فصلنامه اقیانوس شناسی
پیاپی 45 (بهار 1400)

Due to coastal areaschr(chr('39')39chr('39')) dynamic nature, sediment transport frequently changes the shape and morphology of coastal profiles. During the time, coastal areas adjust their sedimentation regimes to such changes. Although constructing structures such as breakwaters and jetties in coastal areas results in disorder in their natural sedimentation regime. To restore the natural regime, Sand Bypassing Systems (SBS) has been introduced and employed for near a century in countries such as Australia and USA. This study aims to assess the possibility of implementing SBS around ports of Iranchr(chr('39')39chr('39'))s Makran coasts. In this regard, first, components of SBS are described. Then, the successful worldwide examples of the established systems and the sediment transport pattern around the ports of Iranchr(chr('39')39chr('39'))s Makran coasts were studied. Finally, by providing general guidelines for using this system in the studied area, results of numerical modeling were also used for two ports of Beris and Ramin to propose SBS in detail.

In this research, observational data are analyzed to explain temperature and salinity inversions and double diffusion in the Oman Sea. The results of this paper show that intrusive structures extend over a depth of about 100-450 meters in the Oman Sea. Temperature and salinity inversions observed depth of 250 m in winter and summer in the Oman Sea. Steps thickness is about 10 to 20 meters. A warm and saline lens in these waters with common diffusive convection on the top layers and salt fingering in bottom layers are expected. Both processes occur (diffusive and finger convection) that have an important role in creating temperature and salinity inversions. Convective diffusion is the dominant factor in dual diffusion in the steady-state. While the warm and saline tongue expands due to the salt fingering and the baroclinicity, Convective diffusion is a major factor limiting the growth of tongues.

Heavy metal pollution in aquatic ecosystems affects microalgae and zooplankton, alters the biomass and abundance of species, and promotes interspecies relationships to the predominance of less sensitive species. In this study, the effect of short-term stress of different concentrations of cadmium heavy metal on Chlorella sp. growth and some biochemical parameters have been investigated. Microalgae were treated at different concentrations of cadmium (0, 150, 250 and 350 μm) in the culture medium for 24 hours. The results showed that the content of chlorophyll a photosynthetic pigments, beta-carotene and total protein content decreased significantly. Also, with increasing cadmium concentration, the content of malondialdehyde in the microalgae of Chlorella sp. increased. The activity of giacacol peroxidase, ascorbate peroxidase and superoxide dismutase antioxidant enzymes increased in Chlorella sp. under short-term stress of cadmium. The highest activity of these enzymes was at the concentration of 150 μM cadmium.

Chabahar Bay is a semi-closed and shallow bay in southeastern of Iran and is strongly affected by the monsoon conditions. The 3D FVCOM model was used to study the hydrodynamic conditions of Chabahar Bay. For this purpose, a horizontal grid with 6290 triangular elements and a vertical grid with 10 sigma layers were created. The model was implemented in baroclinic mode; NCEP data and HYCOM model outputs were used to account for open surface and boundary layer forces. Water level and flow velocity correlations show acceptable agreement with field data. The tidal bay is often semi-daily and mixed and the tidal range is 2.7 m. The flushing time of Chabahar Bay was calculated to be 6.7 days. The modeling results show; The vertically and annual average current velocity is 0.1 m/s and the rotation pattern is often anticyclonic.

Providing faultless proceeding of the engineer in order to protect the rivers, requires understanding the morphological behavior of the river and studying the hydrodynamic phenomena of the area. The intersection of the Karun rivers as the largest and longest river in Iran with the Arvand border river is of considerable importance due to its strategic location. In this paper, using field measurement and numerical modeling, the hydrodynamic processes of this area have been investigated. Measurement of marine parameters related to the border area with hard access at the intersection of Karun to Arvand and it includes water level and current velocity, hydrography, sediment granulation, and hydrodynamic modeling of current and sediment. Current velocity measurements show that the prevailing flow velocity in this area is towards Arvand and Arvand tide can only reduce the flow velocities of this river locally. Hydrographic changes also indicate flood currents in Karun, which act like water jets, causing significant changes in the bed of the intersection of Karun and Arvand rivers and shifting the Talweg line to Iraq. At the intersection of rivers due to sharp changes in depth, sediments are coarser than other points and also the concentration of sediments increases with movement at depth. The results of the numerical model are consistent with field measurements and indicate that sediment flow in the Arvand River is carried out by the Karun River and the effects of sediment flow in the Arvand River on Karun are very small. Also, the intersection of these two rivers has a high potential for sedimentation and increase the thickness of the bed.

In the present study, the sediments of the Gurpi Formation in the Jafarabad section located in the southeast of Ilam were examined from the point of view of calcareous calcareous nannofossils. The sediments of the upper part of Gurpi Formation with a thickness of about 42 m are composed of limy marl sediments. In this study, 34 species belonging to 22 genera from the group of calcareous nannoplankton were identified. In this formation, based on recorded bio-events, bio-zones CC25 (UC19TP-UC20aTP) to (CC26 (UC20bTP, UC20cTP, UC20dTP in sediments belonging to the Upper Cretaceous followed by the bio-zone, NP4 (CNP6-CNP7), NP5 (CNP7-CNP8), NP6 (CNP8) were identified from Paleocene sediments in the upper part of the Gurpi Formation. According to the determined bio-zones, the age of the upper part of Gurpi Formation, late Maastrichtian (Cretaceous) to late Selandian (Middle Paleocene) was identified. In the present study, based on the absence of registration of NP1, NP2, NP3 bio-zones and the lack of fossil data, the boundary between Cretaceous and Paleogene in the upper part of this formation is proposed to be discontinuous. In addition, based on the record of bio-events from the group of calcareous nannofossils, which confirm the warm climate, the conditions prevailing in the sedimentary basin at the time of sedimentation of the Gurpi Formation are inferred with warm climate.

Silver nanoparticles are widely used in various sciences and industries. Widespread use of silver nanoparticles has caused entrance of it to the aquatic environment through Wastewater, so it is necessary to investigate the effects of silver nanoparticles on various aquatic organisms. The present study investigated the lethal concentration and bioaccumulation of silver nanoparticles and its comparison with silver nitrate in the Caspian Sea gammarus (Pontogammarus maeoticus). For this purpose, the first experiment was performed to determine the range finding test of silver nanoparticles in gammarus. Then, to determine the lethal concentration 50 (LC50), the gammarus were exposed to concentrations of 0, 0.25, 0.5, 1, 2, 4 and 8 mg/L of silver nanoparticles and silver nitrate and their mortality was recorded in 96 hours. Then different lethal concentration were calculated by statistical analysis. The bioaccumulation of silver in each of the silver nanoparticles and silver nitrate treatments was also investigated. In this study, the 96-h LC50 values ​​for silver nanoparticles and silver nitrate were 3.77 and 5.78 mg/l, respectively .The results of this study showed that the LC50 of silver nanoparticles was lower than silver nitrate and the gammarus mortality increased with increasing concentrations of silver nanoparticles and silver nitrate as well as increasing exposure time.

Improving the work ethic environment in organizations, causes employees to respond better to moral stress and other causes of dissatisfaction in the work environment and ultimately stay in their jobs, and the appropriate work ethic environment reduces job dissatisfaction and the tendency to Quit work. Accordingly, this study was conducted to identify and rank the factors affecting work ethic based on spirituality in the workplace in the crisis management organization. The method of this study is in the field of quantitative-qualitative research in terms of practical purpose and method of implementation. The statistical population of this study included all the employees of the Tehran Crisis Management Organization in the period of 2020-2021, from which 250 people were selected as a sample based on Cochranchr('39')s formula and stratified random sampling method. It was. Also, the statistical population of this study in the qualitative section includes all managers of the Tehran Crisis Management Organization in 2020-2021. The sampling method from the community was purposeful that based on this type of sampling method, 19 people were selected as the sample. Data collection tools in the qualitative part, interview and in the quantitative part, the researcher designed the questionnaire based on the criteria extracted from the qualitative stage. In this study, data analysis was performed in the qualitative part with MAXQDA software and in the quantitative part using SPSS statistical software. The results of this study showed that moral commitment, professional commitment and relationship related to causal conditions, organizational ethical atmosphere, pivotal phenomenon, ethical Islamic culture in the field of interactive strategies, ethical leadership from intervening conditions and ethical and Islamic education from Underlying factors are the components of work ethic based on spirituality in the workplace in the crisis management organization. The results also showed that the highest average value was equal to 7.90 which is related to the factor of moral leadership and the lowest average value was equal to 4.91 which is related to the factor of moral commitment.