Toxic Effects Of Heavy Metals Research Articles

Computer-aided design of microfluidic resistive network using circuit partition and CFD-based optimization and application in microalgae assessment for marine ecological toxicity

We present an automatic design process for microfluidic dilution network towards marine ecological toxicity assessment on microalgae. Based on the hydraulic-electric circuit analogy, we defined an abstract specification using computer-aided designing system. Several approaches, especially circuit partition, were applied to minimize design effort. Computational fluid dynamics (CFD) simulation was exploited to convert the electrics specification to fabrication model. We automatically designed the combinational-mixing-serial dilution microfluidics to generate parallel stepwise gradients for mixing chemicals (binary/ternary/quaternary mixture) using the present algorithm. We critically discussed design rules and evaluated the microfluidic performance by colorimetric analysis. To examine whether these microfluidic chips can be used for toxicity test on microalgae, single and joint toxic effects of heavy metals (copper, mercury, zinc, and cadmium) were examined on line. In all cases, dose-related toxic responses were successfully detected. These results provided a solution for designing resistive network using circuit partition and CFD-based optimization and a route to develop a promising user-friendly alternative for microalgae bioassays as well as cell-based screening experiments in risk assessment.

Non-Carcinogenic Risk Assessment of Heavy Metals Through Exposure to the Household Dust (Case Study: City of Khorramabad, Iran)

Background: Household dust is known as an important source of toxic heavy metals for all age groups particularly for children and this problem is a major concern around the world. Objectives: This study was designed to assess the non-carcinogenic risk of cadmium (Cd), chromium (Cr), lead (Pb), and nickel (Ni) in indoor dust collected from 20 private residences in the city of Khorramabad, west of Iran, during year 2017. Methods: In this study, a total of 80 household dust specimens were collected using a brush and plastic spatula. After dust samples were naturally air-dried and sieved through a nylon mesh and then acid digested, the element contents were measured using inductively coupled plasma spectrometer. Also, the non-carcinogenic risk was calculated based on the models developed by the United States Environmental Protection Agency. Results: The results showed that the maximum concentrations of elements in dust samples were 17.72 mg/kg for Cd, 22.55 mg/kg for Cr, 101.65 mg/kg for Pb, and 89.47 mg/kg for Ni. Also, based on the results, ingestion (oral) of dust particles was the main exposure pathway to elements. On the other hand, the non-carcinogenic risk levels of all analyzed metals were lower than the allowable limit. Conclusions: Due to adverse effects of toxic heavy metals on human health, it is recommended to pay special attention to other toxic elements of household dust that citizens have long-term exposure to.

Drinking Water Disparities in Tennessee: The Origins and Effects of Toxic Heavy Metals

Several toxic metals, commonly present in drinking water, are believed to play important roles in the development of cancerous tumors. Although the US Safe Drinking Water Act requires drinking water to meet health standards set by the Environmental Protection Agency, violations occur regularly. In this study, we have investigated the role of the two predominant toxic heavy metals identified in the drinking water sources in Tennessee: copper and lead. We have analyzed the levels of copper and lead, as well as the total water hardness among different counties of Tennessee, with different socioeconomic backgrounds. We determined that the effects of lead and copper in drinking water were random, although counties with typically lower average household incomes typically had higher levels of the metals. The contaminant levels were found to remain below the threshold established by the Environmental Protection Agency and the State of Tennessee. Water from the Cumberland River was harder than water obtained from other rivers in Tennessee. Furthermore, the total hardness of water did not correlate with the average household income of the various counties.

Seasonal variations of heavy metals levels in water, sediment and soft parts of edible bivalve Donax trunculus collected from Port Said coast, Egypt

The aim of this study was to get quantitative data on the seasonal variations of heavy metals levels (i.e. Fe, Mn, Cu, Zn, Pb and Cd), in different samples (i.e. surface water, sediment and soft parts of the bivalvian Donax trunculus) collected from four consecutive sites over the four seasons; El-Gamil airport, El-Gamil inlet, El-Fardous, and El-Manasra along Port Said Coast, Port Said, Egypt. The relationships between physicochemical parameters (i.e. pH, Temperature, Salinity and D.O) and heavy metal concentrations were assessed, as well. The obtained results showed that the order of mean of the heavy metals concentration in water was appeared as Zn ˃ Fe ˃ Pb ˃ Cd ˃ Cu, while their order in the soft parts of D. trunculus was appeared as Fe˃ Mn ˃Zn˃ Pb ˃Cu˃ Cd. Furthermore, the data rveaed that the mean of heavy metals concentration in sediment samples was appeared as Fe˃ Mn ˃Zn˃ Pb ˃Cu˃ Cd. Additionally, the concentrations of the heavy metals in water samples recorded the lowest value compering to their concentrations in the soft parts of D. trunculus and sediment samples. As a result, Fe recorded its higher value in the soft parts of D. tranculus during spring season which was 854.8, 542.6, 352.7 mg/g dry weight in El-Gamil airport, El-Gamil inlet and El-Fardous sampling sites, respectively. . The obtained data indicated that there was a noticeable relationship between physicochemical parameters (i.e. pH, Temperature, Salinity and D.O) and heavy metal accumulation in surface water, sediment and soft parts of the molluscan D.trunculus Therefore studies on chronic toxic effects of heavy metals in marine organisms, especially edible bivalvia, are needed as a possible public health threat from sea food dietary.

Effect of copper and vanadium ions on morphology of carrot (Daucus carota L. subsp. sativus (Hoffm.) Schübl. & G. Martens) and wheat (Triticum aestivum L.) plants

In the whole world, researches are conducting on toxic effect of heavy metals on living organisms. The problem with heavy metal occurrence in the environment is not only associated with their toxicity, but also with their ability to accumulate inside living organisms. This study presents the effect of copper and vanadium ions on germination and growth of carrot (Daucus carota L subsp. sativus (Hoffm.) Schübl. & G. Martens.) and winter wheat (Triticum aestivum L.). The experiment was carried out in two independent series with ten repetitions each. The water solutions of copper (CuSO4) and vanadium (H4NO3V) salts with the concentrations: 0.6 mM, 0.3 mM, 3 mM and 6 mM were used. The control groups were objects watered with distilled water. The conducted experiment showed that, the copper and vanadium ions had negative effect on germination and growth of plants. With the increasing of concentration of heavy metal ions an inhibition of seeds germination capacity was observed. The length of D. carota and T. aestivum seedlings in each salt solutions was inhibited, compared to the control group. During the growth phase, the stimulation of wheat leaves growth, only on copper solutions with concentration 3 mM and 6 mM was observed. Changes of a fresh and dry weight, and a water content were observed, depending on the copper and vanadium ions concentration.

Ectomycorrhizal fungi may not act as a barrier inhibiting host plant absorption of heavy metals

Whether the huge external hyphal system of ectomycorrhizae that promotes host plants' acquisition of water and nutrients can selectively inhibit their transport of heavy metals at the same time remains unclear. In this experiment, we designed and conducted two types of soil-pot test to clarify the effects of EMF on the absorption and transport of copper (Cu) and cadmium (Cd) by host Pinus thunbergii seedlings. In the root-bag test, external hyphae took the initiative into the Cu/Cd-contaminated bulk soil, absorb and transport Cu and Cd to the rhizosphere soils and further transport it to the shoots of the host plants. Inoculation with EMF also promoted the uptake of nutrients by host plants, thereby increasing their biomass and improving Cu/Cd tolerance compared with non-inoculated plants. Inoculation with EMF species with higher Cu or Cd tolerance generated more phytostabilization and phytoextraction of Cu or Cd by host plants. In a short-term exposure test, inoculation with EMF accelerated the absorption of Cu and Cd by P. thunbergii within 12 h of Cu or Cd irrigation. Therefore, we concluded that EMF do not act as a barrier inhibiting the absorption of heavy metals by host plants, but rather promote this absorption. Improving the plant's nutritional status and promoting growth, diluting heavy metal concentrations, thereby reducing the toxic effects of heavy metals on host plants. These results provide the theoretical basis for the application of EMF in plant–microbial combinations for the phytostabilization and phytoextraction of heavy metal–contaminated soils.

Uptake effects of toxic heavy metals from growth soils into jujube and persimmon of China.

Compared with other agricultural plants, information about uptake effects of toxic heavy metals from growth soils into persimmon and jujube are scarce. In this study, the single and comprehensive uptake effects of five toxic heavy metals (Pb, As, Cd, Cr, and Hg) between the two fruits and their growth soils were investigated. The results showed that the average concentrations of heavy metals in the two fruits were found to be 30 (Pb), 6.6 (As), 2.3 (Cd), 38 (Cr), and 0.33 (Hg) μg/kg, respectively. The average concentrations of heavy metals in their growth soils were 26.31 (Pb), 9.63 (As), 0.12 (Cd), 57.6 (Cr), and 0.049 (Hg) mg/kg, respectively. An uptake effect was observed for the two fruits. The values of Nemerow pollution index (NPI) in the two fruits and their growth soils were 0.10 and 0.55, respectively. The average bioconcentration factor (BCF) values of Pb, As, Cd, Cr, and Hg in the two fruits were 0.0012, 0.00075, 0.021, 0.00077, and 0.012, respectively. Based on the residue levels of toxic heavy metals in the growth soils and soil parameters, the prediction models for NPI and BCF were established, with the adjusted regression coefficients of 0.65 (NPI) and 0.81 (BCF). The contribution rates of different soil parameters to NPI were 21.7% (OC), 16.1% (Pb), 17.1% (Cr), 19.8% (Cd), and 25.4% (As), respectively. The contribution rates of different soil parameters to BCF were 10.2% (OC), 9.4% (Cr), and 80.4% (Cd), respectively.

Lead and cadmium contamination in a large sample of United States infant formulas and baby foods

Data is limited on lead and cadmium contamination in baby food, a population uniquely susceptible to the toxic effects of heavy metals. The goal of this study was to examine lead and cadmium concentrations in a large convenience sample of US baby foods. We identified the number of baby food product samples that exceeded US FDA and California Proposition 65 limits for daily lead consumption across a range of servings/calories, and the number of samples that exceeded World Health Organization and California Proposition 65 limits for daily cadmium consumption across a range of servings/calories. In total, 564 baby foods were tested across infant and toddler formula, cereals, meals, juices/drinks, jars, pouches, snacks, and electrolyte water. ICP-MS analysis of lead and cadmium was completed using a modified version of EPA method 6020A. Samples were analyzed using kinetic energy distribution mode. Lead was detected in 37% of samples (median = non-detect, 75% = 5.6, maximum = 183.6 μg/kg), and cadmium in 57% (25% = non-detect, median = 2.8, 75% = 9.5, maximum = 103.90 μg/kg). Of 91 infant formula samples, none exceeded FDA lead consumption guidelines in 31 oz, but 22% exceeded the Proposition 65 lead guidelines, 23% exceeded the Proposition 65 cadmium guidelines, and 14% exceeded the WHO tolerable cadmium intake levels for a four-month-old baby. In the solid baby food samples, 1% exceeded FDA lead guidelines in two servings (26% exceeded CA Proposition 65 limits), 3% in 300 cal (34% exceeded CA Proposition 65 limits). For cadmium, 6% exceeded Proposition 65 guidelines in two servings, 8% in 300 cal. There was no association between whether the product was certified organic and its heavy metal concentration. Products containing rice were higher in both lead and cadmium concentrations. Further research is needed to understand the long-term health effects of this chronic daily low level heavy metal exposure in babies.

Benthic foraminifera in a coastal marine area of the eastern Ligurian Sea (Italy): Response to environmental stress

Benthic foraminiferal assemblages from 19 superficial marine sediment samples of a coastal area in the Ligurian Sea were analysed for benthic foraminifera in order to recognize changes in assemblage composition and structure, decrease of faunal density, increased morphological abnormalities and inclusion of heavy metals in carbonate tests as possible evidences of environmental stress. Also grain size was determined as a main factor conditioning foraminifer’s distribution.The generalized low faunal density was considered as indicative of environmental stress, attributable to the well-known natural Cr and Ni enrichment, which characterizes marine sediments of the region. The cluster analysis highlighted distinct foraminiferal assemblages with decreasing species diversity approaching to the coast. This distribution was interpreted as the result of local source of environmental stress, probably due to the stream contribution. Deformed foraminifera more abundant than background levels of unstressed environments were also recorded in 39% of samples.Energy Dispersive Spectroscopy (EDS) analyses were carried out on carbonate tests of 55 specimens to investigate the role of the incorporation of heavy metals in the development of morphological abnormalities. Foraminifera showed the inclusion of heavy metals, not present in control specimens, indicating that environmental stress, due to metal sediment enrichment, plays a role in this phenomenon. Although anomalous elements were detected both in normal and deformed specimens and chambers, it was supposed that deformities develop as a result of the toxic effect of heavy metals on cytological activities because, contrarily to the normal specimens, all the deformed ones included anomalous elements. Higher occurrence of deformities in porcelaneous tests, typically enriched in Mg, is associated to the higher number of incorporated elements (Mn, Fe, Cu and Zn).

Response of the Germination of Bean (Vigna unguiculata�L. (Walp) to the Toxic Effects of Heavy Metals

Objective: To evaluate the toxic effects of metals on the crop Beans (Vigna unguiculata L. (Walp). Materials and Methods: assays of seed germination, elongation of the root, growth of hypocotyl and radicle in these plants as biomonitoring parameters varying concentrations of metals. The metals selected for this study were Cd and Pb. Findings: The seeds of V. unguiculata were sensitive to the presence of metals in comparison to the behavior of plants witnesses, showing all the biomarkers evaluated sensitivity to Cd and Pb however did not complete blockade of the germination and initial growth of seedlings, being the effect more dramatic by the presence of cadmium than with lead, observing a maximum values in the germination rate of 63 and 80%, respectively, in comparison with the control treatment, which were correlated with strongly to changes in morphology and anatomy of the seed. Application/Improvements: The Bean was able to survive and tolerate these polluting metals, so it could be used for the ecotoxicological monitoring of contaminated soils for future studies of phytoremediation. Keywords: Heavy Metals, Seed Germination, Toxic Effects, Vigna unguiculata

The Influence of Heavy Metal Ions on the Viability and Metabolic Enzyme Activity of the Marbled Crayfish <i>Procambarus virginalis</i> (Lyko, 2017)

In the experiment with marbled crayfish Procambarusvirginalis (Lyko, 2017), chronic effects of various concentrations of heavy metal ions on the physiological state and enzyme activity were investigated. The obtained results showed that among the investigated heavy metals nickel ions influenced the weight indexes and mortality of crustaceans the most negatively. According to the results of the research, significant changes were noted in the individual biochemical parameters of marbled crayfish under the influence of manganese, lead and nickel ions. The most significant changes in the activity of lactate dehydrogenase were detected in muscle tissues affected by manganese and nickel ions. A significant decrease in the activity of succinate dehydrogenase in muscle of marbled crayfish was determined after the action of heavy metal ions. Investigation of changes in the activity of alkaline phosphatase under the influence of the ions of manganese, lead and nickel has its own characteristics, which indicates certain violations in the tissues of cell membranes. Changes in the activity of enzymes were also reflected in the overall protein content. Changes in these parameters may indicate a rapid biochemical response of crustaceans to the toxic effects of heavy metals.

The Influence of Heavy Metal Ions on the Viability and Metabolic Enzyme Activity of the Marbled Crayfish <i>Procambarus virginalis</i> (Lyko, 2017)

In the experiment with marbled crayfishProcambarusvirginalis(Lyko, 2017), chronic effects of various concentrations of heavy metal ions on the physiological state and enzyme activity were investigated. The obtained results showed that among the investigated heavy metals nickel ions influenced the weight indexes and mortality of crustaceans the most negatively. According to the results of the research, significant changes were noted in the individual biochemical parameters of marbled crayfish under the influence of manganese, lead and nickel ions. The most significant changes in the activity of lactate dehydrogenase were detected in muscle tissues affected by manganese and nickel ions. A significant decrease in the activity of succinate dehydrogenase in muscle of marbled crayfish was determined after the action of heavy metal ions. Investigation of changes in the activity of alkaline phosphatase under the influence of the ions of manganese, lead and nickel has its own characteristics, which indicates certain violations in the tissues of cell membranes. Changes in the activity of enzymes were also reflected in the overall protein content. Changes in these parameters may indicate a rapid biochemical response of crustaceans to the toxic effects of heavy metals.

Chromium(III) Sensor Using Ion Selective Membrane Immobilized on FET for Ground Water Pollution

The effects of heavy metal toxicity on humans are detrimental. Exposure to these high density transition metals like mercury, lead, chromium and so on beyond tolerable limits can lead to failure of the neurological, gastrointestinal, respiratory systems; in most cases cancer. This report demonstrates development of a bio-sensor to measure concentration of chromium(III) in ground water samples with a detection limit of 10-13M and a response time of ten minutes. The sensor gives best sensitivity in a pH range of 3-5. However, the calibration curve is maintained at neutral pH and hence sample can be tested without pre-treatment. Seamless integration of FET with electronic device manufacturing and simple user-interface is another advantage of the easy-to-use sensor which makes it convenient to manufacture and ideal for daily use.

Growth Responses and Photosynthetic Indices of Bamboo Plant (Indocalamus latifolius) under Heavy Metal Stress.

Investigating factors involved in the alleviation of the toxic effects of heavy metals (HMs) on plants is regarded as one of the important research concerns in the environmental field. The southern regions of China are severely impacted by human-induced heavy metal (HM) contamination, which poses an impediment to growth and productivity of bamboo (Indocalamus latifolius) plants. This necessitates the investigation of the effects of HMs on growth and physiological properties of bamboo. Therefore, the aim of the study was to evaluate some gas exchange and growth parameters in two-year-old bamboo species under HMs stress. A greenhouse-based experiment was conducted at Nanjing Forestry University, where the bamboo plant was treated with three HMs (Cu, Pb, and Zn) at four different concentrations (0, 500, 1000, and 2000 mg kg-1). The results illustrated that excessive HMs (1000 and 2000 mg kg−1) triggered a decline in a number of photosynthetic-related indices including the rate of photosynthesis (μmol CO2 m−2 s−1), intercellular CO2 concentration (μmol CO2 mol−1), conductance to H2O (mol H2O m−2 s−1), and net assimilation as well as transpiration. Morphological indices were also depressed as a result of the adverse influence of HMs, leading to decreased shoot length (10 to 73%) and reduced number of emerged plants (6 to 57%). Also, the results indicated that Pb had the greatest harmful impact on the growth indices.

Salicylic acid triggers adaptation cadmium cytogenetic toxicity in roots of Nigella sativa L.

CADMIUM (Cd) is a toxic heavy-metal pollutant in the environment, it is a nonessential element, which strongly inhibits plant growth and development, and causes plant death even at very low concentrations. Root tip cells of Nigella sativa were separately treated with different concentrations (5, 10, 25 and 50ppm) of cadmium for 3, 6, 12 and 24h and the results were recorded. The results showed that all concentrations of cadmium reduced the mitotic index and caused a disturbance in the frequencies of mitotic phases. The treatment with 50ppm of metal for 24h was the most effective in reducing the mitotic activity and inducing the highest percentage of mitotic abnormalities. The different types of abnormalities were irregulatries, bridges, sickness at different phases, disturbed chromosomes or bi nucleated cells, forward and lagging chromosomes. Also, in this study three concentrations of SA (0.01, 0.1 and 0.2mM) for 6 and 12h were used to recover the cytotoxicity of the cadmium treatment (50ppm for 3 and 24h). This Post treatment with SA resulted in increasing MI and significant reduction of chromosomal abnormalities. These results illustrate the ameliorating effect of SA under stress conditions and reveal that SA is effective in alleviating the toxic effects of heavy metals at all applied concentrations.

Ecotoxicologists must facilitate the setting of standards for safeguarding aquatic life

Intensified agriculture and accelerated development have resulted in large amounts of toxic chemicals entering our natural water bodies, imposing health risks to aquatic fauna. Considering the toxin levels at which ill effects are induced, the existing national guidelines for the release of effluents are seen to be inadequate for ensuring the safety of biota inhabiting these aquatic systems. The volume of research work on various aspects of ecotoxicology in Sri Lanka has increased in the recent past. A large majority of studies have focused on assessing the toxic effects of heavy metals – from among the wide range of toxicants – on selected aquatic and soil biota. Locally, many of the studies have used fish and amphibians for bioassays, while a few have investigated toxicity to earthworms and freshwater prawns. The frequently used endpoints of toxicity are the Lethal Concentrations (LC50 values). Other studies have evaluated the Effective Concentration (EC 50), Low effect concentration (LOEC) and No effect concentration (NOEC) considering sub-lethal impacts such as retardation in growth and development, occurrence of physical abnormalities, and histological, haematological and genetic aberrations. While many of the investigations so far have focused on selected species, ramifications at the community and ecosystem levels have not been assessed and still remain mere predictions. This article presents an overview of recent ecotoxicological research carried out in Sri Lanka on the effects of aquatic and soil toxicants on fauna. The scope of the published work has been outlined and the gaps in research identified. The article also touches upon directions for future ecotoxicological research in Sri Lanka.

Precipitation of Copper (II) in a Two-Stage Continuous Treatment System Using Sulfate Reducing Bacteria

Biologically driven precipitation of dissolved copper and other trace metals has been used to treat contaminated aqueous streams. However, high dissolved trace metal concentrations can lead to toxicity, and their bioremediation difficult. Furthermore sorption of trace metals onto biomass might result in large amounts of contaminated byproducts. The aim of this work was to develop and test a two-stage reactor to bypass the toxic effects on the bacteria and chemically precipitate copper without contaminating the bulk of the biomass. Hence, copper removal using a sulfate reducing bacteria culture was investigated in a two-stage continuous treatment system. The first reactor was a sand-filled biological reactor in which the sulfate is reduced, followed by a second reactor/clarifier where the chemical precipitation and sedimentation of a CuS phase occurs. The influent Cu2+ concentration was varied systematically between 15 and 600 mg/L, and the precipitation of Cu2+ metal as CuS was achieved in the second reactor, resulting in complete (within detection limits) Cu2+ removal. EDS analysis on the solid phase collected from the second reactor confirmed the presence of Cu and S in the precipitate. EDS analysis on the solid phase collected from the second reactor confirmed the presence of Cu and S in the precipitate, and a CuS phase with minimal biomass was obtained. This configuration avoids toxicity effects of heavy metals in the biological reactor, as well as the contamination of biomass with the trace metal. Furthermore, the biomass free CuS precipitates can be easily disposed or even used to recover the trace metal.

Cellular and Molecular Basis of Heavy Metal-Induced Stress in Ciliates

Globally, heavy metals are the major pollutants present in both terrestrial and aquatic ecosystems. Increase in their concentration due to various anthropogenic activities is a matter of concern. Higher concentration of these metals is known to be toxic due to their non-biodegradable nature. Eukaryotic microorganisms, ciliates can be used as cellular tools to assess and study the various mechanisms to overcome heavy metal toxicity. Here we discuss, at cellular level, the effect of heavy metal toxicity on growth rate, behavioural and morphological changes of ciliates. At the molecular level, changes in stress genes like hsp70 , metallothionein and expression of various antioxidant enzymes (superoxide dismutase, glutathione peroxidase) adopted by ciliates have also been deliberated. It is also being argued that ciliates can be used as biosensor/cellular tools for detecting heavy metal pollution.

Heavy Metal Contamination of Soil and Health Hazards Among the Residents of Tannery Industrial Area

Background: Heavy metals like chromium compounds can be carcinogenic usually used in the tanning process during leather production. Chromium is an important health risk factor for the tannery workers which may enter the body by inhalation, ingestion and by direct cutaneous contact and cause several health problems of skin and respiratory tract. With the increase of unplanned industries, Bangladesh poses a new challenge to combat health hazards associated with heavy metal toxicity in soil.Objective: The present study was designed to find out possible toxic effects of heavy metals in soil and health hazards among the people residing at tannery industries area.Materials and Methods: This is a descriptive cross-sectional study and was carried out in two phases during the period of 1st November 2009 to 30 June 2010. In first phase the soil samples were taken from lagoons of Hazaribagh Thana of Dhaka city for laboratory test of heavy metals. In second phase, a total 190 respondents were interviewed using a semi-structured questionnaire to ascertain the common health problem around the tannery industries.Results: All the eight soil samples contained Cr, Mn, Ni, Fe, Pb, Cu, where as Cd was nil. Mean distributor of Cr, Mn, Ni, Fe, Pb and Cu was 43.1325, 354.2217, 28.6633, 22420.1867, 97.5833 and 53.4633 ppm respectively. 75.26% respondents stayed in the study area for six to ten years. Most of the respondents (75) were tannery workers. Total 52.85% households had toxicity related sickness in last six months. Among tannery workers most prevalent sickness were conjunctivitis (7.7%) and Dermatitis (6.7%). Regarding occurrence of clinical manifestations similar to Chromium toxicity in relation to staying in the study area, most of the households complained about allergy (39.2%) and abdominal discomfort (24.4%).Conclusion: Elevated levels of urinary and blood Chromium is associated with high morbidity among the tannery workers. Therefore bio-monitoring of the heavy metals in the exposed workers is considered as a useful tool.Anwer Khan Modern Medical College Journal Vol. 9, No. 1: Jan 2018, P 39-43

Synergistic effect of graphene nanosheets and zinc oxide nanoparticles for effective adsorption of Ni (II) ions from aqueous solutions

The threat of toxic substances such as heavy metals to public health and wildlife has led to an increasing public awareness. Different techniques for neutralizing the toxic effects of heavy metals in wastewater have been used. Here, we prepared a new and efficient type of adsorbent, zinc oxide–graphene nanocomposite (ZnO–Gr), via a green method to remove Ni (II) ions from aqueous solutions. A facile microwave-assisted hydrothermal technique in the presence of an ionic liquid, 1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [C6mim] [NTf2], was used to prepare ZnO–Gr. The synergistic effect between graphene nanosheets and ZnO nanoparticles in this new adsorbent for Ni (II) ions caused a maximum adsorption capacity of 66.7 mg g−1 at room temperature which is much higher than that of graphene nanosheets (3.8 mg g−1) and other carbonaceous nanomaterials used as an adsorbent in the literature. The maximum desorption percentage (90.32%) was achieved at pH 3.6. By thermodynamic study, we found that the adsorption of this heavy metal ion on ZnO–Gr was spontaneous (ΔG° = −6.14 kJ mol−1) and endothermic (ΔH° = 53.31 kJ mol−1) with entropy change of ΔS° = 199.45 J K−1 mol− 1.