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This study investigated the groundwater chemistry, suitability, and potential human health risk in the southwest part of Bangladesh. Groundwater samples were collected from the shallow aquifer throughout the study area. A set of different hydro-chemical analyses, water quality indices, multivariate statistics, and geo-statistical models were applied to achieve the study objectives. Study results show the concentration of NH3-N, HCO3−, Ca2+, As, Fe, and Mn exceeded Bangladesh drinking water standards in 94%, 100%, 100%, 73%, 97%, and 91% of samples, respectively. Groundwater quality indices indicate that about 94% of samples are suitable for irrigation, and about 82% are unsuitable for drinking. In the study area, groundwater is mainly Ca2+-Mg2-HCO3− types, and rock-water interactions dominate the mineralization process. Ca2+ > Mg2+ > Na+ > K+, and HCO3− > Cl− > SO42− are the sequential orders of major cation and major anion, respectively. Multivariate analyses show the geogenic origin is predominant over anthropogenic sources. Semivariogram models show moderate to weak spatial dependence. The non-carcinogenic and carcinogenic health risks via oral exposure pathways for adults and children are in the high (97%) and very high (100%) categories, respectively. [ABSTRACT FROM AUTHOR]

This study comprehensively investigated the distribution, source identification, and potential ecological risk of heavy metals (As, Ni, Pb, Cd, Cr, Cu, and Zn) in surface sediments of the Mongla port area of Bangladesh. The sediment samples were collected from ten sampling points during the wet and dry season and heavy metals were analyzed by atomic absorption spectrophotometer. The average concentration of heavy metal in sediments was higher during the dry season (11.36 to 118.55 mg/kg) as compared with the wet season (8.70 to 88.58 mg/kg). Certain indices, including the enrichment factor, geoaccumulation index, and contamination factor demonstrated that Cd was highly responsible for sediment pollution. The range of pollution load index values was 1.12 to 1.55 during wet and 1.59 to 2.27 during the dry season, indicating progressive deterioration of sediments by studied heavy metals. Multivariate principal component analysis showed that the source of As, Cd, Cr, Ni, Cu and, Zn in the port area surface sediment mainly due to anthropogenic activities. Considering the potential ecological risk, surface sediments of the Mongla port area showed moderate to considerable ecological risk. Potential acute toxicity results in most of the sampling points during the dry season was greater than 4, shows moderate to the severe toxicity of heavy metals in sediment. Further studies to assess the widespread risk of heavy metals are recommended to protect the aquatic ecosystem from heavy metal contamination. [ABSTRACT FROM AUTHOR]

This study analyzed the potential use of Mahagoni wood charcoal (MWC) and Mahagoni bark charcoal (MBC) as biosorbent for reactive red 120 (RR 120) dye removal from aqueous solutions. The effect of different operating parameters such as contact time (1-210 min), pH (3-11), adsorbent dose (1-20 g/L), and initial RR 120 concentration (5-70 mg/L) on adsorption processes was studied under batch adsorption experiments. The maximum removal of RR 120 by MWC (78%) and MBC (88%) was achieved when the optimum conditions were initial RR 120 concentration (5 mg/L), pH (3), adsorbents dose (10 g/L) and equilibrium contact time (150 min). The RR 120 adsorption data of MWC and MBC were better described by the Langmuir and Freundlich isotherm models, respectively. The MWC and MBC showed maximum adsorption capacities of 3.806 and 5.402 mg/g, respectively. Kinetic adsorption data of all adsorbents (MWC and MBC) followed the pseudo-second-order model and this adsorption process was controlled by chemisorption with multi-step diffusion. A lower desorption rate advocated that both strong and weak binding forces could exist between RR 120 molecules and adsorbents. The study results revealed that the utilization of either MWC and or MBC as an adsorbent for treating RR 120 is effective and environmentally friendly. [ABSTRACT FROM AUTHOR]