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  • Sediments  (5)
  • Chemistry
  • United States
  • Acoustical Society of America  (3)
  • Alexandria: National Institute of Oceanography and Fisheries  (3)
  • 2005-2009  (6)
  • 1
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    Geochemical and environmental studies of recent marine sediments and some hard corals of Wadi El-Gemal area of the Red Sea, Egypt (2006)
    Alexandria: National Institute of Oceanography and Fisheries
    Details
    Publication Date: 2021-05-19
    Description: This Journal is published by National Institute of Oceanography and Fishereies, Alexandria, Egypt
    Description: The distribution of (Fe, Mn, Zn, Cu, Pb, Ni, Co and Cd) concentrations were determined in surface marine sediments and coral reefs at Wadi El-Gemal in the Red Sea area. There were significant differences in concentrations of heavy metals in the marine sediments relative to the coral reefs. Some heavy metal concentrations in sediments and coral reefs in the study area are high compared to that in the impact areas of the Egyptian Red Sea coast. The results indicate that the high concentrations of heavy metals in marine sediments and coral reefs are particularly affected by the high contribution of terrigenous materials through the stream of Wadi El-Gemal. Generally, heavy metals concentration in the sediments decreased with increasing distance from the shoreline with the exception of Pb, which increased with increasing distance from the shoreline. On the other hand, Pb concentration in coral reefs is high compared to that in some sediment samples at Wadi El- Gemal area. The grain size, carbonate, organic matter, phosphorus and heavy metals distribution reflect marked changes in lithology, biological activities in the sea and land geology of the study area. Carbonate content mainly of biogenic origin varies from 5.7 –69.5% of the sediments. Organic matter contents of the sediments (1.7 to 6.5%) and phosphorus content (110 to 5097ppm) usually reflect significant terrigenous influences. On the other hand, heavy metals show an increasing tendency in the mud fraction of Wadi El-Gemal area. The present work reflects how much the marine sediments and coral reefs are influenced by natural impacts from this wadi. The collected data will be useful in management and suitable development of the area, beside being helpful as database in the future.
    Description: NIOF
    Description: Published
    Keywords: Hard corals ; Wadi El-Gemal ; Natural impacts ; Heavy metals ; Environment ; Marine ecology ; Environments ; Marine ecology ; Marine pollution ; Sediments ; Coral reefs
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 2
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    Major controls of some metals distribution in sediments off the Nile Delta, Egypt. (2006)
    Alexandria: National Institute of Oceanography and Fisheries
    Details
    Publication Date: 2021-05-19
    Description: This journal is published by NIOF, Alexandria, Egypt
    Description: The sediment samples that are collected during R/V CHAIN 1975 cruise to the southeastern Mediterranean have been used to determine the major controls of metals’distribution. The sediment samples were analysed mineralogically, chemically and texturally. The parameters measured included carbonate minerals, total carbonate, organic carbon, iron, manganese, copper, zinc, chromium, lead, nickel, cobalt, vanadium, calcium, magnesium, strontium, sand, silt and clay. The statistical analysis of data showed that four major factors control the distribution of metals in sediments of the Nile cone; These are: Factor 1 terrigenous mud-calcareous sand; Factor 2 Aragonite mud-terrigenous sand; Factor 3 Algal sand; and Factor 4 Aragonite. The percentages of terrigenous sand, mud and calcareous components of the Nile cone sediments greatly affect the elements spatial distribution. In addition to that, minor controls such as precipitation and coprecipitation may affect the elemental distribution. The distributions of iron, manganese, copper, zinc, chromium, lead, nickel, cobalt, and vanadium are associated mainly with the terrigenous mud fraction of the sediment whereas, calcium and strontium are mainly related to calcareous sands. Iron, copper, cobalt, lead and vanadium are partially related to montmorillonite. Lead is associated with acid feldspars and chromium is mainly controlled by terrigenous sand. The distribution of calcium and strontium is controlled by the coarsecalcareous fraction of sediments. Magnesium and manganese are associate with algal sand. The aragonite and calcite minerals are forming the majority of carbonate mud, which controls partially the distribution of calcium, strontium, lead and copper.
    Description: NIOF, Alexandria, Egypt
    Description: Published
    Keywords: Metals ; Factor analysis ; Coastal oceanography ; Sediments
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 3
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    Ecological and fisheries development of Lake Manzalah (Egypt): hydrography and chemistry of Lake Manzalah (2006)
    Alexandria: National Institute of Oceanography and Fisheries
    Details
    Publication Date: 2021-05-19
    Description: This journal is published by the NIOF, Egypt
    Description: Lake Manzalah; the largest delta Lake in Egypt represents a dynamic system that has been undergoing continuous and pronounced changes since long times. In the last year’s this Lake faced drastic problems that retarded its environmental and fisheries development; the most serious one is the discharge of waste water. It is attempted in the present study to investigate the chemical characters of Lake Manzalah water during 2001-2002. Water temperature ranged from an average of 12.35oC in January and 29.14oC in July. Dissolved Oxygen, pH and total dissolved solids were found in ranges optimum for the living of marine and freshwater fish species. The average concentrations of nutrients lied in the following ranges: 1.24 to 4.89 μmol PO4 -3 l-1 , 5.08 to 28.73 μmol SiO4 -2 l-1 and 1.81 to 17.7 μ_mol NO3-1 l-1 The concentrations of phosphorus and nitrogen compounds were found to be relatively higher at the southern regions of the Lake near to the outlets of the drains.
    Description: NIOF
    Description: Published
    Keywords: Hydrography ; Water ; Chemistry ; Chemical composition ; Water content ; Environment ; Chemical composition ; Environments ; Water content ; Fisheries
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 4
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    High-frequency bistatic scattering by sub-bottom gas bubbles (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1997. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 102 (1997): 806-814, doi:10.1121/1.419906.
    Description: A previous study of high-frequency acoustic backscattering data collected at Eckernfoerde Bay, Germany revealed that scattering is mainly due to methane gas bubbles buried about a meter beneath the seafloor [Tang et al., J. Acoust. Soc. Am. 96, 2930–2936 (1994)]. A backscattering model was developed [Tang, Geo-Marine Lett. 16, 161–169 (1996)] where the gas bubbles were approximated by oblate spheroids. In this paper, a bistatic scattering model is proposed as an extension of the previously developed backscattering model. In this model, gas bubbles are again assumed to be oblate spheroids with varying aspect ratios and a single-scattering approximation is used. The model is compared to bistatic data acquired in Eckernfoerde Bay, Germany. In particular, the azimuthal dependence of the bistatic scattering strength predicted by the model is tested against experimental data and it is found that both the model and the bistatic scattering strength data exhibit a mild azimuthal dependence. Best agreement between model and data requires a 35% reduction in areal bubble density relative to that used in the backscattering model/data comparison. Possible reasons for this are discussed including multiple scattering effects.
    Description: This work is supported by the Coastal Benthic Boundary Layer Special Research Program, Office of Navel Research Grant No. N00014-95-1-G904.
    Keywords: Oceanographic regions ; Acoustic wave scattering ; Backscatter ; Bubbles ; Sediments ; Underwater sound
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Acoustic environment of the Hatteras and Nares Abyssal Plains, western North Atlantic Ocean, determined from velocities and physical properties of sediment cores (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1980. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 68 (1980): 1376-1390, doi:10.1121/1.385105.
    Description: Seventeen piston cores up to 13 m long were recovered from representative acoustic and lithologic environments of the Hatteras and Nares Abyssal Plains in the western North Atlantic. Compressional-wave velocities (corrected to in situ conditions) and bulk physical properties measured on the cores are used to characterize the acoustic framework of these areas. For correlation with conventional seismic data, whole-core averages of properties are a better index to the acoustic nature of abyssal plain sediments than properties of the upper few centimeters of the seafloor because (1) strong changes in lithofacies (and acoustic properties) occur over depth scales of tens of centimeters to meters in the sediment column, and (2) conventional seismic frequencies of 3.5 kHz or less sample these variations to subbottom depths of tens of meters and more. Whole-core properties are a function of the thickness and distribution of high-velocity silt and sand layers in the core; they vary in a complex fashion with proximity to the source of turbidity currents, distance from axial paths of turbidity-current flows, local and regional basin geometry, and seafloor slope. Thus strongly reflective seabed regions with numerous high-velocity layers are not restricted simply to near-source areas nor are weakly reflective seabed regions (clay sediments only) limited to ''distal'' areas. Whole-core properties show a good qualitative correlation to variations in 3.5-kHz reflection profiles, and 3.5-kHz echo character therefore provides a useful means of mapping general acoustic properties over large regions of abyssal plains.
    Description: Data collection and much of the analysis were supported by ONR Contract N00014-75-C-0210 to Lamont- Doherty Geological Observatory (Columbia University) during my residence there. At Woods Hole, support by ONR Contract N00014-79-C-0071, NR083-004 is gratefully acknowledged.
    Keywords: Sediments ; Sound waves ; Velocity ; Physical properties ; Atlantic Ocean
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Geoacoustic inversion by mode amplitude perturbation (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Acoustical Society of America, 2008. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 123 (2008): 667-678, doi:10.1121/1.2821975.
    Description: This paper introduces a perturbative inversion algorithm for determining sea floor acoustic properties, which uses modal amplitudes as input data. Perturbative inverse methods have been used in the past to estimate bottom acoustic properties in sediments, but up to this point these methods have used only the modal eigenvalues as input data. As with previous perturbative inversion methods, the one developed in this paper solves the nonlinear inverse problem using a series of approximate, linear steps. Examples of the method applied to synthetic and experimental data are provided to demonstrate the method's feasibility. Finally, it is shown that modal eigenvalue and amplitude perturbation can be combined into a single inversion algorithm that uses all of the potentially available modal data.
    Description: Funding for the research presented here was provided by the Office of Naval Research, and the WHOI Academic Programs Office.
    Keywords: Geophysical techniques ; Inverse problems ; Sediments ; Seismology
    Repository Name: Woods Hole Open Access Server
    Type: Article
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