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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Paleopedology and magnetic properties of Sari loess-paleosol sequence in Caspian lowland,northern Iran     

Hamed NAJAFI  Alireza KARIMI  Gholam Hosain HAGHNIA  Farhad KHORMALI  Shamsollah AYOUBI  Hossein TAZIKEH 《山地科学学报》2019,(7)

The objective of this study was to characterize the morphological and magnetic properties of Sari loess-paleosol section in northern Iran for paleopedologic and paleoenvironmental interpretation. The section consisted of a modern soil(MS) and three paleosols(PS_1, PS_2, PS_3) separated by loess layers(LS_1, LS_2 and LS_3). Based on particle size distribution, clay mineralogy, carbonates distribution and size of secondary carbonates, pedogenic development of the soils was in order of PS_3PS_2PS_1=MS. Presence of redoximorphic features in PS_3 was attributed to alternate stagnic saturation due to local water or high precipitation. Dominance of smectite and vermiculite as well as large carbonated dolls in PS_3 indicated suitable environment and sufficient time for pedogenic development. Magnetic properties(χ~(lf) and χ~(fd)%) were distinctly higher in MS, PS_1 and PS_2 when compared to loess layers. The Lowest magnetic properties values were observed in PS_3 which can be the result of ferrimagnetic minerals destruction under hydromorphic conditions. The highest Fe_d content occurred in PS_3, however, low χ~(lf)/Fe_d ratio indicated that majority of the iron minerals in PS_3 are not magnetic. In conclusion, the particle size distribution, clay mineralogy and carbonates features were indicative of pedogenesis intensity, whereas, magnetic properties were useful to characterize the pedogenic environment.  相似文献   

A model for soil surface evaporation based on Campbell’s retention curve     

Ghasem Zarei  Mehdi Homaee  Abdol Majid Liaghat  Abdol Hosain Hoorfar 《Journal of Hydrology》2010,380(3-4):356-361

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The Impact of the Degree of Aquifer Confinement and Anisotropy on Tidal Pulse Propagation          下载免费PDF全文

Pin Shuai  Peter S. K. Knappett  Saddam Hossain  Alamgir Hosain  Kimberly Rhodes  Kazi Matin Ahmed  M. Bayani Cardenas 《Ground water》2017,55(4):519-531

Oceanic tidal fluctuations which propagate long distances up coastal rivers can be exploited to constrain hydraulic properties of riverbank aquifers. These estimates, however, may be sensitive to degree of aquifer confinement and aquifer anisotropy. We analyzed the hydraulic properties of a tidally influenced aquifer along the Meghna River in Bangladesh using: (1) slug tests combined with drilling logs and surface resistivity to estimate Transmissivity (T); (2) a pumping test to estimate T and Storativity (S) and thus Aquifer Diffusivity (D_PT); and (3) the observed reduction in the amplitude and velocity of a tidal pulse to calculate D using the Jacob‐Ferris analytical solution. Average Hydraulic Conductivity (K) and T estimated with slug tests and borehole lithology were 27.3 m/d and 564 m²/d, respectively. Values of T and S determined from the pumping test ranged from 400 to 500 m²/d and 1 to 5 × 10^?4, respectively with D_PT ranging from 9 to 40 × 10⁵ m²/d. In contrast, D estimated from the Jacob‐Ferris model ranged from 0.5 to 9 × 10⁴ m²/d. We hypothesized this error resulted from deviations of the real aquifer conditions from those assumed by the Jacob‐Ferris model. Using a 2D numerical model tidal pulses were simulated across a range of conditions and D was calculated with the Jacob‐Ferris model. Moderately confined (K_top/K_aquifer < 0.01) or anisotropic aquifers (K_x/K_z > 10) yield D within a factor of 2 of the actual value. The order of magnitude difference in D between pumping test and Jacob‐Ferris model at our site argues for little confinement or anisotropy.  相似文献