A typical weathering profile of granitic rock in Johor,Malaysia based on joint characterization

Arabian Journal of Geosciences - One of the most important challenges in the study of slope stability, foundation, and excavation in rocks is understanding the weathering states. This issue is more...     

Nuclear geophysical logging for Gondwana coal exploration: a case study at Phulbari Coal Basin, northern part of Bangladesh

Different methods of lithology predictions from geophysical data have been developed in the last 15 years, among which the conventional logs are as follows: sonic, neutron–neutron, natural gamma, and density (backscattered gamma–gamma). This article concentrates on the nuclear geophysical suite, in particular, gamma and gamma–gamma logging, which, to date, provide the most accurate geophysical means of identifying coal seams and estimating their thickness. From the gamma and gamma–gamma logs of boreholes AEN 002, 007, 044, 045, 063, 085, and 105, which were carried out at the Phulbari Coal Basin of Bangladesh, two coal seams—upper and main with two lower seams of limited occurrence and of varying thickness—were identified, together with their regional occurrence.     

Application of VES and TDEM techniques to investigate sea water intrusion in Sidi Abdel Rahman area, northwestern coast of Egypt

The present study is an approach to detect the sea/freshwater interface in Sidi Abdel Rahman area, northwestern coast of Egypt using both vertical electrical sounding and time domain electromagnetic. The measured vertical electrical soundings are interpreted in 1D and 2D manner. The 1D inversion is carried out using the commercial software (RESIST), whereas 2D resistivity nonlinear iterative inversion scheme based on the finite element technique and regularization method was used. The time domain electromagnetic stations are interpreted using Temixxl-4 software by Interpex Ltd. To have the advantages of the vertical electrical sounding in shallow depths and time domain electromagnetic in deep depths, a joint inversion algorithm is applied for the electric profile and the nearby electromagnetic profile. Very low resistivity values have been observed near the coast as well as a considerable salt/fresh water interface. The tip-top portion of the interface lies approximately 1,000 m from the shore line.     

Spatial and Temporal Variability of Sediment Organic Matter Recycling in Two Temperate Eutrophicated Estuaries

This paper deals with the spatial and seasonal recycling of organic matter in sediments of two temperate small estuaries (Elorn and Aulne, France). The spatio-temporal distribution of oxygen, nutrient and metal concentrations as well as the organic carbon and nitrogen contents in surficial sediments were determined and diffusive oxygen fluxes were calculated. In order to assess the source of organic carbon (OC) in the two estuaries, the isotopic composition of carbon (δ ¹³C) was also measured. The temporal variation of organic matter recycling was studied during four seasons in order to understand the driving forces of sediment mineralization and storage in these temperate estuaries. Low spatial variability of vertical profiles of oxygen, nutrient, and metal concentrations and diffusive oxygen fluxes were monitored at the station scale (within meters of the exact location) and cross-section scale. We observed diffusive oxygen fluxes around 15 mmol m^?2 day^?1 in the Elorn estuary and 10 mmol m^?2 day^?1 in the Aulne estuary. The outer (marine) stations of the two estuaries displayed similar diffusive O₂ fluxes. Suboxic and anoxic mineralization was large in the sediments from the two estuaries as shown by the rapid removal of very high bottom water concentrations of NO _x ^? (>200 μM) and the large NH₄ ⁺ increase at depth at all stations. OC contents and C/N ratios were high in upstream sediments (11–15 % d.w. and 4–6, respectively) and decreased downstream to values around 2 % d.w. and C/N ≤ 10. δ ¹³C values show that the organic matter has different origins in the two watersheds as exemplified by lower δ ¹³C values in the Aulne watershed. A high increase of δ ¹³C and C/N values was visible in the two estuaries from upstream to downstream indicating a progressive mixing of terrestrial with marine organic matter. The Elorn estuary is influenced by human activities in its watershed (urban area, animal farming) which suggest the input of labile organic matter, whereas the Aulne estuary displays larger river primary production which can be either mineralized in the water column or transferred to the lower estuary, thus leaving a lower mineralization in Aulne than Elorn estuary. This study highlights that (1) meter scale heterogeneity of benthic biogeochemical properties can be low in small and linear macrotidal estuaries, (2) two estuaries that are geographically close can show different pattern of organic matter origin and recycling related to human activities on watersheds, (3) small estuaries can have an important role in recycling and retention of organic matter.     

Vertically sheared horizontal flow with mass sources: a canonical balanced model

Canonical balanced dynamic equations involving vertically sheared horizontal flow with heat or mass sources have emerged recently in systematic multi-scale modeling of the equatorial wave guide on a wide range of spatio-temporal scales. Here, a new self-contained derivation of these equations is developed briefly in a context for potential applications to the hurricane embryo. These canonical balanced equations are studied through a combination of exact solutions and simple numerics. The results below include elementary exact solutions given by velocity fields that are linear in the spatial coordinates combined with an exact nonlinear stability analysis for vertical vorticity amplification in such a preconditioned environment. Other elementary solutions studied here include the evolution of radial eddies, which represent “hot towers” in the hurricane embryo in a suitable radial preconditioned background environment.     

Delineation of groundwater provenance in a coastal aquifer using statistical and isotopic methods,Southeast Tanzania

Rapid population growth and urbanization has placed a high demand on freshwater resources in southeast costal Tanzania. In this paper, we identify the various sources of groundwater and the major factors affecting the groundwater quality by means of multivariate statistical analyses, using chemical tracers and stable isotope signatures. The results from hierarchical cluster analyses show that the groundwater in the study area may be classified into four groups. A factor analysis indicates that groundwater composition is mainly affected by three processes, accounting for 80.6% of the total data variance: seawater intrusion, dilution of groundwater by recharge, and sewage infiltration. The hydrochemical facies of shallow groundwater was mostly of the Na–Ca–Cl type, although other water types were also observed. The deep groundwater samples were slightly to moderately mineralized and they were of the NaHCO₃ type. This water type is induced mainly by dissolution of carbonate minerals and modified by ion exchange reactions. The signal from the stable isotope composition of the groundwater samples corresponded well with the major chemical characteristics. In the shallow groundwater, both high-nitrate and high-chloride concentrations were associated with localized stable isotope enrichments which offset the meteoric isotopic signature. This is inferred to be due to the contamination by influx of sewage, as well as intrusion by seawater. The depleted stable isotope values, which coincides with a chemical signature for the deep aquifer indicates that this deep groundwater is derived from infiltration in the recharge zone followed by slow lateral percolation. This study shows that a conceptual hydrogeochemical interpretation of the results from multivariate statistical analysis (using HCA and FA) on water chemistry, including isotopic data, provides a powerful tool for classifying the sources of groundwater and identifying the significant factors governing the groundwater quality. The derived knowledge generated by this study constitutes a conceptual framework for investigating groundwater characteristics. This is a prerequisite for developing a sound management plan, which is a requirement for ensuring a sustainable exploitation of the deep aquifer water resource in the coastal area of Tanzania.     

Dokhan volcanics of Gabal Monqul area,North Eastern Desert,Egypt: geochemistry and petrogenesis

The Dokhan volcanics are represented by a thick stratified lava flows succession of basalt, andesite, imperial porphyry, dacite, rhyodacite, rhyolite, ignimbrites, and tuffs. These lavas are interbanded with their pyroclastics in some places including banded ash flow tuffs, lithic tuffs, crystal lapilli tuffs, and agglomerates. They are typical calc–alkaline and developed within volcanic arc environment. All rocks show moderate enrichment of most large ion lithophile elements relative to high field strength elements (HFSE). The incompatible trace elements increase from basalt through andesite to rhyolite. The felsic volcanics are characterized by moderate total rare earth elements (REE) contents (162 to 392 ppm), less fractionated patterns {(Ce/Yb)_N = (1.24 to 10.93)}, and large negative Eu anomaly {(Eu/Eu*) = (0.15 to 0.92)}. The mafic volcanics have the lowest REE contents (61 to 192 ppm) and are relatively steep {(Ce/Yb)_N = (3.2 to 8.5)}, with no negative Eu anomalies {(Eu/Eu*) = (0.88 to 1)}. The rhyolite displays larger negative Eu anomaly (Eu/Eu* = 0.28) than those of other varieties, indicating that the plagioclase was an early major fractionating phase. The mineralogical and chemical variations within volcanics are consistent with their evolution by fractional crystallization of plagioclase and clinopyroxene.     

Heat flux parameterization for sparse and dense grasslands with the analytical land-atmosphere radiometer model (alarm)

The dependence of radiometric surface temperature (_s) on view angle and the unclear definition of the aerodynamic temperature, which is the temperature that gives the correct sensible heat flux estimate at a specified roughness length, bring about a challenge in estimating sensible heat flux from _s. An analytical-land-atmosphere-radiometer model (ALARM) has been developed to convert _s taken at any zenith view angle to a clearly defined equivalent isothermal surface temperature, _i, at a defined scalar roughness length. ALARM is an analytical model based on K-theory that links the foliage temperature profile to the radiometric surface temperature and the temperature felt by the turbulent lower atmosphere. ALARM has previously been applied with slightly different values of its parameters to several grassland sites of varying canopy density. Our objective in this study was to apply ALARM to these and to one additional dataset with a single parameterization. When compared to the reference (measured) values of sensible heat flux H, ALARM estimates of H had root mean square errors of about 35 W m^-2. These results were comparable to those from two other simple canopy models also tested with these datasets.