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Mahmoud M. El Banna 《Environmental Geology》2006,49(5):645-652
Bathymetry of the seafloor in the area in front of Ras El Bar coast, the characters of the seafloor sediments and the effects
of protective structures on seafloor bathymetry were examined. Seafloor depths in front of Ras El Bar seawall ranged between
2 and 4 m. These depths, coupled with wave climate, result in waves breaking directly onto the wall and exerting high, dynamic
pressures on the area at the structure’s toe. The sandy seafloor in front of the wall has been scoured. Sea water has undermined
the wall causing removal of sediment, destabilization of its slope and the whole face of the wall has slipped. Toe protection
in the form of a rocky apron is required to prevent such damage. West of the seawall, the constructed breakwater system has
affected the bathymetry of the seafloor in the area. Shoaling and submerged spits have been formed in the shadow of each breakwater
unit. The gaps between the breakwater units have attained deep depths and steep slopes. Scours and steep slopes adjacent to
the head of the breakwater units have been recorded. Seaward of the breakwater system, deeper depths and gentle slopes characterize
the seafloor. Offshore–onshore current and sediment movements toward the northeast is inferred from the configuration of the
bottom contour lines. 相似文献
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Mahmoud M. El Banna 《Environmental Geology》2007,52(1):41-49
Beach profile data, covering the coast of Ras El Bar, northeast Nile Delta, collected during the years from 1990 to 2002 combined
with landsat images for the area and sedimentological investigation have been used to identify beach and nearshore seafloor
sediment changes. Along the coast of Ras El Bar, two accretion sectors and one of erosion have been recognized. The first
accretion sector is located west of Damietta harbour, where the harbour jetties have halted the littoral transport, while
the second one is behind a system of detached breakwaters protecting Ras El Bar resort. Both the two sectors are characterized
by growing shoreline with maximum rates ∼15 and 10 m/year, respectively. Also, they have maximum nearshore seafloor accretion
rates of ∼18 and 22 cm/year, respectively. The erosion sector is located east of Damietta port and has a maximum rate of shoreline
retreat ∼−10 m/year. Erosion of its nearshore seafloor is indicated recording a maximum rate of ∼−20 cm/year. The rate of
net sediment volume change in the area indicates shifting of the accretion sector (II) westward, responding to installation
of the new breakwaters unit. The two accretion sectors are characterized by dominance of moderately sorted fine sands in their
shore area which change seaward into less sorting very fine sands. Beach sands of the eroded sector are poorly sorted medium
grain size. The dominant constituents of heavy mineral species in beach and sea-bottom sands are the characteristic assemblages
of the Nile deposits. The sands of the eroded zone are relatively enriched in monazite, zircon, tourmaline, garnet, and rutile. 相似文献
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The coastline of Ras Al Khaimah, United Arab Emirates, has three main constructional complexes: Jazirat al Hamra, Julfah, and Jazirat Hulaylah. Archival information, air photographs and maps dating back to 1819, enable the history of coastal change to be reconstructed. Jazirat al Hamra has been much affected by recent reclamation and harbour works, but appears to have been relatively stable. Jazirat Hulaylah also appears to have changed relatively little. However, the Julfah complex, which includes the harbour mouth for Ras Al Khaimah city, has shown very considerable change as a result of coastal breaching and spit growth and decay. 相似文献
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Ras is regarded as one of the most important genes involved in carcinogenesis. Such genes have been characterised in several fish species and the presence of ras mutations have already been described in fish populations from hydrocarbon contaminated areas and following experimental exposure to specific contaminants. The aims of this study were to evaluate the DNA integrity by comet assay, to isolate the normal ras gene of Anguilla anguilla and analyse for the presence of ras gene mutations or changes in gene expression levels induced after one month of benzo[a]pyrene (BaP) experimental exposure. The A. anguilla ras cDNA isolated revealed a 189 amino acid protein and alignment with other vertebrate ras proteins revealed conservation of functionally important regions. Following experimental exposure to BaP, an increase in DNA damage was found by comet assay. However, no point mutations or changes in ras gene expression levels were detected when compared to control samples. In contrast to the majority of fish ras gene sequences, a high degree of polymorphic variation was detected in the A. anguilla ras gene. 相似文献
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