Heavy metals (HMs) are ubiquitous in terrestrial and aquatic environments due to unplanned industrial waste discharge, the release of untreated wastewater, and improper mining activities. In particular, the concentrations of HMs are found to be higher in aquatic environments. As a result, the aquatic biota was heavily affected by HM contamination. This critical review aims to understand the sources and toxicity of HMs in commercial fish species, explore their ecological exchange, and examine the related human health challenges in Bangladesh. A modified PRISMA review technique is used in this paper to analyze the current status and research limitations of HM studies in Bangladesh fish species and their toxicity within aquatic food webs. Briefly, we searched several keywords to explore the research trend of HM concentrations and toxicity in fish species. Furthermore, potential toxicity and risk assessment of HMs through the aquatic food chain in Bangladesh were explored. On the other hand, a cross-tabulation approach was used to process the toxicity findings of HMs. Previous studies indicate that fish species can possess comparatively higher HMs than river water due to ecological exchange factors, including bioaccumulation and biotransformation. This review focuses on Bangladesh, highlighting areas for improvements and the need for further study to achieve a transparent understanding of HM deposition in fish species and the sustainable management of aquatic food chain toxicity.

A key component in a nation's economic progress is industrialization, however, hazardous heavy metals that are detrimental to living things are typically present in the wastewater produced from various industries. Therefore, before wastewater is released into the environment, it must be treated to reduce the concentrations of the various heavy metals to maximum acceptable levels. Even though several biological, physical, and chemical remediation techniques are found to be efficient for the removal of heavy metals from wastewater, these techniques are costly and create more toxic secondary pollutants. However, phytoremediation is inexpensive, environmentally friendly, and simple to be applied as a green technology for heavy metal detoxification in wastewater. The present study provides a thorough comprehensive review of the mechanisms of phytoremediation, with an emphasis on the possible utilization of plant species for the treatment of wastewater containing heavy metals. We have discussed the concept, its applications, advantages, challenges, and independent variables that determine how successful and efficient phytoremediation could be in the decontamination of heavy metals from wastewater. Additionally, we argue that the standards for choosing aquatic plant species for target heavy metal removal ought to be taken into account, as they influence various aspects of phytoremediation efficiency. Following the comprehensive and critical analysis of relevant literature, aquatic plant species are promising for sustainable remediation of heavy metals. However, several knowledge gaps identified from the review need to be taken into consideration and possibly addressed. Therefore, the review provides perspectives that indicate research needs and future directions on the application of plant species in heavy metal remediation.

Salt marshes are highly productive and valuable coastal ecosystems that act as filters for nutrients and pollutants at the land-sea interface. The salt marshes of the mid-Atlantic United States often exhibit geochemical behavior that varies significantly from other estuaries around the world, but our understanding of metal mobility and bioavailability remains incomplete for these systems. We sampled abiotic (water and sediment) and native biotic (three halophyte and two bivalve species) compartments of a southeastern United States salt marsh to understand the site- and species-specific metal concentrations, fractionation, and bioavailability for 16 metals and metalloids, including two naturally occurring radionuclides. Location on the marsh platform greatly influenced metal concentrations in sediment and metal bioaccumulation in halophytes, with sites above the mean high-water mark (i.e., high marsh zone) having lower concentrations in sediment but plants exhibiting greater biota sediment accumulation factors (BSAFs). Transition metal concentrations in the sediment were an average of 6× higher in the low marsh zone compared to the high marsh zone and heavy metals were on average 2× higher. Tissue- and species-specific preferential accumulation in bivalves provide opportunities for tailored biomonitoring programs. For example, mussel byssal threads accumulated ten of the sixteen studied elements to significantly greater concentrations compared to soft tissues and oysters had remarkably high soft tissue zinc concentrations (~5000 mg/kg) compared to all other species and element combinations studied. Additionally, some of our results have important implications for understanding metal mobility and implementing effective remediation (specifically phytoremediation) strategies, including observations that (1) heavy metals exhibit distinct concentration spatial distributions and metal fractionation patterns which vary from the transition metals and (2) sediment organic matter fraction appears to play an important role in controlling sediment metal concentrations, fractionation, and plant bioavailability.

The Cikijing River is one of the rivers of the Citarik River Basin, which empties into the Citarum River and crosses Bandung Regency and Sumedang Regency, Indonesia. One of the uses of the Cikijing River is as a source of irrigation for rice fields in the Rancaekek area, but the current condition of the water quality of the Cikijing river has decreased, mainly due to the disposal of wastewater from the Rancaekek industrial area which is dominated by industry in the textile and textile products sector. This study aims to determine the potential ecological risks and water quality of the Cikijing River based on the content of heavy metals (Cr, Cu, Pb, and Zn). Sampling was carried out twice, during the dry and rainy seasons at ten different locations. The selection of locations took into account the ease of sampling and distribution of land use. Based on the results of this study, it was found that the water quality of the Cikijing River was classified as good based on the content of heavy metals (Cr, Cu, Pb, and Zn) with a Pollution Index 0.272 (rainy season) and 0.196 (dry season), while for the sediment compartment of the Cikijing River, according to the geoaccumulation index (Igeo) were categorized as unpolluted for heavy metals in rainy and dry seasons Cr (-3.16 and -6.97) < Cu (-0.59 and -1.05), and Pb (-1.68 and -1.91), heavily to very heavily polluted for heavy metals Zn (4.7 and 4.1) . The pollution load index (PLI) shows that the Cikijing River is classified as polluted by several heavy metals with the largest pollution being Zn> Cu > Pb > Cr. Furthermore, the results of the analysis using the Potential Ecological Risk Index (PERI) concluded that the Cikijing River has a mild ecological risk potential in rainy season (93.94) and dry season (96.49). The correlation test results concluded that there was a strong and significant relationship between the concentrations of heavy metals Pb and Zn and total dissolved solids, salinity, and electrical conductivity in the water compartment.

Coastal sediments act as sinks of sediment organic matter (SOM) and metals because of their special land-sea location and depositional properties. However, there are few reports on the correlation between the sources of organic matter (OM) and associated potential toxic metals (PTMs). In this study, we combined CN stable isotope analysis and positive matrix factorization to identify the matter and metal sources of OM and glomalin-related soil protein (GRSP) in an estuary under several decades of urbanization. The results of the positive matrix factorization (PMF) reveal a correlation between the sources of total sediment metals and the sources of OM-related metals. The sources of both SOM-bound PTMs and GRSP-bound PTMs are significantly related to the sources of total PTMs. OM sources were elucidated through 13C-15 N stable isotopes, and the potential sources of different types of OM differed. In addition, there is a significant correlation between OM-associated PTMs and organic matter sources. Interestingly, the functional groups of SOM were mainly influenced by multiple PTM sources but no OM source, while the functional groups of GRSP were regulated by a single metal source and OM source. This study deepened the understanding of the coupling between PTMs and SOM. The possibility of combined use of positive matrix factorization and 13C-15 N stable isotope tracing of metals as well as the sources of each metal fractions has been evaluated, which will provide new insights for the transportation of PTMs.

Mining activity is one of the main sources to pollute soil, water and plants. An analysis of soil and plant samples around the Atrevida mining area in Catalonia (NE Spain) was preformed to determine potentially harmful elements (PHEs). Soil and plant samples were taken at eight locations around the mining area. The topsoil (0-15 cm) samples were analysed for physico-chemical properties by standard methods, by ICP-MS for Cd, Co, Cr, Cu, Fe, Ni, Pb and Zn, and were microwave-digested. Plant, root and shoot samples were digested separately, and heavy metals were analysed by AAS. Translocation factor (TF), biological concentration factor (BCF) and biological accumulation factor (BAF) were determined to assess the tolerance strategies developed by native species and to evaluate their potential for phytoremediation purposes. Soil pH was generally acid (5.48-6.72), with high soil organic matter (SOM) content and a sandy loamy or loamy texture. According to the agricultural soil values in southern Europe, our PHEs concentrations exceeded the toxicity thresholds. The highest root content of the most studied PHEs appeared in Thymus vulgaris L. and Festuca ovina L., while Biscutella laevigata L. accumulated more PHEs in shoots. The TF values were > 1 in B. laevigata L., but BAF obtained < 1, except Pb. B. laevigata L., and can be considered potentially useful for phytoremediation for having the capacity to restrict the accumulation of large PHEs amounts in roots and Pb translocation to shoots.

Functioning of coastal wetland habitats is essential for the ecosystem integrity and sustainability of coastal development that enables human progress along transitional waterways. However, these habitats are continuously being affected by a variety of pollutants including metallic elements. In this study, seasonal variation, pollution status and ecological risks of heavy metals (Cr, Mn, Co, Ni, As, Cu, Zn and Pb) in surface sediment of the several types of coastal wetlands (estuaries, mudflats, sandy beaches, mangroves, and saltmarshes) were detected by using X-ray fluorescence (EDXRF) spectrometry. The results showed that the mean concentration level of metals in the surficial sediment samples followed the order of Cu (84.06 ± 8.60 μg/g) > Zn (51.00 ± 8.97 μg/g) > Mn (38.25 ± 11.34 μg/g) > Cr (3.52 ± 0.91 μg/g) > Pb (0.27 ± 0.13 μg/g) > Co (0.24 ± 0.13 μg/g) > As (0.21 ± 0.12 μg/g) > Ni (0.16 ± 0.08 μg/g). In comparison to the pre-monsoon period, the post-monsoon season had higher concentrations of heavy metals while the overall accumulation level of metals in the wetlands exhibited a pattern of estuarine wetland (28.47 ± 31.35 μg/g) > mangrove (22.23 ± 30.79 μg/g) > mudflat (21.79 ± 29.71 μg/g) > sandy beach (21.47 ± 28.15 μg/g) > saltmarsh (21.28 ± 30.02 μg/g). Although, the pollution assessment indices e.g., contamination factor (CF), degree of contamination (CD), geoaccumulation index (Igeo) and pollution load index (PLI) showed minimal levels of contamination in the studied sites, enrichment factor (EF) suggested greater enrichment of the metals in the pre-monsoon season but with the lowest ecological risk (RI < 40) in both seasons. Cluster analysis, principal component analysis (PCA), and Pearson's correlation were performed to determine the sources of heavy metals in collected samples which specified that Pb, As, Co and Ni predominantly came from natural sources whereas Cu, Mn, Zn and Cr emerged from anthropogenic sources such as industrial effluents, domestic wastewater, fertilizer or pesticide consumption on farmland along the riverbank, vessel emissions, and the confluence of tributary rivers.

Contamination of the natural ecosystem by heavy metals, organic pollutants, and hazardous waste severely impacts on health and survival of humans, animals, plants, and microorganisms. Diverse chemical and physical treatments are employed in many countries, however, the acceptance of these treatments are usually poor because of taking longer time, high cost, and ineffectiveness in contaminated areas with a very high level of metal contents. Bioremediation is an eco-friendly and efficient method of reclaiming contaminated soils and waters with heavy metals through biological mechanisms using potential microorganisms and plant species. Considering the high efficacy, low cost, and abundant availability of biological materials, particularly bacteria, algae, yeasts, and fungi, either in natural or genetically engineered (GE) form, bioremediation is receiving high attention for heavy metal removal. This report comprehensively reviews and critically discusses the biological and green remediation tactics, contemporary technological advances, and their principal applications either in-situ or ex-situ for the remediation of heavy metal contamination in soil and water. A modified PRISMA review protocol is adapted to critically assess the existing research gaps in heavy metals remediation using green and biological drivers. This study pioneers a schematic illustration of the underlying mechanisms of heavy metal bioremediation. Precisely, it pinpoints the research bottleneck during its real-world application as a low-cost and sustainable technology.

Anthropogenic toxins are discharged into the environment and distributed through a variety of environmental matrices. Trace contaminant detection and analysis has advanced dramatically in recent decades, necessitating further specialized technique development. These pollutants can be mobile and persistent in small amounts in the environment, and ecological receptors will interact with it. Despite the fact that few researches have been undertaken on invertebrate exposure, accumulation, and biological implications, it is apparent that a wide range of pollutants can accumulate in the tissues of aquatic insects, earthworms, amphipod crustaceans, and mollusks. Due to long-term stability during long-distance transit, a number of chemical and microbiological agents that were not previously deemed pollutants have been found in various environmental compartments. The uptake of such pollutants by the aquatic organism is done through the process of bioaccumulation when dangerous compounds accumulate in living beings while biomagnification is the process of a pollutant becoming more hazardous as it moves up the trophic chain. Organic and metal pollution harms animals of every species studied so far, from bacteria to phyla in between. The environmental protection agency says these poisons harm humans as well as a variety of aquatic organisms when the water quality is sacrificed in typical wastewater treatment systems. Contrary to popular belief, treated effluents discharged into aquatic bodies contain considerable levels of Anthropogenic contaminants. This evolution necessitates a more robust and recent advancement in the field of remediation and their techniques to completely discharge the various organic and inorganic contaminants.

Plants in coastal ecosystems are primarily known as natural sinks of trace metals and their importance for phytoremediation is well established. Salvadora persica L., a medicinally important woody crop of marginal coasts, was evaluated for the accumulation of metal pollutants (viz. Fe, Mn, Cu, Pb, Zn, and Cr) from three coastal areas of Karachi on a seasonal basis. Korangi creek, being the most polluted site, had higher heavy metals (HM's) in soil (Fe up to 17,389, Mn: 268, Zn: 105, Cu: 23, Pb: 64.7 and Cr up to 35.9 mg kg^-1) and S. persica accumulated most of the metals with >1 TF (translocation factor), yet none of them exceeded standard permissible ranges except for Pb (up to 3.1 in roots and 3.37 mg kg^-1 in leaves with TF = 11.7). Seasonal data suggested that higher salinity in Clifton and Korangi creeks during pre- and post-monsoon summers resulted in lower leaf water (ΨW_o) and osmotic potential at full turgor (ΨS_o) and bulk elasticity (ε), higher leaf Na⁺ and Pb but lower extractable concentrations of other toxic metals (Cr, Cu, and Zn) in S. persica. Variation in metal accumulation may be linked to metal speciation via specific transporters and leaf water relation dynamics. Our results suggested that S. persica could be grown on Zn, Cr and Cu polluted soils but not on Pb affected soils as its leaves accumulated higher concentrations than the proposed limits.

The coastal zone of Bangladesh, with a population density of 1278 people per square kilometer, is under serious threat due to heavy metal pollution. To date, many studies have been conducted on the heavy metal contamination in soils, water, aquatic animals, and plants in the coastal zone of Bangladesh; however, the available information is dispersed. In this study, previous findings on the contamination levels, distributions, risks, and sources of heavy metals in sediments and organisms were summarized for the first time to present the overall status of heavy metal pollution along coastal regions. Earlier research found that the concentrations of various heavy metals (HMs), particularly Co, Cd, Pb, Cu, Cr, Mn, Fe, and Ni in water, sediment, and fish in most coastal locations, were above their permissible limits. High concentrations of HMs were observed in sediments and water, like Cr of 55 mg/kg and 86.93 mg/l in the ship-breaking areas and Karnaphuli River, respectively, in coastal regions of Bangladesh. Heavy metals severely contaminated the Karnaphuli River estuary and ship-breaking area on the Sitakundu coast, where sediments were the ultimate sink of high concentrations of metals. Sedentary or bottom-dwelling organisms like gastropods and shrimp had higher levels of heavy metals than other organisms. As a result, the modified PRISMA review method was used to look at the critical research gap about heavy metal pollution in Bangladesh's coastal areas by analyzing the current research trends and bottlenecks.

As a precursor to risk assessment and risk management through consuming contaminated seafood, food safety needs to be quantified and assured. Seaweed is an increasing dietary component, especially in developing countries, but there are few studies assessing uptake rates of contaminants from this route. As such, the present study determined likely human uptake due to the trace elemental (Fe, Mn, Ni, Cu, Zn, Se, Hg, and As) concentrations in the edible red seaweeds (Rhodophyta) Gelidium pusillum and Hypnea musciformis, growing in the industrialised Cox's Bazar coastal area of Bangladesh. Metal and metalloid concentrations in G. pusillum were in the order (mg/kg): Fe (797 ± 67) > Mn (69 ± 4) > Ni (12 ± 5) > Zn (9 ± 4) > Cu (9 ± 4) >Se (0.1 ± 0.1) > Hg (0.1 ± 0.01), and in H. musciformis: Fe (668 ± 58) > Mn (28 ± 5) > Ni (14 ± 2) > Zn (11 ± 5) > Cu (6 ± 4) >Se (0.2 ± 0.03) > Hg (0.04 ± 0.01). Despite the industrial activities in the area, and based on 10 g. day-1 seaweed consumption, it is concluded that these concentrations pose no risk to human health as part of a normal diet according to the targeted hazard quotient and hazard index (THQ and HI) (values < 1). In addition, and as a novel aspect for seaweeds, Selenium Health Benefit Values (Se-HBV) were determined and found to have positive values. Seaweed can be used as an absorber of inorganic metals for removing contamination in coastal waters. The results are a precursor to further research regarding the efficiency and rate at which seaweeds can sequester metal contamination in water. In addition, management techniques need to be developed thereby to control the contaminant inputs.

Heavy metal (HM) contaminated soil can affect human health via ingestion of foodstuffs, inhalation of soil dust, and skin contact of soil. This study estimates the level of some heavy metals in soils of industrial areas, and their exposures to human body via dietary intake of vegetables and other pathways. Mean concentrations of Cr, Fe, Cu, Zn, As and Pb in the studied soil were found to be 61.27, 27,274, 42.36, 9.77, 28.08 and 13.69 mg/kg, respectively, while in vegetables the respective values were 0.53, 119.59, 9.76, 7.14, 1.34 and 2.69 mg/kg. Multivariate statistical analysis revealed that Fe, Cu, Zn, and Pb originated from lithogenic sources, while Cr and As are derived from anthropogenic sources. A moderate enrichment was noted by Cr, As, and Pb in the entire sampling site, indicating a progressive depletion of soil quality. The bioaccumulation factor (BCF) value for all the vegetables was recorded as BCF < 1; however, the metal pollution index (MPI) stipulates moderately high value of heavy metal accumulation in the vegetable samples. Hazard Index (HI) of >0.1 was estimated for adults but >1 for children by direct soil exposure, whereas HI < 1 for both children and adults via dietary intake of vegetables. Estimated Total carcinogenic risk (TCR) value due to soil exposure showed safe for adults but unsafe for children, while both the population groups were found to be safe via food consumption. Children are found more vulnerable receptors than adults, and health risks (carcinogenic and non-carcinogenic) via direct soil exposure proved unsafe. Overall, this study can be used as a reference for similar types of studies to evaluate heavy metal contaminated soil impact on the population of Bangladesh and other countries as well.

Heavy metals occur naturally in very small amounts in living organisms, but exposure to their higher concentrations is hazardous. Heavy metals at hazardous levels are commonly found in foodstuffs of Bangladesh, mainly due to the lack of safety guidelines and poor management of industrial effluents. Several lines of evidence suggest that the level of heavy metals in foodstuffs of Bangladesh is higher than the acceptable limits set by World Health Organization/Food and Agriculture Organization. Literature survey revealed that the sources and transport pathways of heavy metals in the ecosystem and the abundance of heavy metals in the food products of Bangladesh are potential threats to food safety. However, an extensive assessment of the toxicity of heavy metals in food webs is lacking. Although widespread heavy metal contamination in various foodstuffs and environmental matrices have been summarized in some reports, a critical evaluation regarding multi-trophic transfer and the health risk of heavy metal exposure through food chain toxicity in Bangladesh has not been performed. This systematic review critically discussed heavy metal contamination, exposure toxicity, research gaps, existing legislation, and sustainable remediation strategies to enhance Bangladesh's food safety. In particular, this study for the first time explored the potential multi-trophic transfer of heavy metals via food webs in Bangladesh. Furthermore, we recommended a conceptual policy framework to combat heavy metal contaminations in Bangladesh.

Although coastal water marine algae have been popularly used by others as indicators of heavy metal pollution, data within the Bay of Bengal for the estuarine Cox's Bazar region and Saint Martin's Island has remained scarce. Using marine algae, the study herein forms an effort in biomonitoring of metal contamination in the aforementioned Bangladesh areas. A total of 10 seaweed species were collected, including edible varieties, analyzed for metal levels through the use of the technique of EDXRF. From greatest to least, measured mean metal concentrations in descending order have been found to be K > Fe > Zr > Br > Sr > Zn > Mn > Rb > Cu > As > Pb > Cr > Co. Potential toxic heavy metals such as Pb, As, and Cr appear at lower concentration values compared to that found for essential mineral elements. However, the presence of Pb in Sargassum oligocystum species has been observed to exceed the maximum international guidance level. Given that some of the algae species are cultivated for human consumption, the non-carcinogenic and carcinogenic indices were calculated, shown to be slightly lower than the maxima recommended by the international organizations. Overall, the present results are consistent with literature data suggesting that heavy metal macroalgae biomonitoring may be species-specific. To the best of our knowledge, this study represents the first comprehensive macroalgae biomonitoring study of metal contamination from the coastal waters of Cox's Bazar and beyond.