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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]

This study has been conducted on an anthropogenically less influenced transboundary river (Atrai: Indo-Bangladesh) to comprehend the inherent geochemistry and identify potential elemental sources. In doing so, across the Bangladeshi portion, 30 river-bed samples were culled and studied by neutron activation analysis to quantify the abundances of 15 geochemically and toxicologically significant elementals (Na, Al, K, Ti, Cr, Mn, Co, Zn, As, Rb, Sb, Cs, Ba, Th, and U). The results revealed that the mean concentrations (μg/g) of Rb (154.6), Cs (7.53), Th (20.90), and U (4.88) were 1.5–2.0 times higher than crustal values. Besides, geo-environmental indices revealed 'uncontaminated to moderately contaminated' pollution status with minor enrichment or contamination for Rb, Th, Sb, U, and Cs, relatively concentrated in the mid-to-downstream zone possessed geogenic and non-crustal origins. The positive matrix factorization and other statistical approaches revealed predominant geogenic enrichment of Na, K, Al, Ti, Zn, Cs, Rb, As, Th, and U from differential mineralogical compositions via weathering, elemental fractionations, and biogeochemical mobilization. Contrariwise, several anthropogenic sources (for Cr, Sb, Co, Mn, Th) were also ascertained in the vicinity of Atari River. However, sediment characterization based on SQG threshold values manifested that Cr and Mn possess rare biological effects on local aquatic organisms. Nevertheless, SQGs-based and ecological risk indices invoked minor to no potential ecotoxicological intimidations for the considered metal(oid)s (Cr, Mn, Co, Zn, As, and Sb). Hence, this study manifested the usefulness of a less anthropogenically affected river to reckon geogenic and non-crustal elemental origins in the compounded riverine sediment. • Elemental abundances in an Indo-Bangla transboundary river sediments are presented. • Mean concentrations of Rb, Cs, Th & U were 1.5–2.0 times higher than crustal values. • Among the divergent sources, fluvial actions-based geogenic origins are predominant. • Mineralogical sorting governs the elemental distributions. • SQGs-based ecotoxicological and ecological indices invoke trivial risks. [ABSTRACT FROM AUTHOR]