مریم تاج بخشیان

In this study, sediment load in Shirin Darreh Dam basin was estimated based on hydrological, UNESCO and FSM methods. Comparison between the total deposited sediments in the reservoir (17 Mm3) and results of the three methods showed the hydrological and FSM methods with the estimated value of 1158000 and 5565000 m3/year were the most proper and the most improper ways to sediment load estimation, respectively. Annual erosion intensity based on EPM was obtained about 1426300 m3/year, and the actual sediment delivery ratio was calculated about 0.78. The predicted sediment delivery ratio based on the results of EPM method and the three methods of total sediment load, and some of empirical models, was calculated. The results of the calibration showed that the hydrological method and the empirical model, in which the slope is the most important factor to obtain the sediment delivery ratio, with minimum error and maximum accuracy were the most proper methods.

Assessment of drinking water resources quality and determination of natural and anthropogenic effective factors on their chemical composition has an important role in sustainability of ecosystems depending on these resources. In this study, aimed at assessing water quality of rivers and springs in Shirin Darreh dam watershed and the reservoir and investigating the effect of formations lithology on their quality, water quality data in 2018-2019 water year for 33 samples of the rivers, 6 samples of springs and one sample collected from the reservoir were used. Three water quality indices including WQIB, WQIMT, and WQIDD were calculated for these samples. 10 sediment samples were collected from the study area and their mineral content were determined to study the lithology effect on water quality. The results of Gibbs diagram showed that rock weathering was more important than evaporation and precipitation in determining the chemical composition of the study water resources. Also, the major type and face in the collected water samples, and gypsum, shale and marl were detected as the most important source of these ions. The results reflect the effect of the lithology on the chemical composition of the study water resources. Gypsum and the various clay minerals that were in accordance with the hydrogeochemical studies.The stored water in the reservoir had higher quality for drinking that can be contributed to the springs joining in adjacent to the reservoir. The higher quality of these springs can be due to their origin in the Tirgan karstic Formation.

Soil erosion and sediment transportation decrease water resources, and cause many social and economic problems. On the other hand, sediment transportation by rivers causes problems such as water quality degradation, reservoirs sedimentation, redirect of rivers, or decrease in their transportability. Therefore, finding the proper methods in sediment yield study in watersheds is essential in planning and management of land and water resources.  Climatic characteristics, physiography, geology, and hydrology of basins are the most effective factors in producing and transporting sediments according to several sources, but the role and impact of some factors are more pronounced than the others in different areas. As a result, the objective of this study was to investigate and identify the most important climatic, physiographic, geological, and hydrological factors in several watersheds of the northeastern part of Iran, by applying Gamma Test (GT) and principal component analysis (PCA) techniques. In this study, the data of discharge flow and suspended sediment concentration, and daily flow discharge recorded in 15 hydrometric stations in Mashhad and Neyshbour restricts and required maps were provided from the Regional Water Company of Khorasan Razavi, Iran. After drawing statistical bar graph period of suspended sediment, daily discharge, annual precipitation, and relatively adequate data, stations with the longest period and with the lowest deficit data were selected to determine the common statistical periods. Therefore, in this study, the time period of 1983-1984 to 2011-2012 was selected, and the run test was applied to control data quality and homogeneity. Then, the most effective factors of sediment yield were determined by principal component analysis (PCA) and Gamma Test (GT). The results of the principal component analysis showed that 90 percent of the first five components justify the changes. Among the factors, area and gross gradient of the mainstream from the first component, the average annual flow rate of mainstream, meandering waterways of the mainstream from second component, and drainage density of third component were identified as the most important influencing factors on suspended sediment production. Ninety superior combinations of 1500 proposed combinations were obtained by Gamma Test to evaluate the effects of each parameter on suspended sediment yield. To determine the order of importance of the entered parameters, first, Gamma Test was performed on all 12 parameters. Gamma values of all cases for each proposed combination were compared. The results showed that the impact of these statistics was lowered by eliminating high gamma parameters and the removal of low values. The data analysis revealed that the low levels of gamma and high accuracy of ratio to find the desired outputs from entries. By lowering the gradient, the complexity of the model was lowered and more suitable model was provided. As a result, high levels of gradient represented the complexity of the final model. The results of the percentage values of each of the 12 variables were considered among the superior equations for estimating the suspended sediment composition. In this regard, the mean annual discharge, main channel length, area, average annual rainfall, and percentage of the outcrop of erosion sensitive rocks with a total of 63 percent of the proposed equations were the most important factors affecting the sediment yield in the study area. The average height parameter of area, the average and gross slope of the mainstream had the lowest presence among the optimized compounds. Based on the results of the principal component analysis, the two factors of basin area and gross slope of the mainstream were selected as the most important factors affecting the amount of annual suspended sediment load, respectively. Based on the results of the Gamma Test, 12 main variables affecting suspended sediment load were identified and the effect of each of them on the production and transport of suspended sediment was determined. Based on the comparison of the results of the two methods of PCA and GT, it can be concluded that if the purpose of research or study is to prepare a model with the highest accuracy in estimating suspended sediment load, the 12-variable model of GT includes factors related to physiographical, geological, climatic and hydrological factors are suggested. However, if the preparation of a model with appropriate accuracy and a limited number of input variables is considered, a 5-variable model derived from the PCA method is proposed. At the same time, if the purpose is to prepare a model with the least input variables and their easy access and calculation and initial estimation of suspended sediments, a bivariate model (based on basin area and gross slope of the mainstream factors) resulting from PCA is proposed. According to the results of the present study, it can be concluded that the study of more parameters has provided grounds for evaluating their importance in sediment yield. Finally, due to the correlation of many parameters with each other, a limited number of parameters that have a more important role in suspended sediment estimation, were selected. Another finding of this study is the increase in the accuracy of the sediment model’s preparation due to achieving more important and effective parameters in sediment yield and identifying them in order to investigate the best sediment management measures in watersheds. It is suggested that similar research should be done in other watersheds with different conditions in terms of climatic conditions, topography, geology, and so on.

To study soil quality in Shahid Hashemi Nezhad gas refinery region in view of pollution level of produced sulfur in this industrial unit, 22 soil samples collected from inside and adjacent areas of the refinery. Sulfate content of soil was extracted in three phases water soluble, absorbed, and occluded with carbonates by deionized water, 0.032 M NaH2PO4 and 1 M HCl, respectively. The concentration of total sulfate was determined by soil complete digestion with a mixture of HF, HCl and HNO3. The content of organic matter and CO32- and HCO3- anions concentrations in the soil samples were measured using titration method. Organic, occluded with carbonates, water soluble and absorbed sulfate had the maximum concentration in the soil samples respectively, that inside refinery samples had more concentration than the other samples regarding all these phases. Water soluble sulfate had a reverse correlation with soil pH that showed sulfate occurrence could slightly oxidize sulfur and its compounds and acidic environment dominance in the soil.

In this study, 18 surface and groundwater samples and 5 wastewater samples were analyzed to assess water recourses and wastewater quality at Shahid Hashemi Nezhad Gas Refinery region in terms of corrosion and scaling. The parameters measured were pH, EC, temperature, and concentration of major ions, including K+, Na +, Ca2+, Mg2+, SO42, Cl, HCO3- and CO32,. Majority of the water samples showed Na+- SO42- and Na+-Cl- type and face by Piper diagram. To assess corrosion and scaling of the samples, various indices were calculated including LSI, RSI, PSI, AI and S&DSI for CaCO3 deposition, and L&SI and Skillman for sulfates deposition especially CaSO4. The results showed most of the water samples had scale forming due to high hardness and alkalinity, and the wastewater samples were often corrosive and therefore, all of the samples did not have favorable quality for industrial uses. The results of hydrogeochemical studies indicated evaporation, evaporative minerals such as gypsum and anhydrite in the water flow path, carbonate formations and their dissolution were the most important parameters in controlling ionic content of the water resources.

To assess surface and groundwater quality in Shahid Hashemi Nezhad Gas Refinery region and effluent wastewaters from this industrial unit, 18 water and 5 wastewater samples were studied. Major anions and cations concentration ,pH, temperature, EC and TDS were measured in water and wastewater samples. Most of the water and wastewater samples were classified as brackish and saline water based on TDS content. Calculation of sodium hazard indices of irrigation water showed that only 30% of the water samples were in excellent range according to SAR, and the others have good, fair and poor quality. Among the wastewater samples only one sample showed excellent quality according to this parameter. Majority of water and wastewater samples had fair and unfavorable quality based on %Na and KR. Based on SAR and EC, only one wastewater sample had fair quality. RCS and RSCB showed suitable quality for the water and wastewater resources. Gibbs diagram, chloroalkaline index and binary diagrams showed evaporation, normal ion exchange and evaporative mineral dissolution (halite, gypsum and anhydrite) as effective factors on chemical composition of water resources.

Elemental sulfur is byproduct of natural gas refining which during this process, H2S is removed from sour gas and after changes to solid sulfur, it is stored in large block forms. Continuous precipitation of sulfur and its oxidation causes soil acidification and as a result, nutrient cations such as Ca2, Mg2, Na and K will leach from the soil profile. Also, sulfate accumulation led to soil acidification and accelerates the silicates weathering in upper layer of the soil profile. Accumulation of water soluble sulfate in the soil and increase the nutrient cations leaching from the soil depend on sulfate resistance rate. Also, addition of sulfur to the soil for a long time can cause calcium sulfate formation that will cause problems such as increase in soil salinity. Shahid Hashemi Nezhad gas refinery is located about 35 km south of Sarakhs city and about165 km east north of Mashhad. In addition to exploiting, refining and producing 50 × 106 m3.day-1 natural gas, recovered sulfur with %99/9 purity and 2000 tons per day production capacity is one of the byproducts of this gas complex.
22 soil samples were collected from surface soil in Shahid Hashemi Nezhad gas refinery (3 samples) and nearby areas (19 samples) (Fig.1). Soil extracts pH was measured in equilibrium with pure water and with KCl 1M solution in 1:2.5 soil solution ratio. EC of the soil samples was measured in different soil water ratios to obtain the EC 1:1 (Fig.2). Total sulfate content was measured by gravimetry method at geochemistry laboratory of Faculty of Sciences at Ferdowsi University of Mashhad. To get the digestion extract, a mixture of 2 ml concentrated HF, 5 ml HCl and 8 ml HNO3was added to 0.5 gr soil in a teflon vessel, then heated for 60 min at 170° C. After cooling, the solution was evaporated at 130 °C to dry it. Then, the dried salt was dissolved in a mixture of 2 ml HNO3 and 2 ml HCl and diluted with deionized water up to 25 ml. Ca2 and Mg2犉筬쇪 measured through titration of the soil extract with EDTA 0.01 N and in EBT reagent at the first stage, and titration of the soil extract by EDTA 0.01 N and in Moroxide reagent at the second stage. Na and K contents were determined using AAS method at geochemistry laboratory at Ferdowsi university of Mashhad after extraction with CaCl2 0.01 M.
Based on EC values, 77% of the soil samples were non-saline (EC Salinity is the major factor affecting decrease of the samples quality for agriculture. Exposed formations in the area with highly soluble rocks causes to increase the soluble salts in the soil. The second factor is high temperature and low precipitation that led to increase the evaporation from the soil surface and accumulation of salts on the soil. Recovered sulfur from natural gas processing can reduce the soil pH and increases the soluble salts to some extent, especially in the inside refinery samples, and then decreases the soil quality for agricultural purposes. Except for one, all studied samples were classified as non-saline and non-sodic soils. Furthermore, the samples were classified in two classes of flocculated soils and potentially dispersive soils based on SAR and EC. ESP index indicates that there is no serious problem regarding sodium concentration in the soils. The pH values indicate that the samples were almost alkaline soils except for the samples inside the site, which are slightly acidic. Acidity of those few samples are attributed to the sulfur released from gas refinery process and its effect on the soil pH.

Hydrogeochemistry of surface and ground waters is a useful way to identify performing reactions in aquifers and also in recognizing effective natural and anthropogenic polluting factors in these sources. In order to study surface and ground waters quality of shahid Hashemi- Nejad gas refinery region، located 35 km south of Sarakhs town، 17 water samples were collected. Parameters of pH، temperature، electrical conductivity and total dissolved solids were measured in the field، and water samples were analyzed for major anions and cations concentrations in geochemical lab. Using Piper diagram، sodium sulfate and sodium chloride type and facies were determined for the water samples. Ca2+/Mg2+ v. as Mg2+، Ca2+/Ca2++Mg2+ v. as SO42-/SO42-+HCO3- compound diagrams، total hardness and PCO2 proved carbonates dissolution. Na+/Na++Cl-، Ca2+/Ca2++SO42-، HCO3-/Σ anions، HCO3-/SiO2، SiO2/Na++K+-Cl-، Na++K+ and SO42-+Cl- ionic ratios determined factors such as ion exchange، dissolution of Gypsum، Halite and sulfates of sodium-potassium، and weathering of carbonates and silicates as the most important effective parameters on chemical composition of water sources in this area. In Log (aCa2+/a(H+) 2) and Log (aMg2+/a(H+) 2) v. as Log (aNa+/a(H+) 2) diagrams، which are used for specifying soluble silicate minerals in water، all water samples showed the dissolution of Kaolinite except two samples which were located at clinochlore mineral zone. Calculating saturation indices using PHREEQC software proved that Calcite and Dolomite mineral had supersaturation، Halite and Anhydrite undersaturation and Gypsum mineral supersaturation، undersaturation and equilibrium states in all samples. Schoeller and Wilcox diagrams pointed unsuitable quality for drinking and agricultural usages for these water sources. In fact، because of formations presence with high solubility that lay out in large amount of surface، water resources in this area have not suitable quality، and on the other hand shallow water level and high temperature intensify it. Based on obtained results، natural factors have major role in quality area’s water resources.