Sediments from stable sand bars along a 40 km section of the Brahmaputra River in northern Bangladesh were analyzed for their major, trace and rare earth element contents to determine their provenance, compositional maturity, source area weathering and tectonic setting. Geochemically, the sediments were classified as litharenites and the Index of Compositional Variability (ICV) varied between 1.4 and 2.0, indicating low compositional and mineralogical maturity. A high mean SiO₂ concentration (72.9 wt.%) and low Al₂O₃ (11.1 wt.%) were consistent with a low abundance of shale and clay components. The depletion of the oxide components Na₂O, CaO and K₂O relative to average upper crustal compositions (UCC) reflected loss of feldspar during chemical weathering in the source region. Average TiO₂ values for most samples were higher than average crustal levels, consistent with the northern section of the Brahmaputra River being a potential resource for valuable Fe-Ti oxide heavy minerals. Major and trace element ratios indicated the sediments represented erosional products from typical felsic upper continental crustal materials with contamination (30%–40%) from more intermediate/mafic compositions. The rare earth element patterns showed negative Eu anomalies (0.57–0.71), indicating they were derived mainly from fractionated felsic rocks. Resemblance of the sediment compositions to mean compositions from Higher Himalaya crystalline rocks pointed to these being potential source rocks but with components from a mafic source also present. Major element chemistries and low to intermediate weathering indices for all sediments indicated a lack of substantial chemical weathering. Evidence from tectonic discrimination diagrams suggested the Brahmaputra River sediments were derived from rock types that formed in a transitional tectonic setting ranging from an ancient passive margin to an active continental margin. Deposition occurred under cool to semi-arid climatic conditions in an oxic environment.

Groundwater provides the largest source of usable water storage in Bangladesh. Groundwater samples have been analyzed for Fe, Mn, Zn, Ni, Cr, Cu, Cd, Pb, and Co using atomic absorption spectrophotometer to evaluate the heavy metal distribution and contamination level at the southeastern coastal area of Bangladesh. Heavy metals in water samples are in the range of Fe (490–4710 µg/L), Mn (13–1970 µg/L), Zn (70–550 µg/L), Ni (42–255 µg/L), Cr (25–133 µg/L), Cu (34–95 µg/L), Cd (7–26 µg/L), Pb (0–20 µg/L), and Co (43–141 µg/L). The mean concentration of Cr, Cd, Fe, Mn, and Ni exceeded the Bangladesh standards for drinking water. Application of Pearson correlation, principal component analysis (PCA), cluster analysis (CA) and hierarchical cluster analysis (HCA) indicate that groundwater of the study area are influenced by both geogenic and anthropogenic sources of the heavy metals. Heavy metal evaluation index (HEI), degree of contamination (Cd) and heavy metal pollution index (HPI) are employed to evaluate the overall pollution level of groundwater estimating 40, 27 and 60% of samples respectively and exhibit the medium degree of pollution.

Radon (²²²Rn), a radioactive and gaseous progeny of Uranium (²³⁸U) decay series, accounts for almost 50% of the total background radiation in our dwelling environment. Inhalation and ingestion of radon in excessive amounts pose serious health effects to humans. The first-ever measurement of radon concentration in commercial bottled water available in Dhaka city and deep well water samples from the campus of the University of Dhaka was carried out using the RAD7 Radon monitoring system. The concentration of radon in the bottled water ranged from 0.11 Bq/L to 1.30 Bq/L with a mean of 0.59 Bq/L, and the deep well water showed a mean of 4.88 Bq/L with a range of 3.02 Bq/L to 5.98 Bq/L. All twenty-five samples of water had radon concentrations within the recommended limits of USEPA and WHO. The mean annual effective doses from radon in bottled water and deep well water were evaluated to be 0.126 µSv/y and 12.481 µSv/y, respectively. Although the calculated doses indicate the least potential risk according to WHO and UNSCEAR, however, it is expected that the present results play an important role in setting up a national guideline for radon in drinking water, and the monitoring of radon for the safety of public health.