Increasing Cd Concentration Research Articles

Effects of cadmium exposure on gut microbiota and antibiotic resistance genes in Haliotis diversicolor abalone

Heavy metals in soil, water, and industrial production can affect the antibiotic resistance of bacteria. Antibiotic resistance in gut microbiota has been extensively researched. The effects of cadmium (Cd) was investigated on the gut microbiota and antibiotic resistance genes (ARGs) of Haliotis diversicolor, a commercially important abalone species. By exposing H. diversicolor to four concentrations of Cd (0 μg L−1 (control), 6.5 μg L−1 (low), 42.25 μg L−1 (medium), and 274.63 μg L−1 (high)) for 30 and 60 days, 16 types of ARG (aadA-01, aadA-02, cfr, dfrA1, ermB, floR, folA, mecA, sul2, tetB-01, tetC-01, tetD-01, tetG-01, tetM-02, tetQ, vanC-01), and 1213 genus and 27 phylum microbiomes were detected. ARGs can be resistant to aminoglycoside, beta-lactamase, macrolide-lincosamide-streptogramin B, multidrug, florfenicol, macrolide, sulfonamides, tetracyclines, and vancomycin. Cadmium exposure significantly alters the abundance of tetC-01, tetB-01, tetQ, sul2, and aadA-01. About 5% (61) of genus-level microorganisms were significantly affected by Cd exposure. Microbiota alpha and beta diversities in the 60-day 42.25 μg L−1 Cd treatment differed significantly from those in other treatments. In addition, 26 pathogens were detected, and two pathogens (Vibrio and Legionella) were significantly affected by Cd exposure. Significant correlations between pathogens and ARGs increased with increased Cd concentration after 60 days of Cd exposure. Cadmium exposure may cause gut microbiota disturbance in H. diversicolor and increase the likelihood of ARG transfer to pathogens, increasing potential ecological and economic risks.

Factors influencing cadmium accumulation in plants after inoculation with rhizobacteria: A meta-analysis

Rhizobacteria have the potential to enhance phytoremediation by generating substances that stimulate plant development and influence the effectiveness of cadmium (Cd) remediation by adjusting Cd availability via metal solubilization. Furthermore, rhizobacterial inoculation affects plants' metal tolerance and uptake by controlling the expression of several metal transporters, channels, and metal chelator genes. A meta-analysis was conducted to quantitatively assess the effects of rhizobacteria on Cd accumulation in plants using 207 individual observations from 47 articles. This meta-analysis showed an average Cd concentration increase of 8.09 % in plant cells under rhizobacteria treatment. The effects of different plant-microbial interactions on the bioaccumulation of Cd in plants varied. Selecting the proper rhizobacteria-plant association is essential to affect Cd buildup in plant roots and shoots. A more extended planting period (>30 days) and a suitable soil pH (<6, 7–8) would aid in the phytoextraction of Cd from the soil. This study comprehensively and quantitatively investigated the effects of plants, rhizobacteria, soil pH, planting period, experimental sites, and plant organs on plant Cd accumulation. According to the analysis of explanatory factors, plant species, planting period, soil pH, and rhizobacteria species have a more decisive influence on Cd accumulation than other factors. The results provide information for future research on the successful remediation of soils contaminated with Cd. More investigations are required to elucidate the intricate interactions between plant roots and microorganisms.

Effects of cadmium exposure on haemocyte immune function of clam Ruditapes philippinarum at different temperatures

Haemocytes are crucial for the immune defence of mollusks. It is important to explore the immune performance of haemocytes of mollusks under the stress of heavy metals with global warming. In order to study the effects of cadmium (Cd) exposure and temperature stress on the haemocyte immune function of clam Ruditapes philippinarum, clams were exposed to different Cd concentrations (0.05, 0.10 and 0.25 mg/L) at 20 °C, 25 °C and 30 °C respectively. Haemocyte mortality, reactive oxygen species (ROS) and superoxide dismutase (SOD) activity were measured at day 1, day 3, day 5 and day 7. The results showed that the changes of the three indexes were not obvious when exposed to 0.05 mg/L of Cd at 20 °C, while significant differences were observed with the increase of temperature, Cd concentration and exposure time. Under a condition of relative high temperature coupling with high concentration of Cd, the clams were significantly influenced, showing an obvious synergistic effect. Selected indexes reflect the clam's response to the combined stress of temperature and Cd. Moreover, R. philippinarum might be an ideal biological index species to the Cd pollution.

Effects of Priestia aryabhattai on Phosphorus Fraction and Implications for Ecoremediating Cd-Contaminated Farmland with Plant-Microbe Technology.

The application of phosphate-solubilizing bacteria has been widely studied in remediating Cd-contaminated soil, but only a few studies have reported on the interaction of P and Cd as well as the microbiological mechanisms with phosphate-solubilizing bacteria in the soil because the activity of phosphate-solubilizing bacteria is easily inhibited by the toxicity of Cd. This paper investigates the phosphorus solubilization ability of Priestia aryabhattai domesticated under the stress of Cd, which was conducted in a soil experiment with the addition of Cd at different concentrations. The results show that the content of Ca2-P increased by 5.12-19.84%, and the content of labile organic phosphorus (LOP) increased by 3.03-8.42% after the addition of Priestia aryabhattai to the unsterilized soil. The content of available Cd decreased by 3.82% in the soil with heavy Cd contamination. Priestia aryabhattai has a certain resistance to Cd, and its relative abundance increased with the increased Cd concentration. The contents of Ca2-P and LOP in the soil had a strong positive correlation with the content of Olsen-P (p < 0.01), while the content of available Cd was negatively correlated with the contents of Olsen-P, Ca2-P, and LOP (p < 0.05). Priestia aryabhattai inhibits the transport of Cd, facilitates the conversion of low-activity P and insoluble P to Ca2-P and LOP in the soil, and increases the bioavailability and seasonal utilization of P in the soil, showing great potential in ecoremediating Cd-contaminated farmland soil with plant-microbe-combined technology.

Rapid PL Enhancement in Cd doped Alq3 Nanowires

Aluminium tris (8-hydroxyquinoline) (Alq3) is a popular coordination complex extensively used in organic luminescent devices as the emissive layer. Metal doping in Alq3 and its nanoscale synthesis are two strategies which are widely adopted to enhance the functional properties of Alq3. In the present work, Cadmium (Cd) doped Alq3 films having 1-dimensional morphology have been successfully synthesised using thermal vapor transport method. These films have been subjected to different analytical studies to study their functional properties. Scanning Electron Microscopy (SEM) images reveal the dendritic nature of Cd-doped Alq3 nanowires while Energy Dispersive X-ray Spectroscopy (EDAX) analysis confirms the presence of Cd in Cd-doped Alq3 nanowires. X-ray Diffraction (XRD) study reveals the polycrystalline nature of Cd-doped Alq3 nanowires. X-ray Photoelectron Spectroscopy (XPS) analysis of Cd-doped Alq3 nanowires samples indicates the replacement of some Al atoms with Cd atoms in Alq3 matrix. UV–visible spectroscopy study of the Cd-doped Alq3 nanowires shows enhancement in the optical absorbance with increasing Cd concentration while Photoluminescence (PL) spectroscopy analysis shows a 7-fold enhancement in PL intensity for 0.5 mol% Cd-doping. This rapid enhancement in the PL is explained on the basis of electronic charge transfer from Cd ions to Alq3 molecules.

Cd-supported CuO-ZnO binary oxide thin films: Synthesis, microstructural, and optoelectronic properties

This article reports the synthesis of low-cost, repeatable, and low-processing-temperature Cd-doped copper oxide (CuO)/zinc oxide (ZnO) binary nanocomposite thin films. Binary CuO– ZnO thin film samples were fabricated using the solution-based SILAR method. We primarily report the examination of a Cd-doping-induced improvement in the optical and electrical performances of CuO–ZnO binary samples at room temperature by tailoring the surface morphology and crystalline structure. The experimental results confirmed the formation of pure nanostructured composites. The estimated Eg is approximately 2.26 eV, which increases with increasing Cd content in the growth bath. The transmittance spectra exhibit an increase in the transmittance from 58 % to 72 % as the Cd content increases, while the contact resistivity varies from ∼2.97 to ∼22.17 MΩ□. The wider optical bandgap energy is exclusively significant for allowing the designed materials to operate at much higher temperature conditions. The obtained outcome could be used to enhance the impression of photovoltaic devices.

Iron Administration Partially Ameliorates Cadmium‐Induced Oxidative Damage in the Liver and Kidney of Rats

The protective effect of Fe against Cd‐induced toxicity in the liver and kidney of rats during concurrent administration of both metals was investigated in this study. Fifty female rats (130–150 g) were distributed into five groups of 10 rats each (n = 10): Group I (control), received normal saline solution; Group II (1.2 mg CdCl2/kg b.w.); Group III (1.2 mg CdCl2 + 0.25 mg FeCl2/kg b.w.); Group IV (1.2 mg CdCl2 + 0.75 mg FeCl2/kg b.w.); and Group V (1.2 mg CdCl2 + 1.5 mg FeCl2/kg b.w.). Administration of both tested substances lasted for 47 days. Cd was injected intraperitoneally once a week, while Fe was administered to the Cd‐exposed animals by oral gavage thrice weekly. The animals were killed at the end of the study, their blood was collected, and their liver and kidneys were harvested for biochemical and histological analysis. Following Cd administration, the kidney and liver showed a significant increase in Cd concentration, while Fe concentration in the kidney decreased. However, cotreatment with Fe decreased Cd concentration in the kidney and liver and increased Fe concentration in the kidney but not the liver, and the effect was more pronounced in the higher than lower doses. In the kidney, cotreatment with Fe especially at higher doses inhibited Cd‐induced lipid peroxidation and plasma uric acid concentration. In the liver, lipid peroxidation which Cd did not alter was found to be elevated after cotreatment with the highest dose Fe. Inflammatory cell infiltrations of the central vein and renal tubular and glomeruli injury induced by Cd were not obviated by Fe cotreatment. It seems that both tissues respond differently to the concurrent administration of these metals and that Fe protected the kidney against oxidative injury‐induced by Cd but not histopathological changes in both tissues.

Epigenetic modifications of 45S rDNA associates with the disruption of nucleolar organisation during Cd stress response in Pakchoi

The role of the nucleolus in Pakchoi response to Cd stress remains largely unknown. In this work, we focus on exploring the underling mechanism between nucleolus disruption and epigenetic modification in Cd stressed-Pakchoi. Our results indicated that the proportion of nucleolus disruption, decondensation of 45 S rDNA chromatin, and a simultaneous increase in 5' external transcribed spacer region (ETS) transcription were observed with increasing Cd concentration, accompanied by genome-wide alterations in the levels of histone acetylation and methylation. Further results showed that Cd treatment exhibited a significant increase in H3K9ac, H4K5ac, and H3K9me2 levels occurred in promoter regions of the 45 S rDNA. Additionally, DNA methylation assays in the 45 S rDNA promoter region revealed that individual site-specific hypomethylation may be engaged in the activation of 45 S rDNA transcription. Our study provides some molecular mechanisms for the linkage between Cd stress, rDNA epigenetic modifications, and nucleolus disintegration in plants.

The effects of titanium dioxide nanoparticles on cadmium bioaccumulation in ramie and its application in remediation of cadmium-contaminated soil

Cadmium (Cd) is a toxic heavy metal contaminant in agricultural soils. Phytoremediation using hyperaccumulator plants is a promising remediation strategy. This study investigated the effects of TiO2 NPs on Cd uptake and accumulation in the hyperaccumulator ramie (Boehmeria nivea L.) grown in Cd-spiked soil. The aim was to evaluate the potential application of TiO2 NPs to enhance the phytoextraction efficiency of ramie for removing Cd from contaminated soils. Ramie was cultivated in soil spiked with 5 mg/kg Cd, with or without 500 mg/kg TiO2 NPs. The results showed TiO2 NPs significantly increased Cd concentrations in roots, stems, and leaves of ramie by 35%, 75%, and 278% respectively, compared to control plants. Cd levels reached 146 mg/kg in roots and 102 mg/kg in leaves with TiO2 NPs. The bioconcentration factor rose from 21.6 to 29.2 and translocation factor from 0.3 to 0.7 with nanoparticles. This indicates TiO2 NPs increased Cd bioavailability in soil and translocation to shoots. The higher Cd accumulation, especially in leaves, demonstrates the potential of TiO2 NPs to improve ramie's phytoextraction capacity. With TiO2 NP treatment, soil Cd levels decreased by an estimated 20–30% after 8 weeks of ramie cultivation, indicating enhanced phytoextraction. This study provides evidence that the application of TiO2 NPs can enhance the efficiency of phytoremediation using hyperaccumulator plants like ramie for remediation of Cd-contaminated soils.

Ultrahigh Thermoelectric Performance of ZnO-CdO Thin Films

Zinc oxide (ZnO) is emerging as a promising n-type thermoelectric material (TE) for power harvesting due to its high melting point and large Seebeck coefficient. However, the TE performance of ZnO is limited by high thermal conductivity and low carrier mobility. Adding or doping a divalent element such as cadmium oxide (CdO) can lower the thermal conductivity and enhance the carrier concentration of ZnO. In this paper, the thermoelectric transport properties of ZnO-CdO nanocrystalline thin films are investigated by varying the Zn/Cd ratio at temperatures ranging from room temperature (RT) to 423 K. The electrical conductivity, carrier concentration and mobility of ZnO were enhanced by increasing the Cd concentration. The maximum power factor of 2.75 × 10−4 W m−1 K−2 was obtained at 423 K for the Zn/Cd = 1:3 sample. The thermal conductivity was dominated by lattice thermal conductivity in which Umklapp scattering occurs between anharmonic phonons. The thermal conductivity of ZnO decreased significantly with increasing Cd concentration. The highest estimated figure of merit (ZT) of 0.59 was found at 413 K for the Zn/Cd = 1:3 sample, which is 223 times greater than for ZnO, indicating that the film is efficient in energy generation.

The aging of polyethylene mulch films in the presence of cadmium

To determine the fates of the persistent pollutants cadmium (Cd) and micro-plastics in agricultural soils, an in-depth understanding of the interactions between Cd and mulching film is required. In the present work, pot experiments are conducted under natural conditions to study the influence of various Cd concentrations on the aging process of polyethylene mulching film in soil collected from Changzhi, Shanxi Province. The results indicate that during 150 days, the aging degree of the mulch film increases gradually as the increased Cd concentration in the soil. Further, the results of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry and X-ray photoelectron spectroscopy (XPS) demonstrate that the average vinyl index (VI) of the aging mulch film increases from 1.29 to 1.82, while the oxygen-to-carbon (O/C) ratio of the mulch film decreases significantly from 0.344 to 0.045, as the Cd concentration is increased from 0 to 10 mg kg–1. When the aging time exceeds 90 days, the oxygen-containing functional groups (C–O and CO) generated consumed by the adsorbed Cd. In addition, electron paramagnetic resonance (EPR) measurements indicate that Cd both enhances the formation of hydroxyl radical (·OH) on the surface of the mulch film and prevents the combination of ·OH and electrons, thereby accelerating the aging of the mulch. Hence, the present study indicates that the presence of Cd will hasten the decomposition of mulch, which will inevitably result in the faster release of micro-plastics from the mulch into the soil environment.

Overexpression of IlHMA2, from Iris lactea, Improves the Accumulation of and Tolerance to Cadmium in Tobacco.

Long-distance transport cadmium (Cd) from roots to shoots is a key factor for Cd phytoremediation. Our previous study indicated that heavy metal P1B2-ATPases, IlHMA2, was involved in improving the accumulation of Cd via mediated long-distance transport Cd, contributing to the phytoremediation in Cd accumulator Iris lactea. However, whether the overexpression of IlHMA2 could enhance the accumulation and tolerance to Cd remains unclear in plants. Here, we generated transgenic tobacco overexpressing IlHMA2 and tested its effect on the translocation and accumulation of Cd and zinc (Zn), as well as the physio-biochemical characteristics under 50 mg/L Cd exposure. The overexpression of IlHMA2 significantly increased Cd concentrations in xylem saps, resulting in enhanced root-to-shoot Cd translocation compared with wild-type. Meanwhile, overexpressing IlHMA2 promoted Zn accumulations, accompanied by elevating proline contents and antioxidant enzyme activity (SOD, POD, and CAT) to diminish the overproduction of ROS in transgenic tobacco. These pieces of evidence suggested that higher Zn concentrations and lower ROS levels could tremendously alleviate Cd toxicity for transgenic tobacco, thereby improving the growth and tolerance. Overall, the overexpression of IlHMA2 could facilitate Cd accumulation and enhance its tolerance in tobacco exposed to Cd contaminations. This would provide a valuable reference for improving Cd phytoremediation efficiency.

Ecotoxicological assessment of soddy-podzolic soil under the influence of hostilities

Military сonflict on the territory of Ukraine since 2014 has caused and continues to exert a detrimental impact on soil resources. The research results present the changes in ecotoxicological parameters of chernozem soil that underwent degradation due to military actions in Bucha district of Kyiv region in February–March 2022 during the Russian invasion. The use of artillery weapons, including mortars, in the territory of Torf'iane village revealed damage to the soil cover on agricultural and forest lands. Soil degradation resulting from mortar shelling was confirmed by an increase in the content of heavy metals (Cu, Zn, Ni, Cr, Cd, Pb) in the soil layer of 0–20 cm one year after artillery shelling. At a distance of 2.5 m from the edge of the craters (Nо 1 and No 2), there was an increase in the gross content of Zn, Ni, Cr by 1.1–1.2 times, Pb by 1.1–1.6 times, and Cu by 1.5–1.8 times. The increase in Cd content by 1.1–1.2 times at a distance of 2.5 m was observed only within crater No 2. At a distance of 30 m from the craters, a high gross content of zinc (151–155 mg/kg), lead (43–44), chromium (39–41), nickel (24–28), copper (17–18), and cadmium (2–3 mg/kg) was found. Exceedances of the content of mobile forms of heavy metals directly in the crater and within a distance of up to 30 m were detected on average by 3–9 times. The highest concentration coefficient values for heavy metals in the soil were found to be, on average, zinc — 6–14 times higher than the background, chromium — 7–9 times, and lead — 4–8 times. Exceedances of the maximum allowable concentrations (MAC) in the soil around the craters were recorded for chromium by 7–26% and nickel by 15–21%. Slight exceedance of the MAC for lead in the soil was observed by 3–6%. No exceedance of the MAC for copper (0.1–0.3 MAC), zinc (0.2–0.4 MAC), cadmium (0.4–0.6 MAC), and lead (0.5–1 MAC) content in the soil was observed one year after the shelling of these territories.

Physiological and Cellular Ultrastructural Responses of Sesuvium portulacastrum under Cd Stress Grown Hydroponically.

This study aimed to investigate the physiological and cellular mechanisms of Sesuvium portulacastrum under heavy metal stress to evaluate possible tolerance and adaptation mechanisms in a metal-polluted environment. The physiological and cellular ultrastructural responses of S. portulacastrum were studied hydroponically under exposure to a range of cadmium (Cd) concentrations (50 µM to 600 µM) for 28 days. The activity of antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), changes in chlorophyll, and cellular ultrastructural content were examined. There was no significant difference in chlorophyll content in the leaf under the stress of 300 μM, but 400 μM and 600 μM Cd stress showed significantly decreased chlorophyll content. The SOD activity indicates an increase under the Cd stress of 100 μM for leaves, 300 μM for stems, and 50 μM for roots; after that, the SOD activity gradually decreased with increasing Cd concentrations. But POD activity was considerably increased with increasing Cd stress. CAT activity showed a gradual increase in concentrations until 300 μM of Cd stress and then decreased sharply in roots, stems, and leaf tissues. Cd stress had a considerable impact on the structure of the roots, stems, and leaves cells, such as distorted and thinner cell walls and the deformation of chloroplasts, mitochondria, and other organelles. Therefore, the increased number of nucleolus in the cell nucleus suggests that cells may be able to maintain their protein synthesis in a stressful environment. This study concludes that SOD is the dominant antioxidant enzyme activity during low Cd toxicity (<100 μM), while POD is the dominant enzyme activity during higher Cd toxicity (>100 μM).

The potential of black soldier fly larvae faeces and sludge residue as fertilizer under Cu and Cd stress

Black soldier fly larvae (BSFL) are used to digest municipal sludge, and its excretion and the sludge residue (BSFL sand) have attracted much attention. However, little research has been conducted on the quality of the BSFL sand produced with high concentrations of copper (Cu) and cadmium (Cd) and its effect on plant growth. We collected BSFL sand from previous studies to assess its feasibility as an organic fertiliser. The results showed that with the increase in Cu and Cd concentrations, pH (5.84–6.73), electrical conductivity (2.38–3.37), and organic matter (82–96%) increased continuously, moisture (20–25%), and total nutrients (4.19–5.26%, TN + P2O5+K2O) content decreased. Cu and Cd stress significantly (P < 0.05) reduced the content of free amino acids and fatty acids in the BSFL sand, and the germination index of cucumber seed also decreased continuously (30–73%), especially the mildew phenomenon that occurred in the Cu-1500 (mg/kg) group. In conclusion, BSFL sand can be considered a fertiliser when Cu and Cd concentrations in the initial sludge are lower than 900 and 120 mg/kg, respectively. However, considering the problems of Cu and Cd enrichment, their concentrations should be lower than 222 and 2.54 mg/kg, respectively. This study provides a theoretical basis for applying BSFL sands in agricultural production. Environmental implicationStudies on the effects of Cu and Cd on the quality of insect and sludge co-composting products.

Protective effects of polymer amendment on specific metabolites in soil and cotton leaves under cadmium contamination

Polymer materials have great potential for soil heavy metal contamination remediation, but the metabolic mechanism by which polymer amendments regulate the responses of soil-plant systems to cadmium (Cd) stress is still unclear. To clarify the metabolic mechanism by which a self-developed soluble polymer amendment (PA) remediates Cd contamination in cotton fields, the common and differential metabolites in soil and cotton leaves were analyzed during the critical period of cotton growth (flowering and bolling stage) in a field experiment. The results showed that Cd stress increased Cd concentration in the soil-cotton system, and reduced enzyme activity in soil and cotton leaves. Besides, Cd stress also reduced the abundance of α-linolenic acid in soil and the abundance of 2-Oxoarginine and S-Adenosylmethionine in cotton leaves. These ultimately led to reductions in weight, boll number, yield, and fiber elongation. However, the application of PA to the Cd-contaminated soil significantly reduced the soil exchangeable Cd (Ex-Cd) concentration by 41.43%, and increased the boll number, yield, and fiber strength by 14.17%, 21.04%, and 19.89%, respectively compared with the Cd treatment. The results of metabolomic analysis showed that PA application mainly affected the Nicotinate and nicotinamide metabolism pathway, Lysine degradation pathway, and Arginine and proline metabolism pathway in cotton leaves and soil. Besides, in these metabolic pathways, succinic acid semialdehyde of cotton leaves, saccharopine of soil, and S-Adenosylmethionine of soil and cotton had the most significant response to PA application. Therefore, the application of PA to Cd-contaminated soil can increase soil and cotton leaf enzyme activity and cotton yield (boll number and seed cotton yield) and quality (fiber strength), and maintain soil-plant material balance by regulating the distribution of Cd ions and key metabolites in the soil-cotton system. This study will deepen our understanding of the metabolic mechanism of PA remediating Cd-contaminated cotton fields, and provide a technical reference for the remediation of heavy metal contamination in drip-irrigated cotton fields in arid areas.

CaHMA1 promotes Cd accumulation in pepper fruit

The main planting areas for pepper (Capsicum sp.) are high in cadmium (Cd), which is the most prevalent heavy metal pollutant worldwide. Breeding pepper cultivars with low Cd levels can promote sustainable agricultural production and ensure the safety of pepper products. To identify breeding targets for reducing Cd accumulation in pepper fruits, we performed a genome-wide association study on 186 accessions. Polymorphisms were associated with fruit Cd content in a genomic region containing a homolog of Arabidopsis (Arabidopsis thaliana) Heavy metal-transporting ATPase 1 (HMA1) encoding a P-type ATPase. In two cultivars with contrasting Cd accumulation, transcriptome analysis revealed differentially expressed genes enriched for carbohydrate metabolism and photosynthesis in fruits with high Cd accumulation, and a Cd2+/Zn2+-exporting ATPase gene (HMA). Heterologous expression of CaHMA1 in yeast increases Cd sensitivity. Overexpression of CaHMA1 conferred a severe increase in Cd content in Arabidopsis plants, whereas reduced CaHMA1 expression in pepper fruits decreased Cd content. We propose that CaHMA1 expression may be an important component of the high Cd accumulation in pepper plants.

Optical gain of CdxZn1−xTe quantum dot structures

AbstractGain spectra of undoped and doped quantum dot (QD) structures are studied under the inhomogeneous broadening assumption at four mole fractions . For the QD structure, two peaks appear due to the excited state (ES) and ground state (GS) transitions. The gain for the doped structures doubles the undoped ones. The gain increases while the wavelength is reduced with increasing Cd content due to the broader band discontinuity between the QD states. The discontinuity of the bands for each structure (mole fraction) is calculated, which is one of the merits of this work. While the structure offers the peak wavelengths 470 and 630 nm, other mole fractions offer the wavelengths between them. These visible bands are essential in different applications. The effect of QD size effect is also examined. The wavelength is extended by 20 nm for each 1 nm QD height increment.

Effects of cadmium uptake on growth and productivity of Chinese cabbage (Brassica rapa subsp. pekinensis) and pumpkin (Cucurbita moschata Duchesne) vegetables

Cadmium (Cd) is recognized as one of the most toxic elements to plants and humans when available in higher concentrations. In the present study, a pot experiment was carried out to investigate the effect of different Cd levels (0, 10, 20, 30, and 40 mg/kg) on the growth, production, and uptake of Cd using Chinese cabbage (Brassica rapa subsp. pekinensis) and pumpkin leaves (Cucurbita moschata Duchesne) vegetables. The study found significant differences (P < 0.05) in all growth parameters in the studied vegetables. The Cd treatments resulted in decreasing number of leaves, shoot fresh weight, shoot dry weight, and total dry weight in both vegetables compared to the control. The total dry weight of Chinese cabbage was decreased by 6.79%, 48.42%, 5.88%, and 5.43%, at 10, 20, 30, and 40 mg/kg respectively compared to the control. In pumpkin leaves total dry weight was decreased by 28.95%, 28.95%, 18.42%, and 14.47% at 10, 20, 30, and 40 mg/kg respectively compared to the control. Increase and decrease effects on root length were observed for all the vegetables. Pumpkin leaves showed increased root length at 10 mg/kg (61.39%), 20 mg/kg (17.87%), and 30 mg/kg (70.03%) while at 40 mg/kg, there was a decrease in root length by 20.13% as compared to the control. The root length of Chinese cabbage decreased by 25.05%, 8.4%, and 7.26% at 20 mg/kg, 30 mg/kg, and 40 mg/kg compared to the control except at 10 mg/kg which was found to be higher by 0.6% compared to the control.The Cd treatment in soil resulted in the increase of shoot Cd concentration in all the vegetables with maximum concentration observed at 20 mg/kg. Therefore, agricultural soil with elevated Cd levels will affect pumpkin and Chinese cabbage cultivation but also the consumption of such vegetables may result to toxic effects on human health.

Unveiling the impact and mechanisms of Cd-driven ecological assembly and coexistence of bacterial communities in coastal sediments of Yellow Sea

The microbial community assembly processes and underlying mechanisms in response to heavy metal accumulation in coastal sediments remain underexplored. In this study, the heavy metal concentration in samples were found below the marine sediment quality standards. Through partial Mantel tests and linear regression analysis, Cd was identified as the major influencing factor, displaying strongest correlation with the bacterial community in the sediments. The class Desulfuromonadia was identified as a biomarker which showed enrichment in the sediments with high Cd content. Additionally, the results of null model and the neutral community model demonstrated the prominent role of stochastic processes in the assembly of bacterial community. However, with the increase in Cd concentration, the influence of selection processes intensified, resulting in a decline in species migration rate and subsequent reduction in ecological niche width. Furthermore, the intensified competition and an increase in keystone species among bacterial populations further enhanced the stability of the microbial co-occurrence network in response to high Cd concentration. This study offers an insight into the effects of heavy metal on microbial assembly and coexistence, which are conducive to marine ecosystem management and conservation.