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Mapping the Dominant Clay Minerals in the Soils of Isfahan Province and Their Relationship with Climate and Parent Materials
F. Khayamim, H. Khademi, S. Ayoubi,
Volume 24, Issue 2 (Summer 2020)
Abstract
Understanding the abundance of clay minerals in soil and also, their spatial variability can provide more comprehensive information about soil properties, behavior and functions. The objectives of this research were: (i) to map the spatial distribution of  the dominant clay minerals in the soils of Isfahan Province and its relationship with climate and parent materials, and (ii) to determine the quantity of  the dominant clay minerals in different climatic classes of Isfahan Province. The amount of palygorskite, illite, expanded minerals and chlorite were semi-quantitatively determined for 100 soil samples collected from Isfahan Province. Maps of the dominant clay minerals were prepared by the Inverse Distance Weighting method. The results showed that palygorskite mostly occurred in the soils of dry areas with higher temperature throughout the province. This mineral was not present in the more humid areas of the province. Besides, palygoskite was found to be dominant in the soils derived from the Qom Formation, as well as Lower and Upper Red Formations belonging to Miocene and Pliocene. It seems, therefore, that the parent material plays a major role in entering palygoskite to the soil system, while the dry climate mostly guarantees the stability of this clay minerals and, to some extent, its limited neoformation in such soils. Both illite and chlorite occur in all soils throughout the province, regardless of their climate, following no particular trend. This may indicate that parent materials play a major role in the occurrence of these minerals. Both climate and parent material appear to have affected the distribution of expandable clays in the soils. In more humid areas of the province (west and southwest), climate plays a larger role in the distribution of this mineral. In other areas of the study region, especially in the eastern parts of the province with a much drier climate, the role of the parent material on the dominant soil clay minerals is more pronounced.

Seasonal and Spatial Variations of Magnetic Susceptibility of Street Dust in Several Cities of Isfahan Province and their Relationship with the Concentration of Selected Heavy Metals
B. Akbari, H. Khademi,
Volume 27, Issue 4 (Winter 2023)
Abstract
Street dust enters the urban environments due to the resuspension of particles smaller than 100 micrometers. The magnetic properties of street dust and their relationship with the concentration of heavy metals have received less attention from researchers worldwide, and not much study has been performed on this issue in Iran. The objectives of this study were: (i) to investigate the spatial and seasonal changes in street dust, and (ii) to determine their relationships with the concentration of selected heavy metals in several cities in the Isfahan province. Sampling was carried out in the first half of the second month of each season including 20 samples from Isfahan city and 10 samples from Natanz, Shahreza, Falavarjan, Khomeinishahr, and Najafabad. The concentration of selected heavy metals was measured using an atomic absorption spectrometer. Also, the magnetic susceptibility values of the samples at low and high frequencies were determined and frequency-dependent magnetic susceptibility was calculated. The results showed that the presence of ferromagnesian minerals in the parent materials could be the reason for the high values of magnetic receptivity in Natanz City. However, the high level of this characteristic in the street dust of other cities could be due to human activities, especially in Isfahan city. Based on the results of principal component analysis, the high correlation of the first component with magnetic susceptibility and the concentration of zinc, copper, and chromium elements most likely indicates the absorption of these elements by particles close to superparamagnetic (SP). The high correlation of the second component with frequency-dependent magnetic susceptibility and concentration of nickel and cobalt is most likely related to the adsorption of magnetic elements and heavy metals into coarse polyhedral particles that remained on the street floor after the re-deposition of street dust particles. Also, the high correlations between magnetic parameters and the concentration of copper and zinc confirm their anthropogenic origin. On the other hand, low or negative correlations of Pb, Ni, Cr, and Co concentrations with magnetic susceptibility might confirm their natural or non-anthropogenic origin. The higher values of magnetic parameters of street dust in the spring season reflect the significant contribution of magnetic minerals in this season, compared to autumn and winter, and indicate the higher influence of human activities.

Occurrence of Palygorskite and the Major Soil Properties Influencing its Distribution in Selected Soils of Bushehr Province
Z. Naderizadeh, H. Khademi, A. Shamsollah,
Volume 28, Issue 1 (Spring 2024)
Abstract
Although several reports are available on the distribution of Palygorskite in the soils of arid regions of Iran, there is not much information about the presence and abundance of this important fibrous clay mineral in the soils of Bushehr Province. This research was carried out: (1) to investigate the distribution of Palygorskite and other major associated clay minerals, and (2) to evaluate the relationship between the relative quantity of Palygorskite in clay-sized fraction and the most important soil properties in Dashtestan County, Bushehr Province. Five geomorphic surfaces including eroded rock outcrop, rock outcrop, dissected hill, alluvial fan, and alluvial plain were identified in the study area using Google Earth images and field observations. After sampling representative pedons, the clay mineralogy of two horizons from each pedon was determined. X-ray diffractograms and SEM images showed that in the studied soils, which were classified as either Aridisols or Entisols, Palygorskite was present in different quantities on all geomorphic surfaces. Moreover, Illite, Chlorite, Smectite, irregularly interstratified Chlorite/Illite, and Kaolinite were the other clay minerals that existed in the soils studied. The relative quantity of Palygorskite and Smectite was variable on different geomorphic surfaces. Regardless of the type of geomorphic surface, petrogypsic and gypsic horizons showed the highest quantity of Palygorskite as compared to other horizons which seems to be due to the suitable geochemical conditions of these horizons for the formation and stability of Palygorskite mineral. The higher correlation of Palygorskite content with gypsum, as compared to that with the carbonates, indicates the importance of gypsum in Palygorskite distribution in the soils of the study area. The findings also indicated that the amount of Palygorskite was positively correlated with soluble Mg/Ca ratio, pH, gypsum, and soluble Mg. These parameters appear to control the genesis and distribution of Palygorskite in the soils studied. In general, it is necessary to pay special attention to their clay mineralogy, especially the significant amount of Palygorskite to manage the soils of the study area and to reasonably predict their behavior.

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