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1.
Tsering Karma Shrestha Manish Shakya Kiran Bajracharya Birendra Matin Mir Lozano Jorge Luis Sanchez Nelson Jim Wangchuk Tandin Parajuli Binod Bhuyan Md Arifuzzaman 《Natural Hazards》2022,110(3):1821-1845
Natural Hazards - The Hindu Kush Himalayan region is extremely susceptible to periodic monsoon floods. Early warning systems with the ability to predict floods in advance can benefit tens of... 相似文献
2.
Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh 总被引：1，自引：0，他引：1
M. Aziz Hasan Mattias von Br?mssen Prosun Bhattacharya Kazi Matin Ahmed Arif Mohiuddin Sikder Gunnar Jacks Ondra Sracek 《Environmental Geology》2009,57(3):499-511
The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are
mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to
As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey
sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic
matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides
is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of
As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements
determined by X-ray fluorescence (XRF) show that iron (Fe2O3), aluminum (Al2O3) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO3
−, SO4
2− and NO3
− in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis
by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed
dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment.
Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of
biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic
pyrite in the dark grey sediment indicates active reduction in the aquifer. 相似文献
3.
Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to the complex nature of the deformed
rocks and their genesis. Crustal deformation in the Himalayan thrust belt typically occurs in elastico-frictional (EF) or
quasi-plastic (QP) regimes at depths controlled mainly by regional strain-rate and geothermal gradient. However, material
property, grain-size and their progressive changes during deformation are also important controlling factors. We present evidence
of EF deformation from Gondwana rocks developed during the emplacement of one of the frontal horses (Jorthang horse) in the
Lesser Himalayan Duplex (LHD) structure associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the
Rangit window near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand meso-structures
from an undeformed protolith to cataclasite suggesting that it was emplaced under elastico-frictional conditions. Meso- to
micro-scale shear fractures are seen developed in Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates
are deformed by cataclastic flow suggesting that material property and grain-size have played an important role in the deformation
of the Jorthang horse. In contrast, the hanging wall schists and quartzites of the Ramgarh thrust exhibit quasi-plastic deformation
structures. This suggests that the Jorthang horse was emplaced under shallower crustal conditions than the antiformally folded
Ramgarh thrust sheet even though the Ramgarh sheet presently overlies the Jorthang horse. 相似文献
4.
Brian J. Mailloux Nicholas A. Procopio Mark Bakker Therese Chen Imtiaz Choudhury Kazi Matin Ahmed M. Rajib H. Mozumder Tyler Ellis Steve Chillrud Alexander van Geen 《Ground water》2021,59(1):80-89
Geogenic arsenic in drinking water is a worldwide problem. For private well owners, testing (e.g., private or government laboratory) is the main method to determine arsenic concentration. However, the temporal variability of arsenic concentrations is not well characterized and it is not clear how often private wells should be tested. To answer this question, three datasets, two new and one publicly available, with temporal arsenic data were utilized: 6370 private wells from New Jersey tested at least twice since 2002, 2174 wells from the USGS NAWQA database, and 391 private wells sampled 14 years apart from Bangladesh. Two arsenic drinking water standards are used for the analysis: 10 µg/L, the WHO guideline and EPA standard or maximum contaminant level (MCL) and 5 µg/L, the New Jersey MCL. A rate of change was determined for each well and these rates were used to predict the temporal change in arsenic for a range of initial arsenic concentrations below an MCL. For each MCL and initial concentration, the probability of exceeding an MCL over time was predicted. Results show that to limit a person to below a 5% chance of drinking water above an MCL, wells that are ½ an MCL and above should be tested every year and wells below ½ an MCL should be tested every 5 years. These results indicate that one test result below an MCL is inadequate to ensure long-term compliance. Future recommendations should account for temporal variability when creating drinking water standards and guidance for private well owners. 相似文献
5.
Arsenic in shallow groundwater of Bangladesh: investigations from three different physiographic settings 总被引：1，自引：0，他引：1
M. Aziz Hasan K. Matin Ahmed Ondra Sracek Prosun Bhattacharya Mattias von Brömssen Sandra Broms Johan Fogelström M. Lutful Mazumder Gunnar Jacks 《Hydrogeology Journal》2007,15(8):1507-1522
Occurrences of arsenic (As) in the Bengal Basin of Bangladesh show close relationships with depositional environments and sediment textures. Hydrochemical data from three sites with varying physiography and sedimentation history show marked variations in redox status and dissolved As concentrations. Arsenic concentration in groundwater of the Ganges Flood Plain (GFP) is characteristically low, where high Mn concentrations indicate redox buffering by reduction of Mn(IV)-oxyhydroxides. Low DOC, \( {\text{HCO}}^{ - }_{3} \), \( {\text{NH}}^{ + }_{4} \) and high \( {\text{NO}}^{ - }_{3} \) and \( {\text{SO}}^{{2 - }}_{4} \) concentrations reflect an elevated redox status in GFP aquifers. In contrast, As concentration in the Ganges Delta Plain (GDP) is very high along with high Fe and low Mn. In the Meghna Flood Plain (MFP), moderate to high As and Fe concentrations and low Mn are detected. Degradation of organic matter probably drives redox reactions in the aquifers, particularly in MFP and GDP, thereby mobilising dissolved As. Speciation calculations indicate supersaturation with respect to siderite and vivianite in the groundwater samples at MFP and GDP, but groundwater in the GFP wells is generally supersaturated with respect to rhodochrosite. Values of log PCO2 at MFP and GDP sites are generally higher than at the GFP site. This is consistent with Mn(IV)-redox buffering suggested at the GFP site compared to Fe(III)-redox buffering at MFP and GDP sites. 相似文献
6.
7.
Channel braiding and stability of the Brahmaputra River, Bangladesh, since 1967: GIS and remote sensing analyses 总被引：1，自引：1，他引：1
T. Takagi T. Oguchi J. Matsumoto M.J. Grossman M.H. Sarker M.A. Matin 《Geomorphology》2007,85(3-4):294
Spatial and temporal changes in channel distribution in the large, sandy, braided system of the Brahmaputra River, Bangladesh, were analyzed using satellite images and GIS. Supervised classification of the images within the braided belt, i.e., channels and bars between the bank-lines, provided raster land cover data for 14 different years between 1967 and 2002. The width of the braided-belt, the number and width of channels, the distribution of land cover attributes and land stability change were examined from the data. The results indicate that the recent history of the dynamics of the Brahmaputra can be divided into four phases: 1) the late 1960s to early 1970s, 2) the mid-1970s to early 1980s, 3) the mid-1980s to early 1990s, and 4) the mid-1990s to early 2000s. Spatial distributions of the land cover and channels in Phase 4 were the least complex suggesting a state of dynamic equilibrium. Land cover and channel distributions during Phase 2 were partly less complex indicating quasi-dynamic equilibrium. Phases 1 and 3 can be regarded as transitional phases with more complex conditions. Frequent large floods may have triggered significant changes in the river system during Phases 1 and 3. 相似文献
8.
Declining groundwater level and aquifer dewatering in Dhaka metropolitan area,Bangladesh: causes and quantification 总被引：1，自引：1，他引：1
Large abstraction by water-wells has been causing a linear to exponential drop in groundwater level and substantial aquifer dewatering in Dhaka, Bangladesh. The city is almost entirely dependent on groundwater, which occurs beneath the area in an unconsolidated Plio-Pleistocene sandy aquifer. Analysis shows that the pattern of water-level change largely replicates the patterns of change in the rate of groundwater abstraction. Contribution of the aquifer storage to the abstraction is estimated to be more than 15% in the year 2002. This abstraction has caused a sharp drop in water level throughout the city and turned into two cones of depression in the water level. Upper parts of the aquifer are already dewatered throughout the area, with the exception of part of the northeast and southeast corner of the city. It is calculated that about 41 million cubic metres (MCM) of the aquifer dewatered by the year 1988, which increased to 2,272 MCM in the year 2002. Water-level decline may increase non-linearly due to limiting vertical recharge in areas where the aquifer is dewatered and may severely threaten the sustainability of the aquifer. 相似文献
9.
Peter S.K. Knappett Alice Layton Larry D. McKay Daniel Williams Brian J. Mailloux M.R. Huq M.J. Alam Kazi Matin Ahmed Yasuyuki Akita Marc L. Serre Gary S. Sayler Alexander van Geen 《Ground water》2011,49(1):53-65
The goal of this study was to test hollow‐fiber ultrafiltration as a method for concentrating in situ bacteria and viruses in groundwater samples. Water samples from nine wells tapping a shallow sandy aquifer in a densely populated village in Bangladesh were reduced in volume approximately 400‐fold using ultrafiltration. Culture‐based assays for total coliforms and Escherichia coli, as well as molecular‐based assays for E. coli, Bacteroides, and adenovirus, were used as microbial markers before and after ultrafiltration to evaluate performance. Ultrafiltration increased the concentration of the microbial markers in 99% of cases. However, concentration factors (CF = post‐filtration concentration/pre‐filtration concentration) for each marker calculated from geometric means ranged from 52 to 1018 compared to the expected value of 400. The efficiency was difficult to quantify because concentrations of some of the markers, especially E. coli and total coliforms, in the well water (WW) collected before ultrafiltration varied by several orders of magnitude during the period of sampling. The potential influence of colloidal iron oxide precipitates in the groundwater was tested by adding EDTA to the pre‐filtration water in half of the samples to prevent the formation of precipitates. The use of EDTA had no significant effect on the measurement of culturable or molecular markers across the 0.5 to 10 mg/L range of dissolved Fe2+ concentrations observed in the groundwater, indicating that colloidal iron did not hinder or enhance recovery or detection of the microbial markers. Ultrafiltration appears to be effective for concentrating microorganisms in environmental water samples, but additional research is needed to quantify losses during filtration. 相似文献
10.
Pedrazas Micaela N. Cardenas M. Bayani Hosain Alamgir Demir Cansu Ahmed Kazi Matin Akhter Syed Humayun Wang Lichun Datta Saugata Knappett Peter S. K. 《Hydrogeology Journal》2021,29(4):1601-1610
Fluvio-deltaic aquifers are the primary source of drinking water for the people of Bangladesh. Such aquifers, which comprise the Ganges-Brahmaputra-Meghna Delta, are hydrogeologically heterogeneous. Because of widespread groundwater quality issues in Bangladesh, it is crucial to know the hydrostratigraphic architecture and hydrochemistry, as some aquifer units are contaminated, whereas others are safe. Geophysical methods provide a potentially effective and noninvasive method for extensive characterization of these aquifers. This study applies and investigates the limitations of using electrical resistivity imaging (ERI) for mapping the hydrostratigraphy and salinity of an aquifer-aquitard system adjacent to the Meghna River. Some electrical resistivity (ER) sections showed excellent correlation between resistivity and grain size. These suggest that ERI is a powerful tool for mapping internal aquifer architecture and their boundaries with finer-grained aquitards which clearly appear as low-ER zones. However, in parts of some ER sections, variations in electrical properties were determined by porewater resistivity. In these cases, low ER was indicative of brine and did not indicate the presence of finer-grained materials such as silt or clay. Accordingly, the following hydrostratigraphic zones with different resistivities were detected: (1) aquifers saturated with fresh groundwater, (2) a regional silt/clay aquitard, and (3) a deeper brine-saturated formation. In addition, shallow silt/clay pockets were detected close to the river and below the vadose zone. ERI is thus a promising technique for mapping aquifers versus aquitards; however, the observations are easily confounded by porewater salinity. In such cases, borehole information and groundwater salinity measurements are necessary for ground-truthing.
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