共查询到20条相似文献,搜索用时 25 毫秒
1.
Abdelbaset S. El-Sorogy Mohamed A. Mohamed Hamdy E. Nour 《Environmental Earth Sciences》2012,67(3):777-785
In order to assess pollutants and impact of environmental changes along the Egyptian Red Sea coast, seven recent and Pleistocene coral species have been analyzed for Zn, Pb, Mn, Fe, Cr, Co, Ni, and Cu. Results show that the concentration of trace elements in recent coral skeletons is higher than those of Pleistocene counterpart except for Mn and Ni. In comparison with recent worldwide reefs, the present values are less than those of Central America coast (iron), Gulf of Aqaba, Jordan (lead, copper), Gulf of Mannar, India (chromium, zinc, manganese), Costa Rica, Panama (chromium, nickel), North-west coast of Venezuela and Saudi Arabia (copper). The present values are higher than those of Gulf of Aqaba, Jordan (iron, zinc, manganese), Gulf of Mannar, India (lead, cobalt, nickel), North-west coast of Venezuela (lead, zinc, chromium, manganese), Australia (copper, nickel, zinc, manganese). The highest values were recorded in Stylophora pistillata (iron, lead and copper), Acropora cytherea (cobalt), Pocillopora verrucosa (zinc) and the lowest concentrations were recorded in Goniastrea pectinata (iron, chromium, copper and nickel), Favites pentagona (lead, zinc and manganese), and Porites lutea (cobalt). The differences in metals content among the studied species are attributed to differences in microstructure and microarchitecture. 相似文献
2.
The loss of coral coverage from environmental degradation is a progressive phenomenon that occurs in coral communities around the world. However, the consequences of land use changes and its impact on the state of conservation of coral communities are not yet understood. This study compares the impact of coastal land use changes on four coral communities near rural (Isla Faro and El Zapote) and suburban (Caleta de Chon and Playa Manzanillo) sites in the states of Michoacan and Guerrero, along the central Pacific coast of Mexico. Indicators of environmental degradation in coral communities (sediment deposition, water transparency, total suspended solids, and chlorophyll concentration) show that signs of eutrophication are absent from both rural sites in Michoacan. This absence suggests that human impact is not the main cause of the observed degradation (coral Mortality Index MI = 0.85, a high death coral coverage ~42% and the lowest species richness). Instead, the 1997–1998 El Niño-Southern Oscillation (ENSO) event (the strongest in the last decade) appears to be the major factor in this coral cover decline, as it occurred in the eastern Pacific and other regions of the world. In contrast, coral communities near the suburban sites in Guerrero are well developed, and their coral coverage and species richness (up to 67.7% and 7 species, respectively) are comparable to other major coral communities in this region. Nonetheless, indicators of human-derived degradation in the Guerrero coastal zone near Caleta de Chon and Playa Manzanillo, including high sediment deposition up to 1.2 kg m?2 d?1, low water transparency <5 m, presence of filamentous algae on dead corals and a coral Mortality Index of MI ~0.6 show that human impact is beginning to affect the conservation state of these coral communities, reducing their species richness and coral coverage. Although the ENSO impact on coral communities could be more drastic than the anthropogenic impact, the current study confirms that increased land use changes and coastal erosion are causing progressive coral community degradation. Therefore, land and coastal changes must be rigorously regulated. 相似文献
3.
Abdelbaset S. El-Sorogy Hamdy Nour Emad Essa Mohamed Tawfik 《Arabian Journal of Geosciences》2013,6(12):4981-4991
This study focuses on the diagenetic sequence under marine and meteoric conditions as well as isotopes and trace metals contamination in Quseir and Gebel Zeit areas along the Egyptian Red Sea coast through a series of modern and fossil corals, Porites lutea and Favites pentagona. The diagenetic sequence begins with deposition of thin fringes of syntaxial aragonite and micritic high-magnesian calcite in the modern corals to completely altered Porites and partially altered Favites to low-magnesium calcite in the oldest Pleistocene unit. Average δ18O and δ13C values of Pleistocene corals in the two studied areas were lower than those of modern corals. Values of modern corals and lower fossil unit indicated coralline limestone, while those of middle and upper fossil units indicated fresh water influences. Average values of trace metals in modern corals were higher than those of Pleistocene counterpart except for Mn. Modern coral samples recorded enrichment in the average values of Pb, Zn, and Mn at Quseir area and enrichment in Co, Cu, and Ni at Gebel Zeit area. This may be attributed mostly to different tourist activities, landfill due to increase urbanization and nearby of Quseir area from the old phosphate harbor at El Hamrawin area, as well as oil exploration and production activities in the Gulf of Suez area. Also, results indicated that most samples of Porites have high concentration of trace metals than in Favites, especially in Cu, Zn, Mn, and Pb. This may due to high amounts of intergranular porosity and high total surface area of Porites in contrast to Favites. 相似文献
4.
Saber Al-Rousan Rasheed Al-Shloul Fuad Al-Horani Ahmad Abu-Hilal 《Environmental Earth Sciences》2012,67(7):2003-2013
The concentrations of six heavy metals were studied in five living coral species and their fossil counterparts collected along the Jordanian Coast of the Gulf of Aqaba. The study aimed at investigating the validity of using coral skeletons as bioindicators for environmental pollution by heavy metals in the Gulf of Aqaba, Red Sea. The skeletal samples of the collected corals were acid digested and analyzed for Cd, Cu, Fe, Mn, Pb, and Zn content using flame atomic absorption spectrophotometer. The results obtained have shown that higher concentrations of heavy metals were found in coral skeletons from areas hosting intense developments and human activities. The massive Porites sp. coral tended to accumulate the highest metal concentrations among the other species (except for Mn). This was due to interspecific differences or selectivity of heavy metals between different coral species. It was noteworthy that fossil coral species recorded higher average metal concentrations than their living counterparts; this was attributed to surface contamination due to prolonged burial of the fossil corals in sediment over the years. The study concluded that corals (specially the massive Porites species) are vulnerable to the accumulation of high concentrations of heavy metals in their skeletons and therefore can serve as proxies to monitor environmental pollution. 相似文献
5.
VASILIY M. MURATOV ALEXANDR B. OSTROVSKY EFEONORA O. FRIDENBERG 《Boreas: An International Journal of Quaternary Research》1974,3(2):49-60
On the basis of new data a revised stratigraphic scheme for the Anthropogene of the Black Sea region is suggested. Radiological dates are given for the absolute age of the three Black Sea transgressions with a Karangat-type fauna and two Holocene transgressions. The structure of overdeepened estuarine parts of river valleys and the stratigraphy of slope and cave deposits are discussed. 相似文献
6.
Hashem Abbas Madkour 《Arabian Journal of Geosciences》2013,6(6):1739-1752
In order to monitor the heavy metals effect coming from both human activities and natural inputs on coral reef environments of the Egyptian Red Sea coast, metal concentrations in thirty- eight coral reef species and nearby sediment samples collected from seven studied sites were analyzed. Four sites represent impacted areas; included from south to north Hamrawein, Safaga and Hurghada Harbours and Ras El-Behar Area. Wadi El-Gemal represents natural input area while Qola'an and Kalawye Reefs are the control areas. Heavy metal contents were measured in both coral skeletons and nearby marine sediments. Both impact areas as well as natural inputs area recorded the highest values of metals compared with the control ones. However, heavy metal contents recorded high values in sediments of Hamrawein Harbour, while coral species recorded high values in Wadi El-Gemal area. Generally, metal variations in coral reef species reflect natural conditions and human activity. On the other hand, there are no clear relationships between concentrations of heavy metals in coral reef species and those in sediments. 相似文献
7.
P. R. Shanas V. M. Aboobacker Khalid M. Zubier Alaa M. A. Albarakati 《Arabian Journal of Geosciences》2018,11(5):90
The Jeddah coast lies in the central eastern Red Sea, which is characterized by the predominant northwest winds and the associated wind waves throughout the year. A detailed investigation on the spectral wave characteristics in the nearshore regions of the Jeddah coast has not been carried out yet, primarily due to the lack of data. In the present study, we have analyzed the available wave spectra measured at two nearshore locations along the Jeddah coast using wave gauges. The wave spectra were separated into wind sea and swell components using a frequency-based algorithm, and the integral wave parameters corresponding to each component were derived. Although the measurements were limited to the summer season, notable features such as the diurnal variability and the superimposition of wind seas and swells have been identified from the spectra. The superimposition is mainly due to the interaction of the young swells propagated from the northern Red Sea and the local breezes prevailing along the coast at certain periods in a diurnal cycle. Based on the wave speed calculations and the estimated time shifts between the wind and waves, the potential swell regions have been backtracked. 相似文献
8.
Evidence for the recurrence of large-magnitude earthquakes along the Makran coast of Iran and Pakistan 总被引:2,自引:0,他引:2
The presence of raised beaches and marine terraces along the Makran coast indicates episodic uplift of the continental margin resulting from large-magnitude earthquakes. The uplift occurs as incremental steps similar in height to the 1–3 m of measured uplift resulting from the November 28, 1945 (M 8.3) earthquake at Pasni and Ormara, Pakistan. The data support an E—W-trending, active subduction zone off the Makran coast.The raised beaches and wave-cut terraces along the Makran coast are extensive with some terraces 1–2 km wide, 10–15 m long and up to 500 m in elevation. The terraces are generally capped with shelly sandstones 0.5–5 m thick. Wave-cut cliffs, notches, and associated boulder breccia and swash troughs are locally preserved. Raised Holocene accretion beaches, lagoonal deposits, and tombolos are found up to 10 m in elevation. The number and elevation of raised wave-cut terraces along the Makran coast increase eastward from one at Jask, the entrance to the Persian Gulf, at a few meters elevation, to nine at Konarak, 250 km to the east. Multiple terraces are found on the prominent headlands as far east as Karachi. The wave-cut terraces are locally tilted and cut by faults with a few meters of displacement.Long-term, average rates of uplift were calculated from present elevation, estimated elevation at time of deposition, and 14C and U–Th dates obtained on shells. Uplift rates in centimeters per year at various locations from west to east are as follows: Jask, 0 (post-Sangamon); Konarak, 0.031–0.2 (Holocene), 0.01 (post-Sangamon); Ormara 0.2 (Holocene). 相似文献
9.
S. P. Prizomwala S. B. Shukla Nilesh Bhatt 《Journal of the Geological Society of India》2012,79(6):557-562
Indus is one of the major sources of sediments to the Gulf of Kachchh. Yet only its <63 micron fraction is studied in detail
with regards to the offshore current dynamics. Hence here we present our study on characteristic signature of the Indus sediment
load (i.e. mica minerals) in >63 micron size fraction along the coast of Gulf of Kachchh. The spatial distribution of mica
minerals along the Gulf of Kachchh coast was studied which showed in general decreasing trend as we move along the northern
and southern coast of the Gulf of Kachchh but, an increase in amount near the southern mouth at Okha. The study shows that
the earlier proposed tidal barrier is ineffective in restricting movement of mica across the mouth of the gulf due to its
characteristic transport mechanism. Also the presence of mudflats along the gulf of Kachchh coast plays a vital role as sediment
receptors in the active sediment transport processes and mica minerals prove to be a promising simple tracer in studying the
Indus born sediments in the region. 相似文献
10.
Landslide susceptibility assessment along the southern coast of the Caspian Sea,Iran 总被引:1,自引:1,他引:0
Setayeshirad Mohammad Rasoul Nikudel Mohammad Reza Uromeihy Ali 《Natural Hazards》2013,65(3):2215-2239
China is a disaster-prone country, and these disasters have diverse characteristics, a wide scope of distribution, high frequency, and large losses. China has advanced community-based disaster management (CBDM) capacity. Community is the bottom unit of the society, and CBDM is the foundation of the entire society’s disaster management system. A series of domestic major emergency incidents and disasters and international disaster reduction activities have promoted the formation of the CBDM concept, the implementation of capacity building activities, and the improvement of policy and laws. Thus far, the CBDM system has been preliminarily formed in China, and relevant rules and regulations have been promulgated and implemented. Furthermore, disaster reduction activities, such as the construction of the national comprehensive disaster reduction community and national safe community, have been promoted nationwide. As a result, China’s disaster-resistance capacity has largely improved. However, it is only in the initial phase of CBDM implementation, which remains plagued by several challenges and problems, such as the deficiency of community resident participation, management organizations, disaster risk assessment methods, NGO development, and safety culture cultivation. 相似文献
11.
This paper investigates the characteristic features of the coastal atmospheric boundary layer (CABL) along the west coast
of India during the south-west monsoon (SWM) 2002. Extensive surface and upper-air findings were obtained during the same
period from the Arabian Sea Monsoon Experiment (ARMEX; 15th June to 15th August 2002) 2002. The operational general circulation
model (GCM) of the National Centre for Medium Range Weather Forecasting (NCMRWF) was used in this study to see the spatial
variation of the CABL during two specific convective episodes that led to heavy rainfall along the west coast of India. The
impact of a non-local closure (NLC) scheme employed in the NCMRWF GCM was carried out in simulating the CABL. The same episodes
were also simulated using a similar parameterization scheme employed in the high resolution mesoscale modelling system (MM5).
The diurnal variation of CABL is better represented from MM5 simulation. Comparing the MM5 simulation with that of the coarser
grid NCMRWF GCM, we observed that the NCMRWF GCM underestimates the values of both latent heat flux (LHF) and the coastal
atmospheric boundary layer height (CABLH). Results from MM5 therefore indicate that the best way to move forward in addressing
the short-comings of coarse grid-scale GCMs is to provide a parameterization of the diurnal effects associated with convection
processes. 相似文献
12.
Karstified features and surficial calcareous crust (caliche) develop on the upper most surfaces of the Middle Miocene rocks in the area between Quseir and Mersa Alam along the Red Sea coast, Egypt. Detailed studies of the caliche profile revealed various textures and fabrics denoting a cyclicity in deposition as well as diagenetic differentiation crystallization and deformation. The occurrence of these caliche deposits suggest that the Middle Miocene rocks in the study area have been subjected to alternating periods of rainfall and intense evaporation.
Zusammenfassung Karstphänomene und Kalkkrusten (Caliche) haben sich auf den Oberflächen der Gesteine des Mittelmiozäns im Gebiet zwischen Quseir und Mersa Alam entlang der Küste des Roten Meeres in Ägypten entwickelt. Eingehende Untersuchungen von Kalkkrusten Profilen lassen unterschiedliche Strukturen und Gefüge erkennen, die sowohl zyklische Bildung belegen als auch diagenetische Kristallisations-Differentiation und Deformation. Das Auftreten dieser Caliche-Bildungen legt nahe, daß die mittelmiozänen Gesteine im Untersuchungsgebiet abwechselnd regenreichen Perioden und solchen mit starker Evaporation ausgesetzt waren.
Résumé Des structures karstiques et des croûtes calcaires superficielles (caliches), se sont formées à la surface des roches du Miocène moyen dans la région comprise entre Ouseir et Mersa Alam, le long de la côte de la mer Rouge, en Egypte. L'étude détaillée de profils de la caliche révèle des structures variées qui indiquent un dépôt cyclique ainsi qu'une cristallisation différentielle et une déformation diagénétique. La présence de tels dépôts de caliche suggère que les roches du Miocène moyen de cette région ont été soumises alternativement à des périodes de pluie et d'évaporation intense.
Quseir Mersa Alam — . , , , , . , .相似文献
13.
Damien Closson 《Environmental Geology》2005,47(2):290-301
For about four decades, the Dead Sea (DS) level and the surrounding water table has been dropping dramatically. At least from the eighties, the direct vicinity of the Lisan Peninsula (LP), Jordan, has been facing high rates of subsidence and sinkhole hazards. Between 2000 and 2002, the Arab Potash Company (APC) lost two salt evaporation ponds resulting in a loss of $70 million. In the fertile plain of Ghor al Haditha (GAH), three deep and wide bowl-shaped subsidence areas threaten human activities and infrastructures. Over the part of the Lisan Peninsula that emerged before the 1960s, relict fossil sinkholes occurred everywhere, whereas new collapses constantly appear in the southern area only. In this paper, we have integrated 15 years of field observations related to sinkholes and subsidence with interpretation of space borne radar interferometric outputs, aerial photographs and satellite images. This has helped to place hazardous areas in their geological context and to clarify them within the framework of the general tectonic setting of the area. 相似文献
14.
Geomorphic expression of late Quaternary sea level changes along the southern Saurashtra coast, western India 总被引:1,自引:0,他引:1
Geomorphic expression of land-sea interaction is preserved in the form of abandoned cliffs, marine terraces, shore platforms
and marine notches along the southern Saurashtra coast. These features have been used to ascertain the magnitude of sea level
changes during late Quaternary. Notch morphology and associated biological encrustation have been used to estimate the magnitude
and duration of palaeo-sea strands. Marine notches and other erosive features occurring between 12 and 15 m above the present
Biological Mean Sea Level (BMSL) are attributed to the last interglacial corresponding to the Marine Isotopic Stage 5 (MIS-5).
However, 6 to 9 m upliftment of the coastal fringe is attributed to this sea level. The second major high sea strand was identified
during the mid-Holocene when the sea rose 2 m above the present level. Notches corresponding to this high sea level are recorded
4 to 5 m above the present BMSL. 相似文献
15.
16.
The coast of Kuwait can be divided into nine intertidal geomorphological subunits, of which four are found along the northern muddy shoreline and five along the southern sandy shoreline. In the north the coast is characterized by wide intertidal mudflats, bounded landward by an extensive coastal sabkha which is partly covered by sand drifts. The upper part of the intertidal environment is covered with a mixture of aeolian sands and muddy sediments of marine origin. A number of shallow tidal channels dissect the intertidal flats and small sand bars occur near the low water line. In contrast, the southern shore is characterized by relatively steep sandy beaches fronted by narrow to moderately wide rocky intertidal platforms which are partly covered by sand, bioherms, skeletal debris and algal mats. In some areas the rocky surface is dissected by numerous small gulleys and shallow channels. Multiple sand bars lying either parallel or diagonal to the shoreline are developed near the low water line. This southern intertidal environment is bounded landward by a sandy berm and a wave-cut cliff.Ripple marks are developed almost parallel to the shoreline, showing different flow directions. Energy levels are moderate to high along the southern shore, but low along the northern shore. In the south, waves induced by winds blowing mostly from the north-east and south-east form the dominant energy source, whereas tidal and wind-driven currents are the only tangible process acting along the northern shore. 相似文献
17.
福建沿海盆地第四纪构造运动模式与动力学环境 总被引:2,自引:0,他引:2
对福建省福州、泉州、漳州、厦门等城市所在盆地沉积和断裂的研究表明,自漳州地区向北东和向南西各盆地起始沉积、沉积间断和全新世海侵等事件是时间上依次发生的序列沉积事件,漳州及其以北各第四纪盆地构成向南西掀斜的箕状盆地。基于上述规律性,提出了自漳州向北东和向南西依次扩展的第四纪以来地壳隆张的运动模型。分析了菲律宾板块与欧亚板块的接触关系和相互作用,认为菲律宾板块的作用是该区第四纪构造运动的主要驱动力,巴士系构造是该区地壳运动的触发构造。 相似文献
18.
Antony Charls Langodan Sabique Dasari Hari Prasad Knio Omar Hoteit Ibrahim 《Natural Hazards》2021,105(2):1797-1814
Natural Hazards - Knowledge about extreme water levels is essential for efficient planning and design of coastal infrastructure. This study uses a high-resolution (~?60 m) coupled... 相似文献
19.
Marina Aloysius S Sijikumar S S Prijith Mannil Mohan K Parameswaran 《Journal of Earth System Science》2011,120(2):269-279
The circulation dynamics of an event marked by the formation of an aerosol cluster off the coast of Maharashtra on April 22,
2006, its southward migration along the Indian west coast with a mean speed of ~200 km/day and its final dissipation after
reaching the end of the peninsula by April 28, 2006 as revealed by MODIS (Moderate Resolution Imaging Spectroradiometer) against
the pre-monsoon conditions of April 2006 are examined in this study. The maximum aerosol concentration in the cluster was
found getting confined to lower and lower altitudes during its southward movement. The NCEP/NCAR (National Centers for Environmental
Prediction/National Center for Atmospheric Research) reanalysis wind field indicates that the atmospheric circulation, especially
the horizontal wind convergence is the major factor that guides the formation and the dynamics of the cluster. Fine mode fraction
from MODIS suggests that the cluster mainly consists of coarse dust particles. The regional climate model, RegCM3 with an
efficient dust generation module simulates the formation and movement of the cluster appreciably well. The simulations which
also exhibit the altitudinally descending nature of the cluster during its southward movement confirm the mechanism which
governs the cluster dynamics suggested based on MODIS and NCEP/NCAR reanalysis data. 相似文献