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 P_CO2 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   

Application of electrical resistivity to map the stratigraphy and salinity of fluvio-deltaic aquifers: case studies from Bangladesh that reveal benefits and pitfalls     

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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Recommended Sampling Intervals for Arsenic in Private Wells     

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   

A review of the assessment and mitigation of floods in Sindh, Pakistan   总被引：1，自引：0，他引：1  

Asadullah Kazi 《Natural Hazards》2014,70(1):839-864

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The Love wave scattering matrix for a continental margin (numerical)     

M. H. Kazi 《Geophysical Journal International》1978,53(2):227-243

Summary . This paper presents the numerical computation of the results previously obtained by the author through a scattering matrix formulation (together with plane wave and variational approximations) which describes the diffraction of plane, harmonic, monochromatic Love waves incident normally (from either side) upon the plane of discontinuity in a structure consisting of a half-space with a surface step — an idealized model of a continental margin. Magnitudes of reflection and transmission coefficients are computed numerically for different frequencies for a model which has been considered previously by Knopoff & Hudson and also by Alsop in their studies of the same problem. The results obtained under the plane wave approximation are compared with those obtained under the variational approximation in order to assess the effects of the body-wave contributions. Finally, the results of both approximations are compared with those obtained by previous authors.  相似文献   

The impact of intensive groundwater abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh   总被引：1，自引：0，他引：1  

Mohammad Shamsudduha  Richard G. Taylor  Kazi M. Ahmed  Anwar Zahid 《Hydrogeology Journal》2011,19(4):901-916

Quantitative evaluations of the impact of groundwater abstraction on recharge are rare. Over a period (1975??007) during which groundwater abstraction increased dramatically in the Bengal Basin, changes in net groundwater recharge in Bangladesh are assessed using the water-table fluctuation method. Mean annual groundwater recharge is shown to be higher (300??00?mm) in northwestern and southwestern areas of Bangladesh than in southeastern and northeastern regions (<100?mm) where rainfall and potential recharge are greater. Net recharge in many parts of Bangladesh has increased substantially (5??5?mm/year between 1985 and 2007) in response to increased groundwater abstraction for irrigation and urban water supplies. In contrast, net recharge has slightly decreased (??.5 to ???mm/year) in areas where groundwater-fed irrigation is low (<30% of total irrigation) and where abstraction has either decreased or remained unchanged over the period of 1985??007. The spatio-temporal dynamics of recharge in Bangladesh illustrate the fundamental flaw in definitions of “safe yield??based on recharge estimated under static (non-pumping) conditions and reveal the areas where (1) further groundwater abstraction may increase actual recharge to the shallow aquifer, and (2) current groundwater abstraction for irrigation and urban water supplies is unsustainable.  相似文献   

Future changes of the terrestrial ecosystem based on a dynamic vegetation model driven with RCP8.5 climate projections from 19 GCMs     

Miao Yu  Guiling Wang  Dana Parr  Kazi Farzan Ahmed 《Climatic change》2014,127(2):257-271

Future changes of terrestrial ecosystems due to changes in atmospheric CO₂ concentration and climate are subject to a large degree of uncertainty, especially for vegetation in the Tropics. Here, we evaluate the natural vegetation response to projected future changes using an improved version of a dynamic vegetation model (CLM-CN-DV) driven with climate change projections from 19 global climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The simulated equilibrium vegetation distribution under historical climate (1981–2000) has been compared with that under the projected future climate (2081–2100) scenario for Representative Concentration Pathway 8.5 (RCP8.5) to qualitatively assess how natural potential vegetation might change in the future. With one outlier excluded, the ensemble average of vegetation changes corresponding to climates of 18 GCMs shows a poleward shift of forests in northern Eurasia and North America, which is consistent with findings from previous studies. It also shows a general “upgrade” of vegetation type in the Tropics and most of the temperate zones, in the form of deciduous trees and shrubs taking over C3 grass in Europe and broadleaf deciduous trees taking over C4 grasses in Central Africa and the Amazon. LAI and NPP are projected to increase in the high latitudes, southeastern Asia, southeastern North America, and Central Africa. This results from CO₂ fertilization, enhanced water use efficiency, and in the extra-tropics warming. However, both LAI and NPP are projected to decrease in the Amazon due to drought. The competing impacts of climate change and CO₂ fertilization lead to large uncertainties in the projection of future vegetation changes in the Tropics.  相似文献   

Fractal geometry of faults in relation to the 12 October 1992 Cairo earthquake     

Nimr Arab  Asadullah Kazi  Herman H. Rieke 《Natural Hazards》1994,10(3):221-233

The aim of this study is to demonstrate how the 12 October 1992 Cairo earthquake relates to the spatial geometry of the northern Egyptian fault systems. A box-counting algorithm was used, in a focused down approach (from regional to local scales) to analyze the fractal dimensions of the existing faults. The results indicate that these faults display fractal geometries that are self-similar over two to three orders of magnitude. It is shown that the northwest-southeast (Northern Red Sea) trending fault system has the lowest fractal dimension value. Coincidentally, this fault trend is the one that the fault plane solution shows to be active.  相似文献   

Hydrogeology of Wadi Al-Yammaniyah, Saudi Arabia     

Bashir A. Memon  Asadullah Kazi  Abdulghafar S. Bazuhair 《Ground water》1984,22(4):406-411

Quaternary alluvium, ranging in thickness from a few to 100 meters underlain by Precambrian rocks of metamor-phic and igneous origin, constitutes an important source of ground water in Wadi Al-Yammaniyah, Saudi Arabia. The purpose of this report is to assess the hydraulic properties, quality of water, and estimated change in storage in waterbearing rocks in the area. The results of eight pumping tests carried out in hand-dug, large-diameter wells, indicate that the hydraulic conductivity of the alluvial aquifer ranges from 5.6 × 10⁻⁵ to 1.85 × 10⁻³ cm/second (3.36 × 10⁻⁵ to 1.11 × 10⁻³ m/minute) and that its storativity varies from 8.23 × 10⁻² to 1.17 × 10⁻¹. The aquifer is replenished by sporadic but intensive rainfall of short duration. The present withdrawal is only about 10 percent of the annual recharge which is estimated at 52 × 10⁶ m³. It is shown that there is a substantial potential for the future development of potable ground water which would be required for the development of the area.  相似文献   

Finding suitable locations for ecotourism development in Cox’s Bazar using Geographical Information System and Analytical Hierarchy Process     

Kazi Masel Ullah  Roxana Hafiz 《国际地球制图》2013,28(3):256-267

The aim of this study is finding suitable locations for ecotourism development in Cox’s Bazar, Bangladesh. For this, potential ecotourism sites were identified and ranked using Geographical Information System and Analytical Hierarchy Process. Five factors and 15 criteria were identified to evaluate suitability of sites. Factors and criteria were selected based on literature review, local knowledge and experts’ opinions. Considering the national and international contexts and effects of ecotourism, this study proposes treating highly suitable areas more ‘naturally’ and, for conservation programmes, creating tourist facilities in moderately suitable areas by targeting growth centres and protecting agricultural land as well as local primary activities in marginally suitable areas.  相似文献