Heavy Metal Treatment Research Articles

Establishing a Self-Supporting System of H2s Production from So2 with Reflux and Induced Reduction Process for Heavy Metals Treatment

Establishing a Self-Supporting System of H2s Production from So2 with Reflux and Induced Reduction Process for Heavy Metals Treatment

Reeds and Reedmace Bioreactor Technique in Wastewater Heavy Metals Treatment, Rhizofiltration

Direct usage of plants to decrease pollution in groundwater and surface water, has gained popularity in both academic and applied fields. Phytoremediation is a low-cost technique and environmentally beneficial technology; heavy metals are absorbed via aquatic plants also usage aqua plants as fertilizer since Phragmites australis have the capability to regrow when harvesting. This would allow heavy metals to be removed from waterways over multiple growing seasons; there was a significant difference in the concentration of copper between reeds bioreactors before and after treatment. The concentration of Cu decreased from 4.00 to 0.0087 mg/L. The lower concentration of Cu values at end of the experiment might be due absorption of heavy metals from the contaminated media. The concentration of Zn was also lower than before planting having the lower concentration (0.0868 mg/L) in the fifth hydroponic. Reed has a high ability to reduce zinc concentration. The concentrations of Co and Cd decreased from 0.400 to 0.043 mg/L. As shown in the results, the levels of concentration of Cd in the reeds bioreactor were decreased. Also, the concentration of Mn decreased from 20 to 0.0219 mg/L. Moreover, Reedmace has the capacity to clean up contaminated water. The values of Cu concentration decreased from 4.00 to 0.0477 mg/L during the entire growth period. Zn from 20 to 0.1685 mg/L. Also, the concentrations of Co and Cd decreased from 0.400 to 0.043 mg/L. The concentration of Mn decreased from 20 to 0.0133 mg/L. The efficiency of reeds bioreactor for heavy metals removal in the following sequence: Mn (99.89%) > Cu (99.78%) > Zn (99.65%) > Co (89.2%) > Cd (86.08%). On the other hand, the sequence of removal efficiency of the Reedmace bioreactor was in the following sequence: Mn (99.93%) > Zn (99.15%) > Cu (98.81%) > Mn (89.25%) > Cd (88.40%).

Optimal production of bioflocculant from Pseudomonas sp. GO2 and its removal characteristics of heavy metals

Bioflocculant may be a promising bioactivator for heavy metal removal duo to its eco-friendly properties and remarkable ability to adsorb heavy metals. In this study, bioflocculant production from a bacterium, Pseudomonas sp. GO2, was optimized and its removal efficiency for two heavy metal ions was evaluated. Results demonstrated that the maximal flocculation efficiency was achieved with concentration levels of 5 g/L glucose, 3 g/L casein, and 5 g/L NaCl, with an initial pH of 9.0, and a fermentation time of 48 h. Bioflocculant produced by GO2 had a stronger removal efficiency for Cd2+ than that of Pb2+, with highest removal efficiencies of 85.38% and 80.87%, respectively. The adsorption process was mainly dependent on the monolayer and chemisorption based on the adsorption isotherm and kinetic models. This study demonstrated that bioflocculant produced by the GO2 strain has the potential to be used in heavy metal treatment from industrial wastewater.

PHYSIOLOGICAL ANSWERS to METAL TRIGGERED EFFECTS in CROPS

Environmental pollution is one of the most important concerns for today's people. The increasing population growth in the world, together with the industrial revolution and its side effects, brings along the risk of reaching healthy food for every newborn and existing population. Contamination and/or accumulation of heavy metals, known as the source of oxidative stress, in foodstuffs and the environment directly affects human health. Since plants are often the first recipients of heavy metals from different environments (such as air, water and soil), it is not surprising that this results in scary scenarios for all living organisms. Therefore, to determine and dispose of the possible downsides in human diet which relates to heavy metals, we examined whether physiological parameters are reliable indicators of oxidative stress in different crop plants. Either with single or combined CdCl2 and PbCl2 treatments, germination percentage, root and shoot lengths and water contents were measured in the roots and shoots of Triticum aestivum cv. Gerek and Hordeum vulgare cv. Çıldır varieties in this study. According to obtained results, it is concluded that heavy metal treatments trigger the oxidative stress in plants, as all parameters measured are dramatically decreased.

Advances in Applications of Molecular Logic Gates.

Logic gates are devices that can perform Boolean logic operations and are the basic components of integrated circuits for information processing and storage. In recent years, molecular logic gates are gradually replacing traditional silicon-based electronic computers with their significant advantages and are used in research in water quality monitoring, heavy metal ion detection, disease diagnosis and treatment, food safety detection, and biological sensors. Logic gates at the molecular level have broad development prospects and huge development potential. In this review, the development and application of logic gates in various fields are used as the entry point to discuss the research progress of logic gates and logic circuits. At the same time, the application of logic gates in quite a few emerging fields is briefly summarized and predicted.

The Promotion of Festuca sinensis under Heavy Metal Treatment Mediated by Epichloë Endophyte

To more clearly clarify the relationship between the Epichloë endophyte and its host, F. sinensis, the effects of Epichloë endophyte on F. sinensis performance under heavy metal treatment was investigated. The growth performance and physiology variations of F. sinensis with (E+) and without the endophyte (E−) were evaluated after they were subjected to Zn2+ and Cd2+ treatments. The results showed that heavy metal treatments had significant effects on plants, as the performance of plants under Zn2+ and Cd2+ treatments was significantly different with plants under control treatment (p < 0.05). Cd2+ treatments showed a hormesis effect, whereas Zn2+ did not. The endophyte increased host heavy metal stress tolerance by promoting host growth as the E+ plants had significantly higher plant height, tiller number, root length (p < 0.05). The endophyte also promoted ion uptake by the host and induced endogenous hormone production (p < 0.05). These results suggested that the Epichloë endophyte regulated host growth and physiology to improve association tolerance to environmental conditions. This study provides another example that the Epichloë endophyte can increase plant tolerance to metal stress.

IMPACT OF CADMIUM TOXICITY ON LEAF AREA AND STOMATAL CHARACTERISTICS IN FABA BEAN

Although changes in stomatal response to elevated doses of cadmium has already been observed in several plants, few studies have focused on this phenomenon in more detail. The effects of different doses of cadmium Cd2+ (50 and 100 mg.kg-1 soil) on leaf area and stomatal characteristics (number of stomata, number of epidermal cells, stomatal index and size of stomata) of faba bean (Vicia faba L. cultivar Aštar) were studied after 15 days of heavy metal treatment. No visual changes on adaxial or abaxial side of leaves of the tested variety of faba bean were found. The leaf area was higher by 14.15 % at lower and by 12.23 % at the higher doses of Cd. The tested doses of Cd did not lead to a change in the number of stomata. The number of epidermal cells was increased on adaxial side by 4.98 % at dose Cd50. Stomatal index was decreased due to the effect of higher dose of cadmium by 11.38 % on adaxial side of leaves. In stomatal widths, decrease by 2.04 % (adaxial side) and 2.26 % (abaxial side) was observed at higher doses of Cd. In stomatal length decrease by 1.85 % was observed at higher dose of Cd on adaxial and decrease by 3.89 % (Cd50) and 4.63 % (Cd100) on abaxial side of leaves respectively. The variations of response could be signals of tolerance or adaptive mechanisms of the leaves of tested bean cultivar under the used concentrations of cadmium.

Photocatalysis for Heavy Metal Treatment: A Review

Environmental and human health are threatened by anthropogenic heavy metal discharge into watersheds. Traditional processes have many limitations, such as low efficiency, high cost, and by-products. Photocatalysis, an emerging advanced catalytic oxidation technology, uses light energy as the only source of energy. It is a clean new technology that can be widely used in the treatment of organic pollutants in water. Given the excellent adaptability of photocatalysis in environmental remediation, it can be used for the treatment of heavy metals. In this comprehensive review, the existing reported works in relevant areas are summarized and discussed. Moreover, recommendations for future work are provided.

Insight into the performance and mechanism of persimmon tannin functionalized waste paper for U(VI) and Cr(VI) removal

Herein, using dialdehyde waste paper (DAWP) as a cross-linking agent to immobilize persimmon tannin (PT) was first used to remove the U(VI) and Cr(VI) via the “waste control by waste” concept. The microscopic and macroscopic surface properties of the as-prepared adsorbent was characterized by the advanced characterization techniques. Factors that affected the elimination process such as variable pH, coexistence ions and equilibrium time were investigated by batch techniques. The results showed that the maximal removal capacities of U(VI) and Cr(VI) on DAWP-PT were 242.3 mg/g (pH = 6.0) and 178.7 mg/g (pH = 2.0) at 298 K, which exhibited competitiveness with most of the reported solid materials. Meanwhile, adsorption data were fitted perfectly to the Langmuir and Pseudo-second-order equations, which indicated that the monolayer and homogenous chemisorption dominated the removal process. The SEM-EDX, DFT and XPS analysis conformed that adsorption of U(VI) was mainly via surface complexation, while the elimination of Cr(VI) was a redox reaction process, and about 65.33% of Cr(III) and 34.67% of Cr(VI) co-existed onto the surface of DAWP-PT. Thus, this study would provide a high-efficiency and low-cost adsorbent for radionuclide and heavy metal treatment.

Ecophysiological differences between five mangrove seedlings under heavy metal stress

It was studied for the effects of heavy metal stress on the antioxidant activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and lipid peroxidation (MDA) in the leaves of five mangrove plants. The results showed the protein concentrations were significantly higher in B. gymnorrhiza (7.55 mg prot /mL: Cu2+), K. obovata (11.21 mg prot/mL: Cd2+) and R. stylosa (12.51 mg prot/mL: Cd2+) (p < 0.05). Comparably, MDA contents were remarkably high in A. marina than other species under the same conditions (p < 0.05). The SOD, POD and CAT were observed to be significantly high in A. marina, A. corniculatum and B. gymnorrhiza under the same heavy metal treatment (p < 0.05). The PCA revealed that POD, SOD and MDA of five mangrove species were the major indices for response to heavy metal. And A. marina was more tolerant to heavy metal stress than others.

Genome-Wide Identification and Expression Analysis of Metal Tolerance Protein Gene Family in Medicago truncatula Under a Broad Range of Heavy Metal Stress.

Metal tolerance proteins (MTPs) encompass plant membrane divalent cation transporters to specifically participate in heavy metal stress resistance and mineral acquisition. However, the molecular behaviors and biological functions of this family in Medicago truncatula are scarcely known. A total of 12 potential MTP candidate genes in the M. truncatula genome were successfully identified and analyzed for a phylogenetic relationship, chromosomal distributions, gene structures, docking analysis, gene ontology, and previous gene expression. M. truncatula MTPs (MtMTPs) were further classified into three major cation diffusion facilitator (CDFs) groups: Mn-CDFs, Zn-CDFs, and Fe/Zn-CDFs. The structural analysis of MtMTPs displayed high gene similarity within the same group where all of them have cation_efflux domain or ZT_dimer. Cis-acting element analysis suggested that various abiotic stresses and phytohormones could induce the most MtMTP gene transcripts. Among all MTPs, PF16916 is the specific domain, whereas GLY, ILE, LEU, MET, ALA, SER, THR, VAL, ASN, and PHE amino acids were predicted to be the binding residues in the ligand-binding site of all these proteins. RNA-seq and gene ontology analysis revealed the significant role of MTP genes in the growth and development of M. truncatula. MtMTP genes displayed differential responses in plant leaves, stems, and roots under five divalent heavy metals (Cd2+, Co2+, Mn2+, Zn2+, and Fe2+). Ten, seven, and nine MtMTPs responded to at least one metal ion treatment in the leaves, stems, and roots, respectively. Additionally, MtMTP1.1, MtMTP1.2, and MtMTP4 exhibited the highest expression responses in most heavy metal treatments. Our results presented a standpoint on the evolution of MTPs in M. truncatula. Overall, our study provides a novel insight into the evolution of the MTP gene family in M. truncatula and paves the way for additional functional characterization of this gene family.

Molecular and Biochemical Insights Into Early Responses of Hemp to Cd and Zn Exposure and the Potential Effect of Si on Stress Response.

With the intensification of human activities, plants are more frequently exposed to heavy metals (HM). Zinc (Zn) and cadmium (Cd) are frequently and simultaneously found in contaminated soils, including agronomic soils contaminated by the atmospheric fallout near smelters. The fiber crop Cannabis sativa L. is a suitable alternative to food crops for crop cultivation on these soils. In this study, Cd (20 μM) and Zn (100 μM) were shown to induce comparable growth inhibition in C. sativa. To devise agricultural strategies aimed at improving crop yield, the effect of silicon (Si; 2 mM) on the stress tolerance of plants was considered. Targeted gene expression and proteomic analysis were performed on leaves and roots after 1 week of treatment. Both Cd- and Zn-stimulated genes involved in proline biosynthesis [pyrroline-5-carboxylate reductase (P5CR)] and phenylpropanoid pathway [phenylalanine ammonia-lyase (PAL)] but Cd also specifically increased the expression of PCS1-1 involved in phytochelatin (PC) synthesis. Si exposure influences the expression of numerous genes in a contrasting way in Cd- and Zn-exposed plants. At the leaf level, the accumulation of 122 proteins was affected by Cd, whereas 47 proteins were affected by Zn: only 16 proteins were affected by both Cd and Zn. The number of proteins affected due to Si exposure (27) alone was by far lower, and 12 were not modified by heavy metal treatment while no common protein seemed to be modified by both CdSi and ZnSi treatment. It is concluded that Cd and Zn had a clear different impact on plant metabolism and that Si confers a specific physiological status to stressed plants, with quite distinct impacts on hemp proteome depending on the considered heavy metal.

Simultaneous removal of heavy metals and bioelectricity generation in microbial fuel cell coupled with constructed wetland: an optimization study on substrate and plant types.

A microbial fuel cell coupled with constructed wetland (CW-MFC) was built to remove heavy metals (Zn and Ni) from sludge. The performance for the effects of substrates (granular activated carbon (GAC), ceramsite) and plants (Iris pseudacorus, water hyacinth) towards the heavy metal treatment as well as electricity generation was systematically investigated to determine the optimal constructions of CW-MFCs. The CW-MFC systems possessed higher Zn and Ni removal efficiencies as compared to CW. The maximal removal rates of Zn (76.88%) and Ni (66.02%) were obtained in system CW-MFC based on GAC and water hyacinth (GAC- and WH-CW-MFC). Correspondingly, the system produced the maximum voltage of 534.30 mV and power density of 70.86 mW·m-3, respectively. Plant roots and electrodes contributed supremely to the removal of heavy metals, especially for GAC- and WH-CW-MFC systems. The coincident enrichment rates of Zn and Ni reached 21.10% and 26.04% for plant roots and 14.48% and 16.50% for electrodes, respectively. A majority of the heavy metals on the sludge surface were confirmed as Zn and Ni. Furthermore, the high-valence Zn and Ni were effectively reduced to low-valence or elemental metals. This study provides a theoretical guidance for the optimal construction of CW-MFC and the resource utilization of sludge containing heavy metals.

Identification of heavy metal-responsive genes in radish (Raphanus sativus L.) through RNA-Seq meta-analysis

Heavy metals (HMs) are essential to plant life in suitable amounts, but cellular damage might be caused by excess amounts of HMs. In recent years, most reports on unique metal stresses, such as chromium (Cr), lead (Pb) and cadmium (Cd), have utilized radish, especially Liwang Liu's laboratory. However, major activated genes related to HM stress shared in Cr, Pb and Cd stress and their related specific pathways are urgently required in radish. Herein, according to FPKM for four transcriptomes collected from Liu's laboratory, 46 DEGs related to HM stress genes shared among heavy metal (Cr, Cd and Pb) treatments were identified, together with 66 HM-induced genes, comprising those for functional proteins and transcription factors (TFs). Of these genes, 12 DEGs related to the HM stress response were validated using quantitative real-time PCR. The results showed that WRKY33 was significantly changed in response to heavy metal stress (Cr, Cd and Pb) treatment after 24 h in both the sensitive material ‘Hongxin 1’ and the resistant material ‘XCB’. Similar trends were also identified for transcripts of PIN1 protein, MRP protein and ABC transporter. Conversely, the transcripts of LCC4, bHLH143 and GST were found to be significantly changed in the sensitive material ‘Hongxin 1’ compared with the resistant material ‘XCB’ treated at different time points (0 h, 12 h, 24 h, 36 h, 48 h and 72 h). However, ARF1 and ERF-rap2.7 transcripts were found to be significantly decreased after 24 h of treatment in ‘Xichangbai 1’ compared with ‘Hongxin 1’ after heavy metal stress. In addition, most of the DEGs were found to be significantly enriched in the GO terms cellular response to extracellular stimulus, response to extracellular stimulus, auxin mediated signaling pathway, cellular response to chemical stimulus and response to oxidative stress through GO enrichment analysis. These results will expand our understanding of plant responsiveness to HM stress in radish under Cr, Pb and Cd stress and facilitate further genetic manipulation of HM stress genes on uptake and accumulation in radish.

Trophic transfer and toxicity of heavy metals from dengue mosquito Aedes aegypti to predator dragonfly Tramea cophysa.

Heavy metal pollution in aquatic habitats can be detrimental to both prey and predators in a food web. To investigate the potential for bio-transfer and bioaccumulation of heavy metals between specific trophic levels, 3rd instar larvae of Aedes aegypti were exposed to mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) for three consecutive generations and fed to dragonfly (Tramea cophysa) nymphs. Exposure to Hg caused the highest mortality in A. aegypti larvae and T. cophysa nymphs. Bioaccumulation and life-history parameters of A. aegypti, including egg hatching time, larval and pupal duration, male and female life span, and fecundity, were also evaluated after metals exposure. All life-history parameters except larval duration were significantly affected by heavy metal treatments. Bioaccumulation of metals in A. aegypti larvae and adults gradually and significantly increased from 1st to 3rd generation. To the best of our knowledge, this is the first study describing the acute toxicity of heavy metals to mosquitoes. Our study shows that heavy metals cause dietary toxicity to an aquatic predator, dragonfly, via trophic transfer, which could have considerable consequences on aquatic ecosystems.

Growth performance, tolerance and vigor dynamics of Salvia candidissima subsp. occidentalis Hedge against heavy metal contamination

In this study, ecotoxicological and ecophysiological effects of some different heavy metal compounds (CdCl2, PbCl2, and CuCl2) on Salvia candidissima subsp. occidentalis Hedge (Lamiaceae) were examined. Seeds of this plant were exposed to three different concentrations of CdCl2 (2, 6, 10 ppm), PbCl2 (50, 100, 500 ppm), and CuCl2 (20, 60, 150 ppm). The results indicated that increasing CdCl2 and PbCl2 concentrations had no specific inhibitory impacts on seed germination rates, growth performance, biomass, and seedling vigor index, but increasing concentrations of CuCl2 had significant inhibitory effects on these parameters. The metal tolerance index of all applications showed that all heavy metal treatments reduce this value.

Heavy metal treatment and removal using natural zeolites from sewage sludge, compost, and agricultural soils: a review

Heavy metal treatment and removal using natural zeolites from sewage sludge, compost, and agricultural soils: a review

Effects of Wood Vinegar and Bio char on Germination of Pakchoi Seeds under Different Cadmium Stress Conditions

Wood vinegar is widely used as a strong antioxidant, bacteria prevention, plant growth agent, an insecticide, and its effectiveness is shown in heavy metal treatment at this time.Wood vinegar liquid contains organic acids and phenols, which are effective in adsorbing heavy metals. Although a lot of studies have been conducted on the adsorption of heavy metals from biochar, the effect of mixing biochar and wood vinegar liquid on plant budding, and soil heavy metal morphology changes few studies have been analyzed. This paper analyzes the effects of Wood vinegar and biochar on the sprouting of pakchoi grown in different threats of cadmium from the nature of Wood vinegar. As a result, it was confirmed that the optimum concentration of the applied fertilizer wood vinegar that lowers the plant effectiveness of Cadmium was 1.0%. The fresh weight of pakchoi changed significantly in the order of biochar + wood vinegar 1.0% mixing&gt; biochar&gt; control. When 5.0% Biochar was mixed with 1.0% wood vinegar, the immobilization effect of the residual state and the carbonate bound cadmium in the soil was the highest. The combined application of wood vinegar and biochar promotes the germination of pakchoi, and has a significant inactivation effect on cadmium-contaminated soil; the results of analyzing the effectiveness of the mixing of wood vinegar and biochar and separate fertilization for each soil index show that, Compared to before sowing the pH ratio of the mixed treatment of biochar + wood vinegar is higher than that of the single treatment zone, which is as high as between 6.6-6.8, the EC is reduced to 2-59mS/cm width, and the CEC is increased by 0.27-2.21 times. It shows that under heavy metal stress, the mixed treatment of biochar+wood vinegar solution 1.0% is more effective than the treatment of biochar alone and the control.

Microbial community dynamics during composting of animal manures contaminated with arsenic, copper, and oxytetracycline

Effects of the heavy metal copper (Cu), the metalloid arsenic (As), and the antibiotic oxytetracycline (OTC) on bacterial community structure and diversity during cow and pig manure composting were investigated. Eight treatments were applied, four to each manure type, namely cow manure with: (1) no additives (control), (2) addition of heavy metal and metalloid, (3) addition of OTC and (4) addition of OTC with heavy metal and metalloid; and pig manure with: (5) no additives (control), (6) addition of heavy metal and metalloid, (7) addition of OTC and (8) addition of OTC with heavy metal and metalloid. After 35 days of composting, according to the alpha diversity indices, the combination treatment (OTC with heavy metal and metalloid) in pig manure was less harmful to microbial diversity than the control or heavy metal and metalloid treatments. In cow manure, the treatment with heavy metal and metalloid was the most harmful to the microbial community, followed by the combination and OTC treatments. The OTC and combination treatments had negative effects on the relative abundance of microbes in cow manure composts. The dominant phyla in both manure composts included Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. The microbial diversity relative abundance transformation was dependent on the composting time. Redundancy analysis (RDA) revealed that environmental parameters had the most influence on the bacterial communities. In conclusion, the composting process is the most sustainable technology for reducing heavy metal and metalloid impacts and antibiotic contamination in cow and pig manure. The physicochemical property variations in the manures had a significant effect on the microbial community during the composting process. This study provides an improved understanding of bacterial community composition and its changes during the composting process.

Biochemical changes in heavy metal toxicity induced &lt;em&gt;Withania somnifera&lt;/em&gt; (L.)&lt;em&gt; &lt;/em&gt;Dunal plants

Withania somnifera (L.) Dunal (Solanacea) is one of the well-known medicinal plants commonly called as Ashwagandha and also known as “Indian ginseng”. It contains Withanolides which are biologically active secondary metabolites, Anahygrine, Anaferine, sominiferine, sominiferinine, withanine and withananineare are also present in roots and leaves. Withania somnifera (L.) Dunal roots, leaves and preparations of the whole plants are traditionally used in Ayurveda and Unnani for various ailments. It is also having a high medicinal value and possesses potent anti-tumor and antioxidant properties. The present study deals with pot culture experiments with plants were grown in different treatments in black soil, Control (C): a control without any heavy metal treatment to the soil, Treatment No I: Cadmium 10ppm, Chromium 20ppm, Nickel 16ppm were introduced into the soil, Treatment No II: one % of Calcium hydroxide was also added along with heavy metals to soil. Then plants were grown up to the productivity levels. The heavy metal treated plants (Treatment No. I) showed lowest contents of soluble protein, non-reducing sugar, RNA, DNA, phenol, free proline, catalase and peroxides activity when compared to other treatments. The heavy metal treated plants (Treatment No. I) supported increase of total sugar, reducing sugar and polyphenol oxidase activity when compared to control plants and other treatment.