Metal Pollution In Water Research Articles

Aquatic Plants in phytoremediation of contaminated water: Recent knowledge and future prospects

The increase of heavy metals in natural resources, including land and water has been rapidly raised due to a variety of natural methods, higher agricultural activities, contaminated irrigation water, speedy industrial development, amplified industrial wastes and mining. Heavy metals (HM) are able to remain in the environment longer time and go in the food chain, and ultimately accumulate in humans for biomagnification since they are not biodegradable. HMs contamination is extremely dangerous for humans and the ecology due to its poisonous nature. Traditional methods of cleanup are expensive and could harm the environment. Therefore, phytoremediation is an alternate method via plants to eliminate toxic HMs from the atmosphere as well as to avoid additional contamination, due to its environment-friendly, economic, efficient, exclusive and cost-effective approach. Aquatic plants can be utilized to decontaminate the contaminated sites as they are not food crops, thus reducing the danger of food chain contamination. Here, sources of HMs and their impact on human health have been briefly discussed. Several phytoremediation techniques and factors affecting the phytoremediation methods are also described. In addition, different strategies to decontaminate the metal-polluted water using aquatic plants are also reviewed. Finally, future perspectives for usages of aquatic plants in phytoremediation techniques were briefly summarised.

Polymerization regenerating Ca-zeolite by calcium inducing halloysite for enhancing toxic metal ions removal

Traditional techniques can be problematic due to secondary pollution while natural clay aroused great concern. For example, halloysite has high structural activity and excellent potential in toxic metals removal. The polymerization of halloysite to form Ca-zeolite with better metal-binding performance is of great significance for the immobilization of toxic metals. However, halloysite lacks exchangeable cations, which may restrict its polymerization conversion. Thus, it is efficacious to induce halloysite's structural recombination and speciation when calcium is introduced into the polymerization. The curly multilayer halloysite tubes in-situ unfolded and formed kelp-like Ca-zeolite by using calcium as a structure-directing agent. When the calcium content increased, the cubic zeolite was broken into pieces. The pore size distribution showed that micropores and mesoporous structure of halloysite disappeared and converted zeolite hierarchical shape. The characterization analysis indicated that new toxic metal compound groups were generated, confirming the lattice exchange of Ca and toxic metal ions in the Ca-zeolite. Otherwise, the lattice fringe showed that Pb was mainly immobilized on the 001 plane via ion exchange, while Cd formed inner complexes on the 110 plane. Above all, the halloysite-zeolite polymerization technology provides a new method for zeolite synthesis, which is significant for the control of toxic metal pollution in water.

Phycoremediation of Cadmium using Chlorella vulgaris in Photobioreactor

Chlorella vulgaris had the ability to accumulate heavy metals in their bodies, so they could be used as biosorbent in handling heavy metal pollution in waters. The effectiveness of C. vulgaris in the remediation of cadmium (Cd) would be tested in this present study. C. vulgaris were cultured for 14 days in the photobioreactor which was an enclosed chamber that was fully aerated and illuminated with LED lamps. Cadmium with concentrations of 0 (control), 0.05, and 0.1 ppm was mixed with C. vulgaris growth medium. The number of C. vulgaris cells was counted every 3.5 days using a hemocytometer to determine the growth condition. Metal concentrations were also measured on days 0, 7, and 14 using atomic absorption spectrophotometry (AAS). C. vulgaris was able to reduce cadmium levels up to 98%. The decrease in cadmium levels with the highest efficiency occurred at a cadmium concentration of 0.05 ppm.

Regulating ordered structure and multi-functions of zeolite aerogels for solar steam generation and heavy metal ion adsorption

The interfacial solar steam generation (ISSG) is considered to be a promising technology to alleviate the water crisis. However, the salt accumulation on the solar evaporators and the heavy metal pollution in water hinder the commercial potential and practical application of the evaporators. Herein, a solar evaporator with high salt resistance and efficient heavy metal wastewater treatment is designed using commercial artificial zeolite as matrix, modified zeolite (MZ), cellulose acetate (CA), and carbon nanotubes (CNTs), named as MZPC@CNTs. The applicability of the developed MZPC@CNTs in water evaporation, seawater desalination, heavy metal wastewater treatment, and water purification of organic pollutants is studied systematically. Through the regulation of the ordered structure and multiple functions, the obtained MZPC@CNTs based aerogel shows an evaporation rate of 1.72 kg m-2 h−1 with a corresponding efficiency of 95.33% under 1 sun radiation. In addition, the MZPC @CNTs aerogel also exhibits excellent ion desalination performance and excellent salt resistance towards the purification of heavy metal-contaminated wastewater. This solar evaporator has the advantages of simple preparation, low cost, and stable desalination performance, and reveals great potential in alleviating the shortage of global freshwater resources.

Investigation of Some Heavy Metal Resistance Genes in E.coli Isolated from Shrimp and Mussels

One of the biggest problems in the modern world is environmental pollution. All organisms are affected by the resulting pollution, albeit at different levels. One of the most important causes of pollution is the stable and non-perishable compounds formed due to heavy metals used in a wide range of environments. Heavy metal pollution, especially in the seas, causes cumulative accumulations in aquatic life, food and other products obtained from aquatic life, in living things that consume these products, and related diseases. The most critical sign of heavy metal pollution in water is the resistance formed against heavy metals in bacteria living in these waters. To determine the resistance to heavy metals in bacteria, the presence of resistance to Copper, Mercury and Manganese heavy metals in E. coli isolated from 18 mussels and 16 shrimps was genotypically investigated. For this purpose, the presence of pcoR genes for the determination of copper resistance, merA for the determination of mercury resistance, and mntR for the determination of manganese resistance was investigated in both plasmid and genomic DNA. As a result of the study, resistance genes were detected against heavy metals in 31 (91.17%) of 34 E. coli isolates examined. The presence of the pcoR gene (copper resistance) was found in 2 isolates (5.88%), the merA gene (mercury resistance) in only one isolate (2.94%) and the mntR gene (manganese resistance) in 8 isolates (23.52%). While pcoR and merA genes were not observed together in any isolates, pcoR and mntR genes were detected together in the genetic material of 10 isolates (29.41%). In comparison, mntR and merA genes were detected together in the genetic material of 7 isolates (20.58%). In 3 samples, all of the resistance genes against heavy metals were detected (8.82%).

Ni-Fe Alloy Coatings Prepared via Jet Electrodeposition for the Optimization of the Electrochemical Detection Performance of Laser-Induced Graphene for Pb(II)

Heavy metal pollution in water, particularly Pb ion pollution, has seriously threatened human life and health. Therefore, the manufacture of efficient and sensitive heavy metal ion detection materials is essential. The objective of this study was to improve the electrochemical detection performance of laser-induced graphene (LIG) for Pb(II). Considering the excellent ion affinity and high activity of transition metals, Ni-Fe alloy coatings were prepared on the surface of LIG through jet electrodeposition. The prepared LIG and Ni-Fe/LIG were qualitatively analyzed through Raman spectrometry, X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The surface micromorphologies, charge transfer capabilities, and electrochemically active surface areas of LIG and Ni-Fe/LIG were characterized. The detection range and limit of detection (LOD) of Pb(II) for LIG and Ni-Fe /LIG as electrochemical sensors were analyzed. Results showed that compared with LIG, Ni-Fe/LIG had more surface active sites, a higher charge transfer capability, and a larger electrochemically active surface area that reached 0.828 cm2. Ni-Fe/LIG had a detection range of 20–1200 µg/L and an LOD of as low as 0.771 µg/L. Ni-Fe/LIG demonstrated a better electrochemical detection performance for Pb(II) than LIG when used as an electrochemical sensor.

Stability and biomineralization of cadmium sulfide nanoparticles biosynthesized by the bacterium Rhodopseudomonas palustris under light

Cadmium (Cd) pollution is regarded as a potent problem due to its hazard risks to the environment, making it crucial to be removed. Compared to the physicochemical techniques (e.g., adsorption, ion exchange, etc.), bioremediation is a promising alternative technology for Cd removal, due to its cost-effectiveness, and eco-friendliness. Among them, microbial-induced cadmium sulfide mineralization (Bio-CdS NPs) is a process of great significance for environmental protection. In this study, microbial cysteine desulfhydrase coupled with cysteine acted as a strategy for Bio-CdS NPs by Rhodopseudomonas palustris. The synthesis, activity, and stability of Bio-CdS NPs-R. palustris hybrid was explored under different light conditions. Results show that low light (LL) intensity could promote cysteine desulfhydrase activities to accelerate hybrid synthesis, and facilitated bacterial growth by the photo-induced electrons of Bio-CdS NPs. Additionally, the enhanced cysteine desulfhydrase activity effectively alleviated high Cd-stress. However, the hybrid rapidly dissolved under changed environmental factors, including light intensity and oxygen. The factors affecting the dissolution were ranked as follows: darkness/microaerobic ≈ darkness/aerobic < LL/microaerobic < high light (HL)/microaerobic < LL/aerobic < HL/aerobic. The research provides a deeper understanding of Bio-CdS NPs-bacteria hybird synthesis and its stability in Cd-polluted water, allowing advanced bioremediation treatment of heavy metal pollution in water.

Synthesis of magnetic sodium lignosulfonate hydrogel(Fe3O4@LS) and its adsorption behavior for Cd2+ in wastewater

Heavy metal pollution is becoming increasingly serious. Heavy metal pollutants are nonbiodegradable and can be bioenriched through the food chain, and thus, they greatly threaten the environment and human health. Hydrogels, as an ideal adsorbent, have been widely used to treat heavy metal industrial wastewater. Sodium lignosulfonate hydrogel (LS) was prepared by free-radical grafting copolymerization, and nano-Fe3O4 particles were loaded in LS by an in-situ precipitation method (Fe3O4@LS). The magnetic properties and adsorption capacity of Fe3O4@LS are closely related to the load capacity of Fe3O4. XRD, FTIR, XPS, SEM, TEM, BET, and TGA analyses of the materials were performed. Subsequently, the removal effect of the typical pollutant Cd2+ in heavy metal-polluted water was studied with Fe3O4@LS as the adsorbent. The influences of the Fe3O4@LS dosage and initial pH were investigated, and the adsorption kinetics and thermodynamics were further explored and discussed. Finally, the adsorption mechanism of Fe3O4@LS on Cd2+ was obtained. Results show that Fe3O4@LS has a more stable spatial network structure than LS, and the pore size, specific surface area and active sites increase. The maximum adsorption capacity can reach 88.00 mg/g when pH = 6 and the dosage of Fe3O4@LS is 1000 mg/L. The adsorption of Cd2+ by Fe3O4@LS conforms to pseudosecond-order kinetics and the Temkin isothermal adsorption model. Further mechanistic investigations show that the sorption of Cd2+ on Fe3O4@LS is mainly attributed to surface complexation, electrostatic attraction and coprecipitation. The coexistence of cations in water will inhibit the adsorption of Fe3O4@LS. Fe3O4@LS has superparamagnetism and a good response to an external magnetic field. The adsorption rate can still reach >60 % after four elutions with NaCl as the eluent. This material can be reused and has good application potential.

Metabolic Plasticity Endows Mixotrophic Organisms with High Tolerance to Cadmium and Special Potential for Recovering Cadmium-Contaminated Aquatic Environment.

Heavy metal pollution in waters causes serious stress to aquatic ecosystems. Several autotrophs with strong tolerance are extensively used to adsorb heavy metals, but their use may be limited by the specific conditions of polluted waters due to their single nutrition mode. By contrast, mixotrophs possess strong environmental adaptability due to their plastic metabolic modes. However, studies focusing on mixotroph's resistance and its underlying mechanism in response to heavy metals and their bioremediation potentials are currently lacking. In this study, we investigated the population, phytophysiological, and transcriptomic (RNA-Seq) responses of a typical and common mixotrophic organism, Ochromonas, to cadmium exposure and then evaluated their capacity to remove cadmium under mixotrophic condition. Compared with autotrophy, mixotrophic Ochromonas enhanced photosynthetic performances under short-time cadmium exposure and subsequently shifted to stronger resistance with increasing exposure time. Transcriptomic analyses suggested that the genes related to photosynthesis, ATP production, ECM components, and scavenging of reactive oxygen species and damaged organelles were upregulated to boost mixotrophic Ochromonas resistance to cadmium. Consequently, the harm of metal exposure was eventually reduced and cellular stability was maintained. Approximately, 70% of cadmium at 2.4 mg L-1 cadmium was removed by mixotrophic Ochromonas in the end, benefiting from upregulated genes associated with the transport of metal ions. Hence, mixotrophic Ochromonas tolerance to cadmium can be attributed to multiple pathways of energy metabolism and effective transport of metal ions. Collectively, this study advanced a better understanding of the unique mechanism of heavy metal resistance in mixotrophs and their potential use in recovering cadmium-contaminated aquatic ecosystems. IMPORTANCE Mixotrophs widely living in aquatic ecosystems possess unique ecological roles and strong environmental adaptability due to their plastic metabolic modes; however, little is known about their underlying resistance mechanism and bioremediation potential in response to environmental stresses. For the first time, this work investigated how mixotrophs respond to metal pollutants through physiological, population dynamics, and transcriptional regulation, and highlighted the unique underlying mechanism of mixotrophs to resist and remove heavy metal, thereby advancing our understanding of the potentials of mixotrophs in recovering metal-contaminated aquatic environments. These unique properties in mixotrophs are essential for the long-term functional stability of aquatic ecosystems.

Calcium alginate-nZVI-biochar for removal of Pb/Zn/Cd in water: Insights into governing mechanisms and performance

Heavy metals pollution in water caused by the intensification of industrial processes and human activities has attracted worldwide attention. Finding an environmental-friendly and efficient remediation method is in need. In this study, the calcium alginate entrapment and liquid-phase reduction method were used to prepare calcium alginate-nZVI-biochar composite (CANRC), which was firstly used to remove Pb2+, Zn2+, and Cd2+ in water. The effects of pyrolysis temperature, solution pH, and coexisting ions, etc. during adsorption processes were explored. Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the physicochemical properties of CANRC before and after adsorption. Different adsorption models and site energy analysis were used to analyze the possible mechanisms. The results showed that CANRC prepared at 300 °C and a 5 wt% Fe loading ratio had the maximum adsorption capacities with a dosage of 2.5 g/L and pH = 5.0– 6.0. The adsorption process was more in line with the Langmuir isotherm model dominated by monolayer adsorption. The maximum adsorption capacities of Pb2+, Zn2+, and Cd2+ were 247.99, 71.77, and 47.27 mg/g, respectively. Site energy analysis combined with XRD and XPS analysis indicated that surface complexation and precipitation were the main adsorption mechanisms. This study provides an alternative way for the removal of heavy metals from water.

Study on the Combined Behaviour of Montmorillonite and Carbonate Mineralizing Bacteria on Lead Retention and Fixation

Heavy metal pollution management is a global environmental problem that poses a great threat to the ecological environment. Adsorption and biomineralization are considered to be the two most promising heavy metal pollution remediation techniques among the numerous available ones. In this work, a combined heavy metal removal system was constructed employing the adsorption of montmorillonite and the mineralization of carbonate mineralizing bacteria to expand their application potential for controlling heavy metal water pollution. Analysis of changes in pH, CO32− concentration, Pb2+ concentration in the liquid phase, and changes in microscopic morphology, mineral phase, and functional group on sedimentary minerals was done to study the retention and fixation behaviour of montmorillonite and carbonate mineralizing bacteria on Pb2+. The results show that the liquid phase pH may be slightly altered by the ions dissolved in montmorillonite. Based on the conditions of montmorillonite and carbonate mineralizing bacteria functioning separately, the elimination of Pb2+ may reach 35.31% and 45.75%, respectively. However, when montmorillonite is combined with carbonate mineralizing bacteria, which is the heavy metal removal system constructed in this study, montmorillonite can buffer part of the Pb2+ rapidly and reduce its biotoxicity. Subsequently, these buffered Pb2+ are gradually desorbed by carbonate mineralizing bacteria and removed by the effect of mineralized deposition. Results from SEM, FTIR, and XRD indicate that Pb2+ is primarily removed from the liquid phase as rod-shaped PbCO3. It is worth noting that this process is able to significantly increase the removal of Pb2+ up to 90.06%. In addition, the presence of carbonate mineralizing bacteria can increase montmorillonite’s desorption rate to over 81%, greatly enhancing its capacity for reuse. Therefore, our research work contributes to expanding the potential of montmorillonite and carbonate mineralizing bacteria in the treatment of heavy metal-polluted waters.

Application of Herbal Medicine in Cu2+ Removal from Water and Comparison of its Detection Methods

In order to utilize discarded herbal medicine to treat heavy metal pollution in water, various herbal medicines were selected to explore their abilities of metal ions removal. In this experiment, copper ion was used as targeted heavy metal ion and two different treatments of several herbal medicines were compared on the effect of the copper ion removal ability. At the evaluating stage, four metal ion detection methods were employed and analyzed in this herbal medicine Cu2+ removal application. The results showed that directly soaking herbal medicine in the copper aqueous solution was more effective and easier to operate. Iodometry method and EDTA complexometric titration with xylenol orange as indicator were accurate and time-saving in the measurement of copper removal rate. In addition, the EDTA complexometric titration is also applicable in the detection of other metal ions. This experiment provided a basis for the implementation and application of herbal medicine in the deposition of metal ions in polluted water.

Delamination of multilayer Ti3C2Tx MXene alters its adsorpiton and reduction of heavy metals in water

MXenes are considered as an emerging class of two-dimensional (2D) adsorbent for various environmental applications. In this work, two different morphologies of Ti3C2Tx MXene (multilayer (ML-Ti3C2Tx) and delaminated titanium carbide (DL-Ti3C2Tx)) were prepared through mild in situ HF etching and further delamination. The structural differences between the two were explored with a focus on their effects on the performance and mechanism of removing heavy metals from water. In comparison to ML-Ti3C2Tx, DL-Ti3C2Tx had more oxygen-containing functional groups, higher specific surface area (19.713 vs. 8.243 m2/g), larger pore volume (0.135 vs. 0.040 cm3/g), higher maximum Pb(II) adsorption capacity (77.0 vs. 56.68 mg/g), but lower maximum Cu(II) adsorption capacity (23.08 vs. 55.46 mg/g). Further investigation revealed that the removal of Pb(II) by the MXenes was mainly controlled through electrostatic attraction and surface complexation mechanisms, while Cu(II) was removed mainly through surface reduction by Ti-related groups. Because delamination of ML-Ti3C2Tx increased the surface area and surface functional groups, DL-Ti3C2Tx became a better sorbent for Pb(II) in water. During sonication, however, delamination inevitably led to partial oxidation of Ti3C2Tx nanosheets and thus weakened the reducing ability of DL-Ti3C2Tx for Cu(II) in water. Nevertheless, both ML- and DL-Ti3C2Tx not only exhibited excellent heavy metal adsorption capacity under different solution conditions, but also showed good reusability. Findings of this study indicate that Ti3C2Tx MXenes are promising adsorbents for treating heavy metal pollutants in water.

Cadmium accumulation and isotope fractionation in typical protozoa Tetrahymena: A new perspective on remediation of Cd pollution in wastewater

Cadmium (Cd) pollution threatens water safety and human health, which has raised serious public concern. Tetrahymena is a model protozoan, possessing the potential to remediate Cd contaminated water given the rapid expression of thiols. However, the mechanism of Cd accumulation in Tetrahymena has not been well understood, which hinders its application in environmental remediation. This study elucidated the pathway of Cd accumulation in Tetrahymena using Cd isotope fractionation. Our results showed that Tetrahymena preferentially absorb light Cd isotopes, with Δ114/110CdTetrahymena−solution = −0.20 ± 0.02‰ ∼ − 0.29 ± 0.02‰, which implies that the intracellular Cd is probably in the form of Cd−S. The fractionation generated by Cd complexation with thiols is constant (Δ114/110CdTetrahymena−remaining solution ∼ −0.28 ± 0.02‰), which is not affected by the concentrations of Cd in intracellular and culture medium, nor by the physiological changes in cells. Furthermore, the detoxification process of Tetrahymena results in an increase in cellular Cd accumulation from 11.7% to 23.3% with the elevated Cd concentrations in batch Cd stress culture experiments. This study highlights the promising application of Cd isotope fractionation in Tetrahymena for the remediation of heavy metal pollution in water.

Copper Accumulation Efficiency in Different Recombinant Microorganism Strains Available for Bioremediation of Heavy Metal-Polluted Waters.

The aim of this research was to investigate the bioremediation conditions of copper in synthetic water. In the present study, copper ions accumulation efficiency was determined using various genetically modified strains of Saccharomyces cerevisiae (EBY100, INVSc1, BJ5465, and GRF18), Pichia pastoris (X-33, KM71H), Escherichia coli (XL10 Gold, DH5α, and six types of BL21 (DE3)), and Escherichia coli BL21 (DE3) OverExpress expressing two different peroxidases. Viability tests of yeast and bacterial strains showed that bacteria are viable at copper concentrations up to 2.5 mM and yeasts up to 10 mM. Optical emission spectrometry with inductively coupled plasma analysis showed that the tolerance of bacterial strains on media containing 1 mM copper was lower than the tolerance of yeast strains at the same copper concentration. The E. coli BL21 RIL strain had the best copper accumulation efficiency (4.79 mg/L of culture normalized at an optical density of 1.00), which was 1250 times more efficient than the control strain. The yeast strain S. cerevisiae BJ5465 was the most efficient in copper accumulation out of a total of six yeast strains used, accumulating over 400 times more than the negative control strain. In addition, E. coli cells that internally expressed recombinant peroxidase from Thermobifida fusca were able to accumulate 400-fold more copper than cells that produced periplasmic recombinant peroxidases.

Biofilm-Forming Heavy Metal Resistance Bacteria From Bungus Ocean Fisheries Port (PPS) West Sumatra as a Waters Bioremediation Agent.

&lt;b&gt;Background and Objective:&lt;/b&gt; Heavy metals are one of the most worrisome pollutants due to their toxicity. Prolonged exposure to heavy metals and their accumulation and biomagnification properties adversely affect aquatic biota and human health. The ability of microorganisms to bioremediate heavy metals into non-toxic forms is one solution. The research aims of the study were to find biofilm-forming heavy metal-resistant bacteria isolated from the waters of the Bungus Samudra Fishery Port (PPS), Padang City. &lt;b&gt;Materials and Methods:&lt;/b&gt; This study used a marine agar medium modified with the addition of K&lt;sub&gt;2&lt;/sub&gt;Cr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;, Pb(NO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;2&lt;/sub&gt; and CdSO&lt;sub&gt;4&lt;/sub&gt;•H&lt;sub&gt;2&lt;/sub&gt;O, Marine Broth medium and Congo Red Agar medium. The research methods include, the isolation of bacteria, isolate resistance test to heavy metals, testing the ability of isolates to form biofilms and determine the ability of isolates to reduce heavy metals. Furthermore, molecular identification of bacterial isolates was carried out to determine the type of species. &lt;b&gt;Results:&lt;/b&gt; Five heavy metal-resistant bacterial isolates were found that were able to form biofilms, namely isolates B3Cd, B5Cr, B7Pb, B6Pb and B3Pb. The five isolates were able to reduce heavy metal content by 38.67-61.191%. Identification of the best bacterial isolates on each heavy metal tested, namely B3Cd, B5Cr and B7Pb, respectively, showed the type of &lt;i&gt;Acinetobacter schindleri&lt;/i&gt;, &lt;i&gt;Acinetobacter&lt;/i&gt; sp. and &lt;i&gt;Bacillus&lt;/i&gt; sp. &lt;b&gt;Conclusion:&lt;/b&gt; These three selected potential isolates can be used as bioremediation agents in metal-polluted waters in the future.

Assessment of heavy metals in fresh water fishes of river son at Diyapipar village in Shahdol district (M.P.) India

This study was conducted during season of March to May to determine the metal pollution in water and Bioaccumulation into freshwater fishes of Catla catla, Labeo rohita, Notopterus notopterus and Cirrhinus mrigala were collected from the two different places within the river Son. The gill and muscle tissues of fish were analyzed for Cd, Cr, Cu, Pb, Ni and Zn using Atomic Absorption Spectrophotometer (AAS- Model AA500 PG Instruments, UK). The levels of heavy metals in the freshwater were found to be higher than the WHO recommendations. The fish samples were also high levels of heavy metals than the WHO [23] recommendations. The fish tissues of gills were observed highest level of heavy metals than the muscle tissue. The metals were accumulated in descending order as follow: Zn>Cu>Pb>Ni>Cr>Cd. The present study shows that the high-level bioaccumulation of metal in fish and water that could be unsafe for human consumption.

Arsenic pollution remediation mechanism and preliminary application of arsenic-oxidizing bacteria isolated from industrial wastewater

Microbial remediation is vital for improving heavy metal-polluted water. In this work, two bacterial strains, K1 (Acinetobacter gandensis) and K7 (Delftiatsuruhatensis), with high tolerance to and strong oxidation of arsenite [As(III)], were screened from industrial wastewater samples. These strains tolerated 6800 mg/L As(III) in a solid medium and 3000 mg/L (K1) and 2000 mg/L (K7) As(III) in a liquid medium; arsenic (As) pollution was repaired through oxidation and adsorption. The As(III) oxidation rates of K1 and K7 were the highest at 24 h (85.00 ± 0.86%) and 12 h (92.40 ± 0.78%), respectively, and the maximum gene expression levels of As oxidase in these strains were observed at 24 and 12 h. The As(III) adsorption efficiencies of K1 and K7 were 30.70 ± 0.93% and 43.40 ± 1.10% at 24 h, respectively. The strains exchanged and formed a complex with As(III) through the –OH, –CH3, and C]O groups, amide bonds, and carboxyl groups on the cell surfaces. When the two strains were co-immobilized with Chlorella, the adsorption efficiency of As(III) improved (76.46 ± 0.96%) within 180 min, thereby exhibiting good adsorption and removal effects of other heavy metals and pollutants. These results outlined an efficient and environmentally friendly method for the cleaner production of industrial wastewater.

The Effect of Cadmium, Copper, and Lead on Brassica juncea in Hydroponic Growth Medium

This study measured the accumulation of cadmium (Cd), lead (Pb), and copper (Cu) in Brassica juncea grown using the hydroponic method in a water environment contaminated with these heavy metals. The accumulated metal content in each part of the plant was monitored after one, three, and six weeks of exposure. The concentrations of Cd, Cu, and Pb in the biomass of B. juncea were determined using atomic absorption spectroscopy. The results showed that heavy metal pollution in water caused heavy metal accumulation in vegetable biomass. Pb tended to accumulate lower vegetable biomass than Cu and Cd. The metal accumulation level in Cu and Cd was in the order of roots &gt; stems &gt; leaves, while with Pb, the concentration accumulated in roots &gt; leaves &gt; stems. The translocation factors of Cu, Cd, and Pb from shoots to stems and shoots to leaves were less than 1.

Fluorescence off–on nanosensor based on MoS2 nanosheets and oligonucleotides for the alternative detection of mercury(II) ions or silver(I) ions

As traditional methods for detection of heavy metal pollution in water involve complex procedures and require expensive equipment, there is a great deal of interest in the development of rapid and simple methods for determining heavy metal ions in water. Here, a nanobiosensor based on molybdenum disulphide (MoS2) nanosheets and fluorophore (FAM) labeled oligonucleotides was proposed, and fluorescence spectroscopy was adopted for detection of Hg2+ or Ag+ ions in aqueous solution. The principle underlying detection by the sensor involves the formation of T-Hg2+-T or C-Ag+-C mismatches by single-stranded DNA (ssDNA) rich in thymine (T) or cytosine (C), thereby forming stable double-stranded DNA (dsDNA) structures. By exploiting the different adsorption capacity of MoS2 nanosheets for ssDNA and dsDNA, when oligonucleotides were in a single chain state, MoS2 nanosheets possessed a strong adsorption capacity for ssDNA, resulting in fluorescence quenching of FAM. After the addition of Hg2+ or Ag+, ssDNA formed double chains structure, the fluorescence recovered due to the weak adsorption capacity of MoS2 nanosheets for dsDNA. Along this line, an “off-on” mode fluorescence nanobiosensor was designed to alternatively detect these two heavy metal ions in water. The sensor showed high sensitivity and excellent selectivity for both Hg2+ and Ag+ ions, with minimum detection limits of 6.8 nM and 8.9 nM, respectively.