فصلنامه اقیانوس شناسی
پیاپی 8 (زمستان 1390)

Clay minerals in sediments can be controlled by weathering of source rocks, climate condition, transportation and deposition. In this research, clay minerals from Oman sea continental shelf in Chabahar area have been studied in order to interpret paleoclimate and also determine clay minerals provenance. The study of clay mineralogy by XRD, SEM and EDS led to identification of four types of clay minerals including Kaolinite, chlorite, illite and smectite. The most abundant clay mineral is kaolinite, and high percentage of this mineral is indicative of chemical weathering. The main source of clay minerals is felsic rocks. Kaolinite and illite in marine sediments are the products of long washed recycled sediments after several uplifting stages in active Makran subduction zone. The amount of chlorite and smectite is very low in studied sample, which is indicated by the lack of favorite condition for such minerals forming.

In this investigation, coastal sediments of Gawatr bay were studied to assess the degree of heavy metal pollution as a consequence of natural and anthropogenic sources. Samples were collected from 14 stations in summer 2009, and analyzed by Inductively Coupled Plasma Mass Spectrometry for Fe, Mg, Mn, Pb, Zn, Cu, Cr, Cd and Ni. These concentrations were compared with environmental investigation limits. In addition, sediment samples were exposed to wet sieving and Laser Particle Sizing and organic matter determination. Geochemical normalization maps confirmed that most of heavy metal concentrations were related to coastal sediments of Pasabandar harbor in which, concentrations of Fe, Mn, Pb, Zn and Cr were 3.15, 2.53, 1.35, 4.24 and 100 times background concentrations in study area respectively. The reason for these contaminations is reparation and maintenance of fishing vessels as well as wastewater discharge into semi-closed Pasabandar harbor. Due to sedimentological characteristics of bottom, and high organic matter content, mangrove ecosystems growth in Gawatr estuary provide an aggregation area for some heavy metals in Gawatr bay. Correlation coefficients confirm that organic and inorganic colloids such as Fe, Mn hydroxides as well as clay minerals have a significant role in bioavailability of heavy metals in study area. High correlations among Cr, Mg, Ni and Fe showed that dissolution of ophiolitic formations by Bahu-kalat river is an important factor for heavy metal accumulation in Gawatr bay. In this research, it was also delineated that shrimp farm has no obvious effect on heavy metal pollution in the area.

The Persian Gulf is under the influence of sporadic dust transportation from desert sources in North Africa (The Great Sahara) and the Middle East (Arabian Peninsula) particulary during spring and autumn. Mineral dust originated from these arid regions has characteristic of redish yellow-redish brown color due to its high iron oxide content. Following atmospheric transport, mineral dust settles by either dry or wet (washout or rainout) deposition mechanisms. Precipitation samples collected at Bandar Abbas on the North of Persian Gulf coast of Islamic Republic of Iran during the period of December 2006-December 2007 have been investigated with respect to their red dust contents. The backward air mass trajectories corresponding to the rainy days were analyzed to determine the potential source regions of red dust transported to the Persian Gulf. Approximatley,%25 of the total precipitation samples can be evaluated as “red rain”. The mean electrical conductivity and the volume weighted mean “Al” concentration of red rain was found to be approximatley seven times and five times higher than normal rain, recpectively, while the dissolution of the calcite in dust caused an order of magnitude decrease in volume weighted mean hydrogen ion concentration of red rain, by neutralizing (buffering) the acidity of rainwater. Due to the dissolution of atmospheric CO2 in rainwater, natural precipitation is slightly asidic (pH=5.6). In this research, the volume weighted mean pH values were calculated to be 6.09 for normal rain and 7.27 for red rain. Using Al concentration of precipitation samples, wet deposition flux of mineral dust during 2007 was found to be 2.13 g m-2 yr-1. If dry deposition flux is added to this value, a total flux of 4.84 g m-2 yr-1 is found for atmospherically transported mineral dust.

This is an attempt to study the larval stages of Portaunidae from the Iranian coastal waters. Samples were collected monthly with a 300 μm aperture net from the coastal waters of Khuzestan (North of the Persian Gulf) from May 2007 to April 2008. The larval stages are illustrated and described in detail for Portunus pelagicus and Thalamita prymna. Spatial and temporal variations in density of larval stages of 2 species of Poratnidae were calculated. Portunus plagicus and Thalamita prymna were the dominant species with the maximum abundance of 63.3 and 94.3 individual /m3 respectively, in May 2007. As the study area has the subtropical conditions, different species of this family were found from April to November. The composition and abundance of larval stages indicate that Portunid crabs have continuous reproduction strategy with a peak in May.

Water pollution by heavy metals causes serious ecological problems in the world. Therefore, determination of heavy metals such as cadmium in the enviroment samples are needful today. In order to detect metal ions at very low concentration, it is necessary to have a preconcentration to achieve opphorite concentration above the detection limit of analyzing instrument. The used preconcentration methods are based on solid adsorbents which are simple, rapid and usually leads to eliminate the interference elements from the matrix. Amberlite XAD-2 (polystyrene-divinylbenzene polymer) is a very used resin in preconcentration procedure, thanks to its good physical and chemical properties, such as porosity, high surface area, durability and purity. In this study, cadmium ions was absorbed during passage through amberlite XAD-2 resin, modified with iminodi acetic acid. Also, the influence of pH was studied and the best pH for this study was 7.5, with relevant recovery of higher than 90%. The proposed procedure was applied for cadmium determination by Flame Atomic Adsorbtion Spectroscopy (FAAS) after preconcentration in natural water samples. The achieved recovery and its standard deviation, measured by standard addition technique showed that the proposed procedure had good accuracy, enrichmant factor, preconcentration factor and simplicity.

Existence of different pollution sources have adverse effects on the ecosystem health of a region. Therefore, the study of their contaminantion level in the a region is an essential need. In this study, the level of nickel, vanadium, copper and lead concentrations in the sediments and Pacific oysters Crassostrea were measured. 3 samples of the sediment and 30 oysters were collected from intertidal zone of 5 different stations in the Imam Khomeini port in february 2010. Samples were digested by metode Yap (2002) after drying. The concentration of nickel, copper and lead were analysed using Atomic Absorbtion Spectrophotometer (GBC model SavantAAΣ) and Vanadium concentration were analysed using Atomic Absorbtion equipped by graphite furnace (Varian AA 240). Concentration of heavy metals in sediment could be arranged in the following sequence: Ni>V>Cu>Pb and in Bivalves showed following sequence: Cu>Pb>Ni>V. Ni concentration in sediments was found to be higher than available standards, but concentration of Pb was lower than available standards. The mean concentration of vanadium was lower than RSA standard and Cu concentration was higher than USEPA standard. Metal Concentration in the soft tissue of studied oyster was found to be higher than FAO and WHO standards.

Container clearance time is one of the main factors which strongly affects the process of import/export of the country. The time a container spends in a port before clearance is a real cost scenario which will affect the port performance and throughput at all parts of the port. This research aims at studying the operative factors on container clearance in Iranian ports. Achieving this purpose, qualitative factors are converted to quantitative factors, using an empirical-statistical analysis. The results of this research will highlight the problems of container clearance in Iranian ports.

The wave induced internal forces in the body of a seawall have a random temporal change. Since the incident waves have various periods, studying the behavior of a seawall under the variable wave periods can be considered to be of major importance. In order to investigate the effect of wave period on the produced internal forces, three seawalls have been modeled and analyzed subjected to sea waves. The first model is a vertical seawall, while the second and third ones are inclined seawalls with uniform and dual slopes, respectively. The water depth and wave height have been considered to be fixed during the performed analyses, while different values have been assigned to the wave period, ranging from 0.1 to 3 sec, with the increments of 0.05 sec. In each analyzed model, the maximum values of base shearing force and flexural moment have been extracted from the corresponding time histories of internal forces. A modal analysis has also been performed on each model from which the natural period of the wall’s oscillation has been obtained. The results show that when the wave period is shorter than the structure’s natural period of oscillation, increase of the wave period leads to increase of the base shearing force and flexural moment; while under the waves having peak periods longer than the structure’s natural period of oscillation, increase of the period results in the decrease of base internal forces.

Predicting and estimating the sea waves are very important in coastal zone activities, including: fishing industrial, port navigation and management, marine transport, design of costal structures, oil activities and calculation of sediment transport rate. Also, waves and currents play very important roles in changing geometry and shape of the coastal zone. SWAN model has been designed for coastal shallow waters. Therefore, in this study wind driven waves in the Bushehr Gulf has been simulated by this model and then it has been validated. In this simulation, wind data from the GFS and Buoy data of Bushehr meteorology in year 2008 were used. After simulation, the wave characteristics of Bushehr buoy (significant wave height, Hs, and significant wave period, Ts) were employed for validation of the model. Results of this research show that the average scatter index of swan model for high wave and period are 23.44 and 18.45 percent, respectively. Therefore, we can use SWAN model for prediction of characteristics of wind driven waves and providing the hydrodynamic Atlas for Bushehr Bay.