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Geochemical characterization of Shahbazpur structure (Bengal Foredeep) in terms of elemental abundances obtained from INAA are presented by investigating core samples from Shabazpur gas-field, Bangladesh. Major oxides' abundances were 12.4–20.8, 0.63–1.03, 4.45–8.02, 0.05–0.09, 2.60–4.10 and 1.31–1.87% for Al2O3, TiO2, Fe2O3(T), MnO, K2O and Na2O, respectively. Elemental ratios and enrichment pattern (× 1.10–2.11 UCC) indicate that sedimentary processes originated from Himalayan felsic source-rock. Weathering index and Th/U(= 5.90–6.59), V/Cr(= 1.07–1.38) ratios revel that sediments/rocks were experienced moderate to high degree of chemical weathering with oxidizing environment. La-Th-Sc immobile trace elements diagram invoke depositional tectonic settings which was transitional between active and passive continental margin. [ABSTRACT FROM AUTHOR]

• We evaluated the geochemical composition of Padma River sediments. • Major, Trace, REEs were determined to infer the provenance, weathering and tectonic. • Sediments were derived from felsic to intermediate source rock. • Sediments were deposited under semi-arid to semi-humid climatic conditions. • Different Himalayan Rivers are compared with Padma River sediments. The major, trace, and rare earth element (REE) compositions of sediments from the Padma River, Bangladesh have been examined using XRF and INAA analysis to determine their geochemical compositions, provenance, climate, weathering intensity and tectonic setting. The Padma River sediments from the region were remarkably comparable, demonstrating elemental depletion and pointing to a low geochemical maturation. Sediment samples are classified as arkose which are considered as chemically immature sediments, deposited under semi-arid to semi-humid climatic conditions due to the weakening of Indian summer monsoon. The low CIA values (48.6–58.8), PIA (48.1–63.4) and Rb/Sr ratios of the river sediments suggest low intensity of chemical weathering in the source area. The Padma River is originated from the Higher Himalaya and the sediments derived from metasediments (Higher Himalayan Crystalline Series) as are evident by major, trace elements discriminate diagram and REE pattern. Most of the sand samples were derived from felsic source rock (granite) whereas some samples are plotted in the intermediate rock types (granodiorite) in the A-CNK-FM and discriminant function diagrams. High LREE enrichment and relatively flat HREE fractionation in chondrite-normalized REE patterns (La N /Yb N = 7.50–13.20) demonstrated felsic source origin. TiO 2 versus Zr plot shows that Padma River sediments have felsic to intermediate provenance. According to Log (K 2 O/Na 2 O) vs. SiO 2 discriminant diagram and La–Th–Sc, Th–Sc–Zr/10 ternary plot, the Padma River sediments were deposited in passive continental margin. The Padma River sediments have been compared with Yarlung Zangbo River (YZR), Brahmaputra-Jamuna River (BJR), Ganges River (GR) and Upper Meghna River (UMR), which results suggest that there is contrast among the sediments of different Himalayan Rivers in relation to provenance, weathering intensity and tectonic setting. [ABSTRACT FROM AUTHOR]

An anthropogenically less affected transboundary river (Punarbhaba, Bangladesh) was studied to detect associated risks from the combined origin(s) of geochemically and toxicologically significant elements in benthic sediments. A total of 30 river bed sediments were analyzed by instrumental neutron activation analysis targeting the 15 chemical elements viz. , Na, Al, K, Ti, Cr, Mn, Co, Zn, As, Rb, Sb, Cs, Ba, Th, and U. Among the estimated elements, the mean abundances (μg/g) of Rb (136), Sb (0.66), Cs (6.66), Th (14.6), and U (3.92) were 1.4–1.7 times higher than the crustal origin. These elements are primarily responsible for the contaminated state of the Punarbhaba River. The studied area is 'moderately polluted' (I geo : 2.01 to 0.02) and possesses 'minor enrichment' (EF: 1.98 to 0.48) in terms of the measured elements. The output of statistical analyses projected that the studied elements are geochemically fractionated in an oxidizing environment (U/Th = 0.44) and mostly originated from felsic sources, thus confirming the mineral is comprised of aluminosilicates and alkali feldspar. However, SQGs-based and ecological risk indices invoked minor (Cr: 6.67%) to no potential ecotoxicological threats for Cr, Mn, Co, Zn, As, and Sb. Nonetheless, altered distribution patterns caused by geogenic activities increased Cr and Zn in the environment which may cause toxicity (Cr: 22–53%, Zn: 35–70%), and pose potential ecological risks, specifically in upstream locations (P-2, P-3, P-5). Further, this study broadened the perspective of sediment deposition from fractionation, fluvial transportation, and weathering events beyond the industrial disintegration of elements, which will aid researchers and policymakers to comprehend combined risks from suspended sediments. [ABSTRACT FROM AUTHOR]