact was measured in the content of Chl a, Chl b, carotenoids and elements regulating or participating in the biosynthesis of pigments (Mg, Fe, N, Mn).
اظهر المزيد [+] اقل [-]Hydrochemistry of the aquifers in the Rio las Avenidas basin, Pachuca, Hidalgo, Mexico النص الكامل
1997
Huizar Álvarez, Rafael
Groundwater in the Rio de las Avenidas sub-basin corresponds to the bicarbonate-sodium and bicarbonate-calcium hydrochemical facies, which result from the mineralization of water passing through alkaline rocks (andesites) which prevail in this basin. However, the presence of high concentrations of Na⁺ and K⁺ reveals the existence of an external inflow of these elements: the registered mean values are respectively 94.3 and 19.0 ppm, with the Tèllez and Tizayuca areas standing out with reported values of up to 142 ppm. As for the concentration of soluble water cations, we find in decreasing order: Na⁺, Ca²⁺, Mg²⁺, K⁺, along with the anions HCO₃ ⁻, Cl⁻, SO₄ ²⁻, CO₃ ⁻, which combine to form the NaHCO₃, NaCl, Ca(HCO₃)₂, MgSO₄ and KCl salts. The presence of biological contaminants, P and detergents in the groundwater indicates that it may have been contaminated by waste water. In addition to the contaminants mentioned above, large quantities of Pb, B, Zn, Fe, Mn, Cr, Co were detected and although Fe, Pb, Zn, B, and Mn are closely related to the local lithology, the high concentrations of these elements along with the occurrence of Co, Cr, Cd, and Ni confirm the gradual degradation of the aquifers in the sub-basin. The water temperature indicates the existence of low temperature thermal processes in the area.
اظهر المزيد [+] اقل [-]The seasonal changes of keratinolytic fungi in sediments of Catalonian Rivers (Spain) النص الكامل
1997
Ulfig, K. | Łukasik, W. | Guarro, J. | Cano, J. | Gené Badía, Joan | Vidal, P. | Figueras, M. J.
The Catalonian river sediments were found to be rich in keratinolytic fungi. The keratinolytic fungal populations showed clear seasonal changes in the river sediments. The main factors ‘regulating’ these populations in such habitat were temperature, dissolved oxygen concentration, pH, ammonium, nitrates, total fungal number, BOD₅, water poisons (cyanides, detergents, phenols), salinity and, presumably, strong insolation associated with low water levels. The last was probably of special importance in the deterioration of the fungal populations in the spring/summer season. A toxic effect on keratinolytic fungi in sediments was observed.Chrysosporium keratinophilum was found to be most resistant to industrial contaminants and salinity. Therefore, this species could be used as an indicator of water pollution.
اظهر المزيد [+] اقل [-]Variations in sulphur and nitrogen foliar concentration of deciduous and conifers vegetation in Slovakia النص الكامل
1997
Maňkovská, Blanka
The foliage contents of Sₜₒₜₐₗ and Nₜₒₜₐₗ were determined in 405 Permanent monitoring plots in four National Parks and sixteen Landscape Protection Areas and were compared with 1483 Permanent monitoring plots on Slovakia. The foliage content of S ranged from 0.72 to 6.77 g kg⁻¹ in hardwoods and from 0.98 to 4.3 g kg⁻¹ in softwoods. A critical increase was determined in one National Park and in four Landscape Protection Areas. The foliage content of N ranged from 9.7 to 48.7 g kg⁻¹ in softwoods, and from 7.8 to 51.4 g kg⁻¹ in hardwoods. An insufficient level of N was determined in one Landscape Protection Area and a critical increase in four Landscape Protection Areas. The sulphur to nitrogen ratio ranged from 0.08 to 0.176 in softwoods, and from 0.078 to 0.253 in hardwoods. The foliage surface on hitherto explored four National Parks and sixteen Landscape Protection Areas in network 4×4 km was covered by all categories of rigid fallout particles. Fly-ash from coal combustion were observed each of National Parks and Landscape Protection Areas by scanning electron microscopy. Mycelia and spore, mineral matters, sand and soil particles were present on all National Parks and Landscape Protection Areas. Particles derived from aluminium production were observed at three Landscape Protection Areas. Particles derived from cement production and from lime works were observed at two National Parks and six Landscape Protection Areas. Particles derived from ferrous metals industry were observed at each of National Parks and Landscape Protection Areas and particles typical for other technologies were present in three of National Parks and twelve Landscape Protection Areas.
اظهر المزيد [+] اقل [-]Increased cadmium availability to crops on a sewage-sludge amended soil النص الكامل
1997
Tichý, R. | Ný, V. | Kužel, S. | Kolář, L.
Analysis of spatial distribution of sewage-sludge born cadmium on the experimental plot revealed positive correlation of total cadmium and organic matter. Soil pH fluctuated randomly on the field. ‘Bioavailable’ concentrations, as determined by NH₄-acetate extraction, were closely correlated to the total cadmium levels, and only negligible effects of pH and/or organic matter fluctuations were recorded. Desorption model using modified Freundlich isotherm was applied to predict risks of cadmium solubilization at different conditions. Simulations revealed that the organic matter content within the ranges found at the experimental field cannot support a proper immobilization of cadmium at pH-range observed at the field. The phenomenon was explained by ineffective care for the soil in the past.
اظهر المزيد [+] اقل [-]Annual balances of hexachlorocyclohexanes, polychlorinated biphenyls and triazines in the German Bight
1997
Huhnerfuss, H. | Bester, K. | Landgraff, O. | Pohlmann, T. | Selke, K. (Institut fur Organische Chemie der Universitat Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg (Germany))
Fluxes and budgets of contaminants in the German Bight
1997
Sundermann, J. | Radach, G. (Zentrum fur Meeres-und Klimaforschung der Universitat Hamburg, Institut fur Meereskunde, 22529 Hamburg (Germany))
Metals, petroleum hydrocarbons and organochlorines in inshore sediments and waters of Mombasa, Kenya
1997
Williams, T.M. | Rees, J.G. | Ferguson, A. | Herd, R.A. | Kairu, K.K. | Yobe, A.C. (British Geological Survey, Keyworth, Nottingham (United Kingdom))
Fluxes and mass balances of nutrients in a semi-intensive shrimp farm in north-western Mexico
1997
Paez-Osuna, F. | Guerrero-Galvan, S.R. | Ruiz-Fernandez, A.C. | Espinoza-Angulo, R. (Laboratorio de Quimica Marina, Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 811, Mazatlan 82000, Sinaloa (Mexico))