Adverse Effects Of Heavy Metals Research Articles

Effects of Cd2+ and Pb2+ on enantioselective degradation behavior of α-cypermethrin in soils and their combined effect on activities of soil enzymes

Heavy metals may coexist with pesticides in farmland through wastewater irrigation, application of pesticides and chemical fertilizers, or unappropriated waste disposal. Heavy metals are toxic to soil microorganism, which may influence the environmental behavior of pesticides subsequently. In this study, the influence of Cd2+ and Pb2+ on the degradation of α-cypermethrin and its metabolites, 3-phenoxphenoxybenzoic acid (3-PBA) and 3-(2',2'-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCCA), were investigated through soil incubation experiment. It was found heavy metals like Cd2+ and Pb2+ will inhibit the degradation of α-cypermethrin, especially at high concentrations. Pb2+ has a stronger inhibitory effect on the degradation of α-cypermethrin than Cd2+ in the same concentration. With the presence of 10 mg/kg Pb2+, the half-life of α-cypermethrin increased from 41.1 to 99.9 days, even the half-life was 129.3 days with 50 mg/kg of Pb2+. Besides, heavy metals influenced the chiral selective degradation of α-cypermethrin. The enantiomer fraction was near 0.5 when 10 mg/kg of heavy metals existed. Furthermore, the adverse effects of heavy metals on soil urease, catalase, and sucrase activity were assayed. In tested concentrations (10 and 50 mg kg-1), the heavy metals result in strong inhibition of the activity of the enzymes present on soil, jeopardizing the biodegradation by the microbiome and which may inhibit the degradation of α-cypermethrin.

Mercury Chloride but Not Lead Acetate Causes Apoptotic Cell Death in Human Lung Fibroblast MRC5 Cells via Regulation of Cell Cycle Progression.

Heavy metals are important for various biological systems, but, in excess, they pose a serious risk to human health. Heavy metals are commonly used in consumer and industrial products. Despite the increasing evidence on the adverse effects of heavy metals, the detailed mechanisms underlying their action on lung cancer progression are still poorly understood. In the present study, we investigated whether heavy metals (mercury chloride and lead acetate) affect cell viability, cell cycle, and apoptotic cell death in human lung fibroblast MRC5 cells. The results showed that mercury chloride arrested the sub-G1 and G2/M phases by inducing cyclin B1 expression. In addition, the exposure to mercury chloride increased apoptosis through the activation of caspase-3. However, lead had no cytotoxic effects on human lung fibroblast MRC5 cells at low concentration. These findings demonstrated that mercury chloride affects the cytotoxicity of MRC5 cells by increasing cell cycle progression and apoptotic cell death.

Functionalized PP fiber to improve compressive strength and solidification/stabilization performance of cement with heavy metals

To deal with the increasing amount of hazardous solid wastes, a functionalized PP (AM-PP) fiber was prepared and used with cement to solidify these wastes. PP fiber was firstly functionalized with amine groups and then characterized by SEM, FT-IR and XPS analyses. Mechanical property tests indicated that, compared with unmodified PP, AM-PP exhibited lower breaking strength while possessed a higher elongation at break no matter in dry or wet state, as the modification imparted AM-PP lower crystallinity and more amorphous phase. Compressive strength of cement samples containing heavy metals was evidently improved when AM-PP was added, which was owing to the adsorption and bonding of metal ions onto AM-PP and thus reduced the adverse effect of heavy metals on cement hydration. Hydration heat and thermogravimetry analyses also confirmed more hydration products were generated when AM-PP was added, especially in early age. Leaching test showed the amount of Cu2+, Zn2+ and Pb2+ leached from cement samples with heavy metals and AM-PP added was much lower than that from samples without AM-PP. Therefore, the prepared AM-PP fiber could effectively contribute to waste reutilization and environmental sustainability.

Role of Nano-Photocatalysts in Detoxification of Toxic Heavy Metals

Background: Nano-photocatalysis through semiconductor-based materials has become an emerging and eye-catching approach for detoxification of hazardous heavy metals in the aqueous environment. Methods: In this article, photocatalysis, being a green technique along with several other detoxification technologies for toxic heavy metals, has been reviewed. : Furthermore, the adverse effects of heavy metals on human health, agricultural lands, environment, and aquatic systems were investigated. Toxic heavy-metals contribute to numerous environmental issues based on their toxicity. Result: Various types of photocatalysts have been discussed in recent literature for the detoxification of heavy metals. The recycling of photocatalysts may be anticipated as a worthy method for wastewater treatment which is also discussed with recent examples. Conclusion: Moreover, it concludes with efficiency, challenges and new future perspectives for heavy metal detoxification using photocatalysis.

Problems of environmental pollution with heavy metals in the Russian Federation

The causes and sources of pollution of the natural environment with heavy metals are analyzed in the study. Basic information on indicators of environmental pollution with toxic metals was presented. When assessing the state of the natural environment, the author emphasizes the need to take into account that the intake of heavy metals is caused by both natural sources and anthropogenic impact. The study provides a review of scientific sources devoted to analytical methods for determining the content of heavy metals in biological media. Within the framework of the study, the author substantiated the conclusion that it is necessary to modernize methods for determining the content of heavy metals in biological media, given that it is possible to assess the level of the content and the adverse effects of heavy metals on the human body only with accurate quantitative indicators of the background content of elements in biological media. In addition, characteristics of the microelement composition of the environment for the region under study are subject to mandatory registration. The author emphasizes the need to develop methodological approaches and establish the background regional levels of metal content in biological media.

Effects of different loading rates and types of biochar on passivations of Cu and Zn via swine manure composting

Pollution of arable land caused by heavy metals in livestock and poultry manure has become a potential threaten to human health in China. Safe disposal of the contained toxic pollution with animal manure by co-composting with biochar is one of the alternative methods. Biochars from different sources (wheat straw, peanut shells and rice husks) amended with different loading rates were investigated for passivations of copper and zinc (Cu and Zn) in swine manure composting. Results showed that the passivation effects of the three types of biochar on Cu and Zn were enhanced with increasing biochar dose. Contents of Cu and Zn measured by diethylenetriaminepentaacetic acid (DTPA) and Community Bureau of Reference (CBR) showed that wheat straw biochar with the loading rates of 10%–13% (w/w) was superior to the other two types of biochar in this study. Compared with the control, sample from wheat straw biochar was more favorable for the bacterial growth of Proteobacteria, Firmicutes and Actinobacteria. In addition, pot experiment showed that organic fertilizer amended with wheat straw biochar could significantly improve the growth of Chinese pakchoi and enzyme activities (superoxide dismutase, peroxidase, polyphenol oxidase and catalase) as compared with the control. Cu and Zn contents of Chinese pakchoi in the organic fertilizer group containing wheat straw biochar reduced by 73.2% and 45.2%, 65.8% and 33.6%, respectively, compared with the group without loading biochar. There was no significant difference in the contents of vitamin C and reducing sugar between the groups of organic fertilizer amended with/without wheat straw biochar, however, there was significant difference compared with the heavy metal addition group. The application of organic fertilizer formed by adding biochar can effectively reduce the adverse effects of heavy metals on crops.

A New Ex Vivo Model to Evaluate the Hair Protective Effect of a Biomimetic Exopolysaccharide against Water Pollution

As an external appendage, hair is exposed to multiple stresses of different origins such as particles and gases in air, or heavy metals and chemicals in water. So far, little research has addressed the impact of water pollution on hair. The present study describes a new ex vivo model that allowed us to document the adverse effects of water pollutants on the structure of hair proteins, as well as the protective potential of active cosmetic ingredients derived from a biomimetic exopolysaccharide (EPS). The impact of water pollution was evaluated on hair from a Caucasian donor repeatedly immersed in heavy metal-containing water. Heavy metal retention in and on hair was then quantified using Inductively Coupled Plasma Spectrometry (ICP/MS). The adverse effects of heavy metals on the internal structure of hair and its prevention by the EPS were assessed through measurement of keratin birefringence. Notably, the method allows the monitoring of the organization of keratin fibers and therefore the initial change on it in order to modulate the global damage in the hair. Results revealed an increasing amount of lead, cadmium and copper, following multiple exposures to polluted water. In parallel, the structure of keratin was also altered with exposures. However, heavy metal-induced keratin fiber damage could be prevented in the presence of the tested EPS, avoiding more drastic hair problems, such as lack of shine, or decrease in strength, due to damage accumulation.

Ecological risk assessment of heavy metal-contaminated soil using the triad approach

Heavy metal soil-pollution is of concern due to its adverse effects on the ecosystem and human health. However, conventional ecological risk assessments considering only chemical concentration have limitations because of an increased uncertainty in assessing soil-risk. Therefore, this study applied the Triad approach, using a tier system, for assessing site-specific ecological risk in heavy metal-contaminated soil. In addition, risk-level was determined to analyze the necessity of remediation in a contaminated site. Soil samples from six different sites, including heavy metal-contaminated regions (S1–S5) and a control site (C, unpolluted with heavy metals) were collected. Soil properties were assessed based on a tier system to evaluate the ecological risk of each site. The first step tier-1, involved calculating the soil pollution index (SPI) and the second, tier-2, involved assessing site-specific ecological risk based on three lines of evidence (LoEs), viz., chemistry (ChemLoE), ecotoxicology (EcotoxLoE), and ecology (EcoLoE). The total and bioavailable fractions of heavy metals in soil and bio-accumulated heavy metals in earthworms (Eisenia fetida) were measured for ChemLoE. A bioassay involving mortality and weight reduction rates of earthworms, and a root-elongation test of lettuce (Lactuca sativa sp.) was conducted for EcotoxLoE. Soil biological properties, soil basal respiration, and soil enzyme activities, were evaluated for EcoLoE. Final integrated risk (IR) was obtained by combining the risk-values of each LoE, determined using IR values and deviation of each LoE. Although three out of the five sampling sites had SPI > 1 in tier-1, all five sampling sites were subjected to tier-2 to evaluate site-specific ecological risk. In tier-2, ChemLoE (0.53–0.99) was higher than EcotoxLoE (0.05–0.43) and EcoLoE (0.00–0.29), indicating that chemical aspects impacted risk evaluation more than the toxicological and ecological aspects. The final IR ranged between 0.24 and 0.85; risk-level was classified as low (S2, S3, S5), moderate (S1), and high (S4) according to the IR value. Based on the risk-level, site S4 could require remediation for agricultural land-use. The IR of each sampled site varied depending on the impact of heavy metals. Based tier-1 and tier-2 results, a thorough site-specific evaluation is required to understand the adverse effects of heavy metals on soil ecosystems, and the triad approach could be useful for managing heavy metals in soil.

Heavy metal contamination in recorded and unrecorded spirits. Should we worry?

Heavy metals can be released into all alcoholic beverages during production and storage. However, there is at least a theoretical risk that they could be present in higher, and potentially toxic, concentrations in those produced in the household and small-scale stills common in Central and Eastern Europe, which lack quality control and whose products are unrecorded by authorities. Yet, so far, few studies comparing concentrations of heavy metals in recorded and unrecorded spirits have been published. In this study we ask whether there is any difference between heavy metal concentrations in recorded and unrecorded spirits and, thus, the related health risk. The levels of heavy metals were determined in recorded (n = 97) and unrecorded (n = 100) spirits using inductively coupled plasma optical emission spectrometric analysis and applied to population-based risk assessments, considering average, regular and chronic heavy drinkers. Concentrations of Cu, Zn, and Sn were significantly higher in unrecorded spirits than those in their recorded counterparts and recorded spirits contained significantly higher levels of Fe, Mn, and Ni than unrecorded spirits. Combined exposure to heavy metals posed a potential health risk in chronic heavy drinkers consuming recorded spirits. However, when compared to the health risk arising from drinking large volumes of ethanol, the risk is negligible. Consequently, there are no grounds to worry about the adverse effects of heavy metals from spirits.

Ameliorative Effects of Organic Fertilizer, Trichoderma and Silicon on Productivity and Quality of Tomato Grown under Contaminated soil Conditions

The present study was carried out during the summer seasons of 2017 and 2018 in Talkha city, Dakahlia Governorate, Egypt near El-Mansoura-Damietta highway and El Delta Company for Fertilizers and Chemical Industries, where lead (Pb) and copper (Cu) levels in the soil exceed the permissible levels. Therefore, the aim of this study was to alleviate the adverse effects of heavy metals (HMs) on tomato plant (Solanumlycopersicum L.) Super Strain B F1. Twelve treatments were conducted which were the interactions between two silicon (Si) foliar spraying (without or 300 ppm Si) and six soil amendments : 100% chemical fertilizers (CF), 50% farmyard manure (FYM), 100% FYM, 100% CF+ Trichoderma spp. (T.), 50% FYM + T. and 100% FYM + T. Data indicate that Pb and Cu were accumulated in tomato organs to hazardous levels in the following descending order : roots > shoots > fruits and shoots > roots > fruits, respectively which consequently severely reduced tomato plant growth and fruit yield and fruit quality. Results also, showed that the application of Si treatment sole or in combination with soil amendments markedly enhanced plant height, dry weight, total chlorophyll, number of fruits/plant, total yield/fed, Vitamin C, acidity %, TSS and taste index, where as, reduced Pb and Cu concentrations in different plant organs, bio-concentration factor (BCF) and translocation factor (TF). However, Si + FYM + T. treatment was superior in these respects, therefore increased the net return. Also, negative correlations were obtained between fruit yield and BCF of Pb or Cu and between taste index and TF of Pb or Cu.

Protective role of citric acid against oxidative stress induced by heavy metals in Caenorhabditis elegans.

The adverse effects of heavy metals, such as cadmium, zinc, and copper, occur due to the generation of reactive oxygen species (ROS). The use of Caenorhabditis elegans for the purposes of conservation and biomonitoring is of great interest. In the present study, ROS, malondialdehyde (MDA), and citric acid levels and superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in a model organism were tested to study toxicity. C. elegans was exposed to three different concentrations of cadmium (CdCl2, 5, 10, 50 μM), zinc (ZnSO4, 10, 100, 500 μM), and copper (CuSO4, 10, 100, 500 μM) for 3 days. ROS levels increased by 1.3- to 2.1-fold with increasing metal concentrations. The MDA content increased by approximately 7-, 5-, 2-fold after exposure to high concentrations of cadmium, zinc, and copper, respectively. Furthermore, the citric acid content increased by approximately 3-fold in the cadmium (Cd, 5 μM), zinc (Zn, 10 μM), and copper (Cu, 100 μM) treatment groups compared to that in untreated C. elegans. Therefore, citric acid may play an important role in heavy metal detoxification. Excess citric acid also slightly increased the LC50 by 1.3- to 2.0-fold, basic movements by 1.0- to 1.5-fold, decreased the ROS content by 2.4- to 2.1-fold, the MDA content by 4- to 2-fold, the SOD activity by 9- to 3-fold, the GPx activity by 4.0- to 3.0-fold, and the mRNA expression levels of GPxs by 3.2- to 1.8-fold after metals treatment. And it is most significantly in the alleviation of citric acid to cadmium. This study not only provides information to further understand the effects of heavy metal exposure on ROS, MDA, GPx, SOD, and citric acid in worms but also indicates that supplemental citric acid can protect animals from heavy metal stress and has broad application prospects in decreasing oxidative damage caused by heavy metals.

Determination of heavy metals concentration in Astragalus anisacanthus and Ebenus stellata of Balochistan, Pakistan

Various elements along with heavy metals, present in different medicinal plants, play important roles in human’s life. Assuming this, the concentrations of nine different elements including heavy metals were analyzed in selected medicinal plants i.e. Astragalus anisacanthus and Ebenus stellata. Wet digestion method was performed for the mineralization of plant samples employing three strong acids such as sulphuric acid (H2SO4), nitric acid (HNO3) and per chloric acid (HClO4) in ratio of 1:5:0.5mL respectively followed by filtration and analysis by flame atomic absorption spectroscopy. For Na and K, flame photometer was used and samples were diluted up to hundred folds for obtaining results within the range of the instrument. The increasing order of concentration of elements in A. anisacanthus is as: Cd<Pb<Co<Ni<Cu<Mn<Fe<K<Na, whereas in E. stellata was found as: Cd<Co<Ni<Cu<Mn<Pb<Fe<K<Na. The accumulation of heavy metals in plants was different in concentration according to the study. Furthermore, the concentrations were also within the range established by international organization. In future, the usefulness of this research work is that it will result in the synthesis of many new drugs as well as it will also be used for providing public protection regarding the adverse effects of heavy metals. Keywords: Flame atomic absorption spectroscopy; Flame photometer; Flame emission spectroscopy; Heavy metals; Wet digestion http://dx.doi.org/10.19045/bspab.2019.80147

Profiling of various elements in Haloxylon griffithiiand Convolvulus leiocalycinus using atomic absorption spectroscopy and flame photometry

The concentration of nine different elements including heavy metals were analyzed in selected medicinal plants i.e. Haloxylon griffithii and Convolvulus leiocalycinus. The mineralization of plant samples was done using wet digestion method in which three strong acids were used i.e. nitric acid (HNO3), sulphuric acid (H2SO4) and perchloric acid (HClO4) followed by filtration and analyzed through flame atomic absorption. For sodium and potassium, flame photometer was used and samples were diluted to 100 folds for obtaining results within the range of the instrument. The decreasing order of concentration of elements in H. griffithii was K>Na>Fe>Ni>Mn>Cu>Co>Pb>Cd whereas, in C. leiocalycinus was K>Na>Fe>Cu>Mn>Ni>Co>Pb>Cd. The study revealed that heavy metals accumulate in the plants with different concentrations and their concentrations were within the permissible ranges established by international organizations. This will provide knowledge in the invention of many new drugs and the research helps the legislators to provide protection to the public regarding adverse effects of heavy metals. Keywords: Flame atomic absorption; Flame photometer; Flame emission http://dx.doi.org/10.19045/bspab.2019.80094

Microbial levan and pullulan as potential protective agents for reducing adverse effects of copper on Daphnia magna and Vibrio fischeri

Microbial polysaccharides, due to their unique physiochemical properties, have found application in the food industry, cosmetics, pharmacy and medicine. In the environment, microbes can use polysaccharides to alleviate the adverse effects of heavy metals in their close proximity. This adaptive property shows interesting potential for bioremediation. Herein, the effects of the exopolysaccharides (EPS) levan, produced by the bacterium Bacillus licheniformis NS032 and pullulan, produced by the fungus Aureobasidium pullulans CH-1 in the presence of copper (Cu2+) have been investigated for the first time on antioxidant enzyme activity, respiration and Cu2+ bioaccumulation of Daphnia magna as well as the bioluminescence of Vibrio fischeri. Both EPS decreased toxicity of Cu2+ in the acute test with D. magna. The activity of catalase (CAT) was significantly diminished after acute exposure to Cu2+ in comparison to treatments with Cu2+ and EPS, while in the prolonged acute exposure the CAT activity did not show statistically significant (P ≤ 0.05) differences between treatments with and without the EPS. According to ICP-MS results, during prolonged acute exposure of neonates, the bioaccumulation of Cu2+ in treatments without the EPS was 52.03 μg/g of biomass (wet), while in treatments with EPS, the bioaccumulation was lower by one order of magnitude. The respiration of neonates during acute exposure to Cu2+ with or without the EPS was monitored using the MicroOxymax respirometer, and the results show the EPS can positively effect the respiration. In the case of bacterial bioluminescence, the toxicity of Cu2+ decreased in treatments with EPS (30 min EC10) from 3.54 mg/L to 140.61 mg/L (levan) and 45.00 mg/L (pullulan). This study demonstrates protective effect of EPS against Cu2+ toxicity on D. magna and V. fischeri, and opens the door for further investigation of potential application of levan and pullulan in bioremediation of heavy metals and mitigation of their adverse effects in the aquatic environment.

Polyamines modulate growth, antioxidant activity, and genomic DNA in heavy metal-stressed wheat plant.

A pot experiment was performed to assess the useful effects of seed soaking or seedling foliar spray using 0.25mM spermine (Spm), 0.50mM spermidine (Spd), or 1mM putrescine (Put) on heavy metal tolerance in wheat plants irrigated with water contaminated by cadmium (2mM Cd2+ in CdCl2) or lead (2mM Pb2+ in PbCl2). Cd2+ or Pb2+ presence in the growth medium resulted in significant reductions in growth and yield characteristics and activities of leaf peroxidase (POD), glutathione reductase (GR), ascorbic acid oxidase (AAO), and polyphenol oxidase (PPO) of wheat plants. In contrast, significant increases were observed for Cd2+ content in roots, leaves and grains, superoxide dismutase (SOD) and catalase (CAT) activities, radical scavenging activity (DPPH), reducing power capacity, and fragmentation in DNA in comparison to controls (without Cd2+ or Pb2+ addition). However, treating the Cd2+- or Pb2+-stressed wheat plants with Spm, Spd, or Put, either by seed soaking or foliar spray, significantly improved growth and yield characteristics and activities of POD, GR, AAO, PPO, SOD, and CAT, DPPH, and reducing power capacity in wheat plants. In contrast, Cd2+ levels in roots, leaves, and yielded grains, and fragmentation in DNA were significantly reduced compared with the stressed (with Cd2+ or Pb2+) controls. Generally, seed soaking treatments were more effective than foliar spray treatments. More specifically, seed priming in Put was the best treatment under heavy metal stress. Results of this study recommend using polyamines, especially Put, as seed soaking to relieve the adverse effects of heavy metals in wheat plants.

Heavy Metals Accumulation Effects on The Photosynthetic Performance of Geophytes in Mediterranean Reserve

In Bentael natural reserve, Byblos-Lebanon, a recently constructed road, adjacent to its Southside, is threatening the wildlife of the reserve. The first source of this pollution is a vehicle derived contamination of soil, air and plants. This study determines heavy metals contamination levels evaluated by a rare plant species “Urginea maritima”, which is used as a biomonitor of airborne pollution. Four heavy metals were chosen for their toxic effects on the floral species. Lead, cadmium, aluminium and chromium were studied in plant leaves. The analysis of heavy metals is completed by a measurement of the photosynthetic activity of the plant. Two years period study showed lead upgrade in leaves versus a chromium decrease of plant uptake from the first year of road inauguration. Aluminium and cadmium levels increase for the first months after road works beginning then decreased sharply. As for photosynthetic pigments, the study showed an adverse effect of heavy metals on ordinary photosynthetic activities of the plants. Chlorophyll revealed primarily a decline in activities the first year but then amplification, in contrast of pheophytin which concentrations displayed a sharp rise especially in the most closely site to the road. These results indicated that landscape activities near natural reserves initiate heavy metals pollution for plants with a high risk of accumulation.

ROBINIA PSEUDOACACIA L. AND AMORPHA FRUTICOSA L. АS HEAVY METALS PHYTOREMEDIATION

A large amount of heavy metals leads to environmental pollution. Heavy metals are part of the land or may arise as a result of human products. Affecting the normal growth and development of plant systems and only to a certain limit concentrations of metals. Increasing these suitable and permitted a value to metals in the soil leads to changes in the composition and appearance of the environment in a negative direction. To eliminate or reduce elevated concentrations of heavy metals and their adverse effects on the environment, many researchers focus their attention on finding species that can act as scavengers soil and phytoremediations. There are a large number of plant species that are capable of survival on such surfaces, whether it comes to wild species or species that are on the site with the aim planted. The best known and the most common fitoremedijatori by woody species are Acacia (Robinia pseudoacacia L.) and its most closely related to indigo ( Amorpha fruticosa L.). Its advanced adaptation and the possibility of survival in the soil rich with heavy metals, are plant species that are used in order to protect the environment from the adverse effects of heavy metals. These species have developed ability to adapt, and thereby can perform the accumulation of heavy metals from the soil. They absorb these metals or through the root system, through the tree to the leaves and flowers or leaves through the metal while returning the return direction. In this way, that is, the accumulation of metals that are present in concentrations higher than allowed for stay vegetation, stored and purified by environmental influences damaging of elements which are present in the air and in the soil.

Adverse effect of heavy metals (As, Pb, Hg, and Cr) on health and their bioremediation strategies: a review.

Currently, heavy metal pollution becomes a severe problem whole over the world, and these toxic metals enter into the environment either by natural phenomena or due to extensive industrialization. The discharged effluents containing toxic heavy metals mixed with soil/water and change their natural composition. These heavy metals have adverse effects on living beings and cause damage to the vital body organs of animals as well as humans. The heavy metal pollution also inhibits the biodegradation of the chlorinated organic compounds (another type of environmental pollution) by interacting with metabolizing enzymes and inhibits their functioning. Earlier studies described that heavy metals cannot be fully removed from the environment, but they can be effectively neutralized or transformed into less toxic form so that their harmful effect on the environment can be reduced. The distinctive enzymatic apparatus within microbial system plays a major role in the transformation of heavy metals in the environment. A considerable advancement has been made during recent years to transform the heavy metals by utilizing the bioremediation potential of genetically engineered (GE) microorganisms. These transgenics are very much efficient in heavy metal transformations and still, we have to discover more to additionally utilize their full biotransformation potential.In the present review article, the detailed description of the adverse effects of four heavy metals (arsenic, lead, mercury, and chromium) and their adverse effect on our environment and human beings is discussed. Furthermore, the use of microorganisms/GE organisms for the bioremediation of heavy metals from the environment is also discussed along with their detailed bioremediation mechanism.

Deciphering adverse effects of heavy metals on diverse wheat germplasm on irrigation with urban wastewater of mixed municipal-industrial origin.

The current study provides one of the first attempts to identify tolerant, moderately sensitive, and highly sensitive wheat genotypes on the basis of heavy metal accumulation, biochemical attributes, and human health risk assessments on urban wastewater (UW) irrigation. Mean heavy metals (Fe, Co, Ni, Cu, Zn, Pb, Cd, Cr, Mn) and macro-nutrients (Na, K, Ca, Mg) levels increased in the roots, stem, and grains of studied genotypes. Except K (stem > root > grain), all metals were accumulated in highest concentrations in roots followed by stem and grains. Principal component analyses (PCA) identified three groups of UW-irrigated genotypes which were confirmed by hierarchical agglomerative cluster analyses (HACA). Wheat genotypes with the lowest metal accumulation were regarded as tolerant, whereas those with maximum accumulation were considered highly sensitive. Tolerant genotypes showed the lowest hazard quotient for heavy metals, i.e., Co, Mn, Cd, Cu, Fe, Pb, and Cr, and hazard index (HI) values (adults, 2.04; children, 2.27) than moderately and highly sensitive genotypes. Higher health risks (HI) associated with moderate (adults 2.26; children 2.53) and highly sensitive (adults 2.52; children 2.82) genotypes revealed maximum uptake of heavy metals. The heatmap showed higher mean biochemical levels of chlorophyll, carotenoids, membrane stability index (MSI%), sugars, proteins, proline, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in tolerant genotypes than remaining genotypes. With the lowest metal accumulation and advanced biochemical mechanisms to cope with the adverse effects of heavy metals in their plant bodies, tolerant genotypes present a better option for cultivation in areas receiving UW or similar type of wastewater.

Development of multi-metal interaction model for Daphnia magna: Significance of metallothionein in cellular redistribution

Despite the great progress made in metal-induced toxicity mechanisms, a critical knowledge gap still exists in predicting adverse effects of heavy metals on living organisms in the natural environment, particularly during exposure to multi-metals. In this study, a multi-metal interaction model of Daphnia manga was developed in an effort to provide reasonable explanations regarding the joint effects resulting from exposure to multi-metals. Metallothionein (MT), a widely used biomarker, was selected. In this model, MT was supposed to play the role of a crucial transfer protein rather than detoxifying protein. Therefore, competitive complexation of metals to MT could highly affect the cellular metal redistribution. Thus, competitive complexation of MT in D. magna with metals like Pb2+, Cd2+ and Cu2+ was qualitatively studied. The results suggested that Cd2+ had the highest affinity towards MT, followed by Pb2+ and Cu2+. On the other hand, the combination of MT with Cu2+ appeared to alter its structure which resulted in higher affinity towards Pb2+. Overall, the predicted bioaccumulation of metals under multi-metal exposure was consisted with earlier reported studies. This model provided an alternative angle for joint effect through a combination of kinetic process and internal interactions, which could help to develop future models predicting toxicity to multi-metal exposure.