Quaternary stratigraphy, sediment characteristics and geochemistry of arsenic-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in central Bangladesh

摘要: Abstract This study focuses on the Quaternary stratigraphy, sediment composition, mineralogy, and geochemistry of arsenic (As)-contaminated alluvial aquifers in Ganges–Brahmaputra floodplain central Bangladesh. Arsenic concentrations 85 tubewells Manikganj area, 70 km northwest Dhaka City, range from 0.25 µg/L to 191 µg/L with a mean concentration 33 µg/L. Groundwater is mainly Ca–HCO 3 type high dissolved As, Fe, Mn, but low level SO 4 . The uppermost aquifer occurs between 10 m 80 m below surface that has 35 µg/L. Deeper (> 100 m depth) 18 µg/L. Sediments upper are mostly gray dark-gray, whereas sediments deep yellowing-gray brown. Quartz, feldspar, mica, hornblende, garnet, kyanite, tourmaline, magnetite, ilmenite major minerals both aquifers. Biotite potassium feldspar dominant shallow aquifer, although plagioclase garnet abundant sediments. Sediment composition suggests mixed provenance supplies orogenic belts cratons. High found within 50 m drilled core samples. Statistical analysis shows Ca, P strongly correlated Concentrations Cd, Cu, Ni, Zn, Bi also show strong correlations cores. Authigenic goethite concretions, possibly formed by bacteria, sediments, which contain as 8.8 mg/kg. associated fine-grained were derived recycled orogens relatively rapidly deposited meandering channels during Early Middle Holocene rising sea-level conditions.