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1.
Regional distribution pattern of groundwater heavy metals resulting from agricultural activities 总被引：18，自引：0，他引：18
Contaminations of groundwater by heavy metals due to agricultural activities are growing recently. The objective of this study
was to evaluate and map regional patterns of heavy metals (Cd, Zn and Cu) in groundwater on a plain with high agricultural
activities. The study was conducted to investigate the concentration of heavy metals and distribution in groundwater in regions
of Shush Danial and Andimeshk aquifers in the southern part of Iran. Presently, groundwater is the only appropriate and widely
used source of drinking water for rural and urban communities in this region. The region covers an area of 1,100 km2 between the Dez and Karkhe rivers, which lead to the Persian Gulf. For this study, the region was divided into four sub-regions
A, B, C and D. Additionally, 168 groundwater samples were collected from 42 water wells during the earlier months of 2004.
The flame atomic absorption spectrometry (AAS-Flame) was used to measure the concentration of heavy metals in water samples
and the Surfer software was used for determination of the contour map of metal distribution. The results demonstrated that
in all of the samples, Cd and Zn concentrations were below the EPA MCLG and EPA secondary standard, respectively. However,
the Cu contents of 4.8 % of all samples were higher than EPA MCL. It is also indicated that the concentrations of metals were
more pronounced at the southern part of the studied region than at the others. The analysis of fertilizers applied for agricultural
activities at this region also indicated that a great majority of the above-mentioned heavy metals were discharged into the
environment. Absence of confining layers, proximity to land surface, excess agricultural activities in the southern part and
groundwater flow direction that is generally from the north to the southern parts in this area make the southern region of
the Shush plain especially vulnerable to pollution by heavy metals than by other contaminants. 相似文献
2.
A study of the dynamics of the Mersa Matruh Gyre and the Mid-Mediterranean Jet flow system in the southwestern Levantine basin is presented. Data-driven simulations in the Levantine basin, using an eddy-resolving quasigeostrophic model initialized with two quasi-synoptic hydrographic data sets, reveal intense mesoscale meander and ring formation events involving the Mid-Mediterranean Jet, the Mersa Matruh Gyre and the Rhodes Gyre. The dynamics of these events are quantified via local energy and vorticity budget analyses. The dominant processes are investigated and compared with previously studied events in the Gulf Stream Ring and Meander region. 相似文献
3.
Abbas-Ali A Bidokhti Maryam Gharaylou Nafiseh Pegahfar Samaneh Sabetghadam Maryam Rezazadeh 《Journal of Earth System Science》2016,125(2):431-442
Determination of dust loading in the atmosphere is important not only from the public health point of view, but also for regional climate changes. The present study focuses on the characteristics of two major dust events for two urban areas in Iran, Kermanshah and Tehran, over the period of 4 years from 2006 to 2009. To detect extreme dust outbreaks, various datasets including synoptic data, dust concentration, reanalysis data and numerical results of WRF and HYSPLIT models were used. The weather maps demonstrate that for these events dusts are mainly generated when wind velocity is high and humidity is low in the lower troposphere and the region is under the influence of a thermal low. The event lasts until the atmospheric stability prevails and the surface wind speed weakens. The thermal low nature of the synoptic conditions of these major events is also responsible for deep boundary layer development with its thermals affecting the vertical dust flux over the region. Trajectory studies show that the dust events originated from deserts in Iraq and Syria and transported towards Iran. The main distinction between the two types of mobilizations seems to affect the dust concentrations in the Tehran urban area. 相似文献
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To determine the role of mangroves for fisheries in the arid region of the Persian Gulf, we investigated fish community structure and trophic diversity in intertidal creeks with and without mangroves. Fish community abundances and biomass were compared across habitats and seasons. To identify variations in overall community trophic niches among habitats and seasons, we measured niches with size-corrected standard ellipse areas (SEAc) calculated from C and N stable isotope values. Although there was a slightly greater species richness occurred in mangrove creeks, we found a general similarity in the diversity patterns in creeks with and without mangroves. Also, there were no consistent differences in fish abundance or biomass for mangrove vs. non-mangrove fish collections. Community trophic diversity measured as SEAc also showed no significant difference between mangrove and non-mangrove sites. Instead, strong seasonal patterns were observed in the fish assemblages. Winter samples had consistently higher fish abundance and biomass than summer samples. Winter SEAc values were significantly higher, indicating that the fish community had a larger isotopic niche in winter than summer. Overall, we found that seasonality was much stronger than habitat in determining fish community structure and trophic diversity in the mangrove and non-mangrove ecosystems of Qeshm Island, Iran. 相似文献
7.
Behzad Khani Mohammadreza Kamali Maryam Mirshahani Mahmood Memariani Mahmood Bargrizan 《Arabian Journal of Geosciences》2018,11(2):39
The Upper Jurassic Sargelu and the Cretaceous Garau formations are important source rocks in the Lurestan basin, southwest Iran. In this study, the maturity evolution and burial history of these source rocks are investigated using 1D modeling in 15 wells within the Lurestan basin. These models are calibrated using temperature and vitrinite reflectance readings at well locations. Results indicate that thermal maturity of studied source rocks increases towards the northwest of the Lurestan basin and is the lowest over the Anaran High. The present-day level of maturity suggests that these formations are suitable candidates for shale gas resources in the Lurestan basin. 相似文献
8.
Shape optimization of two-dimensional cavitators in supercavitating flows, using NSGA II algorithm 总被引：1，自引：0，他引：1
The reduction of energy consumption of high speed submersible bodies is an important challenge in hydrodynamic researches. In this paper, shape optimization of two-dimensional cavitators in supercavitating flows is studied. A two dimensional supercavitation potential flow passes a symmetric two dimensional cavitator, which is placed perpendicular to the flow in a channel of infinite length and immediately a cavity is formed behind the cavitator. This is because of the generation of a gas or vapor cavity between the body and the surrounding liquid due to the change in a high speed flow direction passing the cavitator. Drag force acting on this supercavitating body dictates the thrust requirements for the propulsion system, to maintain a required cavity at the operating speed. Therefore, any reduction in the drag force, by modifying the shape of the cavitator, will lead to decrease this force. This study concentrates on the optimization of two dimensional cavitators in order to decrease drag coefficient for a specified after body length and velocity in a potential flow. To achieve this goal a multi-objective optimization problem is defined to optimize cavitator shapes in supercavitating flow. The so-called NSGA II (Non-dominated Sorting Genetic Algorithm) algorithm is used as an optimization method. Design parameters and constraints are obtained according to supercavitating flow characteristics and cavitator modeling and objective functions are generated using Linear Regression Method. The obtained results are compared with other classic optimization methods, like the weighted sum method, for validation. 相似文献
9.
Jian Chu Volodymyr Ivanov Maryam Naeimi Viktor Stabnikov Han-Long Liu 《Acta Geotechnica》2014,9(2):277-285
Bioclogging and biocementation can be used to improve the geotechnical properties of sand. These processes can be performed by adsorption of urease-producing bacterial cells on the sand grain surfaces, which is followed by crystallization of calcite produced from the calcium salt and urea solution due to bacterial hydrolysis of urea. In this paper, the effect of intact cell suspension of Bacillus sp. strain VS1, suspension of the washed bacterial cells, and culture liquid without bacterial cells on microbially induced calcite precipitation in sand was studied. The test results showed that adsorption/retention of urease activity on sand treated with washed cells of Bacillus sp. strain VS1 was 5–8 times higher than that treated with culture liquid. The unconfined compressive strength of sand treated with the suspension of washed cells was 1.7 times higher than that treated with culture liquid. This difference could be due to fast inactivation of urease by protease which was present in the culture liquid. The adsorption of bacterial cells on sand pretreated with calcium, aluminum, or ferric salts was 29–37 % higher as compared with that without pretreatment. The permeability of sand varied with the content of precipitated calcium. For bioclogging of sand, the content of precipitated calcium had to be 1.3 % (w/w) or higher. The shear strength of biotreated sand was also dependent on the content of precipitated calcium. To achieve an unconfined compressive strength of 1.5 MPa or higher, the content of precipitated calcium in the treated sand had to be 4.2 % (w/w) or higher. These data can be used as the reference values for geotechnical applications such as bioclogging for reducing the permeability of sand and biocementation for increasing the shear strength of soil. 相似文献
10.
Land assessment for flood spreading site selection using geospatial information system 总被引：3，自引：1，他引：2
A. A. Alesheikh M. J. Soltani N. Nouri M.Sc. M. Khalilzadeh 《International Journal of Environmental Science and Technology》2008,5(4):455-462
Irregular patterns of precipitations from temporal as well as spatial perspectives not only cause destructions but also waste surface water resources. Hence, controlling surface water and leading the flood to underground stores improve the efficiency of water usage. Selecting appropriate sites for optimal use of water floods is one of the most important factors in recharging underground water tables in dry lands where the agricultural and rangelands are vulnerable. Traditional methods of site selections are, however, time consuming and error prone. This paper attempts to; analyze existing schemes of site selection; introduces an appropriate method of locating flood-spreading sites using Geospatial Information System; implements the strategy in a case study; and scientifically assesses its results. The study area of this research is Samal sub-basin covering 31571.7 ha of Ahrom basin in Boushehr province. In the present research, factors pertain to earth sciences (quaternary units, slope and landuse) and hydrology (runoff infiltration rate and aquifers’ depth) are considered. Information layers are weighted, classified and integrated through several models such as boolean logics, index overlay and fuzzy logics. The results are then checked against the existing sites to estimate their accuracy. The results of this research demonstrated that fuzzy logic operators including gamma=0.1, gamma=0.2 and products of fuzzy logics yield the best when compared to control fields and therefore, the models are introduced as the most suitable site selection strategies for flood spreading. 相似文献