خلاصة:
1 Introduction Nabkhas are sand dunes that form around vegetation. They have been reported in many parts of the world. Nabkhas are often associated with areas having degraded soil and vegetation. In these landscapes, information on the formation, structure and growth of coppice dunes can provide distinct clues about environmental changes. Therefore, to evaluate and control desertification resulting from vegetation change it is critical to understand the coppice dune dynamics. Many studies have showed the importance of aeolian processes, including the erosion of sediments and their deposition under the shrub canopies. This study focused on evaluation of morphoscopy and granulometry characteristics of nebkha sediments in Shahdad-Kerman. 2 Materials and Methods The study was conducted in the Southwest Lut playa, Shahdad, Kerman province. A coppice dune was selected. The height of the selected dune was measured from the base of the dune to the center of the mesquite canopy, which typically protrudes about 15m. Sediment sampling was conducted on the top 10cm of the sediment. Sediments were sampled every 0.5m coppice dune. The samples were transported to laboratory for determining morphoscopy and granulometry characteristics such as sorting and skewness and sediments physiochemical properties such as EC, pH, SAR, particle size distribution (sand, silt and clay). 3 Results and Discussion The samples belonging to lower part of nebkha had higher EC than those of the upper parts. Average pH of the samples was 4.23. Mean grain size for sediments on the upper and lower parts of the dune was 208μm and 115μm, respectively. Mean sorting was 1.29. The lower samples are generally better sorted compared with the upper samples. Skewness of grain-size distribution was 0.16-0.82. Mean kurtosis of all the samples was 1.74. The results of kurtosis showed that the upper samples exhibited the lowest kurtosis. The results of morphoscopy showed distance of deposited sediments around Nebkha from their source area was approximately 20-50 km exhibiting their short distance from source area.
ملخص الجهاز:
Since nebkha sediments are transported from adjacent areas, studying nebkha sediments can allow for the investigation of playa transformations; therefore, the form of the dunes and sedimentation characteristics serve as criteria for environmental changes on a regional scale, including dune migration, aeolian sediment transport (Forman et al.
After performing investigations such as collecting local information, sampling from the sand dune, statistical factors, sedimentology, and drawing sedimentological curves, they concluded that the grain size of the sediments shows that sediments at four points of the sand dune have differences in sorting, which arises from the sediment source position and wind strength.
(2013), after investigating the morphoscopic and granulometric characteristics of sand particles in the Kharatouran Citadel of Shahroud, reached the results that the presence of new sediments in some western areas is an indication of active wind erosion within the citadel and also extraction from its natural source.
(Refer to the page image) Figure 4- Work method chart 2-3- Determination of physical and chemical characteristics The samples were sent to the laboratory of the Faculty of Natural Resources and Environment for the analysis of grain size parameters (granulometry), sodium and calcium percentages, electrical conductivity (EC), pH, clay, silt, and sand percentages, as well as measuring the SAR value.
In the morphoscopic investigation of the samples, it was determined that the distance between collection and sedimentation is not large and the sand particles are mostly the result of wind erosion.
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