The Dhaka University Journal of Earth and Environmental Sciences

Benthic Foraminifera as Bio-Indicators of Trace Element Pollution at St. Martin’s Island, Bangladesh

2024-05-12T12:30:55+00:00

Benthic Foraminifera occupied all marine environments. The practice of utilizing benthic foraminifera for monitoring the state of the marine environment has garnered widespread recognition all over the world. Changes in foraminiferal assemblage indicate the level of environmental stress. The prime concern of the present research is to evaluate the abundance and distribution of benthic foraminifera stress and how anthropogenic stresses affect their diversity in St. Martin's Island, Bangladesh. About 250 foraminifera specimens were collected, of which 22 species, 19 genera, and 17 families of predominantly benthic provenance were recognized. Astrorhiza holds the first position in order of relative abundance and frequency of occurrence followed by the Elphidium, Robulus, and Eponoides. The stress-tolerant and heterotrophic genera (Quinqueloculina, Elphidium, Ammonia, Trochammina) dominated the sensitive or symbiont genera (Calcarina, Operculina, Cibicides, Nummulites). Analysis of various diversity indices reveals that the northern part of the island near the boat terminal shows a lower diversity of benthic foraminifera. The southern part of the island shows moderate diversity indicating less pollution. For the investigation of the Foraminiferal shell, in addition to statistical computing, SEM (Scanning Electron Microscopy), EDX (Energy Dispersive X-ray Analysis), and XRD (X-ray Diffraction) analyses have been utilized. From the EDX analysis, it has been found that lower oxygen (O) with a weight range of (36.51-53.71%) and calcium (Ca) with a weight range of (30.44-53.38%) are the primary components of the foraminifera test. The shells also contain higher percentages of trace elements such as silicon (Si), magnesium (Mg), iron (Fe), chlorine (Cl), sodium (Na), aluminum (Al), and manganese (Mn). Anthropogenic activity is the main source of these trace elements, which clearly demonstrates the island's environmentally stressed condition. The intrusion of these elements in the benthic foraminiferal shell indicates they react to anthropogenic contaminants. These exogenous trace elements are responsible for particular morphological distortion of foraminifera shells which are also observed in St. Martin’s Island. The outcomes from the current research will build a foundation for future researchers focusing on anthropogenic impact assessment and sustainable coastal management in Bangladesh.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 1-14

Cross-Sectional Analysis of Water Access and Health Conditions in Salinity and Cyclone Prone Areas: A Case Study of Nishanbaria Village in Southern Bangladesh

2024-05-12T12:50:04+00:00

The present study was conducted in Nishanbaria, a remote coastal village of Barguna district, Bangladesh where access to fresh water is the biggest problem due to salinity and cyclones along with poverty. The study applied several research methods (household survey, Key Informant Interviews, Focus Group Discussion, and observation) to conduct a cross-sectional analysis in order to identify the severity of the water problems and their impacts on people's health in this village. The study reveals that drinking and using saline and dirty water for a long time have direct impacts on health; 87.9% of the families had sick members during the field survey in 2022. The major health problems are skin diseases (according to 30.65 % of the respondents), gastric problems (25.39%), and waterborne diseases (19.35%). According to 90.3% of residents, the salinity of water has a direct impact on pregnancy and children's health and well-being. As the majority of the people collect drinking water from tube wells (80.43%), the number of people using tube wells goes down to only 24.4% after cyclones. Women are the main water collectors in this village; drinking water is collected by female members in 86.86% of the families, domestic water in 98.19%, and water for cleaning purposes in 93.56% of the families. Women are at risk of health problems; different types of pains (according to 49.36% of the residents), accidents (34.33%), and gender-based violence stem from carrying water from distant sources. Poverty (97.84% of the residents live below the poverty line) creates disparity among the residents in accessing proper treatments for all these health problems as well as collecting fresh water from distant sources. A comprehensive and context-based hazard and disaster management plan is required to help this disaster-prone village in improving freshwater availability, and their health and well-being.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 15-26

Estimation of Consolidation and Settlement Characteristics of Madhupur Clay Formation from Dhaka City and Adjacent Area (Savar), Bangladesh

2024-05-13T03:51:03+00:00

Pleistocene Madhupur Clay covers mostly the investigated region including Dhaka and the surrounding area (Savar). Without knowing the consolidation characteristics and settlement of this Clay, it is difficult for any construction sites to build infrastructure. In Bangladesh, the research on this parameter is limited hence for better understanding the consolidation and settlement behavior of Madhupur Clay samples in this area, a detail investigation is carried out by conducting one dimensional consolidation test. The undisturbed samples, Pleistocene Madhupur Clay and the fill materials which are also partly composed of the Madhupur Clay, are collected from 2.4 m to 4.11 m depths of many distinct points. The compression index C_cand coefficient of compressibility, a_vof the samples are range from 0.073 to 0.23 and from 0.059 to 0.14m²/mn respectively. The values recommend that both types of specimens are medium plastic clay. The Madhupur Clay are stiff consolidated clay and slightly compressible in nature whereas the Madhupur Clay fill samples are less stiff over consolidated and moderately compressible in nature. Fill samples are settled more with time and are not suitable for Shallow foundation of light or heavy infrastructure. However, the Madhupur Clay samples are only appropriate for light infrastructure foundation.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 27-39

Mapping Environmental Quality Indices of Dhaka City by Using Geospatial Techniques

2024-05-13T04:06:37+00:00

Dhaka, the city of over 10 million people is one of the most polluted cities due to rapid urbanization, commercial development and population pressure. The present study assessed an overall environmental quality of Dhaka South City Corporation (DSCC) and Dhaka North City Corporation (DNCC) using an Environmental Quality Index (EQI) based on five indices: Air Quality Index (AQI), Water Quality Index (WQI), Soil Quality Index (SQI), Noise Quality Index (NQI), and Vegetation Index (VI). The final EQI was determined through selecting components from background literature and an overlay analysis using predefined weights for each distinct indices. The study reveals that the west and west-central part of DSCC have experienced the most severe environmental degradation, affecting noise levels, vegetation cover, air, soil, and water quality. However, the air is less polluted especially in the peripheral zones of the city corporations. Overall, the study indicates that the environmental quality of DNCC is comparatively better than DSCC. The results of the study provides an insight on environmental quality of the city for legislators, urban planners, environmentalists, and researchers to monitor and preserve environmental quality in making the city livable, healthy and sustainable.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 41-53

Hydrogeochemical Investigation and Estimation of Aquifer Properties at Dhaka University Campus

2024-05-13T04:26:02+00:00

The University of Dhaka has its own water supply system and entirely relies on groundwater. Ten groundwater samples were collected from 10 production wells of 120-320 m depth across the University campus from upper and lower Dupi Tila aquifers. The pH values revealed that water is mildly acidic to neutral and electrical conductivity (EC) values ranging from 325 to 654 μS/cm, indicating fresh groundwater. The total hardness (TH) of the samples ranges from 76-203 mg/L, suggesting moderately hard to very hard water. Of the ten groundwater samples, nine are of Ca-Mg-HCO₃ type, whereas one shows Ca-Na-HCO₃ type of groundwater. The saturation indices show that the groundwater samples are near-saturated for calcite, dolomite, gypsum, siderite, and rhodochrosite, indicating the low potential for dissolution-precipitation of these mineral. Notably, the results of WQI indicate that all the wells are safe for drinking. As of July 2023, the groundwater level was 72 m below ground level with a declination rate of 2.8 m/year. The estimated hydraulic conductivity values of 20 to 90 m/day and transmissivity values of 637 to 2740 m²/day suggest better permeability and water transmission potential within the lower aquifer. These results provide essential information for the university authority to implement appropriate strategies for efficient groundwater management.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 55-67

Deciphering Mineralogical Composition and Clay Diagenesis in Exposed Shales of Jaintiapur, Surma Basin: Unveiling Insights into Burial Diagenesis

2024-05-13T05:14:03+00:00

Mineralogical analysis of exposed shale samples in the Jaintiapur region was conducted utilizing X-ray diffraction (XRD) techniques. The studied shales are characterized by illite, chlorite, illite/ smectite mixed layer clay, and kaolinite as the predominant clay minerals, with a relatively lower proportion of smectite. Additionally, the non-clay fraction consists mainly of quartz, feldspar, dolomite, and trace amounts of pyrite. Notably, illite and chlorite exhibit prominent abundance within the clay portion, while quartz is the prevailing non-clay mineral. Furthermore, the investigation reveals a notable enrichment of illite and chlorite with the advancement from younger to older stratigraphic formations in the studied shale samples, indicating greater intensity in clay mineral diagenesis in deeper stratigraphic formations. The transition from smectite to illite minerals can release Si, Ca, Fe, and Mg ions, potentially entering nearby sandstones and leading to cementation with quartz, chlorite, and calcite. This process aids in retaining pore water in shales. In this context, overpressure development influenced by clay diagenesis is not primarily due to cementation while undergoing smectite to illite conversion but due to illite packet formation within smectite, reducing shale permeability. During this conversion, interlayer water shifts to free water, causing volume reduction compounded by the low permeability of shale, trapping fluids in the pores. This expansion of pore water, reduced velocity, and increased pore pressure suggest that mineral transformation with burial depth might contribute to overpressure development. However, the observed decline in smectite clays in sediments transitioning from younger to older, culminating in their absence in older shale-dominated formations, explains the presence of diagenetic illite and chlorite. This study underscores the progressive diagenetic transformation in clay mineralogical composition with progressive burial across the sedimentary succession.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 69-82

Rainfall-Runoff Estimation in the North-Eastern Region of Bangladesh Using SCS-CN Method

2024-05-13T05:32:27+00:00

Measuring discharge in a developing nation like Bangladesh is very important for flood prediction, land management, and sustainable development. Rainfall-induced runoff is a part of the cycle of hydrology and is required for efficient water resource planning. The most significant debatable procedure in hydrology is calculating and determining catchment surface runoff. The study aims to estimate runoff using the GIS-based Soil Conservation Service-Curve Number method (SCS – CN) method, where this hydrological model has a physical foundation and spatial distribution, and the curve number plays a key role in this model's runoff computation. The Hydrologic Soil Group (HSG) present in the study area and the land use pattern are used to find the Curve Number (CN). The calculated weighted CN for Antecedent Moisture Condition (AMC) I, II, and III for the study area was roughly 74.78, 87.12, and 94.06 respectively with the incorporation of Land use and land cover (LULC) and HSG. For total average rainfall of 35163.8mm, the SCS-CN approach determined the total average runoff 16077.55 mm for the period of 2009-2018. With a correlation coefficient of 0.966, the average rainfall and SCS-CN discharge have a significant linear relationship. The runoff regulates the amount of water that enters stream systems and returns extra precipitation to the ocean benefitting the hydrological cycle. With this runoff estimation, the quality and amount of water resources can be better understood, managed, and tracked.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 83-96

Geospatial Assessment of Wetland Changes in the Fringe Area of Dhaka City: Past, Present and Future Scenarios

2024-05-13T05:58:07+00:00

This study examines the changes in wetlands in the fringe area of Dhaka city using geospatial assessment techniques. The wetland in the area is crucial as they serve as a buffer zone for the Dhaka Metropolitan Area (DMA) and play a significant role in maintaining the region's ecological balance. Thirty-meter NASA Landsat 4-5TM and Landsat 8 OLI satellite imagery were used to extract wetland features in the fringe area of Dhaka city. The Modified Normalized Difference Water Index (MNDWI) was applied to delineate wetland features. Finally, ArcGIS geometric computing was used to detect yearly changes, and a Cellular Automaton (CA) Markov Model was applied to predict future transitions. The research findings reveal that wetlands in the Dhaka Metropolitan Area are declining at a rate of 1.1% between 1991 and 2016, indicating the urgency of addressing this issue to ensure the sustainability of the region's natural resources. The percentage of wetlands in the fringe area has been decreasing significantly over the years, with wetlands making up only 12.98% of the fringe area in 2022, down from 28.22% in 1989. This trend is predicted to continue, with wetlands accounting for only 8.02% of the total area by 2034. The strong negative correlation coefficient between the year and wetland area suggests that the trend of decreasing wetland is likely to continue unless significant measures are taken to protect wetlands. The study highlights the importance of conserving and restoring wetlands in Dhaka's fringe areas to maintain the ecological balance of the region and support the well-being of both humans and wildlife.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 97-117

Evaluation of Reservoir Properties of Sylhet Limestone of Jaintia Group, North-Eastern Sylhet, Bangladesh

2024-05-13T06:10:14+00:00

The Sylhet Limestone in the Bengal Basin, formed in the Eocene Epoch and known for its fossil content, is significant in understanding the reservoir characteristics. Despite exposure in Jaflong and Takerghat of the Bengal Basin, little research has been conducted on reservoir characteristics. This study aimed to comprehensively examine the Sylhet Limestone Formation, encompassing its crystalline upper and fossiliferous lower sections. It utilized field investigations and laboratory analyses to address the gaps of sporadic or insufficient earlier studies. A thorough examination of thin sections from the Sylhet Limestone, exposed in the Dauki River area, provides insights into the textural and mineralogical attributes and the presence of skeletal fossils within the limestone. Based on the analysis of thin sections, the limestones are categorized as Rudestones and Packstones. The porosity observed in the exposed rocks ranges from 5% to 12%, with most pores associated with interconnected fractures and joints. However, thin-section studies also indicate evidence of diagenetic recrystallization and calcite cementation. Hence, closely spaced, interconnected joints and fractures filled with diagenetic calcite might deteriorate the reservoir quality. Notably, this limestone exhibits fossilized specimens such as Nummulite, Discocyclina, Alveolina, Assilina, and Ostracoda, among others. The combination of the fossil assemblage, limestone texture, and composition strongly suggests that this limestone formation was deposited in a shallow marine environment with minimal sediment input under a warm and humid climate. The petrographic analysis of the limestones concludes that the upper portion of the formation is fine-grained while the lower part is coarse-grained.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 119-137

Application of GPR to Detect Lost Valve Chambers in a Utility Network

2024-05-13T06:18:58+00:00

The exact geographic location of the fresh water transmission network of Dhaka WASA was not known to the agency. With time and development works, access to many such underground valve chambers were lost. Their recovery was usually done through manual digging and trenching. This was expensive, time- and labour-consuming, often led to traffic jams, and the rate of success was low. This study was conducted to use the non-intrusive method of Ground Penetrating Radar to locate those valves as an alternative. A total of 27 out of the 41 lost nodes in the network was successfully recovered and their precise location was recorded using RTK-GNSS. The article presents the detail procedure of locating the valve chambers of underground pipeline network. It also highlights how the lack of collaboration between agencies are causing water supply and maintenance problems to this day, and how infrastructure development of one agency may erode successes of another.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 139-151

Manufacturing Environmentally Friendly Hollow Blocks using Different Aggregates: Effect on Mechanical Properties

2024-05-13T06:32:58+00:00

Hollow concrete block (HCB) is one of the most fundamental materials in building and construction worldwide. Therefore, HCB has emerged as a viable alternative to traditional building materials likebrick. It is an excellent choice for constructing walls, pavements, and other masonry work construct a long-lasting structure. Today's new world requires a green, eco-friendly, and sustainable world, and HCB can play a significant role in achieving that goal. HCB has superior thermal and fire resistance properties, greater strength, cost-effectiveness, and eco-friendliness. Only a small amount of construction in Bangladesh is done using HCBs. However, as sustainable structural technology advances, more frequent use of HCBs will be required. As a result, this article will provide a brief overview of the various applications of HCBs in Bangladesh, including the manufacturing process and its benefits and drawbacks. Specifically, this work investigates and compares the effect of different natural fine aggregates collected from different areas of Bangladesh on the mechanical properties of HCB. The fine aggregates used in this study came from the Dharala, Patgram, Lalmonirhat, and Someshwari rivers in Durgapur, Netrokona, Bangladesh. HCBs were manufactured using a hydraulic press machine and were constructed using mix design ratios of 1: 5: 1: 3 (Cement: Gravel Sand: Sylhet Sand: Crushed Stone), 1: 4.17: 1.67: 1.5 (Cement: Gravel Sand: Sylhet Sand: Crushed Stone), 1: 2.33: 2: 1.33 (Cement: Gravel Sand: Stone Dust: Crushed Stone), 1: 3.33: 2.33 (Cement: Gravel Sand: Stone Dust) and 1: 2.5: 1: 0.50 (Cement: Gravel Sand: Stone Dust: Crushed Stone) with water cement (W/C) ratio of 0.37. The specimens' dimensions were chosen to be 390 mm x 190 mm x 100 mm. The specimens were tested for unit weight, water absorption, compressive strength, and tensile strength after 28 days of water curing. The results showed that HCBs made with different fine aggregates from the Dharala, Patgram, Lalmonirhat, and Someshwari rivers in Durgapur, Netrokona, Bangladesh, have different compressive strengths at 28 days, namely 978 PSI, 1604 PSI, 1267 PSI, 1162 PSI, and 2128 PSI.

The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 153-158