heavy metal

A Gateway to Metal Resistance: Bacterial Response to Heavy Metal Toxicity in the Biological Environment

Published on: 3rd September, 2018

OCLC Number/Unique Identifier: 7893781761

Heavy metals and metalloids are dangerous because they have the tendency to bioaccumulate in biological organisms over a period of time. However, it is conceived that a number of phytochemical agents as well microorganism can act as heavy metal removing agent both from human beings and the environment surrounding. For instance, microbes are used for the removal of heavy metals from the water bodies including bacteria, fungi, algae and yeast. This review shows that bacteria can play an important role in understanding the uptake and potential removal behaviour of heavy metal ions. The bacteria are chosen based on their resistance to heavy metals (incl. their toxicities) and capacity of adsorbing them. Due to specific resistance transfer factors, cell impermeability is drastically inhibited by several ion (i.e. mercury, cadmium, cobalt, copper, arsenic) forms. Between these elements, free-ion cadmium and copper concentrations in the biological medium provide more accurate determination of metal concentrations that affect the bacteria, than with most of the other existing media. Metal toxicity is usually assessed by using appropriate metal ion chelators and adjusting pH factor. Bacteria and metals in the ecosystem can form synergistic or antagonistic relationships, supplying each other with nutrients or energy sources, or producing toxins to reduce growth and competition for limiting nutritional elements. Thus, this relation may present a more sustainable approach for the restoration of contaminated sources.
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Studies of Grafts in vegetables, an alternative for agricultural production under stress conditions: Physiological responses

Published on: 3rd January, 2018

OCLC Number/Unique Identifier: 7347068189

Vegetable production by grafting is a technique which it has made possible to resume agricultural soils which previously could not be produced due to stress generated by various abiotic factors, like a lack of water, stress by high or low temperatures, and or heavy metal contamination, among them. It has been documented and defined a number of graftings which they are tolerant to different factors; however, when it comes to auscultating information related to understand the molecular responses and observe what are the biochemical changes and physiological responses of grafted plants, it is dispersed. The current paper attempts to provide basic information documented on technique, addressing the molecular, biochemical and physiological responses, and thus get a clear perspective on the use of grafts, making this practice be used with most frequently by all its advantages.
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Effect of cement solidification on strength and leaching properties of Heavy Metals Contaminated Soil

Published on: 13th August, 2018

OCLC Number/Unique Identifier: 7844539292

This study investigated the effect of Portland cement on stabilization of heavy metal contaminated clayey soils that may give range of geo environemntal benefits. The absolute concentration of heavy metals: Lead (Pb), Zinc (Zn), Chromium (Cr), Cadmium (Cd) and Copper (Cu) were measured using an inductively coupled plasma atomic emission spectroscopy (ICP-AES). A series of laboratory scale experiments such as unconfined compression test (UCT), pH test and synthetic precipitation leaching procedure (SPLP) were performed to study the effects of curing time and cement content on the unconfined compressive strength (UCS) and leaching characteristics of heavy metals. According to results, excessive concentration of heavy metals are present in the topsoil of Shanghai Jiao Tong University (SJTU) among which Pb, Zn and Cd were most prominent. Other test results showed that the dry density of both C4 and C8 soil samples increases with curing time. Similarly the compressive strength (qu)of C4 and C8 samples at 21 d of curing increases by 40% (113 kPa-288 kPa) and 15% (745kPa-864 kPa) respectively, as compared to the 7 d of curing. Besides, the test results showed a prominent decrease in the leached concentration of heavy metals with increasing curing time.
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Simulating the dispersion of poisonous organic chemical compounds in wastewater treatment process through the active sludge method using the TOXChem model

Published on: 24th June, 2021

OCLC Number/Unique Identifier: 9124851637

Naturally, microorganisms decompose the organic material existing in nature, both in the presence or absence of oxygen. The majority of materials such as poisonous chemical compounds, heavy metals, would prevent the treatment process from taking place, lead to the entry of these contaminants into the environment results in the emergence of numerous diseases. In the present study, using the TOXChem4.1 simulation model, attempts were made to simulate a wastewater treatment plant and then assess the dispersions of contaminants including 1,2-Dimethylnaphthalene, 1,3-Dinitropyrene, 1,6-Dimethylnaphthalene, 1,6-Dinitropyrene, and 17a-ethinylestradiol (EE2) in concentrations of a common scenario. The results of computer simulations showed that the EE2 contaminant is of the highest percentage of decomposition among others, due to its wider chemical structure. Consequently, it is clear that such contaminant is of the highest mass in the sludge exiting the treatment plant. In addition, the results of the simulations demonstrated that the highest volumes of gaseous pollutants take place in the modulation and initial sedimentation units.
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Nano-silica from kaolinitic clay used as adsorbent for anionic and cationic dyes removal: linear and non-linear regression isotherms and kinetics studies

Published on: 24th May, 2022

The increasing occurrence of wastewaters associated with industrial development has begotten a permanent search for new and more efficient techniques for the removal of hazardous substances such as heavy metals and dyes. The use of natural and available resources to develop improved and sustainable commodities for this purpose remains crucial and is among promising emerging green technologies for water treatment. It offers the gradual shifting of hazardous industrial chemicals precursors to the abundant non-metallic mineral resources that receive an added value. This work investigated the uptake capacity by the adsorption process of methylene blue (MB) and azocarmine G (AG) onto nano-silica synthesized from kaolinite clay. The effects of contact time (0-30 min), the adsorbent dosage (5-100 mg), the initial pH of the solution (1-11 for MB and 1-7 for AG), and the initial dye concentration (5-50 mg/L) were studied. The selected conditions to carry out kinetic and isotherm adsorption experiments were: 15 mins, 20 mg, 11 for MB, 1.01 for AG, and 50 mg/L. Four adsorption isotherms and three kinetic models were used to model the adsorption data thanks to linear and non-linear regression methods. From the obtained results, the Freundlich isotherm model fitted well the adsorption phenomenon while the pseudo-second-order kinetic model described well the adsorption mechanism. Furthermore, the free energy of adsorption was similar for the two absorbents, 0.71 kJ, pointing physisorption as the dominant adsorption mechanism. The optimum MB and AG uptake were respectively 13.8 and 36.1 mg/g. Conclusively, the nano-silica represents a potentially viable and powerful adsorbent whose use could lead to a plausible improvement in environmental preservation.
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Optimization of the fermentation process, characterization and antioxidant activity of exopolysaccharides produced from Azotobacter As101

Published on: 20th December, 2022

Azotobacter was selectively isolated and purified from the soil samples of Xinjiang Salt Lake Scenic spot, the fermentation technology of exopolysaccharides (EPS) by Azotobacter was optimized, and the antioxidant activity of exopolysaccharides (EPS) was studied. The bacteria were isolated and purified from the soil samples by the scribing method and the 16SrRNA gene was used for molecular identification. The carbon source, fermentation time, inoculation amount and pH of target bacteria in the exopolysaccharides (EPS) fermentation process were optimized through single-factor experiments and their antioxidant activity was measured. Eight types of Azotobacter were isolated and purified from the soil samples of Salt Lake scenic spot. Among them, As101, which showed 99.58% homology with Azotobacter salinestris, was selected as the target strain. Through single-factor experiments which used exopolysaccharides (EPS) yield and exopolysaccharides content as indexes, the optimal conditions for the As101 fermentation process were determined as follows: fermentation temperature 35, fermentation time 96h, pH 7 and mannitol as carbon source. Exopolysaccharides content from Azotobacter salinestris  was 61.35% and the yield was 6.34 g/L. The results of the exopolysaccharides (EPS) antioxidant activity experiment under optimal conditions showed that As101 EPS had excellent scavenging ability against DPPH free radical, ABTS free radical and hydroxyl free radical, with IC50 values of 6.11 mg/ml, 2.42 mg/ml and 9.57 mg/ml, respectively. As101 with high yield and high exopolysaccharides content was isolated from saline soil in a special environment of Xinjiang, and the EPS obtained showed excellent antioxidant activity. The Azotobacter found in this study would provide the material basis for further opening up the adsorption of exopolysaccharides on heavy metals and the improvement of saline-alkali soil and contribute to further understanding of the structure and other activities of exopolysaccharides derived from Azotobacter.
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Decline in human sperm parameters: How to stop?

Published on: 31st January, 2023

A large systematic review and meta-regression analysis found that sperm counts all over the world appeared to be declining rather than stabilizing. The decline in male sperm counts does not necessarily translate to a decline in male fertility. The cause of declining sperm counts remains unknown; however, several potential causative factors have been identified: 1. Chronic diseases: diabetes mellitus, hypertension; hyperlipidemia, hyperuricemia and skin Diseases & metabolic syndrome. 2. Environmental factors: bisphenol a; phthalates; heavy metals and heat. 3. Lifestyle: obesity, diet, tobacco, alcohol, marijuana, stress, reduced sleep & sedentary life. Addressing these causes is required to stop or decrease male fertility decline. Action to improve semen quality such as prevention & treatment of chronic disease, decreasing unhealthy lifestyle behaviors such as smoking, poor diet, or lack of physical activity & eliminating toxic environmental chemicals.
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Study of kabul river canal sediments for heavy metals status and its accumulation in wheat plant (triticum aestivum)

Published on: 21st April, 2023

Canal cleaning is a routine activity on the canals diverted from the Kabul River. As a result, thousands of tons of sediment are removed as sludge and flushed back into the Kabul River. In Peshawar city, most people use this sediment as a soil conditioner in lawns. But the farmers are hesitant to apply it in agricultural fields. It is perceived that the sediment may be rich in heavy metal contents and, if used as a soil conditioner, may contaminate the food chain. To unveil the facts, this study was conducted with the aim of analyzing sediment samples for selected heavy metals and their uptake and accumulation in different parts of the wheat plant. For this purpose, the sediment collected from Warsak Gravity Canal (WGC) was analyzed for total essential heavy metals including iron (Fe), copper (Cu), cobalt (Co), manganese (Mn), and Zinc (Zn). Wheat crop was grown in four different pots consisting of pure soil, pure sediment, and two amendments i.e. soil mixed with 25% and 50% sediments. In comparison to sediment, the soil samples were high in copper, cobalt, and Zinc concentration. The concentration of iron and manganese was comparatively high in pure sediment but within permissible limits. The heavy metals uptake by the wheat crop was also within the permissible limits. The highest accumulation of copper, iron, and Zinc was observed in the roots of wheat plants. The highest value of cobalt was observed in the seed (0.407 mg Kg-1), which was within the safe range. Therefore, it is concluded that the sediment of the Kabul River canal cannot be considered a source of pollution in terms of heavy metals and can be used as a soil conditioner.
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Evaluation of Heavy Metals Concentration in Poultry Feed and Poultry Products

Published on: 11th July, 2023

The study was conducted to determine the absorption of essential and non-essential trace minerals from poultry feed to poultry products. Poultry feed, liver, muscles, and egg samples were collected from six poultry farms in Rawalpindi and Islamabad. Mercury, Lead, Cadmium, Chromium, and Iron were analyzed in the samples using Inductively Coupled Plasma Optical Emission Spectrophotometer. Iron, Lead, and Chromium exceeded the permissible limits set by World Health Organization and National Research Council in Poultry feed. Lead was high in the liver, breast muscles, thigh muscles, egg albumen, and egg yolk. Chromium was found in feed, egg yolk, egg albumen, and two (02) of the liver and breast muscle samples. Mercury was not detected in any of the samples. The liver contains significantly higher concentrations of detected heavy metals as compared to thigh and breast muscles and egg yolk contained significantly high concentrations of Iron, Cadmium, and Lead as compared to egg albumen. Standards requirements for feed manufacturers and poultry farmers should be maintained to monitor and mitigate routes of entry of contaminants in the food chain.
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Isolation and Influence of Carbon Source on the Production of Extracellular Polymeric Substance by Bacteria for the Bioremediation of Heavy Metals in Santo Amaro City

Published on: 9th February, 2024

The city of Santo Amaro (Bahia, Brazil) gained visibility among the scientific community due to the contamination of the Subaé River by lead and cadmium from the PLUMBUM Mineração e Metalurgia Ltda industry, on the banks of the river in 1956, which produced lead ingots The present work aimed to investigate the adsorption capacity of heavy metals (Pb and Cd) of EPS produced by bacterial species from the Subaé River, for possible future application of these biopolymers in bioremediation processes in areas impacted by the aforementioned heavy metals. Subaé river water was collected for physical-chemical analysis and bacterial isolation. It was verified that all isolated bacteria produced an expressive amount of Exopolysaccharide (EPS). Thus, the optimization of this production in different sugars (sucrose, glucose, and mannitol) and in three different pHs: 5.5; 6.5, and 7.5. All bacteria produced EPS in large quantities and the best sugar was sucrose at pH 7.5. In order to use the EPS for the bioremediation area, the adsorption test of lead and cadmium was carried out by the isolated EPS. 0.5 g of the EPS was dissolved in 50 ml of deionized water, then the solutions of metals, lead acetate, and cadmium sulfate (procedure performed separately) were incubated at 28 °C for 16 h after that period, and were centrifuged. Samples were filtered to separate the insoluble EPS and the filtrates obtained were used in the quantification of the metals by atomic absorption (FAAS- Flame Atomic Absorption Spectrometry). Bacillus spp., Bacillus cereus, Staphylococcus spp., and Serratiamarcescens, all showed tolerance to the tested metals, due to the efficiency in the adsorption capacity of the EPS, and it was possible to distinguish seven genera, Klebsiella pneumonia, Pseudomonas aeruginosa, Lysinibacillus spp. to be used in the bioremediation of environments contaminated with heavy metals.
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Optimizing Milk Safety: Applying Nuclear Techniques in X-ray Fluorescence Spectroscopy for Heavy Metal Quantification in Powdered Milk Consumed in Senegal

Published on: 9th February, 2024

This study conducted an elemental analysis and assessed heavy metal concentrations in five powdered milk samples (V1, L1, H1, G1, and D1) from Senegal, utilizing X-ray Fluorescence (XRF). The analysis focused on aluminum (Al), calcium (Ca), potassium (K), phosphorus (P), and chlorine (Cl). Aluminum was either undetected or found at negligible levels in all samples. Calcium levels consistently surpassed the Acceptable Maximum Level (AML) in all samples, with H1 exceeding the AML by approximately 11.1 times (27,745.06 ± 310.16 ppm). Potassium concentrations varied, with G1 exhibiting the highest levels, significantly exceeding the AML (51,058.15 ± 456.13 ppm), while V1 remained within acceptable limits. Chlorine concentrations generally complied with the AML, except for G1, which slightly exceeded the limit (3631.04 ± 31.23 ppm). Phosphorus concentrations in H1 were notably higher than the AML (13,750.94 ± 275.35 ppm). The non-uniformity in heavy metal concentrations among samples emphasizes the need for ongoing research and regulatory scrutiny to address potential risks and ensure the safety of powdered milk.
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Evaluation of Heavy Metals in Commercial Baby Foods

Published on: 21st February, 2024

Nutritious and safe foods are essential to meet normal physiological and metabolic functions. This study evaluated heavy metals in selected food products for newborns and toddlers. These substances may result in adverse health risks and young children are extremely vulnerable due to their immature immune systems and organs. Industrialization and technological advancement have contributed to an increase in heavy metals in the soil; therefore, entering the food system in potentially harmful amounts. Safe levels have been established by monitoring agencies to reduce the presence of heavy metals. Ten national brands of baby foods were analyzed for selected heavy metals. The main ingredients ranged from vegetables, fruits, dairy, poultry, meats, and grains. The products were analyzed in triplicates using QQQ-ICP-MS instrumentation to detect the presence of arsenic, cadmium, zinc, lead, nickel, aluminum, and chromium. Based on the Agency for Toxic Substances and Disease Registry [1] guidelines for safe quantities, aluminum (4.09 µg/g and 2.50 µg/g) and zinc (33.5 µg/g 69.5 µg/g, and 30.2 µg/g) exceeded the recommended levels of 1 µg/g/day and 2 - 3 µg/g /day respectively. Mixed model analysis found significant differences in metal concentrations (F6,24 = 2.75, p = 0.03) with an average metal concentration of 0.96 µg/g. However, no significant correlations were found between the packaging materials used and the observed metal concentrations in the food samples. The study concluded that the presence of heavy metals may be due to food type and the soil on which it is grown and not the packaging materials, establishing food system contamination by heavy metals.
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