Human risk assessment of toxic elements (As, Cd, Hg, Pb) in marine fish from the Amazon

Variations in seafood consumption and health risk associated with trace element exposure in the Zhoushan Fishing Ground, China: A questionnaire-based study

This study determined the concentrations and health risks of trace elements (Cu, Pb, Zn, Cd, Cr, Hg, and As) in 184 samples of 13 seafood species (8 fish, 2 shrimp, and 3 crab) collected from Zhoushan Fishing Ground (ZFG), during October and December 2020, and April and June 2021. To address the limitations of evaluating risk using regional average consumption, 399 questionnaires (359 valid) were collected to analyze how residents' consumption patterns influenced individual health risk. For all the samples, exceedances of national safety limits were observed for Pb (1.09 %), Cd (5.43 %), and As (21.20 %), and crabs exhibited the highest trace element concentrations. Species and body size further played a role in determining the concentrations. Seafood consumption frequency was the strongest predictor of consumption rates (IR), following the pattern IRfish > IRshrimp > IRcrab. In addition, age, gender, and residence duration influenced IRfish and IRshrimp. While the risk of most trace elements was acceptable, average Target Hazard Quotient (THQ) values of As exceeded 1, and both Cd and As exceeded the carcinogenic risk threshold of 10-4. The findings suggested that As and Cd posed certain health risks, especially in crabs (with the highest concentrations) and fish (with the highest IR). These results highlighted that differences in both element concentrations and individual consumption together affected the health risks associated with seafood. Future efforts should focus on enhancing the detection of trace elements, especially Cd and As, and promoting balanced seafood consumption to protect public health.

Heavy metal contamination in fish and human health risks from lakes of a mega inter-basin water diversion

Heavy metals in freshwater lakes under inter-basin water diversions may pose harms to lake ecosystems and human health but have rarely been studied. We studied fish heavy metals in water diversion lakes, Gao-Bao-Shaobo Lakes (GBSLs), along the South-to-North Water Diversion Project in China, and evaluated associated human health risks from fish consumption. A total of 322 muscle samples from 29 fish species were collected to characterize contamination patterns of copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), and arsenic (As). The studied heavy metals in fish were found within China's food safety standards. Among the studied metals, Cu, Cd, Pb, and As had higher concentrations temporally in autumn and spatially in Gaoyou Lake. Moreover, Cd, Pb, and As in carnivores were significantly higher than other feeding groups, and Cd and As in upper-middle and upper water layers were significantly higher than other layers. Consumption of GBSLs fish did not pose a non-carcinogenic risk to human health. However, consumption of fish species such as Protosalanx hyalocranius, Carassius auratus, Culter alburnus may pose potential carcinogenic risks to human health due to Cr and Cd. The current study had implications for assessing aquatic ecological conditions and reducing human dietary health risks related to heavy metals in water diversion lakes.

Toxic and essential elements determination in edible tissues of different elasmobranch species from Southeastern Brazil and potential human health risks

Brazil is the largest consumer of shark meat, which is sold by fishmongers under the umbrella term cação. The population consumes this meat due to its low cost and lack of fish bones. In this work, morphometric measurements and metal/metalloid concentration (75As, 202Hg, and 82Se) were assessed in the muscle tissue of species from Dasyatis spp., as well as Rhizoprionodon porosus and Zapteryx brevirostris, obtained from Farol de São Tomé beach in Southeastern Brazil. A principal component analysis (PCA) was conducted to evaluate the separation of species based on morphometric variables and elemental concentrations. Additionally, human health risk assessment indices-estimated daily intake (EDI), target hazard quotient (THQ), target cancer risk (TCR), and selenium health benefit values (HBVSe)-were calculated to estimate the risks associated with the consumption of elasmobranch meat in the region. The PCA revealed distinct clustering patterns by species. The human health risk assessment indices indicated potential risks associated with the consumption of the analyzed species. For Dasyatis spp., the EDI of As, THQ of inorganic As (iAs), and TCR exceeded their respective thresholds. For R. porosus, the EDI of As, THQ of iAs and Se, and TCR exceeded the established thresholds. For Z. brevirostris, the EDI of As and Hg, THQ of iAs and MeHg, TCR, and HBVSe exceeded the thresholds. These results suggest a potential risk to public health associated with the consumption of elasmobranch meat from the analyzed species, especially Z. brevirostris.

Bioaccumulation and Trophic Transfer of Heavy Metals in Marine Fish: Ecological and Ecosystem-Level Impacts

Heavy metal contamination in marine ecosystems poses a critical environmental challenge, with significant implications for biodiversity, trophic dynamics, and human health. Marine fish are key bioindicators of heavy metal pollution because of their role in food webs and their capacity for bioaccumulation and trophic transfer. This review synthesizes current knowledge on the pathways and mechanisms of heavy metal accumulation in marine fish, focusing on factors that influence the uptake, retention, and tissue distribution. We explore the processes governing trophic transfer and biomagnification, highlighting species-specific accumulation patterns and the risks posed to apex predators, including humans. Additionally, we assess the ecological consequences of heavy metal contamination at population, community, and ecosystem levels, emphasizing its effects on fish reproduction, community structure, and trophic interactions. By integrating recent findings, this review highlights key knowledge gaps and suggests future research directions to improve environmental monitoring and risk assessment. Given the persistence and bioavailability of heavy metals in marine environments, effective pollution control strategies and sustainable fisheries management are imperative to mitigate long-term ecological and public health risks.

Trace elements contamination in fish and human health risks from the upper reaches of the Pearl River Basin

Evaluating the concentration of trace elements in fish in the river is crucial for assessing the potential risks to humans from eating fish. In this study, we collected 315 muscle samples of seven indigenous fish species Abbottina rivularis (Basilewsky, 1855), Cobitis taenia (Linnaeus, 1758), Hemiculter leucisculus (Basilewsky, 1855), Misgurnus anguillicaudatus (Cantor, 1842), Oreochromis mossambicus (Günther, 1889), Rhinogobius cliffordpopei (Rutter, 1897), Rhinogobius giurinus (Nichols, 1925) from the upper reaches of the Pearl River Basin in July, August of 2017 to investigate the concentration of zinc (Zn), copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) and further evaluate their health risk to humans. Trace elements analysis revealed that the average concentration of Zn (9.56 ± 3.72 mg/Kg) was the highest, followed by Cr (1.67 ± 1.15 mg/Kg), Cu (0.47 ± 0.44 mg/Kg), Pb (0.78 ± 0.12 mg/Kg), Cd (0.06 ± 0.11 mg/Kg), As (0.19 ± 0.56 μg/Kg), and Hg (0.01 ± 0.03 μg/Kg). As the hazard quotient index is <1, the THQ and TTHQ associated with fish consumption represent a negligible non-carcinogenic risk to the health of local consumers. Instead, Cr (cancer risk value: 2.72 × 10-4) and Cd (cancer risk value: 2.72 × 10-4) pose a potential cancer threat to local residents who eat the fish studied, and it needs more attention in the monitoring of the aquatic product on human health. Our study could be utilized to implement essential interventions in ecological security and protection, and preventing the emergence of adverse situations.

Bioaccumulation of Metals in Fish Collected from Macapá Urban Aquatic Environments (Brazilian Amazon) and the Risks to Human Health

Macapá City, located in the Brazilian Amazon, faces critical aquatic pollution challenges due to inadequate sanitation infrastructure, leading to metal contamination in fish within its urban water bodies. Our study evaluated the concentrations of metals (Cu, Cd, Cr, Fe, Mn, Ni, Pb, Zn, and Hg) in muscle tissues of fish from igarapés, ressaca areas, and canals. Samples were collected from six sampling sites to investigate the bioaccumulation of these metals and their potential human health risks. All metals were quantified by atomic absorption spectrometry, except Hg, which was quantified by inductively coupled plasma optical emission spectrometry. Metal concentrations were determined in three carnivorous and seven omnivorous fish species. Cd concentrations exceeded the Brazilian maximum limit established for human consumption in all fish species evaluated. The estimated daily intake (EDI) of Pb and Hg exceeded their reference doses. Our risk assessment, which combined the risk quotient (RQ) for individual metals and the risk index (RI) for metal mixtures, indicated health risks associated with the consumption of fish collected from the study areas. These results demonstrated a worrying exposure to metals (mainly Cd, Pb, and Hg), highlighting the need for environmental management measures and continuous monitoring to protect public health in vulnerable urban areas.

Heavy metal contamination of vegetables in China: status, causes, and impacts

Exposure to heavy metals from vegetable consumption poses a serious health risk to the Chinese population. The lack of knowledge on the overall status of vegetable contamination at the national level hinders the development of national regulations on preventing heavy metal exposure. To address this issue, the study presents an overview of heavy metal contamination in vegetables across China based on 96 peer-reviewed studies published over the past 20 years. The average concentrations of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn in the edible parts of vegetables are 3.7 ± 12.9, 1.6 ± 4.0, 4.3 ± 10.3, 18.6 ± 27.6, 164 ± 281, 4.5 ± 5.5, 7.7 ± 23.7, and 105 ± 283 mg kg-1 (dry weight), respectively. The associated daily exposures are 0.1-5.7, 0.1-1.7, 0.6-4.2, 4.1-20.5, 26-107, 0.7-3.0, 0.4-16.0, and 13-93 μg kg-1 d-1, respectively. General linear models explained 80%, 44%, 83%, 79%, 64%, 81%, 65%, and 55% of the total variance in As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn concentrations in vegetables, respectively, based on vegetable type and selected geological, meteorological, economic, and environmental factors. Agroforestry is the main source of heavy metal contamination, accounting for 3%-30% of the total variance in heavy metal concentrations in vegetables. Mining, smelting, refining, metalworking, and electrical equipment manufacturing are important source of As, Cr, Cu, Mn, Ni, and Pb, accounting for 7%-17% of the total variance.

Blood mercury concentrations in preschool children and potential risk factors in São Paulo, Brazil

Environmental exposure of preschool children to mercury can elevate blood mercury levels (BML) and negatively affect their health. This study aimed to determine BML in preschool children from Brazil's largest city and explore potential associated risk factors. Blood samples were collected in 2013 from 2436 children (age 1-5 years) attending 50 daycare centers (DCC) located in São Paulo, Brazil. Parents or guardians answered questionnaires collecting information on sociodemographics and potential risk factors. BML was determined by Cold Vapor Atomic Absorption Spectrophotometry (CV-AAS) and categorized using a cutoff point of 2.77 μg L⁻1, corresponding to the 75th percentile. Multiple logistic regression was performed (p < 0.05). Data were georeferenced and associations with air pollution, wind frequency and direction were evaluated. The results showed a geometric mean for BML of 1.65 μg L⁻1 (95% CI: 1.60-1.70), arithmetic mean of 2.15 μg L⁻1 (95% CI: 2.09-2.22), 75th percentile of 2.77 μg L⁻1 (95% CI: 2.67-2.91) and 95th percentile of 5.51 μg L⁻1 (95% CI: 5.18-5.92). DCCs located in the Northwest and East zones (p < 0.001) and fish consumption in the past two days (p = 0.04) were associated with high BML. The elevated BML observed in children living in the eastern zone might be attributed to the southeasterly winds passing through a petrochemical complex located nearby. The 95th percentile of BML in this study exceeded the U.S. 95th percentile by five times. BML in São Paulo preschool children was associated with individual and environmental risk factors. This finding highlights the need to identify and control hot spots in São Paulo, Brazil, especially in peripheral and surrounding areas, where individuals are more vulnerable. Further research is needed in Latin America to identify additional sources of urban environmental mercury exposure and guide interventions for protecting the environment and safeguarding children's health.

The global issue of metal contamination in sharks, rays and skates and associated human health risks

Elasmobranchs, including sharks, rays, and skates, are a global protein source but face threats from overfishing and population declines. Despite their lower market value, increased consumption raises sustainability and public health concerns. Commonly landed species like the Blue Shark, Shortfin Mako, and Spiny Dogfish are particularly vulnerable to bioaccumulation of metals such as mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As), posing health risks to consumers. Although metal and metalloid contamination levels in elasmobranchs are frequently reported, studies on specific human health risks remain limited. Sensitive populations, including pregnant women, fetuses, infants, the elderly, and individuals with pre-existing health conditions, face elevated risks from consuming contaminated seafood. Vulnerable communities, especially coastal populations and lower-income groups, encounter further exposure risks due to limited access to safer food alternatives and information. This review explores metal and metalloid contamination in commonly consumed elasmobranch species, associated health risks, and impacts on vulnerable groups, emphasizing the need for informed consumption and the role of contamination awareness in conservation efforts. Arsenic was the most commonly detected element in elasmobranch meat, followed by Se, Hg, Pb, and Cd, with Pb and Se consistently reported at safe levels. Arsenic levels exceeded safety thresholds in most studies, posing health risks, while THQ evaluations indicated significant risks, especially in sharks, where values often surpassed safe thresholds. For C. falciformis, THQ ranged from 5.7 in North America to 38 in Asia, making the consumption of this species inadvisable. Elevated HQ values suggest that cumulative risks likely exceed safe limits, highlighting the need for cautious consumption and further risk assessments.

Bioaccumulation of chemical elements in fish from areas affected by oil on the coast of Bahia, Brazil

In 2019, the Brazilian coast was affected by the largest oil spill in its history. We assessed the levels of chemical elements in Lutjanus synagris and Haemulon aurolienatum fish from Itacaré (least affected area), Tinharé-Boipeba (most affected area) and Madre de Deus (chronically affected area). The level of metals differed between species, tissues, life cycle phases, maturation stages and between sampled locations, indicating the influence of biological and environmental aspects on bioaccumulation. Only fish in Madre de Deus showed lead contamination, while arsenic concentrations in the three areas exceeded the maximum value acceptable by Anvisa (National Health Surveillance Agency). It is suggested that the oil spill may have impacted species differently, also having an impact in fish from less affected areas. However, metal concentrations in fish in Madre de Deus stood out when compared to populations in other studied areas.

What does scientometry tell us about mercury toxicology and its biological impairments?

Mercury is a toxic pollutant that poses risks to both human and environmental health, making it a pressing public health concern. This study aimed to summarize the knowledge on mercury toxicology and the biological impairments caused by exposure to mercury in experimental studies and/or diagnosis in humans. The research was conducted on the main collection of Web of Science, employing as a methodological tool a bibliometric analysis. The selected articles were analyzed, and extracted data such as publication year, journal, author, title, number of citations, corresponding author's country, keywords, and the knowledge mapping was performed about the type of study, chemical form of mercury, exposure period, origin of exposure, tissue/fluid of exposure measurement, mercury concentration, evaluation period (age), mercury effect, model experiments, dose, exposure pathway, and time of exposure. The selected articles were published between 1965 and 2021, with Clarkson TW being the most cited author who has also published the most articles. A total of 38% of the publications were from the USA. These studies assessed the prenatal and postnatal effects of mercury, emphasizing the impact of methylmercury on neurodevelopment, including motor and cognitive evaluations, the association between mercury and autism, and an evaluation of its protective effects against mercury toxicity. In observational studies, the blood, umbilical cord, and hair were the most frequently used for measuring mercury levels. Our data analysis reveals that mercury neurotoxicology has been extensively explored, but the association among the outcomes evaluated in experimental studies has yet to be strengthened. Providing metric evidence on what is unexplored allows for new studies that may help governmental and non-governmental organizations develop guidelines and policies.

Risk Assessment and Determination of Arsenic and Heavy Metals in Fishery Products in Korea

The purpose of this study is to quantify several heavy metals (Pb, Cd, Hg, Me-Hg, and metalloid arsenic) contained in Korean fishery products (seven categories, 1186 samples) and assess their health risk. Heavy metals quantification was conducted using inductively coupled plasma mass spectrometry (ICP-MS) and a direct mercury analysis (DMA). The good linearity (R2 > 0.999), limits of detection (1.0-3.2 µg/kg), limits of quantification (3.1-9.6 µg/kg), accuracy (88.14-113.80%), and precision (0.07-6.02%) of the five heavy metals were obtained, and these results meet the criteria recommended by the AOAC. The average heavy metal concentrations of fishery products were in the following order: As > Cd > Pb > Hg > Me-Hg for sea algae, crustaceans, mollusks, and echinoderms, As > Hg > Me-Hg > Pb > Cd for freshwater fish and marine fish, and As > Pb > Cd > Hg > Me-Hg for tunicates. Heavy metal concentrations were lower than MFDS, EU, CODEX, and CFDA standards. In addition, the exposure, non-carcinogenic, and carcinogenic evaluation results, considering the intake of aquatic products for Koreans, were very low. It was concluded that this study will provide basic data for food safety and risk assessment.

A Novel One Health Approach concerning Yeast Present in the Oral Microbiome of the Endangered Rio Skate (Rioraja agassizii) from Southeastern Brazil

The current climate change scenario caused by anthropogenic activities has resulted in novel environmental pressures, increasing the occurrence and severity of fungal infections in the marine environment. Research on fungi in several taxonomic groups is widespread although not the case for elasmobranchs (sharks and rays). In this context, the aim of the present study was to screen the oral fungal microbiota present in artisanally captured Rioraja agassizii, a batoid that, although endangered, is highly fished and consumed worldwide. Oropharyngeal samples were obtained by swabbing and the samples were investigated using morphological and phenotypic methods by streaking on Sabouraud Dextrose Agar (SDA) and subculturing onto CHROMagar Candida (BD Difco) and CHROMagar Candida Plus (CHROMagarTM), as well as molecular techniques by amplification of the ITS1-5.8S-ITS2 ribosomal DNA region and a MALDI-TOF MS assessment. The findings indicated the presence of Candida parapsilosis (seven isolates), Candida duobushaemulonii (one isolate) and Rhodotorula mucilaginosa (three isolates), several of these reported for the first time in Rioraja agassizii. In addition, a 100% agreement between the MALDI-TOF results and partial ITS region sequencing was noted, demonstrating that the MALDI-TOF MS is a rapid and effective alternative for yeast identification in Rioraja agassizii isolates and potentially in other elasmobranch species. These findings highlight the need for further research to determine the potential impact on elasmobranch health, ecology, and commercial fisheries. Furthermore, this research is paramount in a One Health framework and may be employed to predict elasmobranch responses to an evolving ocean, keep healthy populations in check, monitor species, and assess the public health consequences of consuming these species.

Contamination, sources and health risks of potentially toxic elements in the coastal multimedia environment of South China

Coastal ecosystems are vulnerable to the accumulation of potentially toxic elements (PTEs), which pose a threat to marine ecosystems and human health. In this study, the concentrations of eight PTEs in a typical area of South China were analysed, and their distributions, seasonal variations, pollution degrees, potential health risks and sources in seawater, sediment and organisms were evaluated. The comprehensive pollution index (CPI), pollution load index (PLI), potential ecological risk index (PERI) and target hazard quotient (THQ) were applied to assess seawater, sediment and organism quality, respectively. The annual mean concentrations of Zn, Hg, Cr and As in the bottom seawater were higher than those in the surface water while those of Pb, Mn and Cu were higher in the surface seawater. The mean content of Hg was higher than the corresponding background value of that in China Shelf Sea sediment. Marine organisms have a high enrichment capacity for Cu, Zn, Cr, Hg, As and Mn in seawater. Based on CPI, the seawater was generally not polluted by PTEs. The PLI and PERI results demonstrated that Hg was the main contamination element in surface sediment. The total target hazard quotient (TTHQ) analysis illustrated that long-term consumption of some fish by children poses a noncarcinogenic health risk, while that risk to adults is negligible. Natural sources, agricultural activity sources, coal burning and industrial emission sources were the main sources of the PTEs in surface sediments according to positive matrix factorization (PMF) model.

Flood pulse as a driving force of Pb variation in four fish guilds from Puruzinho Lake (western Amazon)

The Brazilian Amazon is heavily impacted by mining activities, especially by gold and cassiterite mining. Pb is a contaminant released during cassiterite extraction, and it stands out for its high toxicity. The present study aimed to evaluate the effect of flood pulse on Pb dynamics in four fish species with different feeding habits (Cichlapleiozona: carnivorous, Mylossomaduriventre: herbivorous, Prochilodus nigricans: detritivorous, and Serrasalmus rhombeus: piscivorous) over four hydrological periods in Puruzinho Lake (Brazilian Amazon), which receives water from the Madeira River. The risk assessment for daily Pb intake through the consumption of these fish by the local riverside population was also carried out. Fish species were sampled during four Amazonian hydrological periods: rising water, high water, falling water, and low water. Pb and stable isotopes (δ¹⁵N and δ¹³C) measurements were carried out on fish muscle. The flood pulse had the same effect on Pb concentrations of all the fish species regardless of their feeding habits, as we found a nonsignificant interaction between these variables. The Pb in fish muscle increased in the flood season (rising and high water) and decreased in the dry season (falling and low water). The Pb concentration in fish increased significantly with their trophic level (δ¹⁵N), evidencing the occurrence of biomagnification of the element along the trophic chain (R² = 0.24). The main food source of the herbivorous fish (δ¹³C) was very distinct from that of the others, which had a large overlap in their values. Regarding risk assessment, the daily Pb intake through consumption of the herbivorous species during high water (17.82 ± 19.68 µg∙day^-1) exceeded the limit determined by the Food and Drug Administration (FDA) of 12.5 µg∙day^-1, representing a health risk to the riverside population of Puruzinho Lake.

Covalently Functionalized Cellulose Nanoparticles for Simultaneous Enrichment of Pb(II), Cd(II) and Cu(II) Ions

Cellulose nanoparticles are sustainable natural polymers with excellent application in environmental remediation technology. In this work, we synthesized cellulose nanoparticles and covalently functionalized them with a multi-functional group possessing ligands. The hybrid material shows excellent adsorption properties for the simultaneous extraction of multiple metal ions in the sample preparation technique. The sorbent shows excellent sorption capacity in the range of 1.8-2.2 mmol/g of material. The developed method was successfully employed for the simultaneous extraction of Pb(II), Cd(II) and Cu(II) from real-world samples (industrial effluent, river water, tap and groundwater) and subsequently determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The method shows a preconcentration limit of 0.7 ppb attributes to analyze the trace concentration of studied metal ions. The detection limit obtained for Pb(II), Cd(II) and Cu(II) is found to be 0.4 ppb.

Metal bioaccumulation in fish from the Araguari River (Amazon biome) and human health risks from fish consumption

Recently, high concentrations of metals have been found in the waters from sampling sites located in the Araguari River lower section. These metals can be bioaccumulated by fish, but also biomagnified, representing a potential risk through human consumption. Here, we aimed to (1) determine the metal concentrations in muscle samples from fish; (2) evaluate bioaccumulation of metals in muscle tissue of fish species with different feeding behaviors; and (3) investigate the risks of single metals, as well as mixture of metals, to human fish consumption. Eleven fish species were sampled (3 carnivorous, 5 omnivorous, and 3 detritivorous). In four fish species, Cd and Pb concentrations exceeded the Brazilian maximum limits (MLs) for human consumption. Individually, Pb and Cd concentrations in the muscle of these fish indicate risks to human health. When considering the mixture of metals, the consumption of all fish species represents risks. The highest risks implicate detritivorous species. For all fish species evaluated, the estimated daily intake (EDI) of Hg shows values above its reference dose (RfD). Our results suggest the need to establish an environmental monitoring program that aims to preserve environmental quality, biodiversity, and human health. It is also necessary to develop actions that aim to educate Amazonian populations on safe fish preparation and consumption.

Graphene Oxide Deposited with Transition Metal Chalcogenide for Selective Extraction and Determination of Hg(II): Experimental and Computational Analysis

A graphene oxide (GO/CdS) nanocomposite was synthesized by an in situ hydrothermal process and studied to develop a micro solid phase extraction procedure. Microscopic and spectroscopic characterizations have confirmed the successful preparation of the GO/CdS composite. The prepared nanocomposite selectively extracts Hg(II) ions from various water samples (tap, river, and groundwater). The intriguing characteristic of GO sheets is to provide exceptional hydrophilicity and Hg(II) accessibility to surface-decorated CdS nanoparticles. The GO/CdS nanocomposite shows excellent extraction of trace Hg(II) in a short interval of time. Computations based on density functional theory (DFT) suggest that energetically favorable multinuclear S-Hg binding leads to rapid adsorption with high sorption capacity at GO/CdS sites. The analytical features of merit suggested that the developed method has a low detection limit (0.07 µg L^-1) and shows good accuracy and precision (with RSD 3.5%; N = 5). The developed method was verified by analyzing SRM 1641d (Standard Reference Material) and real samples after spiking to a predetermined amount.

Covalently linked mercaptoacetic acid on ZrO2 coupled cellulose nanofibers for solid phase extraction of Hg(ii): experimental and DFT studies

Zirconium oxide (ZrO₂) nanoparticles were introduced onto cellulose nanofibers after being covalently functionalized with mercaptoacetic acid. We experimentally demonstrate that the nanocomposite is capable of selectively capturing Hg(ii) from aqueous samples down to trace level concentrations. Density functional theory (DFT) calculations indicate that energetically favorable R-S → Hg ← O-R bidentate complex formation enhances the rapid adsorption, leading to selective extraction of Hg(ii). Furthermore, the loss of ZrO₂ particles during flow-through studies is controlled and restricted after binding to CNF rather than being used directly in the column. The Hg(ii) selectivity is primarily due to the Lewis soft-soft acid-base chelation of Hg(ii) with the mercapto functionalities of the adsorbent. The experimental observations depict a high sorption capacity of 280.5 mg g^-1 for Hg(ii). The limit of detection and quantification of the proposed approach were found to be 0.04 μg L^-1 and 0.15 μg L^-1, respectively. Analytical method accuracy and validity were determined by analyzing Standard Reference Materials and by the standard addition method (recovery > 95% with a 5% RSD). The findings of a Student's t-test were found to be lower than the critical Student's t value. Real water samples were successfully analyzed using the developed procedure.