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To investigate the interplay between varying anthropogenic activities and sediment dynamics in an urban river (Turag, Bangladesh), this study involved 37-sediment samples from 11 different sections of the river. Neutron activation analysis and atomic absorption spectrometry were utilized to quantify the concentrations of 14 metal(oid)s (Al, Ti, Co, Fe, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn). This study revealed significant toxic metal trends, with Principal coordinate analysis explaining 62.91 % of the variance from upstream to downstream. The largest RSDs for Zn(287 %), Mn(120 %), and Cd(323 %) implies an irregular regional distribution throughout the river. The UNMIX-model and PMF-model were utilized to identify potential sources of metal(oid)s in sediments. ∼63.65-66.7 % of metal(oid)s in sediments originated from anthropogenic sources, while remaining attributed to natural sources in both models. Strikingly, all measured metal(oid)s' concentrations surpassed the threshold effect level, with Zn and Ni exceeding probable effect levels when compared to SQGs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The uncontrolled release of harmful metal/loids from mega-scale shipbreaking activities in Bangladesh is a significant concern. This study investigated the impact of shipbreaking activities on soil and crop quality and human health in relation to metal/loid contamination. This work covered an area of 1221 km 2 surrounding the shipbreaking yards in Chittagong during the wet and dry seasons between 2019 and 2020. Amongst the sixteen elements measured, the concentrations of Pb, Cd, As, V, Cr, Mn, Cu, Zn, Fe, Co, Ni, and Sn in the soil, rice, and vegetables from the four exposure sites were significantly higher compared to the control site in both seasons. Soil pollution indices indicated moderate to higher contamination levels of Pb, Zn, Cd, As, and Se in 30-50% of soil, supporting their accumulation in food crops. Source apportionment analysis identified uncontrolled shipwrecking operations as the primary anthropogenic activity mainly contributing to metal/loid pollution. Health risk analysis showed inorganic arsenic (estimated), Cd, and Pb in food crops could pose potential health threats to the general population. Spinach leaf and gourd were identified as the highest-risk contributing vegetables in the dry and wet seasons. These findings help to inform management strategies to protect agroecosystems and public health., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

The acidophilic sulfur oxidizing bacterium (SOB), Acidithiobacillus ferrooxidans, has been found to stimulate elemental sulfur (S 0 ) oxidation and mineral weathering in alkaline Fe ore tailings. However, A. ferrooxidans growth and activities depend on the pH conditions surrounding their interfaces with minerals. The present study aimed to investigate how pH influences bacterial growth and functions in Fe ore tailings. A simulated aquatic 'homogeneous' incubation system was initially adjusted into acidic (pH 4), neutral (pH 7) and alkaline (pH 9) conditions, which mimicked the microenvironmental conditions of the water-cell-mineral interfaces in the tailings. It was found that A. ferrooxidans grew well and oxidised S 0 under the prevailing and initially acidic conditions (pH < 6). These stimulated the weathering of biotite and amphibole-like minerals and the formation of nanosized jarosite and ferrihydrite-like minerals mediated by extracellular polymer substrate (EPS). In contrast, the initially neutral/alkaline pH conditions (i.e., pH > 7) with the presence of the alkaline tailings restricted SOB growth and functions in S 0 -oxidation and mineral weathering. These findings suggest that it is essential to prime acidic conditions in microenvironments to support SOB growth, activities, and functions toward mineral weathering in tailings, providing critical basis for involving SOB in eco-engineered pedogenesis in tailings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The Karnaphuli River is one of the prime and most important streams in the southeastern part of Bangladesh. The favorable water current and the geographic location have rendered the Karnaphuly River estuary a suitable habitat and a breeding ground for diverse fish species. Reversely, this estuary has been polluted by discharges from many point and non-point sources due to its location in the catchment area of a heavily industrialized area, Chattagram port city. However, published research concerning the status of toxic and trace elements in some commercially important benthic and pelagic coastal fish species in Karnaphuli River estuary was not found in the existing literature. Therefore, it's an important field of study on the assessment of toxic and trace elements concentration in the commercially important benthic and pelagic coastal fish species and their health taxation in the Karnaphuli River Estuary. Energy dispersive X-ray fluorescence (ED-XRF) was used to quantify trace metal concentration in edible parts of the fish species. This study revealed that the rank of the trace metals concentration was as follows (mg/kg): Zn (37.1) > Mn (16.12) > V (11.16) > Cu (9.49) > Rb (5.62) > Pb (2.98) > Cr (1.59) > Co (1.17). The F-test showed that a significant difference at 95 % confidence level in the distribution pattern of trace metals concentration among the examined fish species in the study area. The metal pollution index (MPI) in the muscle of fishes were found to be in the following order: L. bata > P. monodon > T. cirratus > M. bleekeri > O. pabda > H. nehereus > L. calcarifer > P. argenteus > P. paradiseus > T. toli, and the MPIs for most of the benthic fish species were higher compared to the pelagic fishes. On the other hand, the examined fish species were significantly bio-accumulative with the highest bio-accumulation factor value for benthic species. The multivariate analysis identified that the sources of the trace metals were associated with anthropogenic activities. For the human health risk assessment concern, estimated daily intake, target hazard quotient and cancer-causing risk were estimated. The results for non-cancer hazardous index values were found to be lower than unity. On the other hand, the total cancer risk data ranging from 1.24E-05 to 1.70E-05 were fallen within the range for the threshold values (1.0E-06 to 1.0E-04). However, considering the suggested values set by the environmental and regulatory agencies, it has been recommended that no significant non-carcinogenic and cancer-causing health risk for humans was seen due to the consumption of the studied fish species., Competing Interests: Declaration of competing interest The authors are declaring that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Bauxite residues generated from alumina refineries worldwide have accumulated to more than 4 billion tons, at an annual increment of ~ 0.15 billion tons. It is imperative and urgent for the alumina sector to develop field-operable disposal solutions for rapid and cost-effective stabilisation of alkaline bauxite residues (BR) in the storage facility to minimise/prevent potential environmental risks. Taking advantage of the availability of coal ash (CA) on site, we studied a feasible way to synthesise geopolymer from active (amorphous) aluminosilicate components of BR and CA via the alkaline hydrolysis under ambient conditions. The new geopolymeric binder effectively solidifies BR-CA mixtures into indurated monoliths whose unconstrained compressive strength (UCS) can reach as high as ~ 20 MPa after 8 weeks. The Full Factorial Experimental Design was used to study relative influences of BR:CA ratio, modulus of activating solution, and H 2 O/Na 2 O ratio on UCS. Micro-spectroscopic structural analyses using electron-dispersive X-ray spectroscopy and X-ray Photoelectron Spectroscopy suggested a co-occurrence of cement-like calcium aluminosilicate hydrate (C-A-S-H) and Na-rich aluminosilicate 3D-extended network (geopolymer) within the binder phase. The advantage of this ambient geopolymerisation, without resorting to elevated temperature curing, renders a feasible way of valorising BR and CA for environmental management of alkaline wastes at alumina refineries., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The focus of this study was to determine the depth-wise variability of physicochemical properties (i.e., pH, TOC, TN, and EC), and heavy metals (i.e., Pb, Cu, Zn, As, and Cr) concentration, and the associated biological and ecological risks of the mangrove sediment. The accumulation of metal contents and the phytoremediation and phytoextraction were also investigated in a mangrove species, Acanthus ilicifolius. The mangrove sediment consists of a higher proportion of sand fraction (56.6-74.7%) followed by clay (10-28%) and silt (10.1-15. 7%) fractions. The concentrations (mg/kg) of Pb, Cu, Zn, As, and Cr were ranged from 22.05-34.3, 8.58-22.77, 85.07-114, 5.56-12.91, and 0.98-5.12 in all the sediment layers. The hierarchy of the mean metal concentration in sediment was Zn (102 mg/kg) > Pb (25.6 mg/kg) > Cu (14.8 mg/kg) > As (8.79 mg/kg) > Cr (2.74 mg/kg) respectively. The examined metal concentrations were below the respective average shale values (ASVs). The degree of environmental, ecological, and biological risks was minimal according to various pollution indices like geoaccumulation index (I geo ), contamination factor (CF), and pollution load index (PLI). According to sediment quality guidelines (SQGs), the adverse biological risk effect was not likely to occur. The result of the potential ecological risk index (PERI) demonstrated that the study area was in the low-risk condition as the corresponded RI value < 100. A combined influence of geogenic and anthropogenic factors was identified as the metal sources by multivariate analysis. The study found that the accumulation rate of the metal contents was higher in leaves than that of roots. The mean descending metal concentration values were Zn (107) > Pb (28. 7) > Cu (16.9) > As (11.2) > Cr (4.99) in leaves and Zn (104.32) > Pb (27.02) > Cu (15.29) > As (10.39) > Cr (3.80) in roots. The translocation and bioaccumulation factors of heavy metals suggested that the mangrove plant species, A. ilicifolius can be used for phytoremediation and phytoextraction since the bio-concentration factor and translocation factor > 1. The studied species exhibited the metal tolerance associated with two following strategies, metal exclusion, and metal accumulation. However, excess metal tolerance can impact the surrounding marine environment., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A clear understanding of various hydrogeochemical processes is essential for the protection of groundwater quality, which is a prime concern in Bangladesh. The present study deals with the geochemistry of groundwater at various depths to investigate the hydrogeochemical processes controlling the water quality of Meghna floodplain, the sources and mechanisms of arsenic (As) liberation, and the estimation of carcinogenic and non-carcinogenic health risks (using probabilistic and deterministic approaches) to the adults and children of the Comilla district, central-east Bangladesh. The groundwaters were generally of Ca-Mg-HCO 3 type, and water-sediment interaction was the dominant factor in evolving the chemical signatures. The dissolution of carbonates, weathering of silicates, and cation exchange processes governed the major ion chemistry. Dissolved As concentration ranged from 0.002 to 0.36 mg/L and Monte Carlo simulation-based probabilistic estimation of cancer risk suggested that; (1) ~ 83% of the waters exceeded the higher end of the acceptable limit of 1 × 10 -4 ; (2) the probability of additional cases of cancer in every 10,000 adults and children were on average ~9 and ~5, respectively; (3) adults were more susceptible than children; and (4) ingestion was the main pathway of As poisoning and the contribution of dermal contact was negligible (<1%). According to sensitivity analysis, the duration of exposure to As and its concentration in groundwater posed the greatest impact on cancer risk assessment. However, hydrogeochemical investigations on the sources and mobilization mechanisms of As suggested that the reductive dissolution of Fe and Mn oxyhydroxides was the principal process of As release in groundwater. The oxidation of pyrite and competitive exchange of fertilizer-derived phosphate for the sorbed As were not postulated as the plausible explanation for As liberation., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Extensive catchment modification since European settlement on the eastern coast of Australia results in poor coastal water quality, which poses a major threat for near shore coral communities in the iconic Great Barrier Reef (GBR). Long lived inshore corals have the potential to provide long-term temporal records of changing water quality both pre- and post-anthropogenic modification. However, water quality proxies require more study and validation of the robustness of coral-hosted geochemical proxies for a specific site is critical. This study investigated the long-term (1958-2010) influence of environmental drivers on high-resolution Ba/Ca and Y/Ca proxies obtained from Porites sp. coral from Great Keppel Island, southern GBR, Australia. Geochemical proxy records were influenced by environmental change on a seasonal to decadal scale. Although seasonal oscillations of Ba/Ca and Y/Ca were related to rainfall and discharge from the Fitzroy River catchment, some uncorrelated anomalous peaks were evident throughout the time series. Regardless, the behaviour of these proxies was significantly consistent over the longer time scale. Most long-term drought-breaking floods, including one that occurred in winter, resulted in significant increase in the targeted elemental ratios owing to higher terrigenous sediment flux to the near shore marine environment from a catchment with reduced groundcover. Following this intense flushing event, elemental ratios were reduced in subsequent wet periods as a result of less sediment being available for transport to coastal seawater. Ba/Ca and Y/Ca proxies can be valuable tools in reconstructing multiyear variations in terrestrial runoff and associated inshore water quality. As these proxies and their regional and local controls are better understood they will aid our understanding of how reefs have responded and may respond to changing water conditions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Coral reefs maintain extraordinary biodiversity and provide protection from tsunamis and storm surge, but inshore coral reef health is degrading in many regions due to deteriorating water quality. Deconvolving natural and anthropogenic changes to water quality is hampered by the lack of long term, dated water quality data but such records are required for forward modelling of reef health to aid their management. Reef corals provide an excellent archive of high resolution geochemical (trace element) proxies that can span hundreds of years and potentially provide records used through the Holocene. Hence, geochemical proxies in corals hold great promise for understanding changes in ancient water quality that can inform broader oceanographic and climatic changes in a given region. This article reviews and highlights the use of coral-based trace metal archives, including metal transported from rivers to the ocean, incorporation of trace metals into coral skeletons and the current 'state of the art' in utilizing coral trace metal proxies as tools for monitoring various types of local and regional source-specific pollution (river discharge, land use changes, dredging and dumping, mining, oil spills, antifouling paints, atmospheric sources, sewage). The three most commonly used coral trace element proxies (i.e., Ba/Ca, Mn/Ca, and Y/Ca) are closely associated with river runoff in the Great Barrier Reef, but considerable uncertainty remains regarding their complex biogeochemical cycling and controlling mechanisms. However, coral-based water quality reconstructions have suffered from a lack of understanding of so-called vital effects and early marine diagenesis. The main challenge is to identify and eliminate the influence of extraneous local factors in order to allow accurate water quality reconstructions and to develop alternate proxies to monitor water pollution. Rare earth elements have great potential as they are self-referencing and reflect basic terrestrial input., (Copyright © 2016 Elsevier B.V. All rights reserved.)