Muneki Mitamura

Geological structure of an arsenic-contaminated aquifer at Sonargaon, Bangladesh

Continuous sediment core samples and groundwater were collected in the northern part of Sonargaon, central Bangladesh, to document the hydrogeological constraints on As‐contaminated aquifers. The study area spans the alluvial plain of the Old Brahmaputra River and a Pleistocene terrace, the Madhupur Tract. The Quaternary sequence comprises Plio‐Pleistocene sand, Upper Pleistocene mud, and Holocene sand units. Highly As‐contaminated groundwater (50–1000 μg/L) is found in the upper aquifer, corresponding to the Holocene sand unit that underlies the alluvial plain, and it plausibly appears to be closely related to the distribution of lenses of silt to fine sand. As‐free (<1 μg/L) groundwater occurs only within sediments coarser than medium sand. Highly As‐contaminated groundwater is characterized by low concentrations of Cl− and \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Possible Age Models for Lake Onuma Lacustrine Sediments Based on Tuffs Recovered in Three Cores

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A geochemical study of redox behavior of As in a contaminated aquifer from Sonargaon, Central Bangladesh

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Quaternary stratigraphy of the Osaka Plain, central Japan and its correlation with oxygen isotope record from deep sea cores

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Variations in the redox state of As and Fe measured by X-ray absorption spectroscopy in aquifers of Bangladesh and their effect on As adsorption

\end{document} , suggesting that the As is released in association with reduction of water recharged during rainy season. The restricted occurrence of strongly As‐contaminated (>100 μg/L) groundwater is associated with (1) the intercalation of silt to fine‐sand lenses in the Holocene sandy aquifer, (2) the stagnant condition of the aquifer along the buried valley, and (3) the vertical infiltration of groundwater in close proximity to installed tube wells.

Stratigraphy and Correlation of the Plio-Pleistocene Volcanic Ash Layers from a 1, 700m Core Taken from Higashinada, Kobe City, Southwestern Japan

Abstract A 3.5-km-long shallow seismic reflection profile was acquired along Yodo riverbank across the active Uemachi fault, Osaka City, Japan. The study aimed to explore the subsurface geological structures in and around the Uemachi active fault system and to assess the feasibility of using reflection seismology to investigate subsurface structure in urban areas where large amount of cultural noise is expected to interfere with the seismic signal. Field recording parameters were adapted to the accessibility limitation and safety precautions in the study area. The quality of collected data was marginal and the signal to noise (S/N) ratio was considerably low. The data processing involved intensive frequency–wave number (f–k) filtering and summing adjacent common midpoints (CMPs) before stack as well as weighted stacking. The f–k filtering removed most of the ground roll and guided waves while summation of adjacent common midpoints increased the fold and enhanced the apparent signal to noise ratio of the final section. Trace weighting before stack was remarkably effective in increasing the identity and continuity of reflections. The visual and statistical comparison between weighted stack and the basic stack proved that weighted stacking produces significantly more coherent section. The interpretation of the final seismic section and the correlation with the borehole data in the vicinity confirmed the location of the Uemachi fault plane. The fault is shown in the seismic section as a reverse fault that dips to the east with an angle of about 75°. The seismic line also revealed the possibility of the presence of other two shallow faults on the hanging wall of the Uemachi fault. The two faults are dipping to the same dip direction of Uemachi fault with slightly larger dip angle.