Development and magnetic properties of loess-derived forest soils along a precipitation gradient in northern Iran

In order to investigate the development of forest soils formed on loess, six representative modern soil pedons were selected along a precipitation gradient extending from eastern Golestan(mean annual precipitation, MAP = 500 mm)to eastern Mazandaran Provinces(MAP = 800 mm).Physiochemical, micromorphological and magnetic properties, as well as clay mineralogy of soils were studied using standard methods. Soils are mainly classified as Alfisols and Mollisols. Downward decalcification and the subsequent clay illuviation were the main criteria of soil development in all study areas. Pedogenic magnetic susceptibility of pedons studied varied systematically across the precipitation gradient in Northern Iran, increasing from 14.66 ×10~(-8) m~3 kg~(-1) at the eastern part to 83.75 × 10~(-8) m~3 kg~(-1) at the western margin of this transect. The frequencydependent magnetic susceptibility showed an increasing trend with rainfall as well. The micromorphological study of soils indicated that there is a positive relationship between climate gradient (increasing rainfall) and the micromorphological index of soil development(MISECA). The area and thickness of clay coatings showed an increasing trend with rainfall. Grain size analysis indicates that pedogenic processes are responsible for changing original grain size distribution of loess in our soils.The correlation achieved among modern soil properties and precipitation could be applied to the buried paleosols in the whole study area to refer degree of paleosol development and to reconstruct the paleoclimate.     

Remote structural health monitoring with serially multiplexed fiber optic acoustic emission sensors

Development and testing of a serially multiplexed fiber optic sensor system is described. The sensor differs from conventional fiber optic acoustic systems, as it is capable of sensing AE emissions at several points along the length of a single fiber. Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm was developed for signal recognition and tagging of the AE waveforms for detection of crack locations. Laboratory experiments on plain concrete beams and post-tensioned FRP tendons were performed to evaluate the crack detection capability of the sensor system. The acoustic emission sensor was able to detect initiation, growth and location of the cracks in concrete as well as in the FRP tendons. The AE system is potentially suitable for applications involving health monitoring of structures following an earthquake Supported by: National Science Foundation, Grant number CMS-9900338     

Micromorphology and quality attributes of the loess derived soils affected by land use change: A case study in Ghapan watershed, Northern Iran

In order to study the effects of different land vegetative covers on soil quality attributes, a loess hill slope was selected in eastern Golestan Province, Ghapan watershed, Iran. Four profiles in four land uses, including Quercus natural forest; Pinus artificial forest; Cupressus artificial forest and a cultivated land, were studied. Results showed that MWD was significantly different in the studied land uses, and it varied between 1.6 mm in Quercus natural forest and o.31 mm in cultivated land use. The lowest CEC, microbial respiration rate and organic carbon were 28.4 cmol·kg^1, 177 μgCO2·g^-1·day^-1 and 1.32 % found in cultivated land use, respectively. The organic matter was considerably higher content in the forest areas than that of cultivated land use. The studies on soil profile development revealed that the natural forest soils were highly developed. The soils of the Quercus natural forest were classified as Calcic Haploxeralfs with a well developed argillie horizon unlike the cultivated soils which showed the minimum development and classified as Typic Xerorthents. The soils of the artificial forests had both mollic epipedons and were classified as Typic Calcixerolls with moderate profile development. Micromorphological studies revealed that argillic horizons had speckled and partly crystallitic b-fabric in the natural forest indicating the high landscape stability. In contrast, the crystallitic b-fabric of other land uses shows the absence of enough leaching of carbonate and the subsequent migration of clay particles indicating the unstable conditions and high soil erosion. Intense erosion of the surface horizons of cultivated land use has resulted in the outcropping of the subsurface carbonate rich horizons preventing soil development.     

Hydrochemistry and Classification of Groundwater Resources of Ishwardi Municipal Area,Pabna District,Bangladesh

The chemical property of groundwater depends largely on the mineralogical composition of the rocks through which the water has moved and the rate of movement and these characteristics of surface water depend on organic and inorganic reactions, industrial effluents, rainfall and temperature etc. The underground water tends to contain more dissolved materials than those in surface water because of their more intimate and longer contact with organic materials of soil and rock particles. The groundwater of the studied area is dominant of alkaline earth’s (Ca²⁺ and Mg²⁺) and weak acids (HCO₃ ⁻) which may be classified as Magnesium-Bicarbonate and Calcium Carbonate types. Genetically, the groundwater of the area belongs to both “Normal Chloride” “Normal Sulphate” and “Normal Carbonate” to “Super Carbonate” group. Based on EC, SAR and RC, the groundwater of the area varies from good–excellent quality for irrigation purposes with low alkali hazard and medium salinity hazard.     

The Paleozoic Ozbak-Kuh carbonate-hosted Pb-Zn deposit of East Central Iran: Isotope (C,O, S,Pb) geochemistry and ore genesis

Lead and zinc mineralization occurs in dolostones of the Middle Devonian Sibzar Formation at Ozbak-Kuh, which is located 150 km north of Tabas city in East Central Iran. The ore is composed of galena, sphalerite and calcite, with subordinate dolomite and bitumen. Wall-rock alterations include carbonate recrystallization and dolomitization. Microscopic studies reveal that the host rock is replaced by galena and sphalerite. The Pb–Zn mineralization is epigenetic and stratabound. The δ¹³C values of hydrothermal calcite samples fall in the narrow range between ?0.3‰ and 0.8‰. The δ¹⁸O values in calcite display a wider range, between ?14.5‰ and ?11.9‰. The δ¹³C and δ¹⁸O values overlap with the oxygen and carbon isotopic compositions of Paleozoic seawater, indicating the possible important participation of Paleozoic seawater in the ore-forming fluid. The δ¹⁸O signature corresponds to a spread in temperature of about 70 °C in the ore-bearing fluid. The δ¹³C values indicate that the organic materials within the host rocks did not contribute significantly in the hydrothermal fluid. The δ³⁴S values of galena and sphalerite samples occupy the ranges of 12.2‰–16.0‰ and 12.1–16.8‰, respectively. These values reveal that the seawater sulfate is the most probable source of sulfur. The reduced sulfur was most likely supplied through thermochemical sulfate reduction. The sulfur isotope ratios of co-precipitated sphalerite–galena pairs suggest that deposition of the sulfide minerals took place under chemical disequilibrium conditions. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of the galena samples represent average values of 18.08, 15.66, and 38.50, respectively. These ratios indicate that galena Pb likely originated from an orogenic source in which supracrustal rocks with high ²³⁸U/²⁰⁴Pb and ²³²Th/²⁰⁴Pb ratios are dominant. The average lead isotope model age portrays Cambrian age. This model age is not coeval with the host rocks, which are of middle Devonian age. It is probable that the pre-Middle Devonian model age shows the derivation of Pb from older sources either from host rocks of Cambrian age or from deposits previously formed in these rock units. The Pb isotopic composition of galena accords with the occurrence of an orogenic activity from Late Neoproterozoic to Lower Cambrian in Central Iran. The proposed genetic model considers the fact that mineralization formed in fractured and brecciated host rocks along shear zones and faults from metal-bearing connate waters that were discharged due to deformational dewatering of sediments.     

The effects of the polytropic coefficient on plasma sheath in two cases isothermal and adiabatic ion thermal flow

Recently it has been shown that for finite and small values of the electron Debye length, the ion polytropic coefficient is approached to some constant value in the plasma sheath region by decreasing the plasma density. In this paper, using a plasma multi fluid model, the effect of ion polytropic coefficient γ _i on the plasma sheath structure have been examined. The numerical calculations of the basic equation of the model show that the polytropic coefficient strongly affects on the plasma sheath characteristics. The results show that by transition from an isothermal flow (γ _i =1) to an adiabatic flow (γ _i =3), the net current to the wall and the electric potential distribution increase and the sheath width decreases in a thermal plasma sheath.     

Regional intensity–duration–frequency analysis in the Eastern Black Sea Basin,Turkey, by using L-moments and regression analysis

The analysis of rainfall frequency is an important step in hydrology and water resources engineering. However, a lack of measuring stations, short duration of statistical periods, and unreliable outliers are among the most important problems when designing hydrology projects. In this study, regional rainfall analysis based on L-moments was used to overcome these problems in the Eastern Black Sea Basin (EBSB) of Turkey. The L-moments technique was applied at all stages of the regional analysis, including determining homogeneous regions, in addition to fitting and estimating parameters from appropriate distribution functions in each homogeneous region. We studied annual maximum rainfall height values of various durations (5 min to 24 h) from seven rain gauge stations located in the EBSB in Turkey, which have gauging periods of 39 to 70 years. Homogeneity of the region was evaluated by using L-moments. The goodness-of-fit criterion for each distribution was defined as the Z^DIST statistics, depending on various distributions, including generalized logistic (GLO), generalized extreme value (GEV), generalized normal (GNO), Pearson type 3 (PE3), and generalized Pareto (GPA). GLO and GEV determined the best distributions for short (5 to 30 min) and long (1 to 24 h) period data, respectively. Based on the distribution functions, the governing equations were extracted for calculation of intensities of 2, 5, 25, 50, 100, 250, and 500 years return periods (T). Subsequently, the T values for different rainfall intensities were estimated using data quantifying maximum amount of rainfall at different times. Using these T values, duration, altitude, latitude, and longitude values were used as independent variables in a regression model of the data. The determination coefficient (R ²) value indicated that the model yields suitable results for the regional relationship of intensity–duration–frequency (IDF), which is necessary for the design of hydraulic structures in small and medium sized catchments.