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    Wyświetlanie 1-6 z 6
    Tytuł:
    Alexandrium minutum cysts in sediment cores from the Eastern Harbour of Alexandria, Egypt
    Autorzy:
    Ismael, A.A.
    Khadr, A.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/48863.pdf
    Data publikacji:
    2003
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    sediment core
    cyst
    Alexandria
    organic carbon
    Egypt
    Alexandrium minutum
    Opis:
    Alexandrium minutum cysts were studied in sediment cores from its type locality, the Eastern Harbour of Alexandria, following the disappearance of the species from the plankton since 1994. Three cores were sampled in the summer of 1999 along the north-south axis of the harbour. The sediments were subjected to grain size analysis and their organic carbon content was determined. The sediments consisted of medium, coarse and very coarse sand. Grain size and organic carbon content were negatively and significantly correlated in core 1 but followed a parallel trend in cores 2 and 3. Seven dinoflagellate cysts, representing 6 genera were identified from the cores. Their relative abundance showed a remarkable difference. A. minutum cysts contributed a maximum of 17.4% to the total cysts. The distribution profile of A. minutum cysts in the cores reflects the bloom duration but not its productivity. The cyst distribution in the cores is the resultant of two opposite processes, the sedimentation rate and the continuous erosion of the bottom sediments, which is not related to sediment texture.
    Źródło:
    Oceanologia; 2003, 45, 4
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spatial and temporal distribution of heavy metals in coastal core sediments from the Red Sea, Saudi Arabia
    Autorzy:
    Al-Mur, B.A.
    Quicksall, A.N.
    Al-Ansari, A.M.A.
    Powiązania:
    https://bibliotekanauki.pl/articles/48599.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    Red Sea
    Saudi Arabia
    heavy metal
    spatial distribution
    temporal distribution
    pollution
    coastal sediment
    sediment core
    Opis:
    Jeddah is the most industrialized city on the west coast of Saudi Arabia and is under increasing influence of human activities. Heavy metals data were obtained from four near-coast Red Sea sediment cores in close proximity to Jeddah. Chromium, manganese, iron, copper, zinc, and lead were analyzed from depth-resolved sections of each core via heavy acid digestion and inductively coupled plasma-mass spectrometry (ICP-MS). The average concentrations of all four sites were 245.96 mg kg1, 478.45 mg kg1, 8506.13 mg kg1, 251.82 mg kg1, 623.09 mg kg1, and 362.75 mg kg1, respectively. The depth-resolved results showed that highest concentrations of Mn, Cu, and Pb were found in the top 15 cm of the core profile distributions compared to other depth sub-samples. Heavy metal concentrations in core sediments are increased near central Jeddah and have become higher in recent years. The results of enrichment factor calculations indicate little anthropogenic supply of Mn and Cr while Pb, Zn, and Cu show strong anthropogenic input. The Pollution Load Index was higher in the two sites closer to central Jeddah where power and desalination plants and wastewater release are known. This indicates that the area has suffered from heavy metal pollution compared to other non-industrialized sites in the Red Sea. Heavy metal contaminations due to anthropogenic activity should be taken into account to protect the Red Sea during future growth. The results of this work should be considered as a baseline for heavy metals monitoring in the sediments of the Red Sea coast near Jeddah, Saudi Arabia.
    Źródło:
    Oceanologia; 2017, 59, 3
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Holocene evolution of the Pomeranian Bay environment, Southern Baltic Sea
    Autorzy:
    Kostecki, R.
    Janczak-Kostecka, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/48852.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    aerobic condition
    anaerobic condition
    Ancylus Lake
    Baltic Sea
    diatom assemblage
    ecological group
    geochemistry
    Holocene
    lacustrine sediment
    marine diatom
    marine environment
    paleogeographic development
    Pomeranian Bay
    sediment core
    shallow lake
    Opis:
    This article focuses on the diatom assemblages and geochemical composition of sediment cores retrieved from the Pomeranian Bay. We also discuss similarities and differences in the diatom assemblages and the palaeogeographic development of nearby regions. Our main objective was to determine the characteristics and rate of the Littorina transgression in the Pomeranian Bay area. Sediments were divided into units based on differences in the distribution of diatom ecological groups and in geochemical ratios, such as Mg/Ca, Na/K and Fe/Mn. This study identified lacustrine sediments deposited during the time of the Ancylus Lake. This lacustrine-period sedimentation took place in a shallow lake under aerobic conditions. The record of the onset of marine environment dates to 8900–8300 cal BP and corresponds to the Littorina transgression. After about 8300 cal BP, sedimentation took place in a deeper marine environment with higher biogenic production and anaerobic conditions. The abrupt appearance of marine diatom species and increased geochemical salinity indicators reflect the large impact of the Littorina transgression on the Pomeranian Bay environment.
    Źródło:
    Oceanologia; 2011, 53, (1-TI)
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Estimating long term sediment yields from sediment core analysis
    Oszacowanie dlugookresowej dostawy rumowiska na podstawie analizy rdzeniowej
    Autorzy:
    Kennie, P
    Bogen, J.
    Olsen, H.C.
    Powiązania:
    https://bibliotekanauki.pl/articles/81703.pdf
    Data publikacji:
    2010
    Wydawca:
    Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
    Tematy:
    sediment yield
    core analysis
    glacial river
    sediment transport
    Lake Nigardsvatn
    Norway
    Opis:
    Sediment cores from lakes and reservoirs can be used to estimate sediment yields. In proglacial lakes, the bed sediment typically accumulates as varves, reflecting changes in seasonal and annual sedimentation. This report compares the results from two different methods of measuring suspended sediment transport in a Norwegian glacial river and lake. Sediment yields obtained from a study of sediment cores in the proglacial lake Nigardsvatn along with measurements of the delta topset were compared with a 25-year record of sediment transport based on automatic water sampling and water discharge measurements at a monitoring station at the inflowing river. During the period from 1980 to 2005, analyses of sediment cores taken from the lake bed along with measurements and grain size distribution analysis of the delta indicated that a volume of 175,670 to 202,697 m3 was deposited in the lake Nigardsvatn and corresponding river delta. The year 1980 was selected as a convenient starting point because a large-magnitude flood with a 100-year recurrence interval occurred at the end of 1979, leaving an easily recognizable sediment layer and accurate reference point. Sediment cores were taken at a total of 24 locations throughout the lake and 25 locations in the delta. The densities of the sediment cores were found to vary between 1.3 and 1.5 g/cm3 during the period examined in this study, giving a total suspended sediment load of between 175,670 and 202,697 tons. The measurements carried out at the sediment station in the glacier melt-water river gave a value of 294,800 tons during the same period. A final value of 211,100 tons is calculated from the monitoring station results after deduction of the sediment fraction which passes through the lake without being deposited. This gives a discrepancy between the two methods of 8,403 to 35,430 tons (4–20%). This can be partially attributed to the difficulties of measuring the water discharge in the unstable glacier meltwater river. In conclusion, sediment cores may be used to extrapolate or correct measurements from sediment monitoring stations over longer periods but caution should be made when considering single years.
    W pracy przedstawiono wyniki badań prowadzonych według dwóch różnych metod pomiaru ilości rumowiska unoszonego, dostarczonego w latach 1980–2005 do jeziora Nigardsvatn w Norwegii, które zasilane jest wodami roztopowymi z lodowca Jostedalsbreen. Wielkość dostawy rumowiska, określoną na podstawie analizy rdzeniowej z sondowania geologicznego osadów dennych jeziora, porównano z wynikami uzyskanymi na podstawie danych z 25-cio letniego ciągu pomiarów zmącenia w rzece zasilającej jezioro. Stwierdzono, że różnica w wielkości dostawy rumowiska do jeziora określona dwiema metodami wynosi 4–20%, przy czym mniejsze wartości uzyskano na podstawie analizy rdzeniowej osadów. Autorzy uważają, że metoda ta może być stosowana do oszacowania lub korygowania wyników pomiarów zmącenia w rzekach zasilających jeziora i zbiorniki wodne w dostatecznie długich okresach.
    Źródło:
    Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation; 2010, 42, 1; 115-126
    0208-5771
    Pojawia się w:
    Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Exposure assessment of heavy metals pollution enriched in core sediment samples of river Nile, Aswan, Egypt
    Autorzy:
    Fawzy, E.M.
    Rashed, M.N.
    Soltan, M.E.
    Powiązania:
    https://bibliotekanauki.pl/articles/9993.pdf
    Data publikacji:
    2017
    Wydawca:
    Fundacja na Rzecz Młodych Naukowców
    Tematy:
    exposure assessment
    heavy metal
    environment pollution
    core
    sediment
    Nile River
    Aswan city
    Egypt
    Opis:
    The river Nile is a dominating physical feature of the north- eastern part of the African continent, covering areas exhibiting varieties and contrasts in topography, climate vegetation and people. So, in this study, we estimated the contamination of the Nile sediment with some major and trace heavy metals in core samples which can cause some undesirable health effects. Concentrations of all elements shows that the maximum enrichment is found in the top subsamples, while the most elements shows low contents in the lower layer reflecting the impact of human activity on the sediment contents. Different normalizing methods were used, i.e. geoaccumulation (Igeo) and enrichment factor (EF), for the influence of the natural variability in sediment mineralogy and to assess whether the concentrations observed in surface sediment represent background or contaminated levels. The study has also shown the importance of different sediment characteristics in spatial distribution of heavy metals in the sediments of river Nile. To protect the ecological system of river Nile watershed, industrial mining and agricultural activities along river stream should to be strictly regulated.
    Źródło:
    Environment, Earth and Ecology; 2017, 1, 1
    2543-9774
    2451-4225
    Pojawia się w:
    Environment, Earth and Ecology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessing the reliability of foraminiferal Mg/Ca thermometry by comparing field-samples and culture experiments: a review
    Autorzy:
    Kontakiotis, G.
    Mortyn, G. P.
    Antonarakou, A.
    Drinia, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059914.pdf
    Data publikacji:
    2016
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Mg/Ca palaeothermometry
    core-top sediments
    sediment traps
    plankton tows
    laboratory culture experiments
    palaeoceanography
    Opis:
    Trace elements incorporated into foraminiferal test carbonate are commonly used as palaeoproxies. For instance, benthic and planktonic Mg/Ca ratios are frequently used for reconstructing bottom and sea surface temperature (SST) changes, respectively. However, over the past few decades it has been shown that the incorporation of Mg2+ into foraminiferal calcite is controlled by more than one environmental parameter, with significant variations of their sensitivities between culture and field-based studies. Opinions differ as to whether the laboratory conditions during culturing experiments or the natural conditions during field sampling (core-tops, sediment traps and plankton tows) better trace the wealth of information with improved accuracy. Laboratory culture experiments that isolate the effects of individual environmental parameters have been used to identify secondary controls on Mg uptake into planktonic foraminifer tests. However, field-based data (core-top sediments and plankton tows) from high salinity super-saturated settings have shown the additional presence of high-Mg inorganic precipitates leading to significant salinity (S) biases on the Mg/Ca palaeothermometer. Testing such synergistic effects between temperature, salinity and calcite saturation state would require an experimental design where all these parameters are varied systematically, but such experiments have yet to be conducted. Since the synergistic effects cannot presently be ruled out through culturing experiments, it is imperative to initially confirm the amplitude and geographic distribution of the detectable diagenetic precipitations (Scanning Electron Microscopy analysis) through field-based work, further quantify their importance (discrimination of distinct diagenetic stages and quantification of the diagenetic imprint) and finally estimate its potential effect on Mg/Ca-T calibration (e.g., overgrowth-corrected species-specific calibration equations). The example of the marginal high-salinity settings, among others, clearly highlights that the optimal use of Mg/Ca as a palaeotemperature proxy urgently requires the complementarity of both culture- and field-based data. To this end, we here present advantages and disadvantages to each approach. These insights reinforce the potential of the combined use of culture- and field-based foraminiferal studies, where possible, in order to minimize the observed inconsistencies, and to advance Mg/Ca thermometry by both providing a framework for better understanding the nature of Mg/Ca dependence on seawater temperature, and the effects of complicating factors.
    Źródło:
    Geological Quarterly; 2016, 60, 3; 547--560
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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