جستجوی مقالات مرتبط با کلیدواژه "geology" در نشریات گروه "آب و خاک"

Mineralogical composition, soil morphological properties, and magnetic susceptibility were affected along soil evolution in soils. That is why micromorphology helps in performing soil classification and evolution studies, as well as making soil management practices much more efficient. Clay mineralogy is a useful tool that helps in better understanding soil forming factors and processes. Soil magnetic properties are complex reflections of chemical, geological, and biological soil characteristics. Thus, knowledge about factors affecting magnetic susceptibility can help in better understanding and interpreting the results obtained in an area. Assessment of soil magnetic behavior might be used in pedology, soil mapping, investigation of soil process variations, parent material composition, sedimentary processes, soil drainage conditions, soil pollution, and separation and identification of soil unit boundaries. The present study was performed to investigate the effects of magnetic susceptibility, clay mineralogy, and micromorphology on soil characteristics, genesis, and evolution.

Seven representative pedons were selected in sedimentary and igneous sections in uncultivated land use and physiographic units: hill, piedmont plain, alluvial plain, and lowland. Physicochemical properties measurements were performed on the collected samples from representative pedons using standard methods. The pedogenic (Fed) and amorphous (Feo) iron concentrations of the extracts were determined using a Vario Atomic Absorption Spectroscope (AAS) instrument. Undisturbed soil samples were selected for micromorphology studies and thin section preparation. Additionally, three soil samples were used for X-ray diffraction (XRD) analyses after carbonates, organic matter, and Fe were removed using Jackson (1965) and Kittrik and Hope (1963) procedures. Finally, the mass-specific magnetic susceptibility of soil samples was determined using a Bartington MS2 meter equipped with the MS2B Dual Frequency sensor, capable of taking measurements at both low (χlf at 0.46 kHz) and high (χhf at 4.6 kHz) frequencies.

Salinization, leaching, and illuviation processes of gypsum and carbonates were observed in the studied pedons. The soils were classified as Aridisols (Soil Taxonomy system) and Solonchacks, Solonetz, Gypsisols, and Calcisols RSGs (WRB system) due to the presence of calcic, gypsic, salic, argillic, and natric diagnostic horizons. The presence of gypsum, carbonates, salt, clay accumulation, and argillic horizon reduces χlf values. The calcite coating located on the clay coating could probably be attributed to the presence of a climate with more available humidity in the past. The range of soil magnetic susceptibility was from 4.3×10-8 to 1264×10-8 m3kg-1. Gypsum infillings, different forms of gypsum, clay accumulation and coatings, and weathered calcite crystals were among the dominant micromorphological features observed in the studied pedons. Montmorillonite, chlorite, illite, kaolinite, quartz, and vermiculite minerals were observed in the studied pedons. Chlorite and illite minerals were dominant in the clay fraction of the studied soils, whereas a portion of these minerals was probably converted to vermiculite. Discontinuities observed in pedon 2 could be accounted for as proof of more available humidity in the past compared to the present time periods. Moisture has caused the removal of potassium and transformation of illite and chlorite to vermiculite. The dominance of illite and chlorite can be proof of initial weathering and evolution in the other studied pedons.

The χlf variations was related to depth trend and physicochemical properties. The χlf values showed a noticeable negative correlation with argillic horizon, gypsum content, carbonate calcium, and salinity. It seems that most of the clay minerals originated from the parent material in the present study, and pedogenic source has rarely taken place. Besides, the χlf and Fe contents were directly correlated. In general, the results indicated young soils with primary development stages in the area under study. Pedon 2 with buried polygenetic soils is an exception.

Soil erodibility and gully erosion and their expansion occur under geological formation and soil characteristics. This study aims to find the rate of soil and formation effects on gully erosion in Seifabad watershed. To that end, aerial and field work were used together to determine the rate & expansion of 17 gullies in 12 year's period from 1997 to 2009. The soils were sampled for each gully in 50% interval distance with 0-30 cm horizontal surfaces and >30 cm depth. Some factors were estimated from the soil such as EC, PH, Silt, Clay, Sand & limeston percentages. Statistical analysis was done using SPSS 14 through non-parametric tests such as Kruskal-Wallis & Mann-Whitney. Spearman coefficient was used to investigate the relation between volume of gully & litological factors. The results showed a positive correlation at 1% level for the PH with the gully erodibility in surface soil, but for the depth of soil this relation belonged to the silt percentage, and sand showed a negative relation at 5%level with the volume of the gully sediments. Finally, there was no statistical relationship between geological formation and the sediment yield in gullies.

In this study landslides occurred in a part of Haraz watershed were determined using aerial photos and field studies, then landslide hazard zonation was determined using geomorphological factors (slope, aspect and elevation) and geological factors (lithology and distance fault) as the most important effective factors on landslide hazard. So each of the effective factors as information layer was used in ILWIS environment for analysis based on fuzzy set theory using MATLAB 7.1 software before that membership functions were determined for each effective element on landslide. Then output of software computed hazard for each pixel inacase study map transformed to ILWIS software environment and landslide hazard zonation was made using fuzzy Gaussian and Triangular membership functions. Evaluation of results showed that landslide hazard mapping using gaussian membership function QS (0.23) is more accurate in comparison with map made by using triangular membership function QS (0.0515).

Most construction materials required for construction projects directly or indirectly supplied from nature. In fact، the resources of construction materials are formed from geological formations or rock units or sediments caused by erosion them in nature. Thus to exploration of construction materials، not only the engineering characteristics and physical properties of geological formations which selected as the mining of construction materials can be estimated from geological data، but also can play an important roles in the region for recognition and determination of the regional resources potential. This paper is a summary of study of the exploration borrow materials resources to use for hydraulic structures in the coastal area of south of IRAN (flood control project for South Pars Energy Zone). In this study، the potentials for various materials have been identified using regional geological information such as lithology of rock units، the description each of them، the conditions of their formation and their depositional environments and the geological structures and phenomena which effect on them. The potentials of region were prioritizing using the above data and other parameters (such as volume، availability…). Also، this knowledge can help to determination of the sampling points and the selection of optimized materials with the lowest risk of considerable. Results this research shows that rock layers with the same litology belonging to different geological formations can have different properties due to various condition of formation. Thus، the regional geological data and geological engineering knowledge can help estimate the engineering characteristics and physical properties of geological formations and determine regional potentials، cost reduction and reduction of duration of studies at various stages of study of the construction materials.