Metal Contamination In Environment Research Articles

Assessment of Heavy Metal Contamination and Health Risks in Crabs (Scylla senrata) from Oil and Non-Oil Producing Communities in Rivers State, Nigeria

Heavy metal contamination in aquatic environments poses significant risks to public health, particularly in regions affected by industrial activities such as oil exploration. These contaminants can accumulate in marine organisms, posing risks to both ecosystems and human health through dietary exposure. The study investigates the health risks associated with heavy metal contamination in Scylla senrata harvested from Abonnema (non-oil producing community, NOPC) and Kula (oil producing community, OPC) in the Niger Delta region, Nigeria, at both low and high tides. The metals analyzed include iron (Fe), lead (Pb), nickel (Ni), manganese (Mn), zinc (Zn), copper (Cu), cadmium (Cd), and chromium (Cr). The analyses were conducted using flame atomic absorption spectrophotometry. Data were analyzed using SPSS software (version 21.0). The results showed significant variation in metal concentrations. Results showed elevated levels of Fe (94.7–146.8 mg/kg), Pb (8.3–38.28 mg/kg), Ni (3.62–6.45 mg/kg), Mn (42.79–71.43 mg/kg), Cu (18.5–27.95 mg/kg), and Cd (1.25–2.00 mg/kg) above WHO/FEPA (2003) limits, particularly in Kula. Chromium (Cr) levels were relatively lower, with concentrations ranging from 0.21 to 0.28 mg/kg at low tide and <0.001 mg/kg at high tide. In addition, zinc (Zn) concentrations remained within the permissible limit. The Estimated Daily Intake (EDI) and Target Hazard Quotient (THQ) calculations indicated that the concentrations of these metals are within safe limits for human consumption, with none of the THQ values exceeding the threshold of 1.0. In conclusion, these findings suggest that while anthropogenic activities, particularly oil exploration, contribute to metal contamination, the consumption of these crabs poses minimal health risk based on current metal exposure levels. Further research and continuous monitoring is recommended to evaluate long-term health and environmental impacts.

MACHINE LEARNING-BASED FORECASTING OF BIOACCUMULATION AND HISTOPATHOLOGICAL EFFECTS IN AQUATIC ORGANISMS

Heavy metal contamination in freshwater environments poses significant risks to aquatic organisms and human health, as these heavy metals enter freshwater systems through various sources, including industrial waste, agricultural runoff, mining and atmospheric deposition. Efforts to develop efficient methods for removing heavy metals from wastewater have gained momentum in recent years. This study focuses on machine learning (ML) models for predicting the bioaccumulation and histopathological effects of heavy metal pollutants on aquatic life under various climate change scenarios. The ML models have shown promise in forecasting the impacts of heavy metal pollution on freshwater ecosystems and informing conservation strategies. It is crucial to understand the complex interactions between environmental factors, climate change and ecosystem health. This study discusses the importance of incorporating diverse species and environmental factors in these models and acknowledges potential challenges, such as inaccuracies and data misinterpretation. Enhancing the predictive capabilities of ML models is essential for better environmental management and conservation practices via refinement and validation of models using updated data and advanced methodologies. This study also emphasizes the broad potential of ML in environmental research, improvement of model capabilities and challenges posed by heavy metal pollution and climate change.

Synergistic effects of combined lead and iprodione exposure on P53 signaling-mediated hepatotoxicity, enterotoxicity and transgenerational toxicity in zebrafish.

Environmental heavy metal contamination, combined with inappropriate use of fungicides, has led to the co-existence of lead (Pb) and iprodione (IPR), presenting signification risks to ecosystems and human health. The toxic effects resulting from concurrent exposure to Pb and IPR, however, remain poorly understood. In the study, we conducted a comprehensive 60-day subchronic study to investigate the toxic effects on the liver and gut in parental male zebrafish through employing multi-omics analyses. We also explored the potential transgenerational toxicity to unexposed offspring embryos. The results demonstrated that exposure to both Pb and IPR exacerbated intestinal pathological damage, decreased the expression of intestinal tight junction molecules, and activated the expression of intestinal inflammatory molecules in the gut. Metabolic and microbial analyses, utilizing 16S rRNA sequencing and non-targeted metabolic profiling, revealed alterations in the intestinal flora structure and disruptions in metabolite synthesis. Notably, we observed a significant negative correlation between the abundance of the Lactobacillus genus and uracil synthesis. Furthermore, liver RNA-seq analysis identified a marked enrichment of the P53 signaling pathway, confirmed by the activation of P53-mediated apoptotic markers, which was consistent with the observed increase in inflammatory infiltration and pathological damage within the liver. Importantly, P53-mediated apoptosis and inflammatory responses were activated in offspring embryos, suggesting that long-term parental exposure to Pb and IPR may induce transgenerational toxicity, potentially impacting offspring health. Despite the identification of these molecular changes, the phenotypic effects remain to be elucidated. Future studies are necessary to evaluate the potential phenotypic changes in offspring to fully understand the long-term effects of Pb and IPR exposure. Overall, these findings enhance the understanding of the molecular mechanisms underlying the toxic effects of Pb and IPR and emphasize the importance of a comprehensive risk assessment of environmental pollutants.

Enhancing source identification of water-soluble heavy metal contamination in urban road sediments: a receptor model approach for water and sediment quality in a Chinese metropolitan area

Abstract This study investigates the concentrations and sources of 8 heavy metals in urban road sediments and a total of 116 samples were collected from 29 locations, with four samples per location from Zhengzhou, China. Pb concentrations significantly exceeded background values, while Hg levels showed variability across locations. Pollution indices reveal that Cu and Cd, two hazardous metals, contribute significantly to urban road dust pollution. Notably, Hg shows high contamination levels, while Pb and Cr exhibit moderate contamination. The measured concentrations of the heavy metals are: Cr (28.32 μg l–1), Cu (334.65 μg l–1), Cd (2.87 μg l–1), Ni (83.20 μg l–1), Zn (204.10 μg l–1), As (45.10 μg l–1), Pb (4.11 μg l–1), and Hg (0.27 μg l–1). Using principal component analysis (PCA), three primary components (PC1, PC2, and PC3) were identified, explaining 86.85% of the variance in heavy metal concentrations. PC1, dominated by Cr and Pb, suggests industrial activities as the main source. PC2, influenced by As and Cd, reflects pollution from agrochemical use, while PC3, with high Ni values, indicates sources from alloy production and electroplating processes. These findings highlight the urgent need for targeted environmental management strategies to mitigate the health and ecological risks posed by heavy metal contamination in urban environments.

Small intestine structural and functional responses to environmental heavy metal stress in tree sparrow Passer montanus nestlings.

Tree sparrow nestlings predominantly consume protein-rich insect larvae, making them vulnerable to environmental heavy metal contamination through the food web, potentially affecting their growth. Understanding the effects of heavy metals on the structure and function of the small intestine, the principal organ responsible for protein digestion and absorption, is therefore crucial. This study investigated tree sparrow nestlings at three developmental stages (3, 6, and 12days old) in Liujiaxia (LJX), a comparatively unpolluted area, and Baiyin (BY), a heavy metal polluted area, to elucidate the factors and mechanisms by which heavy metals affect nutrient absorption. We compared heavy metal accumulation levels, structural integrity, and protein digestion and absorption functions of the duodenum, jejunum, and ileum. The increase of fluctuating asymmetry and decrease in body condition in tree sparrow nestlings were found to be associated with environmental heavy metal accumulation in the small intestine. Structural impairments of villi and crypts were observed in the duodenum and jejunum of tree sparrow nestlings at 3-, 6-, and 12-day-old in the polluted site BY. Conversely, structures related to the ileum were elevated, and the small intestine of nestlings at all stages exhibited abnormally elevated protein digestibility but diminished absorption of amino acids. However, there was no significant difference in small peptide absorption. These findings indicate that environmental heavy metal pollution impacts the structure of the small intestine in tree sparrow nestlings through the food chain and further affects their digestion and absorption function of proteins.

Microplastic abundance, characteristics, and heavy metal contamination in coastal environments of Western Sri Lanka

This study was conducted to assess the abundance of microplastics and associated metal contamination at selected beaches in the Western Province of Sri Lanka. Beach sand samples were collected from four beaches: Modera, Negombo, Mount Lavinia, and Panadura. Microplastics were extracted from dried sand samples using a saturated NaCl solution, followed by sieving. Particles were identified using Fourier Transform InfraRed Spectrophotometer, and associated heavy metals; Cr, Pb, Cu, Zn, and Ni were subjected to acid digestion for 24 h before analysis using Microwave Plasma Atomic Emission Spectrometry. More than half of the extracted plastics (56.31%) were identified as microplastics. The average microplastic abundance in beach sand samples ranged from 42.0 to 91.3 items/kg. The sand collected at Mount Lavinia exhibited the lowest sbundance, whereas those from Panadura beach revealed the highest. Hydrodynamic factors like ocean currents, wave patterns, associated with Southwest monsoon period, and human activities may have caused the variability in microplastic abundances and metal contamination. The majority of the microplastics (52.29%) were polyethylene, followed by polypropylene (35.18%), resembling the records of the most common plastic waste types in the country. Most of the microplastics were found to be fragments (87.95%), while white being the prominent color (53.49%). The toxic trace element concentration ranged from 5.0 × 10−3 to 1.8 × 102 μg/g in beaches. This study establishes a baseline for the west coastline prior to the X-press Pearl Ship Disaster in 2021. Future studies are encouraged to assess the beach microplastic pollution across the- Sri Lankan coastline.

Salix humboldtiana as an Indicator of Air Pollution by Trace Metals in the Urban Areas of the City of Loja, Southern Ecuador

Air pollution is the most important environmental problem in urban areas related to vehicular traffic and industrial activities. The widespread presence of common urban trees, such as Salix humboldtiana, and their ability to tolerate diverse environmental conditions make this species an especially promising candidate for assessing environmental metal contamination. Therefore, biomonitoring with vascular plants has been widely used to assess air pollution, especially the accumulation of trace metal concentrations. Therefore, for the first time, we analyzed the concentration of trace metals using Salix humboldtiana in twelve areas with different levels of pollution in a city in Southern Ecuador. For this purpose, samples were taken from each site to assess the accumulation of trace metals such as Zn, Mn, Fe, Cd, Cr, Pb, Cu, Al, and Ni. The results obtained showed significant differences in the concentrations of Zn, Mn, Fe, and Cd between the urban areas and the control area, indicating that the central areas were the most polluted by vehicular traffic. However, these findings suggest that Salix humboldtiana may not be a particularly effective tool for quantifying levels of environmental metal contamination such as Cu and Ni, at least in urban areas in the city of Loja. This study has demonstrated that Salix humboldtiana leaves can effectively monitor trace metals associated with road traffic emissions in areas with varying levels of vehicular activity, indicating that vascular plants can be utilized for this purpose in tropical cities.

The acquired pco gene cluster in Salmonella enterica mediates resistance to copper.

The pervasive environmental metal contamination has led to selection of heavy-metal resistance genes in bacteria. The pco and sil clusters are located on a mobile genetic element and linked to heavy-metal resistance. These clusters have been found in Salmonella enterica serovars isolated from human clinical cases and foods of animal origin. This may be due to the use of heavy metals, such as copper, in animal feed for their antimicrobial and growth promotion properties. The sil cluster can be found alone or in combination with pco cluster, either in the chromosome or on a plasmid. Previous reports have indicated that sil, but not pco, cluster contributes to copper resistance in S. enterica Typhimurium. However, the role of the pco cluster on the physiology of non-typhoidal S. enterica remains poorly understood. To understand the function of the pco gene cluster, a deletion mutant of pcoABCD genes was constructed using allelic exchange mutagenesis. Deletion of pcoABCD genes inhibited growth of S. enterica in high-copper medium, but only under anaerobic environment. Complementation of the mutant reversed the growth phenotype. The survival of S. enterica in RAW264.7 macrophages was not affected by the loss of pcoABCD genes. This study indicates that the acquired pco cluster is crucial for copper detoxification in S. enterica, but it is not essential for intracellular replication within macrophages.

Significant alleviation of cadmium toxicity in Thalassiosira weissflogii through the combined effect of high silicon and zinc supplementation

Cadmium (Cd), a prevalent pollutant in near-shore seawater ecosystems, poses a significant threat to marine biota. Zinc (Zn) and Cd can have interchangeable physiological effects in marine plankton, and both can influence the synthesis of siliceous walls. Consequently, the concentrations of zinc and silicon may jointly impact the toxicity of Cd. This study endeavors to elucidate the combined effect of silicon (Si) and zinc (Zn) on the growth and physiological responses of the marine diatom species Thalassiosira weissflogii when subjected to Cd-induced stress conditions (190.7 μg L−1). Our results reveal statistically improvements (p<0.05) in biomass production, reductions (p<0.05) in superoxide dismutase (SOD) activity and extracellular secretion in T. weissflogii when high concentrations of Si (172 µmol L−1) and Zn (18.3 nmol L−1) were applied simultaneously. Additionally, examination of Cd bioconcentration factors (BCF) derived from Cd uptake kinetics and intracellular Cd content measurements underscores the ability of elevated Si and Zn concentrations to reduce intracellular Cd accumulation (p<0.05). The ability of Si and Zn to mitigate Cd toxicity was further evidenced by increased cellular biosilica content and maintenance of cell morphology, suggesting a protective role in preserving structural integrity and growth. Our findings underscore the synergistic benefits of Si and Zn in enhancing the resilience of T. weissflogii to Cd stress, providing valuable insights into the potential use of nutrient amendments as a strategy for mitigating heavy metal contamination in marine environments.

Assessment of health risks associated with heavy metal contamination in selected fish and crustacean species from Temsah Lake, Suez Canal

Marine pollution caused by heavy metals has emerged as a significant environmental concern, garnering increased attention in recent years. The accumulation of heavy metals in the tissues of marine organisms poses substantial threats to both marine ecosystems and human populations that rely on seafood as a primary food source. Fish and crustaceans are effective biomonitors for assessing heavy metal contamination in aquatic environments. In this study, we determined the concentrations of several heavy metals, including cadmium (Cd), lead (Pb), nickel (Ni), mercury (Hg), and tin (Sn), in four fish species (Mugil cephalus, Mugil capito, L. aurata, and Morone labrax) and five crustacean species (S. rivulatus, Cerastoderma glaucum, Paratapes undulatus, R. decussatus, Callinectes sapidus, and Metapenaeus Stebbingi) from Temsah Lake during both winter and summer seasons. To evaluate the potential ecological and health risks associated with consuming these fish and crustacean species, we calculated the metal pollution index (MPI), weekly intake (EWI), target hazard quotient (THQ), and carcinogenic risk (CR) values. The results revealed a noticeable increase in metal levels during the summer compared to winter in the studied samples. Moreover, the concentration of heavy metals in the muscles of the species generally exceeded those in the liver and gills. The MPI values indicated that Morone labrax exhibited the highest values during winter, while L. aurata showed the highest values during summer. Mugil cephalus demonstrated the lowest MPI values in both seasons. The EWI values for the studied metals were found to be lower than the corresponding tolerable weekly intake (TWI) values. Additionally, under average exposure conditions, the THQ and HI data were generally below one for most study species in the area. The calculated CR values for investigated metals in the studied species indicated acceptable carcinogenic risk levels. Therefore, this suggests that consuming studied species within Temsah lake does not present any potential health hazards for consumers.

Impact of Exposure to Leaves From Metal-Polluted Sites on the Developmental Parameters of Larvae of the Dark Sword-Grass, Agrotis ipsilon (Lepidoptera: Noctuidae)

Insects are impacted by pollutants in their environments and food sources. Herein, we set out a semi-field study to assess the impact of environmental heavy metal contamination on developmental parameters, energy reserves, and acidic and alkaline phosphatases in the larval Agrotis ipsilon (Lepidoptera: Noctuidae). Castor leaves from contaminated and uncontaminated (reference site) areas were fed to A. ipsilon larvae in all treatments. The heavy metal concentrations in the plant from different areas (contaminated and reference sites) and in the larvae were analyzed. Toxic effects were observed in the larvae feeding on the leaves from the metal contaminated areas. Larval and pupal weights, growth indices, and larval fitness were all significantly lower than in the reference group. Likewise, in the third and fourth instars, there was a significant decrease in both the survival and moth emergence rates. In contrast, the pupation duration was significantly longer. Total protein, lipid, and glycogen content showed significant reductions in treated larvae. Larval homogenate samples contaminated with heavy metals showed a significant increase in acid- and alkaline- phosphatase levels. The results obtained could provide a basis for a long-term evaluation of the risk associated with heavy metals and their impact on plant populations and important agricultural pests.

Accumulation and Phytoremediation Potentiality of Trace and Heavy Metals in Some Selected Aquatic Plants from a Highly Urbanized Subtropical Estuary

The global concern over trace and heavy metal contamination in aquatic environments necessitates the development of effective remediation strategies. Using aquatic plants for heavy metal removal is a relatively economical and sustainable technology worldwide. This study involved collecting sediment and aquatic plant samples (Acanthus ilicifolius, Typha elephantina, and Cynodon dactylon) from a highly urbanized estuary to analyze metal concentrations in sediment, assess ecological risks, and explore the phytoremediation potential. Trace and heavy metals were detected using Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF). The sediment metal concentrations were found in decreasing order of Fe, Ti, Mn, Rb, Zr, Zn, Sr, Cu, Co, and As. Fe, Sr, and As concentrations were below certified values, whereas Cu, Zn, and Rb exceeded them. Cumulatively, the pollution load index (PLI) values were close to 1 (0.845), indicating that the study area is likely experiencing metal pollution. The Contamination Factor (CF) values, ranging from 1 to 3, indicated a moderate degree of sediment pollution for Ti, Mn, Cu, Zn, and Rb. The Enrichment Factor (EF) values similarly showed moderate enrichment for these metals, with Cu exhibiting the highest degree of enrichment. Ecological risk assessment highlighted the only metal, Cu, as posing the greatest risk among the studied metals. In terms of phytoremediation potential, the bioconcentration factor (BCF) followed the decreasing order of C. dactylon &gt; A. ilicifolius &gt; T. elephantina for most metals, with low BCF values (&lt;1) indicating low accumulator potential. However, the translocation factor (TF) values for Zn (1.464) and Rb (1.299) in A. ilicifolius species were greater than 1, indicating low accumulation potential but hyper-metabolizing capabilities, allowing the plant to accumulate metals in its aerial parts, making it effective for phytostabilization.

Ecotoxicological consequences of urbanization: A multi-biomarker approach to assessing sewage treatment plant effects on free-living birds

Birds are good bioindicators of disturbance in the environment. They are present in different habitats and trophic levels. In addition, rapid urbanization has led birds to use cities as shelter and for seeking food resources. Sewage treatment plants (STPs) are suitable locations for free-living birds within cities. However, few studies address the impacts of emerging pollutants from sewage treatment plants on wild birds. In this sense, the aim of this study was to analyze the genotoxic, mutagenic, and immunological impacts from metal and pollutant exposure on free-living birds collected at a STP. For comparison, birds were collected in a preserved environment, the Silvania National Forest (FLONA). To achieve this, we used non-destructive biomarkers sensitive to environmental changes. Birds were collected in both environments using mist nets. After collection, birds were weighed, measured, species-identified, and released. Blood was collected for comet assay, micronucleus test, and leukocyte profile, while feathers were collected for metal concentration analysis. Water physicochemical parameters were measured at both sites, and water samples were collected for metal analysis. Our results demonstrated that birds collected at the STP exhibit a higher frequency of genotoxic damage and erythrocyte abnormalities, and increased immune response compared to FLONA birds. Traces of potentially toxic metals, such as Hg and As, were found in the birds feathers from both environments, raising concerns about metal contamination in both environments. Trophic guilds appear to respond similarly to exposure. The parameters and metals found in the water reflect environmental characteristics and may be influencing pollutant availability. Finally, despite the advancement of our findings, studies linking these damages to detrimental effects on behavior and reproduction are encouraged.

Assessment of ecological risk and metal contamination caused by the Lihoud River emissary along the Bay of Tangier Littoral in Morocco (Southwestern Mediterranean Sea)

AbstractThis study aimed to evaluate the environmental risks and metal contamination at Marqala Beach, a popular destination. Wet and dry beach sediments were collected from along this coastline for a full comprehensive analysis of the area. The assessment involved both physicochemical characterization of the sediments and determination of heavy metal contamination levels. Various pollution indices, including the geo‐accumulation index (Igeo), enrichment factor (EF), contamination factor (CF), modified contamination degree (mCd), pollution load index (PLI), potential ecological risk factor (Ef), and potential ecological risk index (RI) were used to evaluate the ecological and health risk. These indices highlight the impact of human activities and indicate that contamination is primarily due to elevated levels of As, Cr, Zn, and Pb. Furthermore, X‐ray fluorescence (XRF) analysis showed that SiO2 was the dominant element in the sediment samples, followed by CaO and Al2O3. This suggests a mineralogical and compositional combination. X‐ray diffraction (XRD) characterization confirmed quartz dominance and the presence of aluminosilicate and calcium silicate minerals, aligning with XRF findings. Additionally, the scanning electron microscope (SEM) analysis revealed a non‐crystalline structure with a sandy texture, as evidenced by the macrostructure and granulometric analyses, while the polluted sediments showed smaller particle sizes, consisting of tiny particles (oxides) and organic matter on quartz crystals.

Synergistic effect on simultaneous treatment of Cr(VI) and chloramphenicol using a non-thermal plasma technology

Toxic organic and heavy metal contaminants commonly exist in industrial waste stream(s) and treatment is of great challenge. In this study, a dielectric barrier discharge (DBD) non-thermal plasma technology was employed for the simultaneous treatment of two important contaminants, chloramphenicol (CAP) and Cr(VI) in an aqueous solution through redox transformations. More than 70% of CAP and 20% of TOC were degraded in 60 min, while Cr(VI) was completely removed in 10 min. The hydroxyl radicals were the main active species for the degradation. Meanwhile, the consumption of hydroxyl radicals was beneficial to the reduction of Cr(VI). The synergistic effect was investigated between CAP degradation and Cr(VI) reduction. The reduction of Cr(VI) would be enhanced in the presence of CAP with a low concentration and could be inhibited under a high concentration, because part of hydroxyl radicals could be consumed by the low-concentration CAP and the obtained intermediates with a higher kinetic rate. However, CAP with a high concentration could react with such reductive species as eaq− and •H, which could compete with Cr(VI) and inhibit the reduction. In addition, the presence of Cr(VI) enhanced the degradation and mineralization of CAP; the study of obtained intermediates indicated that the presence of Cr(VI) changed the degradation path of CAP as Cr(VI) would react with reductive species, enhance the generation of hydroxyl radicals, and cause more hydroxylation reactions. Moreover, the mechanism for the simultaneous redox transformations of CAP and Cr(VI) was illustrated. This study indicates that the DBD non-thermal plasma technology can be one of better solutions for simultaneous elimination of heavy metal and organic contaminants in aquatic environments.

Tracing and source fingerprinting of metals from the southern coastal sediments in Bangladesh.

Trace element pollution from anthropogenic sources is increasingly widespread. This pollution in terrestrial environments threatens agricultural crop production, while in aquatic environments, it threatens fish cultivation. The contamination of these crucial food sources raises significant concerns regarding food safety, security, and its potential adverse effects on human health. Coastal areas are particularly vulnerable to heavy metal pollution due to their proximity to industrial and urban centres, as well as their susceptibility to contamination from marine sources. In attempting to identify the sources of heavy metals (As, Cu, Cr, Cd, Fe, Hg, Mn, Ni, Pb, and Zn) and measure their contributions, we collected soil samples from thirty sites along the three coastal districts (Patuakhali, Barguna, and Bhola) in Bangladesh. Using atomic absorption spectroscopy, heavy metal concentrations in soil samples were measured and three receptor models (PMF, PCA-MLR, and UNMIX) were applied to detect their sources. Pairwise correlation analysis of metal concentrations in 30 sites across 3 coastal districts showed all possible patterns, including both significant and insignificant positive and negative relationships between different metals, except for As and Hg which did not display any significant relationships with other metals. The concentrations of Cu, Fe, Mn, Ni, and Zn exceed the US-EPA sediment quality standard. The applied PCA-MLR, PMF, and UNMIX models identified several sources of heavy metal contamination, including (i) mixed anthropogenic and natural activities: contribution of 59%, 37%, and 43%, and (ii) vehicle emissions: contribution of 23%, 26% and 29%. The recognized metal sources should be prioritised to avoid the discharge of poisonous pollutants from anthropogenic factors and any possible future exposure. This study's findings have implications for ongoing monitoring and management of heavy metal contamination in coastal environments to mitigate potential health and ecological impacts and can inform policy development and management strategies.

Editorial: Metal contamination, bioaccumulation, and toxicity in coastal environments under increasing anthropogenic impacts

Editorial: Metal contamination, bioaccumulation, and toxicity in coastal environments under increasing anthropogenic impacts

Electrochemical Sensors Go Nano: Carbon Nanomaterials for Ultrasensitive Heavy Metal Analysis

Background: Heavy metal contamination of food and the environment is a major concern worldwide. Conventional detection techniques like atomic absorption spectroscopy (AAS), inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) have limitations including high costs and insufficient sensitivity. Electrochemical sensors based on carbon nanomaterials have emerged as an attractive alternative for rapid, affordable, and ultrasensitive heavy metal analysis. Methods: This review summarizes recent advances in using carbon nanomaterials like ordered mesoporous carbon, carbon nanotubes, graphene and carbon dots for electrochemical sensing of toxic heavy metals. Synthesis methods, characterization techniques, functionalization strategies and detection mechanisms are discussed. Results: High surface area, electrical conductivity and electrocatalytic activity of carbon nanomaterials enable preconcentration of metal ions and signal amplification at electrode interfaces. This results in remarkably low detection limits down to parts per trillion levels. Functionalization with metal nanoparticles, molecularly imprinted polymers and other nanocomposites further improves sensor selectivity and sensitivity. These sensors have been applied for the quantitative detection of arsenic, mercury, lead, cadmium, chromium, and other toxic metals in lab samples Conclusion: Electrochemical sensors based on carbon nanotubes, graphene, mesoporous carbon, and carbon dots are rapidly emerging as an ultrasensitive, cost-effective alternative to conventional techniques for on-site screening of heavy metal contamination in food and environment. Further validation using real-world samples and integration into portable field testing kits can enable widespread deployment.

Heavy Metals (As, Cd, Hg and Pb) in Hare Tissues: A Survey

Concerns have been escalating over the increase in heavy metal levels in the envi- ronment due to anthropogenic impacts. Toxic heavy metals (As, Cd, Hg and Pb) are especially dangerous, as they negatively affect organisms and cause outbreaks of diseases. The hare has been proven to be a good indicator of environmental heavy metal contamination. The liver and kidney are the tissues most commonly used in biomonitoring. Hares inhabiting a contaminated habitat have higher concentrations of heavy metals in these tissues than those from a referential habitat. As is mostly accumulated in the nails and hair, Cd in the kidney, Hg in the brain and kidney, and Pb in the brain and diaphragm. Cd and Hg concentrations in hare liver and kidney increased with animal age. In most countries, hare meat is safe for human consumption, while the consumption of entrails is not recommended.

Distribution and accumulation of Cadmium in different trophic levels affecting Serangium japonicum, the predatory beetle of whitefly Bemisia tabaci, biologically, physiologically and genetically: An experimental study

Cadmium (Cd) is a heavy metal that is of great concern in agroecosystems due to its toxicity to plants, herbivores, carnivores, and human beings. The current study evaluated the allocation and bioaccumulation of Cd from soil to cotton plants, cotton plants to herbivore pests, and herbivorous pests to a natural enemy predator. When soil was spiked with 100 mg/kg Cd, results demonstrated that cotton roots accumulated more Cd than the stems and leaves. The bioaccumulation of Cd was less in 4th instar larvae, pupa, and adults of Serangium japonicum than in Bemisia tabaci adults. The bioaccumulation in S. japonicum elongated the immature development period and reduced adult longevity, oviposition days, fertility, and total pre-oviposition duration. The net reproduction of S. japonicum was also reduced, as was female mature weight and feeding potential; as a result, Cd exposure could reduce the future population size compared to uncontaminated populations. There was decreased activity of the antioxidant enzymes (SOD, CAT, and POD) and energy-conserving lipids (glycogen, triglyceride, and total cholesterol) in Cd-contaminated S. japonicum compared to controls. The detoxifying enzyme activity of GST and P450 increased while AChE activity did not change. The qRT-PCR research showed that SOD1, CAT, POD, glycogen, and triglyceride gene expression was higher than in controls, whereas detoxification gene expression did not change. Our results indicate that Cd exposure has a physiological trade-off between its adverse effects on life history traits and elevated detoxification and antioxidation of S. japonicum, which could result from gene expression alteration. Further studies are needed to assess whether Cd exposure causes irreversible DNA damage in S. japonicum.