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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 36 (1998), S. 235-258 
    ISSN: 1432-0495
    Keywords: Key words Delta lagoons ; Fish resources ; Manzala Lagoon ; Nile Delta ; Pollution ; Waste water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The Manzala Lagoon in Egypt's Nile Delta has become a sediment sink of reduced area and depth, with increased contaminant levels. Loss of much-needed fresh to brackish water reserves and decreased fish catches have serious ramifications. Herein, maps of temporal and regional sediment distributions in Manzala incorporate petrological and statistical analyses of 200 surficial and short core samples. These provide baseline information needed to help implement protection measures for this vital wetland. Four periods are considered: 1920s, 1940s, ∼1965, and 1990. Important depositional changes between 1940s and ∼1965 resulted from anthropogenic effects on this quasi-closed lagoon system, including industrial buildup, wetland conversion to agricultural land, and irrigation waterway development. Further modification from ∼1965 to 1990 is associated with closure of the Aswan High Dam, continued construction of waterways that discharge waste water into lagoon margins, and marine incursion into the northern lagoon. If current practices continue, the lagoon could be reduced to about one-third of its present area by 2050 AD.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 34 (1998), S. 183-193 
    ISSN: 1432-0495
    Keywords: Key words Manzala lagoon ; Nile delta ; Chernobyl ; Radionuclides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  This study was undertaken to determine whether recent anthropogenic changes in the Nile basin have affected the modern rate of sediment accumulation in the Nile delta. Excess 210Pb, 137Cs, and 239,240Pu were used to develop a sediment chronology for a core from central Manzala lagoon, the delta sector which has had the highest average rate of sediment accumulation during the Holocene (to about 0.7 cm year–1). Excess 210Pb was detected in the top 32 cm of the core, yielding an accumulation rate of 1.2 cm year–1, higher than the mean rate for the Holocene. A high 137Cs/239,240Pu ratio requires a reactor source (possibly Chernobyl) for these nuclides. Low concentrations of excess 210Pb and weapons-fallout nuclides precluded recognition of changes in sediment accumulation rate in Manzala lagoon during this century and may limit the use of tracer radionuclides for modern sediment chronology in the Nile delta.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1939
    Keywords: Key wordsBromusrubens ; Mojave Desert ; Elevated CO2 ; C/N ratio ; Maternal effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seeds were collected and compared from parent plants of Bromusrubens L. (Poaceae), an exotic Mojave Desert annual grass, grown in ambient (360 μmol mol−1) and elevated (700 μmol mol−1) CO2 to determine if parental CO2 growth conditions affected seed quality. Performance of seeds developed on the above plants was evaluated to determine the influence of parental CO2 growth conditions on germination, growth rate, and leaf production. Seeds of B. rubens developed on parents grown in elevated CO2 had a larger pericarp surface area, higher C:N ratio, and less total mass than ambient-developed seeds. Parental CO2 environment did not have an effect on germination percentage or mean germination time, as determined by radicle emergence. Seedlings from elevated-CO2-developed seeds had a reduced relative growth rate and achieved smaller final mass over the same growth period. Elevated-CO2-developed seeds had smaller seed reserves than ambient seeds, as determined by growing seedlings in sterile media and monitoring senescence. It appears that increased seed C:N ratios associated with plants grown under elevated CO2 may have a major effect on seed quality (morphology, nutrition) and seedling performance (e.g., growth rate and leaf production). Since the invasive success of B. rubens is primarily due to its ability to rapidly germinate, increase leaf area and maintain a relatively high growth rate compared to native annuals and perennial grasses, reductions in seed quality and seedling performance in elevated CO2 may have significant impacts on future community composition in the Mojave Desert.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    GeoJournal 45 (1998), S. 5-15 
    ISSN: 1572-9893
    Keywords: Information and Technology ; futures ; globalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Type of Medium: Electronic Resource
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