جستجوی مقالات مرتبط با کلیدواژه « رسوبات » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

The excessive use of water and soil resources, especially in arid and semi-arid regions, causes increased soil erosion, followed by the appearance of destructive floods, the emergence of dust, and intensifying the phenomenon of desertification. Therefore, in order to prevent the environmental problems of these areas, there is a need for efficient management of their water and soil resources. The rainwater catchment systems are one of the strong points of dry and desert areas, which have a high ability to develop these areas. This study investigated the effect of rain catchment systems on the physical and chemical characteristics of rainwater catchment systems soil in the Mil Nadir area of Sistan. For this purpose, six soil samples were taken from the rainwater catchment systems and the control area and their physical and chemical properties were measured. The results of this study showed that there is a significant difference of 1% between the average percentage of clay, silt, and sand in the soil of the rainwater catchment systems areas compared to the control area (P<0.01). With the increase in the percentage of clay and silt, the soil texture from class Loamy-sandy in the control area was changed to loamy class in rainwater catchment systems, which caused a 28% increase in soil moisture compared to the control area. In the examination of soil chemical properties, the findings indicate that the amount of acidity, electrical conductivity, sodium, and sodium absorption ratio significantly (P<0.01) in the soil of rainwater catchment systems decreased, but the amount of organic matter, nitrogen, and potassium increased. The effect of rain catchment surface systems has improved the physico-chemical properties of the soil, due to the existing environmental crises and the acceleration of the desertification process in this region. The use of these catchment systems in the Sistan Region provides suitable conditions for improvement. It provides ecological and environmental protection of these areas.

Experimental investigation on scoring and determination of depth of scoring are among the most important issues in T-shape spur dike designation with model T-shape spur dike was measured in a laboratory flume with 180 degree bend under clear water. In this study, we conducted evaluate the effect of relative distance between two T-shape spur dikes in the bend on the occurred scour. For this purpose, two spur dikes were installed at four different relative distances and four different relative lengths in the first half of an180 degree bend. All experiments were performed in four Froude number and a constant flow depth. The results show that with increasing the relative distance of T-shape spur dikes, the relative maximum scour depth increase at the opening of the spur dikes. Measuring depth of scouring based on experimental observation, an empirical relation is developed with high regression coefficient 0.98.

In this study, in order to examine the joint of the cable and the collar in control of scour around the bridge piles, experiments were carried out in a rectangular plexiglass flume as a direct path. The experiments were carried out using three different cable diameters, three different thread angles and three rounds of the cable threaded at a steady current in clear water. The results of this study showed that, installing a cable and collar around the base of the cylinder is an effective factor in reducing the depth of scouring around it. Also, in all conditions of use of cable and collar, compared with the without collar mode, it increases the percentage of reducing scour depth around the cylindrical base. The use of collar on average reduces scour depth by about 43 percent compared to without collar condition. Also, the maximum scour depth in cable and collar conditions at a thread angle of 15 degree, a diameter ratio of 0.1 percent and triple threaded was about 63 percent.

Coastal sediments as sensitive indicators are employed for monitoring pollution in the coastal areas. Heavy metals in surface sediments originate from natural and/or man-made sources. This study was conducted to determine natural and anthropogenic sources of some heavy metals (Zn, Cu, Cd, Pb) of surface sediment in the southern Caspian Sea during four seasons in 2013-2014. 72 surface sediment samples (with triplicate) were collected at two transects (Tinekabon and Amirabad) and tree depths (5, 10, 20 m) using Van Veen Grab sampler. The heavy metals concentrations of different extraction were measured using atomic absorption spectrometry (AAS) with flame and furnace. Results showed that maximum and minimum concentrations of copper, zinc, lead, and cadmium in the non-resistance part were 0.58-19.31, 0.83-4.21, 4.21-7.86, and 0.31-0.68 and in the resistance part were 4.70-23.33, 4.88-79.19, 7.06-14.84, and 0.23-0.46 µg/g.dw, respectively. In a conclusion, percentage of Cd in the non-resistance part was 58.58% that it contained maximum level among various heavy metals which represents a greater distribution in the anthropogenic origin. While Cu (32.14%), Zn (4.28%) and Pb (35.77%) have natural origin.

Flood spreading has an effective role in the soil improvement and fertility، ground water storage، revival of vegetation and prevention of fluent sands movement. One of the main problem of flood spreading projects is the entrance of sediment to the spreading systems and sedimentation in it. Sediment reduces the efficiency of the flood spreading system and after awhile lose its efficiency. The main aim of this research is the investigation of infiltrate changes trend under effect of flood spreading in Tangestan flood spreading station (Bushehr province). In this research، soil surface infiltration in spreading and control area were measured with double rings method. For investigating of these changes the intervals between flood spreadng channels، the first، second and third rows were selected. Data were analyzed by Kruskal-Wallis test. Due to the significant level of this test، less than 0. 01، can be expressed that between the infiltration of flood spreading rows and control area were significant difference.