Geochemistry characterization of groundwater in an agricultural area of Razan,Hamadan, Iran

This study was conducted to evaluate factors regulating groundwater quality in an area with agriculture as main use. Thirty groundwater samples have been collected from Razan area (Hamadan, Iran) for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater. The chemical compositions of the groundwater are dominated by Na⁺, Ca²⁺, HCO₃ ⁻, Cl⁻ and SO₄ ²⁻, which have been derived largely from natural chemical weathering of carbonate, gypsum and anthropogenic activities of fertilizer’s source. The production of SO₄ ²⁻ has multiple origins, mainly from dissolution of sulphate minerals, oxidation of sulphide minerals and anthropogenic sources. The major anthropogenic components in the groundwater include Na⁺, Cl⁻, SO₄ ²⁻ and NO₃ ⁻, with Cl⁻ and NO₃ ⁻ being the main contributors to groundwater pollution in Razan area.     

Studying Hygienic Status of Mechanized Long Wall Face from the Perspective of the Existing Dust Containing Silica in Tabas Coal Mine

In order to consider the quantity of the existing negative effect in mechanized longwall mining face in Tabas coal mine, the concentration of the available coal dust and amount of its toxicity in every part of the mining face and tail gate were investigated and compared with the permissible amount. After sampling and preparing dust, its concentration was determined by gravimetric method. Then, using Zetasizer, the particle size distributions were determined and also the available amount of silica in the samples was found using SEM and XRF device. The results of the elemental analysis of dust in the mine showed that the weight percentage of silica in dust was between 27.9 and 26.7 %. The correction of the permissible dust concentration from the perspective of silica was done and the result was reported as 0.36 mg/m³. Computational fluid dynamics can be used to determine dust accumulation zones and the zones with high dust concentration. Finally, D₅₀ of the samples showed that the existing toxicity in dust can be transferred to dozens of meters far from the source (shearer).     

Geochemistry and mineral chemistry of pyroxenite xenoliths and host volcanic alkaline rocks from north west of Marand (NW Iran)

Mineralogy and Petrology - The Plio-Quaternary alkaline volcanic rocks from the northwest of Marand (NW Iran) consist of trachy-andesites, trachy-basaltic andesites, leucite-tephrites and...     

Structural pattern and emplacement mechanism of the Neka Valley nappe complex,eastern Alborz,Iran

International Journal of Earth Sciences - The Neka Valley nappe complex is exposed in the south of Gorgan County in the eastern Alborz fold-and-thrust belt. We use the results of a regional survey...     

Validation of TRMM 3B42 V6 for estimation of mean annual rainfall over ungauged area in semiarid climate

This research compares data from the Tropical Rainfall Measuring Mission 3B42 V6 with data obtained from 19 synoptic rain gauges during the period 1998–2010 over the semiarid climate of Khorasan Razavi, Iran. Validation was performed using three spatial extents, including 1 TRMM grid face from the synoptic station (1PTRM), 3 TRMM points surrounding the synoptic station (3PTRM) and 5 TRMM points surrounding the synoptic station (5PTRM), using ArcGIS 10.2 software. The perfect and poor r were obtained at stations S08 and S19, with values of 0.92 and 0.26, respectively. According to the Nash–Sutcliffe efficiency coefficient, the TRMM satellite can predict the spatial variation of the mean annual rainfall by 0.23, 0.43 and 0.38 for 1PTRM, 3PTRM and 5PTRM, respectively, at 19 stations. The agreement significantly increases by 0.88, 0.83 and 0.80 for 1PTRM, 3PTRM and 5PTRM, respectively, when gauges S05, S07, S11 and S13 are excluded from the dataset, which may be associated with orographic or instrumental error at the stations.     

Seismotectonics and consequences of the 1930s large earthquakes in eastern Mazandaran,north of Iran

Early in the 1930s,two relatively large earthquakes (Kosout,magnitude 6.8,and Talarrud,magnitude 5.8) shook the eastern Mazandaran,northern Iran.Despite the his...     

Dynamics of charged dust particles in protoplanetary discs

We study the effect of an imposed magnetic field on the motion of charged dust particles in magnetically active regions of a protoplanetary disc. Assuming a power law structure for the vertical and the toroidal components of the magnetic field for the regions beyond magnetically dead region of the disc, the radial and the vertical velocities of the charged particles, in the asymptotic case of small particles, are calculated analytically. While grains with radii smaller than a critical radius significantly are affected by the magnetic force, motion of the particles with larger radii is independent of the magnetic field. The critical radius depends on the magnetic geometry and the charge of the grains. Assuming that a grain particle has one elementary charge and the physical properties of the disc correspond to a minimum-mass solar nebula, we show that only micron-sized grains are affected by the magnetic force. Also, charge polarity determines direction of the radial velocity. For such small particles, both the radial and the vertical velocities increase due to the magnetic force.     

Anthropogenic Decline of Ancient,Sustainable Water Systems: Qanats

Qanat is an ancient underground structure to abstract groundwater without the need for external energy. A recognized world heritage, Qanat has enabled civilization in arid and semi-arid regions that lack perennial surface water resources. These important structures, however, have faced significant challenges in recent decades due to increasing anthropogenic pressures. This study uses remote sensing to investigate land-use changes and the loss of 15,983 Qanat shafts in the Mashhad plain, northeast of Iran, during the past six decades. This entails obtaining a rare aerial imagery from 1961, as well as recent satellite imagery, over a region with the highest density of Qanats in Iran, the birthplace of Qanat. Results showed that only 5.59% of the Qanat shafts in 1961 remained intact in 2021. The most prominent Qanat-impacting land-use changes were agriculture and urban areas, that accounted for 42.93 and 31.81% Qanat shaft destruction in the study area, respectively. This study also showed that groundwater table decline, demographic changes, and reduction in the appeal of working in the Qanat maintenance and construction industry among the new generation are existential threats to Qanats, and may result in the demise of these ancient structures in the future. Findings of this study can be used for urban planning in arid and semi-arid areas with the aim of protecting these historic water structures.     

Spatial correlation between groundwater seepage faces and fault zone in high bedrock channel: method and application

The groundwater may recharge the surface water bodies through seepage faces and springs.The spatial correlation between the fault zones and the groundwater seepage faces results in deep understanding of the hydrogeologic regime,especially where there is no monitoring boreholes.Locating these recharging zones by conventional methods is a challenging task;particularly in areas where(1)there is no hydrogeologic monitoring boreholes or reliable data,(2)private pumps withdraw the stream,and(3)intense canopy limits the use of drones and satellite images.This paper aims to study the relationship between the fault zones and occurrence of the groundwater seepage faces by using the high resolution handheld thermal imaging cameras as a tool to locate the seepage faces along a small river in the Damavand County,north of Iran.The correlation between the structural geology features and occurrence of the groundwater seepage faces revealed that the stream in the study area is being recharged by the groundwater at extensive fault zones.Additionally,this study suggests that the handheld thermal imaging cameras are a useful robust tools to evaluate the surface-groundwater interaction.However,it is essential to use the field structural geologic and hydrogeologic observations to interpret the thermal images.     

Formation of fluctuations in a molecular slab via isobaric thermal instability

Frictional heating by the ion-neutral drift is calculated and its effect on the isobaric thermal instability is studied. Ambipolar drift heating of a one-dimensional self-gravitating magnetized molecular slab is used under the assumptions of quasi-magnetohydrostatic and local ionization equilibrium. We see that ambipolar drift heating is inversely proportional to density and its value in some regions of the slab can be significantly larger than the average heating rates of cosmic rays and turbulent motions. The results show that isobaric thermal instability can occur in some regions of the slab, and thus it may produce slab fragmentation and formation of astronomical unit scale condensations.