Analyzing the Sedimentological Parameters and Size Distribution Pattern in Hamoun Hirmand Sediments

Extended Abstract IntroductionSistan, located in the southeast of Iran, is one of the driest areas in the world that has been impacted by dust storms. The region characterized by a shortage of water resources and fragile ecosystems that are highly sensitive to climate change. Due to the lack of vegetation, this region is considered one of the windiest deserts in the world, with a high speed of wind erosion and sand movement. Sistan dust is believed to come from the sediments found in the Hamon Hirmand wetland in Sistan and Baluchistan province, yet there is little information available about their condition, which restricts our comprehension of the dynamics of wind-blown dust and the mechanisms of sediment movement. Identifying the characteristics and distribution pattern of sediments in the Hamon lagoon bed is the primary objective of this research. Material and MethodsAfter the initial visit and determining the boundary of the study area, 271 sediment samples were taken from the depths of 30 cm and 60 cm in Hamon Sabri area and a part of Hamon Hirmand. The samples were granulated by a sieving machine and particles smaller than 0.063 microns were separated. The isolated samples were used for study with a Zeiss 47 2500-9901 binocular microscope and a lens with 4X magnification, grain measurement by sieve and laser. The size of the particles in the collected sediment samples ranges from 75 to 600 microns and they are sieved with sieves with a diameter of 25, 35, 50, 60, 80, 120, 140, 200 and smaller than 200 mesh. The sedimentology laboratory examined the texture (size, texture, circulation) and mineralogy of the samples after preparing them. In this research, particles smaller than 63 microns were measured by sieving and laser method using the Laser Scattering Particle Size Distribution Analyzer, Horiba-LA950 at the National Institute of Oceanography. The final step was to draw the zonings by interpolation in the Arc GIS 10.3 software environment Results As the abundance of destructive particles shifts from east to west, the direction of sediment carrier flow is shifting from east to west of the region. This causes the eastern part to have larger particles. As we move further west in the studied area, we find that there is a greater amount of fine-grained clay particles and less destructive large-grained and well-circulated particles like quartz and unstable mica minerals. It is evident that there is a trend of changes from the north to the south of the studied area. The study's middle part has the maximum displacement of destructive coarse-grained particles, while the southern part is filled with particles ranging from sand to clay. It appears that the carrier flow's direction can be divided into two directions, north to south and west to east. At the top of the Lagoon, where the sediments are from multiple sources and the velocity is higher, coarse and fine particles are transported together, and sedimentation is weaker. By moving towards the center of the basin, the wind speed is decreased, and with the sediments coming from only one source, the settling will gradually improve. A trend has been observed in the Hamon wetland area that deviates from the defined path, but it can be justified. Wetland sediments are supplied by wind in addition to water, which indicates that there is weak sedimentation. The particles become more elongated as they move away from the border and towards the center of the basin. This shows that the sediments have suffered more erosion under the influence of wind and the long distance from the source. The wetland does not follow this trend. Due to the low water velocity and short distance from the source, particles tend to not have good elongation towards the center of the study area. The direction of the wind is indicated by tilts with low values in the samples under study. Moving away from the border and closer to the center of the basin causes a decrease in the multi-origin sediments and an increase in tilting degree. This research indicates that the particles are gradually becoming smaller and have a similar origin. A low degree of tilting is observed in the wetland part, which indicates that the sediments come from multiple sources and are blue in color. Three main breaking points have been observed in particles with sizes of 1, 2, and 3 Fe. Different mechanisms have influenced the transport of sediment particles in the Sistan Basin, and they have different origins and are not of a single origin, as shown by this issue. Folk's gravel-sand-mud triangle indicates that the Sistan samples lie in the sand-mud axis, and their concentration is frequently at the top of the sand and mud of the Folk diagram. The clay particles of these samples contain the most colloidal particles in the southern part of Hamon Hirmand. The distribution map of clay particles shows that the northwest, center-west, and southeast of the studied area have the highest polymodal abundance. The southwest of the region has the least abundance observed. The study area's clay particle distribution method reveals that sediments originate from two regions in Afghanistan and an internal origin. Conclusiondue to the windy nature of the feeding system in the west and southwest of the study area, fine and colloidal particles have the highest amount in this area and in the center of the study area, especially the wetland. Due to the multi-origin nature of the sedimentary system, Hamoun includes a wider range of particles in terms of size. The distribution of clay particles in the studied area shows that the sediments originate from two different regions. The findings of this research can help to improve the management of wind erosion in the sediment source areas and the sustainable development of the region.