Hydrogeochemical evaluation and statistical analysis of groundwater of Sylhet,north-eastern Bangladesh

To investigate the hydrogeochemical characteristics of groundwater 23 shallow, 30 intermediate and 38 deep wells samples were collected from Sylhet district of Bangladesh, and analyzed for temperature, pH, Eh, EC,DO, DOC, Na^+, K^+, Ca²⁺, Mg²⁺, Cl^-, SO_4^2-, NO_3^-,HCO_3^-, SiO_2^-, Fe, Mn and As. Besides, 12 surface water samples from Surma and Kushiyara Rivers were also collected and analyzed to understand the influence into aquifers. Results revealed that, most of the groundwater samples are acidic in nature, and Na–HCO_3 is the dominant groundwater type. The mean value of temperature, EC,Na^+, K^+, Ca²⁺, Mg²⁺, Cl^-, NO_3^- and SO_4^2- were found within the range of permissible limits, while most of the samples exceeds the allowable limits of Fe, Mn and As concentrations. However, relatively higher concentration of Fe and Mn were found in deep water samples and reverse trend was found in case of As. The mean concentrations of As in shallow, intermediate and deep wells were 39.3, 25.3and 21.4 lg/L respectively, which varied from 0.03 to148 lg/L. From spatial distribution, it was found that Fe,Mn and As concentrations are high but patchy in northern,north-western, and south-western part of Sylhet region. The most influential geochemical process in study area were identified as silicate weathering, characterized by active cation exchange process and carbonate weathering, which thereby can enhance the elemental concentrations in groundwater. Pearson's correlation matrix, principal component analysis and cluster analysis were also employed to evaluate the controlling factors, and it was found that, both natural and anthropogenic sources were influencing the groundwater chemistry of the aquifers. However, surface water has no significant role to contaminate the aquifers,rather geogenic factors affecting the trace elemental contamination. Thus it is expected that, outcomes of this study will provide useful insights for future groundwater monitoring and management of the study area.     

Paleoproterozoic granitoids in the basement of Bangladesh: A piece of the Indian shield or an exotic fragment of the Gondwana jigsaw?

We present the first precise age for Precambrian basement rocks in Bangladesh. These lie within the Dinajpur block, located between the Indian Craton to the southwest and the Shillong Massif to the east. There are no surface outcrops and the rocks were intersected by drill holes. They consist of a suite of tonalitic and granodioritic rocks, variously deformed to granitic gneiss and intruded by younger monzogranite. A tonalite obtained at a depth of 227.48 m in drill hole BH-2 at Maddhapara, in northwestern Bangladesh, records a SHRIMP zircon ²⁰⁷Pb/²⁰⁶Pb magmatic age of 1722 ± 6 Ma. Paleoproterozoic rocks with similar magmatic ages are unknown in the adjacent Indian blocks of the Chotanagpur Plateau (Indian Craton) or Shillong Massif. This lack of comparable ages may be due to the paucity of precise radiometric ages from the Indian terrains or, more likely, because there are real age differences, with the buried rocks at Maddhapara representing a separate and discrete microcontinental fragment (the Dinajpur block) that was trapped by the northward migration of India during Gondwana dispersal.     

Access tunnel convergence prediction in longwall coal mining

Summary The paper describes theoretical andin situ studies of tunnel deformation in longwall coal mining. It develops a method to predict tunnel convergence profiles from the faceline in longwall mining. The method accounts for the effect of panel width, extracted seam height, deformation moduli of the goaf material and coal pillar, depth of cover,in situ structural defects, tunnel shape and tunnel size in addition to the strength characteristics of surrounding strata. The analytical technique has been validated by reference toin-situ deformation measurements in 26 face-access tunnels in Cape Breton Coalfield mines. Based on this method a series of vertical convergence profiles for different depths and extracted panel widths have been presented.     

Sea level in the Mediterranean Sea: seasonal adjustment and trend extraction within the framework of SSA

The sea level change is a crucial indicator of our climate. The spatial sampling offered by satellite altimetry and its continuity during the past years are the major assets to provide an improved vision of the Mediterranean sea level changes. In this paper, an automatic signal extraction approach, based on Singular Spectrum Analysis (SSA), is utilized for analysis and seasonal adjustment of the Mediterranean Sea level series. This automatic approach enables us to overcome the difficulties of visual identification of trend constituents that sometimes we encounter when using the conventional SSA method. The results indicate that the Mediterranean mean sea level is dominated by several harmonic components. The annual signal is particularly strong and almost covers 73.62 % of the original sea level series variation whiles its amplitude is about 15 cm. The extracted trend also indicates that the Mediterranean main sea level has significantly been raised during the period 1993–2012 by 2.44?±?0.4 mm yr^?1. As an important consequence, considering the current situation, if this trend continues, the Mediterranean Sea level will be raised about 22 cm by the end of this century, which makes a dramatic effect on several issues such as land, flora, fauna, and people activities established along the Mediterranean coastlines.     

Simulation of physical and socioeconomic factors of vulnerability to cyclones and storm surges using GIS: a case study

The objective of the present study is to simulate the physical and socioeconomic factors of human vulnerability to tropical cyclones and storm surges at the household level in existing and changing status of households. The primary data were collected from a cyclone prone coastal area in Bangladesh, through structured questionnaire and GPS survey, key informants interviews and field observations. In order to simulate the physical and socioeconomic factors geographical information systems based Structured Query Language (SQL) query has been used. The study simulated the physical and socioeconomic factors of human vulnerability to tropical cyclones and storm surges on the basis of collected data through pre-designed SQL query. The study found the number of most vulnerable households under existing conditions and how much it will be afterward of a favourable or adverse change of the factors of vulnerability associated with households. The major findings of the study unveil that the socioeconomic and physical factors of human vulnerability have important function to determine the household’s level of vulnerability to the cyclone induced disaster. It has been demonstrated that the degree of vulnerability of households is changed with its physical and socioeconomic status. This study provides a conceptual model for assessing and simulating vulnerability to other natural hazards like floods, droughts, riverbank erosions and so forth. This study highlights that the households’ intrinsic vulnerable conditions are responsible for its defencelessness to the hazards and the reduction of vulnerability is the first measure of integrated and sustainable disaster management in the coastal Bangladesh.     

The cyclical reversible transitions of the universe’s evolution

In this work we propose cyclical reversible transitions as the scenario in which the universe evolves, through a series consisting of reversible expansion, temporary stability, and contraction. Our model is based on the comparison between local and global time-dependent densities {ρ ₀(τ ₀),ρ(τ)} instead of the critical density ρ _c, local and global time-dependent Hubble parameters {H ₀(τ ₀),H(τ)}, and the variations {Δρ(τ),ΔH(τ)} due to cosmological chaotic fluctuations, which are generally ignored in certain oscillating models. By taking into account all these factors, a rate equation in the form of (H ₀/H)² ∝(ρ ₀/ρ) has been established, and from it we derive some others, to provide a mechanism that is responsible for the cyclical reversible transitions. Also, the problems of singularities, black hole overproduction, and the second law of thermodynamics arising in oscillating universe models are conceptually resolved.     

Geochemistry and petrography of REE-bearing Fe-oxide assemblages in Choghart iron deposit,Yazd, Iran

The Choghart magnetite-apatite deposit situated in the Bafq district, Central Iran, has been scrutinized for rare earth elements (REEs) by precise geochemical investigation. The Central Iran is a susceptible area of rare earth elements. One of the Choghart’s prominent points is the existence of hydrothermal zones which made prediction of REEs occurrence within the deposit possible. Choghart is placed within felsic volcanic tuffs, rhyolitic rocks, and volcanic sedimentary sections belonging to the lower Cambrian. Abundance and distribution pattern of REEs in Choghart iron deposits reveal a part of deposit formation and its mineralogical modifications. Petrography and mineralogy of the ore body demonstrated two main types of alterations (sodic and calcic) associated with iron ore mineralization in Choghart deposit. The main ore includes a large quantity of massive magnetite in the lower part of Choghart deposit. The minor mineralization involves apatite, pyrite, alkaline amphibole, especially actinolite and tremolite, calcite, talc, quart, monazite, and bastnasite. Geochemical sampling from north–northeast (N-NE) side of the mine denotes the presence of these elements in hydrothermal zones. Statistical populations of the area were categorized by fractal geometry into four main differentiations: host rock type (albitofyre), iron, metasomatose, phosphate zones, and a subset of the phosphate zone which is named high iron high phosphate type. REEs like lanthanum, neodymium, yttrium, and niobium constitute the most quantity of Choghart. Deposit characteristics demonstrate its similarity to Kiruna type. The significant feature of iron oxide-apatite deposits of Kiruna ore type is the existence of monazite inclusions within apatite. These inclusions were also observed within apatite type I and II of Choghart mineralization. Moreover, REEs geochemistry in Choghart deposit was identified by investigation on geochemical data analyses. The analysis represents negative Eu anomaly and further enrichment of light REEs compared to the heavy ones. Chondrite normalized REEs patterns are defined by negative anomalies of Eu, which is the main characteristic of Kiruna ore type. The results showed that REEs concentration in phosphate zone, as a high absorption of REEs, is much higher than metsomatose, albitofyre, and iron zones. REEs distribution in N-NE side of the mine indicated that the contact of iron ore with tailings in N-NW side of the mine leads REEs to be enriched nearly 1% , as well as that of NE with high contents of REEs 1.5% ), which is very significant.     

Co-metabolic decolorization of a textile reactive dye by <Emphasis Type="Italic">Aspergillus fumigatus</Emphasis>

In the present study, a widely used reactive dye, Color Index (C.I.) Reactive Blue 268 was utilized for mycoremediation by Aspergillus fumigatus isolated from textile effluent. Complete decolorization of the test dye (0.1 g L^?1) was recorded within 6 days of static incubation at 27 °C in Czapek Dox broth (CDB). However, the isolate was unable to utilize the dye as a sole source of energy in Czapek Dox agar and CDB in absence of sucrose and obligate requirement of a labile carbon source, i.e., sucrose needed for induction of decolorization. Biosorption seems to play the pivotal role in decolorization as evident by coloring of the fungal biomass as that of dye color. The optimal conditions for the highest decolorization were found at 30 °C and pH 6.0 with 6-day-old inoculums supplemented with sucrose (10 g L^?1) and ammonium chloride (2 g L^?1) as a carbon and nitrogen source, respectively. The response of the isolate to increasing dye concentrations was found to be growth inhibitory. Surprisingly, about 65 % of dye decolorization was recorded with heat-inactivated biomass powder within 6 days of static incubation supporting the fact of fungal biosorption. Results of this study have established the candidature of the isolate for biotechnological removal of dyes from disreputable dying effluents.     

Delineation using geophysical data of the hydrocarbon bearing zone in the Begumganj structure, Hatia Trough, southern Bengal Basin, Bangladesh

The Begumganj structure of the Hatia Trough in Bengal Basin has proved it’s hydrocarbon potentiality. Several seismic sections have been analyzed to construct different maps and to interpret subsurface geology, structure and stratigraphy. These maps reveal that the Begumganj structure is an elongated to oval shaped asymmetrical anticline having the general trend NNW-SSE. No major faults affecting the structure could have been identified. Most of the reflectors are strongly affected by channels, especially at the western flank. Based on the analysis of seismic and available well data, the only gas bearing strata at depth of 2995 m (or TWT 2.02 seconds) has been identified. The structure is interpreted as a strati-structure entrapment because shale fill channel truncated this layer on western flank and at the crestal part of the anticline. The structure probably formed after the deposition of sediments. The channel has formed after the corresponding unit cut has been deposited. The channels eroding the reservoir unit range from Late Miocene to Early Pliocene age where the anticline probably begun to form during the Pliocene. Strong increase in amplitude (bright spot), possibly associated with hydrocarbon, has been apparent on seismic lines BG 9 and BG 10. The stratigraphic succession based on the information of the wells drilled on this structure and it’s surrounding fields reveals that the lithological sequences range from Miocene to Recent age where the only proven gas producing sand zone is located in the Bhuban Formation.