جستجوی مقالات مرتبط با کلیدواژه « carbonates » در نشریات گروه « آب و خاک »

The dissolution of carbon dioxide in water is one of the sources of soil carbonates, which have an inverse relationship with water temperature. The origin of soil-forming carbonates formed in glacial sediments, and the effect of glacial processes on their formation were investigated. This study was conducted in the year 2021 in Alborz province, and eight profiles located in Karaj and Hashtgerd regions with glacial-alluvial parent materials were described and sampled. Physical and chemical characteristics, including soil texture before and after the removal of carbonates by the hydrometer method, pH, and EC in saturated extract, organic carbon by the Walkley-Black method, Calcium Carbonate Equivalent (CCE) measured by the calcimetric method in 27 samples were determined. Cation Exchange Capacity (CEC) measured by the ammonium acetate method. Soil description and classification were performed based on the American classification system. A micromorphological study of undisturbed samples, before and after the removal of carbonates, was carried out following their impregnation with polyester resin, cutting, sawing, mounting on glass slides, and reducing the thickness to about 30 microns. Imaging was done with a polarizing microscope, and the analysis and interpretation of the results were carried out according to the guide for the analysis of thin sections. The results showed that the petrocalcic horizons formed on glacial tills and moraines are the result of the long-term infiltration of cold water rich in dissolved carbonates into the soil. This model of the formation of secondary carbonates in the soil is different from other models that mainly consider the origin of carbonates to be the dissolution and recrystallization of primary carbonates or the biological respiration of roots and living organisms.

The flow duration curve (FDC) is one of the most important and widely used signatures of catchment runoff response. It has been used in numerous hydrological applications as a part of planning activities related to agriculture, industry, urban water supply, navigation, flood control, reservoir and sedimentation studies, in-stream flow assessment, water quality management, and impacts of land use changes. The FDC is a graph of river discharge plotted against exceedance frequency and is normally derived from the complete time series of recorded river flows. Representation of the relationship between the frequency and magnitude of stream flows, making it a compact signature of a catchment’s functioning; it can be used to diagnose the rainfall-runoff responses in gauged catchments at a holistic functional level, as well as to regionalize them to ungauged catchments. For these reasons, in the past few decades, considerable effort has been expended towards detailed studies of FDCs, especially in the context of predictions in ungauged basins (Smakhtin, 1998, 2001, Castellarina, 2004, Niadas, 2005, Santhi, 2008. Li, 2010). However, most recent studies on the FDCs have been empirically based, which generally fall into two categories: graphical and statistical. The graphical approach focuses on exploring the controls of catchment climatic and physiographic characteristics on the shape of the FDC (Smakhtin et al), while the statistical approach employs statistical distributions to fit the FDC and then relates the parameters of the distribution to the catchment’s physical characteristics (Castellarin et al., 2004; Li et al., 2010). Several studies have been conducted on the impact of geometric and hydrologic parameters on the FDC. (Booker and Snelder, 2012. Brown, 2013). In unregulated streams, the shape of FDC is controlled chiefly by the geology of the basin and research on the effects of lithology on FDC in a certain area, leading to obtaining information for use in water resources management (Bloomfield, 2009).
Although both graphical and statistical methods demonstrated that different climatic and landscape characteristics impact the shape of the FDCs in different regions of the world (Li et al., 2010), it has been difficult to generalize the results from one region to another.
The aim of this research was to determine the factors affecting the flow duration curve with emphasis on the role of lithology in the estimation of flow duration indices.
The study area comprises 18 basins with areas from 69.1 to 3941 km2 which are located in the North part of Iran and is underlain mostly by rocks belonging to the hard formations. Carbonate formations in this area are appropriate distribution and cover about 28% of the studied area. Mean annual rainfall varies from 427 to 1131 mm/ year. Median slopes vary from 2.85 to 15.9%.
In this research, using data from the daily flow of rivers, flow duration curve indices, in eighteen hydrometric stations of the Caspian Basin were determined. Physiographic parameters extracted from the GIS environment and the various factors of climate, geology and land use were also calculated. Lithological units using digital geological map, with a scale of 1: 250,000 and based on expert opinions were divided into 4 classes and the area covered by each unit was calculated. Land use map based on satellite images with the division of forest, pasture, agriculture, surface water resources, and rock outcrops were prepared. Factor analysis and cluster analysis were conducted and the regression equations were derived. The accuracy of models using the coefficient of determination and standard errors were investigated. Finally, the most appropriate models in 1% and 5%, significant of levels extracted.
Factor analysis of 21 variables showed, six factors were chosen as the most important independent factors. In the multivariate regressions between agents of geologic formations, particularly carbonate hard formation and alluvial and between morphometric parameters, slope, and main river length and from land use classes, agricultural land use was determined as the best predictor of duration curve indices. Also, according to the power and exponential models, annual precipitation as the most important factors between climatologically factors was diagnosed. The validation results showed that the distributions of errors in all models were normalized and Durbin-Watson index was varied between 1.5 to 2.5.According to regional relations obtained, the contribution of hard carbonate formations along with Quaternary deposits, indicating their role in ensuring the continuity of the region's rivers.

Vis-NIR spectroscopy has been introduced as a non-destructive, fast, and cheap technique, with minimal sample preparation and no loss or damage to the environment. No investigation has yet been carried out to examine the ability of this method to estimate soil properties in Iran. The objective of this research was to investigate the capability of Vis-NIR spectroscopy to predict the amount of organic matter, carbonate and gypsum in surface soils of Isfahan province. A total of 248 surface soil samples were collected from the study area. Soil organic matter content, gypsum and carbonates percentages were measured by standard laboratory methods. Soil spectral analyses were performed by a field spectrometer using 350-2500 nm wavelength range. Different pre-processing methods were evaluated after recording the spectra. Partial least squares regression was used to predict soil parameters. R2 values for organic matter, carbonates and gypsum were 0.61, 0.45 and 0.8, respectively. Based on RPD (Ratio of Prediction to Deviation) values, the precision of prediction model for gypsum was quite good, and acceptable for organic matter, whereas the prediction of the model for soil carbonates was poor. Consequently, vis-NIR spectroscopy is capable of predicting some soil properties simultaneously and the model accuracy is acceptable.

Magnetic susceptibility measurement is a simple and quick technique for characterizing soils and sediments and describing soil-forming processes. The interpretation of soil magnetic susceptibility data needs sufficient knowledge about the factors affecting this parameter. To identify the effects of parent material، gypsum and calcium carbonate equivalent، 42 samples were taken from horizons of soils developed on loessial، alluvial، granitic and marly materials in southern Mashhad. Gypsum and carbonates of soil samples were removed by successive washing with distilled water and diluted HCl، respectively. Magnetic susceptibility of bulk samples (lfbulk)، gypsum free samples (lfGf)، gypsum and carbonates free samples (lfGCf) and gypsum، carbonates and sand free samples (lfGCSf) was measured. The results revealed a strong 1:1 correlation between the measured and calculated lfGf and lfGCf. Despite the high amounts of gypsum and carbonates in soils developed on marls، their lfbulk was much more than that of the other soils and reached up to 121. 8×10-8m3 kg-1. In contrast، the lfbulk values of saprolitic granite were less than 10. 4×10-8m3 kg-1. The lfbulk values of loessial and alluvial soils were less than those of marly soils but higher than those of soils developed on saprolitic granite. lfbulk values were negatively correlated with the amount of sand. However، reduction in magnetic susceptibility values of marly soils after removing sand reflects the different nature of this soil. The correlation between lfbulk and amount of silt and clay is positive، but the magnetic susceptibility values are more sensitive to clay percentage، indicating the more important contribution of clay to magnetic susceptibility values. The results of this study highlight the role of parent materials، gypsum and carbonates in the soil magnetic susceptibility values that should be considered.