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Sediment samples from the Gomti River basin were investigated to determine and evaluate trace metal concentrations, their biological effect, and potential ecological and human health risks for adults and children. The mean concentrations of trace metals were organized in the descending order of mercury (Hg) (0.08 mg/kg) > chromium (Cr) (0.06 mg/kg) > lead (Pb) (0.05 mg/kg) > arsenic (As) (0.02 mg/kg) > cadmium (Cd) (0.01 mg/kg). The current study illustrated that metals were attributed to the area from natural sources and different anthropogenic sources especially from industries. However, the concentration levels were lower than the sediment quality guidelines (SQGs) based on the effect-range classifications of threshold effect concentration (TEC) and probable effect concentration (PEC). Therefore, the concentration of the elements showed no adverse biological effects on aquatic organisms. The evaluated potential ecological risk index also revealed the low toxicity to the aquatic environment. Moreover, the applied sediment quality indices, geo-accumulation index (Igeo), contamination factor (CF), and contamination severity index (CSI) suggested that the contamination levels of the elements were in the acceptable range, and the contamination had not notably impacted on the sediment quality. The risk index (HI) concerning age groups was significantly less than the threshold limit of 1 indicating that the contamination had no non-carcinogenic risk effect. The total carcinogenic risk (TCR) was less than a risk value of 1 × 10−4. Hence, the current study suggests that immediate remediation is not required due to an absence of alarming conditions in the study area. Proper monitoring of the attribution of the metal elements should be done for the betterment of human and environmental health.

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.

Sediment samples were collected from twelve selected sites of the Sangu River estuary and seven metals (As, Cr, Cu, Cd, Pb, Ni, Zn) were analyzed with Inductively Coupled Plasma-mass Spectrometry (ICP-MS) to assess the contamination degree of heavy metals in the Sangu River estuary and to represent it as a reference site. This study revealed the descending order of studied metals (mg/kg) observed in sediment as Zn (88.97 ± 58.97) > Ni (32.75 ± 16.09) > Cu (29.2 ± 10.78) > Cr (25.14 ± 5.20) > Pb (19.57 ± 7.01) > As (2.58 ± 2.55). Cadmium was observed below the detection level. Various indices like geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI) suggested that the Sangu River estuary is not contaminated by studied metals excepting Pb. PCA and correlation matrix analysis indicates that Pb and Zn may have anthropogenic sources and As, Ni, Zn, Cu, Cr may come from natural sources.

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 (Igeo), 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 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.

This study describes the distribution of five heavy metals in water of the Gomti River and the evaluation of human health risk for both adults and children. Metal contents were detected using ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Analysis of results revealed that the range of concentrations were arranged as descending order (mg/l) of Hg (0.118−0.125) > Pb (0.022−0.170) > Mn (0.002−0.098) > As (0.014−0.028) > Cd (0.004−0.007). As the level of metals exceeded some international standards, water from this river is not suitable for drinking. However, the selected metals were justified to recognize a non-carcinogenic risk of hazard quotient (HQ). The estimated hazard index (HI) was in the acceptable limit (HI