Trophic transfer and biomagnification potential of environmental contaminants (heavy metals) in aquatic ecosystems

Lead toxicity in plants: mechanistic insights into toxicity, physiological responses of plants and mitigation strategies

Soil toxicity is a major environmental issue that leads to numerous harmful effects on plants and human beings. Every year a huge amount of Pb is dumped into the environment either from natural sources or anthropogenically. Being a heavy metal it is highly toxic and non-biodegradable but remains in the environment for a long time. It is considered a neurotoxic and exerts harmful effects on living beings. In the present review article, investigators have emphasized the side effects of Pb on the plants. Further, the authors have focused on the various sources of Pb in the environment. Investigators have emphasized the various responses including molecular, biochemical, and morphological of plants to the toxic levels of Pb. Further emphasis was given to the effect of elevated levels of Pb on the microbial population in the rhizospheres. Further, emphasized the various remediation strategies for the Pb removal from the soil and water sources.

Zeolites in wastewater treatment: A comprehensive review on scientometric analysis, adsorption mechanisms, and future prospects

Zeolites possess a microporous crystalline structure, a large surface area, and a uniform pore size. Natural or synthetic zeolites are commonly utilized for adsorbing organic and inorganic compounds from wastewater because of their unique physicochemical properties and cost-effectiveness. The present review work comprehensively revealed the application of zeolites in removing a diverse range of wastewater contaminates, such as dyes, heavy metal ions, and phenolic compounds, within the framework of contemporary research. The present review work offers a summary of the existing literature about the chemical composition of zeolites and their synthesis by different methods. Subsequently, the article provides a wide range of factors to examine the adsorption mechanisms of both inorganic and organic pollutants using natural zeolites and modified zeolites. This review explores the different mechanisms through which zeolites effectively eliminate pollutants from aquatic matrices. Additionally, this review explores that the Langmuir and pseudo-second-order models are the predominant models used in investigating isothermal and kinetic adsorption and also evaluates the research gap on zeolite through scientometric analysis. The prospective efficacy of zeolite materials in future wastewater treatment may be assessed by a comparative analysis of their capacity to adsorb toxic inorganic and organic contaminates from wastewater, with other adsorbents.

Hexaflumuron insecticide exposure induces behavior alterations, hemato-biochemical disorders, antioxidant-immune dysfunction, and histopathological alterations in Nile tilapia (Oreochromis niloticus)

Hexaflumuron (HEX) insecticide is widely used in agriculture practices to fight crop insects. The toxicological effect of HEX on Nile tilapia (Oreochromis niloticus) was investigated in this study. Two hundred and forty fish (35.50 ± 1.45 g) were divided into six groups in four replicates (40 fish/group; 10 fish/replicate) and were exposed to six distinct HEX concentrations (0, 2, 4, 6, 8, and 10 mg L-1) for 96-h. The 96-h lethal concentration 50 (96-h LC50) of HEX was calculated to be 7.19 mg L-1. The fish exhibited reduced surface and middle swimming, aggressiveness, and tail-spreading behaviors with increasing bottom swimming and resting patterns after HEX exposure. HEX exposure resulted in body bleeding and fin rot. The erythrogram (red blood cell count, hemoglobin, and packed cell volume %) was significantly reduced with increased mean corpuscular volume by HEX exposure. HEX exposure decreased the white blood cells (WBCs) and differential WBC counts. Acute HEX exposure raised 8-hydroxy-2-deoxyguanosine level while lowering brain acetylcholine esterase activity. HEX exposure caused hepato-renal dysfunction and increased stress-related parameters (glucose and cortisol). Exposure to HEX reduced the immune responses (lysozyme, nitric oxide, immunoglobulin M, and complement 3). A substantial decrease in the antioxidant variables (reduced glutathione content and catalase) with increasing the malondialdehyde was noted by HEX exposure. Moreover, histopathological changes resulted from HEX exposure in the gills, liver, kidney, and spleen. These results indicate that HEX exposure induced behavioral changes, hepato-renal dysfunction, and immune-antioxidant disruption, indicating a possible physiological disruption in O. niloticus.

Seasonal fluctuations of heavy metal accumulation and gastrointestinal helminth induce oxidative stress and histological lesions in resident catfish Clarias gariepinus

The exposure of the African catfish (Clarias gariepinus) to various environmental contaminants leads to physiological and histological alterations. Therefore, the study aimed to assess the impact of seasonal variations of ecological contaminants as external stressors and internal stressors via helminth infections on oxidative stress and histopathology in resident C. gariepinus at EL-Salam Canal, Egypt. Seasonal water and sediment samples were collected to assess physicochemical parameters and heavy metals. The length, weight, and sex were recorded for each fish sample. The gastrointestinal tract was dissected from the visceral cavity, and the helminths were extracted and identified using SEM photos based on their morphological characteristics. The parasitic dominance in the gastrointestinal helminths was calculated. The heavy metal concentrations, bioaccumulation (BAF), and biosedimentation (BSF) factors were considered in the muscles and intestine. Specimens of muscles and intestines were removed to determine oxidative status. In addition, pieces of skin, muscles, stomachs, and intestines were subjected to light microscopy to determine the alterations. The calcium, magnesium, and potassium levels were within safe limits. Sulfate levels consistently remained below the maximum permissible thresholds throughout the seasons. Among the heavy metals examined, the highest accumulation was found in the intestinal tissues of C. gariepinus, while muscle tissues showed lower levels. The variability in metal concentrations across water, sediment, muscles, and intestines underscores the different capacities of these environments to accumulate heavy metals. The elevated metal levels in fish tissues raise concerns about potential health risks for humans who consume contaminated fish, highlighting significant bioaccumulation within the food chain. The result indicated that Cu in the sediment samples was associated with parasite abundance. The dual stress from environmental pollutants and parasitic infections exacerbates oxidative stress and causes notable histopathological changes in the tissues of the catfish. These results highlight the intricate interplay between external and internal stressors, emphasizing the need for continuous monitoring and management of aquatic ecosystems to safeguard the health of resident fish populations. It provides insight into how these factors affect fish health.

An anodic stripping voltammetric approach for total mercury determination in sea sponges from the Niger Delta region of Nigeria

Mercury pollution from ongoing crude oil refining and waste disposal activities threatens aquatic ecosystems and human health in the Niger Delta. Mercury monitoring exercise in this region is challenging due to the high cost of traditional instruments and the complexity of marine samples. This research presents a novel analytical method using differential pulse anodic stripping voltammetry (DPASV) with a glassy carbon electrode (GCE) to determine mercury levels in sea sponges from the Niger Delta. Using a 2.36 M HCl + 2.4 M NaCl supporting electrolyte, -0.6 V deposition potential, and 300 s deposition time, average mercury levels were found to be 0.98 mg kg-1, 0.63 mg kg-1 and 0.42 mg kg-1 for Ibiotirem, Kaa and Samanga, respectively. The result showed that the Niger Delta is polluted, and remediation efforts are necessary. Furthermore, the DPASV method could be used for routine mercury monitoring as it is cost-effective, user-friendly, and highly sensitive.

Differential response of heavy metal accumulation in freshwater aquatic organisms to organic matter pathway (δ13C) and trophic level (δ15N)

The migration of heavy metals into aquatic ecosystems is a concern for the safety of aquatic organisms and human health. However, the migration of heavy metals from habitats to the food chain in freshwater ecosystems requires extensive exploration. We extensively investigated the levels of heavy metals in multiple media of freshwater ecosystems and explored their migration from freshwater habitats to the food chain. The results showed that the concentrations of Cr, Cu, Cd, Zn, Sb, and Pb in sediments, Cr in mollusks, and Cd in clams exceeded their standard limit values. Feeding habits, species, and body length considerably affected heavy metal levels in fish, whereas regional differences, body length, and weight considerably affected heavy metal levels in mollusks. The bioconcentration capacity (improved biotawater (sediment) accumulation factors) of the muscles was higher than that of the gills and visceral mass. Mollusks were strongly enriched in Cu, Cd, Zn, and Mn in their habitats, whereas fish were more favourable for the accumulation of Cu, Zn, and Cr. Heavy metals in sediments pose a higher risk to aquatic organisms than those in the overlying water. Trophic level (TL) (δ15N) considerably diluted levels of most metals, whereas Cu and Zn levels increased along the organic matter pathway (δ13C) in the entire aquatic food chain. The levels of typical pollutants, such as Cu, Zn, As, Cd, Pb, and Cr changed considerably along the organic matter pathway in mollusks. The levels of heavy metals in fish were not affected by TL or organic matter pathway, except for Cu. The potential risk of consuming aquatic organisms from Poyang Lake was ranked as clams > snails > fish for adults and children and As in aquatic organisms was the primary contributor to health risk.

Assessment of potentially toxic element contamination in commercially harvested invertebrates from the Beibu Gulf, China

Marine pollutants, especially potentially toxic elements (PTEs), increasingly threaten the ecological environment and fishery resources of the Beibu Gulf due to their bioaccumulative nature, toxicity, and persistence. However, the occurrences of multiple PTEs in marine invertebrates within this region remains unclear. Hence, a total of 18 species of commercially harvested invertebrates (shrimp, crab, cephalopod, shellfish, and sea cucumber) were collected from the Beibu Gulf, and the concentrations of nine important PTEs (As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were examined. Subsequent stable isotope analysis for δ13C and δ15N facilitated investigations into biomagnification and human health risk assessment. The results showed that, except for As, the concentrations of the PTEs in the invertebrates were below the national safety limits. Furthermore, significant positive correlations were found between trophic levels (TLs) and log-transformed concentrations of As (P < 0.001, R2 = 0.20) and Cr (P < 0.001, R2 = 0.13), indicating biomagnification of these two metals across trophic positions among species. Finally, the human health risk assessment revealed that the consumption of cephalopod, shellfish, and sea cucumber poses a higher risk of adverse effects compared to shrimp and crab.

Evaluation of lead exposure effects on tissue accumulation, behavior, morphological and hemato-biochemical changes in common carp, Cyprinus carpio

BACKGROUND

Heavy metal pollution, particularly lead (Pb), poses a significant threat to aquatic ecosystems and their inhabitants, threatening their delicate balance and long-term viability. This study highlights the urgent need to mitigate heavy metal pollution in aquatic ecosystems.

OBJECTIVE

This study investigates Pb(NO3)2 exposure effects on tissue accumulation, behavioral abnormalities, and hemato-biochemical parameters in common carp (Cyprinus carpio), a widely distributed freshwater fish species.

METHODOLOGY

Fish (115 ± 5.23 g) were exposed to various Pb(NO3)2 concentrations for 10 and 20 days, representing control (0 %), 25 %, 50 %, and 75 % of the LC50 equivalent to 19.33, 38.66, and 58.0 mg/l, respectively. The standard manual procedure was used for blood sampling. The lead concentration in fish tissue was determined using an atomic absorption spectrophotometer.

RESULTS

Results revealed that fish gills showed significant (P < 0.05) increase in Pb(NO3)2 after 10 days, further rising after 20 days. Liver concentrations also rose significantly (P < 0.05) with prolonged exposure and increasing Pb levels. Muscle had lower concentrations. Hematological parameters (RBC, WBC, HB, HCT) decreased with higher Pb(NO3)2 levels. Behavioral and morphological changes were significantly more pronounced in the exposure groups when compared to the control group. Hepatic enzyme activities (AST, ALT), glucose, and lipid levels increased, while total protein decreased.

CONCLUSIONS

The study highlights Pb(NO3)2 harmful effects on common carp, impacting tissue accumulation, hematological parameters, and biochemical disruptions. It emphasizes the need to monitor and mitigate heavy metal pollution in aquatic environments to safeguard freshwater organisms and ecosystems, and to further increase our understanding of Pb toxicity in freshwater ecosystems.

Aqueous VOCs in complex water environment of oil exploitation sites: Spatial distribution, migration flux, and risk assessment

Pollution of the aqueous environment by volatile organic compounds (VOCs) has caused increasing concerns. However, the occurrence and risks of aqueous VOCs in oil exploitation areas remain unclear. Herein, spatial distribution, migration flux, and environmental risks of VOCs in complex surface waters (including River, Estuary, Offshore and Aquaculture areas) were investigated at a typical coastal oil exploitation site. Among these surface waters, River was the most polluted area, and 1,2-Dichloropropane-which emerges from oil extraction activities-was the most prevalent VOC. Positive matrix factorization showed that VOCs pollution sources changed from oil exploitation to offshore disinfection activities along River, Estuary, Offshore and Aquaculture areas. Annual volatilization of VOCs to the atmosphere was predicted to be ∼34.42 tons, and rivers discharge ∼23.70 tons VOCs into the Bohai Sea annually. Ecological risk assessment indicated that Ethylbenzene and Bromochloromethane posed potential ecological risks to the aquatic environment, while olfactory assessment indicated that VOCs in surface waters did not pose an odor exposure risk. This study provides the first assessment of the pollution characteristics of aqueous VOCs in complex aqueous environments of oil exploitation sites, highlighting that oil exploitation activities can have nonnegligible impacts on VOCs pollution profiles.

Hg, Cd, and Pb in fish of the Moulouya River, Morocco, and human health risk

Concentrations of toxic metals (Hg, Pb, and Cd) were determined in the muscles of Lepomis macrochirus, Barbus callensis, and Barbus nasus caught from the Moulouya River of Morocco by graphite furnace (for Pb and Cd) and cold vapour (for Hg) atomic absorption spectrometry, after acid digestion. Although the concentration of metals in some species was relatively high, no health risk has been identified in comparison to the maximum limits as set by the European Commission. The order of increasing concentrations was Cd < Hg < Pb. Calculated Target Hazard Quotients and Hazard Indices were below 1, indicating that the intake of metals via consumption of the muscles of both fish species does not represent a hazard to human health.

Nectopsyche sp (Trichoptera: Leptoceridae) sublethal effects caused by different concentrations of arsenic (As): a biochemical markers approach

Environmental impacts related to arsenic (As) contamination are a persistent issue of particular interest in Latin American countries with increasing mining activities. In Ecuador, the redefinition of public policies to promote the increase in mining since 2008 has led to a significant rise in the presence of this heavy metal in rivers and effluents, sometimes exceeding the 0.1 mg L-1, limit recommended by Ecuadorian Environmental Regulations. This study aimed to evaluate the sublethal effects through the detection of biochemical biomarker changes (Catalase, Antioxidant capacity by FRAP, and Glutathione S-transferase) generated in larvae of Nectopsyche sp following prolonged exposure to different concentrations of As (C1 = 0.05 mg L-1, C2 = 0.1 mg L-1, C3 = 0.8 mg L-1) in a controlled environment, emulating the maximum limits allowed by current Ecuadorian legislation. While As concentration levels in water increased, so did levels in the tissue of Nectopsyche sp specimens. On the other hand, behavioral parameters (mortality and mobility) did not show differences in either time or As concentrations. However, both Catalase and Antioxidant capacity by FRAP levels tended to decrease with increasing As concentration, and in both cases, the differences were significant. Additionally, Glutathione S-transferase activity did not increase significantly. These results preliminarily demonstrate that biochemical responses change with varying As concentrations in Nectopsyche sp and are affected at behavioral and biochemical levels produced by the As at chronic levels.

Relationship between potentially toxic elements and macrophyte communities in the Sava river

Freshwater ecosystems are at significant risk of contamination by potentially toxic elements (PTEs) due to their high inherent toxicity, their persistence in the environment and their tendency to bioaccumulate in sediments and living organisms. We investigated aquatic macrophyte communities and the concentrations of As, Cu, Cd, Cr, Pb, Zn, Ni and Fe in water and sediment samples to identify a pollution pattern along the Sava River and to investigate the potential impact of these PTEs on the diversity and structure of macrophyte communities. The study, which covered 945 km of the Sava River, showed a downstream increase in sediment concentrations of the analyzed elements. Both species richness and alpha diversity of macrophyte communities also generally increase downstream. Ordinary and partial Mantel tests indicate that macrophyte communities are significantly correlated with sediment chemistry, but only weakly correlated with water chemistry. In the lowland regions (downstream), beta diversity decreases successively, which can be attributed to an increasing similarity of environmental conditions at downstream sites. Species richness is relatively low at sites with low concentrations of Cr, Cd, Fe, and Cu in the sediment. However, species richness increases to a certain extent with increasing element concentrations; as element concentrations increase further, species richness decreases, probably as a result of increased toxicity. Some species that are generally more tolerant to high concentrations of PTEs are: Ceratophyllum demersum, Iris pseudacorus, Najas marina, Butomus umbellatus, Vallisneria spiralis, Potamogeton gramineus and Bolboschoenus maritimus maritimus. Potamogeton perfoliatus and the moss species Cinclidotus fontinaloides and Fontinalis antipyretica have narrow ecological amplitudes in relation to the concentrations of PTEs in the sediment.

Improper toy waste handling can harm human health via seafood consumption: A comprehensive health risk assessment of heavy metals

Toy production has been increasing over the last few decades to meet the growing demands for toys across the globe, which has inevitably worsened the problem of toy waste. Given the lack of modern waste disposal facilities, rural villagers in many developing countries often discard and incinerate toy waste in backyards or riverbanks, which may release the pollutants from toys (e.g., heavy metals), contaminate the surrounding areas, and eventually threaten the health of residents. As such, this study examined the impact of improper toy waste handling on the nearby aquaculture site by measuring the contamination level of heavy metals (As, Cd, Cu, Pb, and Zn) in the sediment and seafood (crabs, shrimps, and fish). The health risk of heavy metals via seafood consumption was assessed in different groups of people (males, females, teenagers, and seniors). Results showed that the sediment and seafood at the aquaculture site were generally not contaminated with heavy metals (contamination factor and bioaccumulation factor <1). However, consuming the seafood cultured at this site, especially for crabs, could pose a health risk to humans due to As and Cd (hazard quotient > 1), irrespective of their age and gender. This risk could not be lowered by cooking, except As by boiling. Overall, we revealed that improper toy waste handling did not cause severe heavy metal pollution in the surrounding environment, but the consumption of contaminated seafood could still threaten human health. To safeguard public health, we propose that toy waste should be appropriately treated by the authorities concerned. In addition, consuming seafood with long culture periods (e.g., crabs) should be reduced to minimize the dietary intake of heavy metals and their associated health risk.

Heavy Metal Concentrations in Water, Sediment, and Fish Species in Chashma Barrage, Indus River: A Comprehensive Health Risk Assessment

The increasing levels of heavy metals in aquatic environments, driven by human activities, pose a critical threat to ecosystems' overall health and sustainability. This study investigates the bioaccumulation of heavy metals (Pb, Cu, Cr, and Cd) in water, sediment, and three fish species (Catla catla, Labeo rohita, Cirrhinus mrigala) of different feeding zones within Chashma Barrage, located in the Mianwali district of Punjab, Pakistan, on the Indus River. A comprehensive analysis, including an assessment of associated human health risks, was conducted. Thirty samples from all three sites for each fish species, with an average body weight of 160 ± 32 g, were collected from Chashma Barrage. Water quality parameters indicated suitability for fish growth and health. Heavy metal concentrations were determined using an atomic absorption spectrometer. Results indicated elevated levels of Cd, Cr, and Cu in sediment and Pb and Cd in water, surpassing WHO standard limits. Among the fish species, bottom feeder (C. mrigala) exhibited significantly (P < 0.05) higher heavy metal levels in its tissues (gills, liver, and muscle) compared to column feeder (L. rohita) and surface feeder (C. catla). Liver tissues across all species showed higher heavy metal bioaccumulation, followed by gills. Principal component analysis (PCA) revealed strong correlations among heavy metals in sediment, gills, muscle, and water in every fish species. However, the vector direction suggests that Cr was not correlated with other heavy metals in the system, indicating a different source. The human health risk analysis revealed lower EDI, THQ, and HI values (< 1) for the fish species, indicating no adverse health effects for the exposed population. The study emphasizes the bioaccumulation differences among fish species, underscoring the higher heavy metal concentrations in bottom feeder fish within Chashma Barrage.

Effects of Heavy Metal Pollution on the Element Distribution in Hydrobios

At a time when heavy metal pollution is increasing, assessing the levels of contamination and associated health risks is crucial. Samples of water, aquatic plants, and fish were collected from four key areas of heavy metal pollution prevention and control in Zhejiang Province. The levels of elements were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). A human health risk model was also developed. The study revealed that heavy metal pollution in the five industrial zones exceeded the national standard for Class V water. Elements like arsenic (As), cadmium (Cd), and chromium (Cr) exceeded permissible levels in aquatic plants across all industrial zones; the exception was lead (Pb). Moreover, the heavy metal concentrations in subject fish tissues collected from each industrial area exceeded safe limits, especially in the gut. According to the human health risk evaluation model, the health risk (1.12 × 10-3) and children's health risk (1.10 × 10-3) in these prevention and control zones surpassed the maximum acceptable human risk values. In conclusion, heavy metal elements, along with other pollutants, accumulate and become concentrated in the examined aquatic plants and fish. These pollutants move through the food chain, impacting the entire aquatic ecosystem and posing a health risk to nearby populations.

Algal toxicity and food chain transport characteristics of three common bisphenols and their mixtures

Various bisphenols (BPs) have been frequently detected in the aquatic environment and coexist in the form of mixtures with potential huge risks. As we all know, food chain is a media by which BPs mixtures and their mixtures probably enter the organisms at different trophic levels due to their environmental persistence. As a result, the concentrations of BPs and their mixtures may continuously magnify to varying degrees, which can produce higher risks to different levels of organisms, and even human health. However, the related researches about mixtures are few due to the complexity of mixtures. So, the ternary BP mixtures were designed by the uniform design ray method using bisphenol A (BPA), bisphenol S (BPS) and bisphenol F (BPF) to investigate their food chain effects including bioconcentration and biomagnification. Here, Chlorella pyrenoidosa (C. pyrenoidosa) and Daphnia magna (D. magna) were selected to construct a food chain. The toxic effects of single BPs and their mixtures were also systematically investigated by the time-dependent microplate toxicity analysis (t-MTA) method. Toxicity interaction within the ternary mixture was analyzed by the concentration addition model (CA) and the deviation from the CA model (dCA). The results show that the C. pyrenoidosa and D. magna had obvious bioconcentration and biomagnification effects on BPs and their mixture. The mixture had the potential to enrich at higher nutrient levels. And BPF had the largest bioconcentration effect (BCF1 = 481.86, BCF2 = 772.02) and biomagnification effect (BMF = 1.6). Three BPs were toxic to C. pyrenoidosa by destroying algal cells and decreasing protein and chlorophyll contents, and their toxicity order was BPF > BPA > BPS. Moreover, their ternary mixture exhibits synergism with time/concentration-dependency. The obtained results are of significant reference value for objectively and accurately assessing the ecological and environmental risks of bisphenol pollutants.

Exploring zeolite-based composites in adsorption and photocatalysis for toxic wastewater treatment: Preparation, mechanisms, and future perspectives

Water scarcity has become a critical global concern exacerbated by population growth, globalization, and industrial expansion, resulting in the production of wastewater containing a wide array of contaminants. Tackling this challenge necessitates the adoption of innovative materials and technologies for effective wastewater treatment. This review article provides a comprehensive exploration of the preparation, applications, mechanisms, and economic environmental analysis of zeolite-based composites in wastewater treatment. Zeolite, renowned for its versatility and porous nature, is of paramount importance due to its exceptional properties, including high surface area, ion exchange capability, and adsorption capacity. Various synthetic methods for zeolite-based composites are discussed. The utilization of zeolites in wastewater treatment, particularly in adsorption and photocatalysis, is thoroughly investigated. The significance of zeolite in adsorption and its role in the photocatalytic degradation of pollutants are examined, along with its applications in treating volatile organic compounds (VOCs), dye wastewater, oil-field wastewater, and radioactive waste. Mechanisms underlying zeolite-based adsorption and photocatalysis, including physical and chemical adsorption, ion exchange, and surface modification, are elucidated. Additionally, the role of micropores in the adsorption process is explored. Furthermore, the review delves into regeneration and desorption studies of zeolite-based composites, crucial for sustainable wastewater treatment practices. Economic and environmental analyses are conducted to assess the feasibility and sustainability of employing zeolite-based composites in wastewater treatment applications. Future recommendations are provided to guide further research and development in the field of zeolite-based composites, aiming to enhance wastewater treatment efficiency and environmental sustainability. By exploring the latest advancements and insights into zeolite-based nanocomposites, this paper aims to contribute to the development of more efficient and sustainable wastewater treatment strategies. The integration of zeolite-based materials in wastewater treatment processes shows promise for mitigating water pollution and addressing water scarcity challenges, ultimately contributing to environmental preservation and public health protection.

Sorption capacity of Eichhornia crassipes (Mart.) Solms for zinc removal from electroplating industry wastewater

Various industrial operations in the dye, fertilizer, pesticide, battery, mining, and chemical industries have been associated with releasing heavy metals in wastewater, such as lead, zinc, copper, arsenic, cadmium, chromium, nickel, and mercury. These metals are dangerous to aquatic life as well as to humans, who may consume them directly or indirectly. Therefore, before being released into open water and land resources, it is necessary to minimize the concentration of toxic ions below the discharge limit. This study used Eichhornia crassipes (Mart.) Solms to remove zinc from wastewater from the electroplating industry in a constructed wetland. Experimental investigations were conducted for removing zinc ions from electroplating industry wastewater using various process parameters such as nutrient dosages, dilution ratios, potential of hydrogen ions, biomasses, and contact times. The outcome of this study revealed that the maximum zinc removal percentage in electroplating industrial wastewater was found for the optimum nutrient dosages of 60 g, dilution ratios of 10, potential hydrogen ion levels of 8, and biomass amounts of 100 g. The maximum zinc removal by Eichhornia crassipes (Mart.) Solms was found to be 88.3 ± 0.6 and 93.4 ± 0.4% at the optimum parameter values for the electroplating industry wastewater and the aqueous solution, respectively, against the optimum contact time of 22 days. This study suggests using this phytoremediation technology to remove all pollutants from industrial wastewater in general, not just wastewater from the electroplating industry.

Trophodynamics and potential health risk assessment of heavy metals in the mangrove food web in Yanpu Bay, China

Mangroves are the cradle of coastal water biodiversity and are susceptible to heavy metal pollution. However, the trophic transfer mechanism of heavy metals in the mangrove food web and the resulting human health risks are not fully understood. Heavy metal concentration (Cr, Ni, Cu, Zn, As, Cd, Pb, V, Co) and stable isotope ratios of carbon and nitrogen (δ13C and δ15N) were evaluated in sediments and particulate organic matter, litter, and aquatic organisms (plankton, arthropods, mollusks, omnivorous fish, and carnivorous fish) from the Yanpu Bay mangroves. The results revealed that heavy metals exhibited different trophic transfer patterns. As and Hg were efficiently biomagnified, with trophic magnification factors of 1.17 and 1.42, respectively; while Cr, Ni, Cu, Cd, Pb, V, and Co were efficiently biodiluted. Zn exhibited a trophic magnification factor > 1 and was not significantly correlated with δ15N (p > 0.05), suggesting no biomagnification or biodilution. The heavy metals in the important fishery species (omnivorous fish and carnivorous fish) were below the permissible limits, except for Zn in Ophichthus apicalis. The assessment of probabilistic health risks revealed that fish consumption in adults and children posed an acceptable risk (total target hazard quotient <1).

Resilience of rotifers and cladocerans communities in four reservoirs with eutrophication pollution and lead concentrations in Aguascalientes, Mexico

Pollution in aquatic ecosystems has been increasing drastically worldwide changing their water quality. Therefore, species must be adapted to these new scenarios. In Aguascalientes City, four representative urban reservoirs contain lead in the water column and extremely high concentrations of sediments. Therefore, an analysis was conducted to evaluate the resilience of zooplankton species to lead exposure in each reservoir using dormant and organisms. Results demonstrated a decrease range from 57.5 to 22.5% in overall diapausing egg hatching rate, while survivorship rate also decreased from 98 to 54% when organisms were exposed to the water of the four reservoirs and increasing lead concentrations. When Pb exposure increased, results showed a global negative effect on both hatching rate (decreasing from 58 to 30% at 0.09 mg L-1) and survivorship levels (decreasing from 100% to 0.07% at 0.09 mg L-1). We provide Species Sensitivity Distribution for both water reservoir dilutions and lead concentration to analyze diapausing eggs hatching and survivorship of offspring in the presence of same polluted conditions or lead of the autochthonous species found in reservoirs. Furthermore, specific analysis with two populations of the cladoceran Moina macrocopa showed clear dissimilar hatching patterns that suggested a different adaptive mechanism. Niagara population shows a hatching rate of approximately 25% in the first two days of reservoir water exposure, while UAA population drastically increased hatching rate to 75% on exposure at day seven. We provide the first record of bioaccumulation in ephippia of M. macrocopa.

Soil-mustard revitalization via rice husk ash, a promising soil amendment material for sustainable management of heavy metal contamination in tropical ecosystem

Prolonged wastewater irrigation in agriculture has led to the accumulation of heavy metals in soil, endangering both the soil quality and food safety, thereby posing a potential threat to human health through the consumption of contaminated crops. The present study aimed to enhance the yield of mustard (Brassica juncea L. cv. Varuna and NRCHB 101) plants and stabilize heavy metals (Cd, Cr, Ni, Cu, and Zn) in wastewater-irrigated soil using rice husk ash (RHA), rice mill by-product, collected from Chandauli region of Eastern Uttar Pradesh, India. Results demonstrated significant improvements in growth, biomass, physiology, and yield of mustard plant with increasing RHA application in wastewater irrigated soil (p ≤ 0.05). Heavy metal accumulation in different parts of mustard plants decreased as RHA application rate increased. Applying RHA at 2% in soil proved to be most effective in reducing Cd, Cr, Ni, Cu, and Zn accumulation in seeds by 29%, 29.6%, 23.1%, 21.3% and 20.1%, respectively in Varuna and 30.1%, 21.4%, 11.1%, 12.1%, and 28.5%, respectively in NRCHB 101cultivars. The present findings showed that RHA amendment in wastewater irrigated soil had reduced bioaccumulation of Cd, Cr, Ni, Cu, and Zn and consequently their toxicity in cultivated mustard plants. A novel application of RHA is unveiled in this research, offering a promising solution to promote sustainable agriculture and to reduce heavy metal associated health risks within the soil-mustard system.

Adsorption of copper by naturally and artificially aged polystyrene microplastics and subsequent release in simulated gastrointestinal fluid

Microplastics, especially aged microplastics can become vectors of metals from environment to organisms with potential negative effects on food chain. However, a few studies focused on the bioavailability of adsorbed metals and most studies related to aged microplastics used artificial method that cannot entirely reflect actual aging processes. In this study, virgin polystyrene was aged by ozone (PS-O3), solar simulator (PS-SS) and lake (PS-lake) to investigate adsorption of Cu by virgin, artificially and naturally aged microplastics and subsequent release in simulated gastrointestinal fluids (SGF). Characterization results show carbonyl was formed in PS-O3 and PS-SS, and the oxidation degree was PS-O3 > PS-SS > PS-lake. However, Cu adsorption capacity followed this order PS-lake (158 μg g-1) > PS-SS (117 μg g-1) > PS-O3 (65 μg g-1) > PS-virgin (0). PS-O3 showed highest Cu adsorption capacity at 0.5 h (71 μg g-1), but it dropped dramatically later (10 μg g-1, 120 h), because PS-O3 could break up and the adsorbed Cu released in solutions subsequently. For PS-lake, precipitation of metallic oxides contributes to the accumulation of Cu. The addition of dissolved organic matter (DOM) could occupy adsorption sites on PS and compete with Cu, but also can attach PS and adsorb Cu due to its rich functional groups. The simultaneous ingestion of microplastics with food suggested that adsorbed Cu is solubilized mostly from aged PS to SGF.