Single Cd Research Articles

Unveiling the impacts of biodegradable microplastics on cadmium toxicity, translocation, transformation, and metabolome in lettuce

Biodegradable microplastics (BMPs) may impact the environmental fate and ecotoxicity of Cd, but the effect mechanism in soil-plant system remain poorly understood. This study investigated the impact of BMPs (poly(lactic acid) (PLA) and poly(butylene adipate terephthalate) (PBAT) microplastics) on the Cd toxicity, translocation, transformation, and metabolome in lettuce (Lactuca sativa L.) by pot experiments. The results show that co-exposure to BMPs and Cd synergistically inhibited the shoot growth. 0.2 % PLA MPs enhanced but 2.5 % PLA MPs inhibited the photosynthesis; however, the dose of PBAT MPs was negatively correlated with the content of chlorophyll a. Moreover, the presence of 2.5 % PBAT MPs increased the nitrate content of leaves by 9.5 % compared to single Cd exposure. The partial least squares path model (PLS-PM) indicates that BMPs exacerbated the inhibitory effects of Cd on lettuce growth. PLA MPs enhanced K, Ca, Cu, and Zn accumulation in root stele, whereas PBAT MPs promoted Fe and Mn enrichment in epidermis. Furthermore, co-exposure resulted in higher inorganic and water-soluble Cd proportions in shoots. PLA MPs elevated Cd contents in cell wall fractions of both roots and shoots, while PBAT MPs increased Cd contents in shoot cell walls and root cells and soluble Cd ratio in shoots. BMPs enhanced Cd toxicity and bioaccumulation by downregulating the expression of ABC transporters and phenylpropanoid biosynthesis pathways, and the relative abundance of related metabolites.

Spin-lattice relaxation of (Cd,Mn)Te co-doped with Co ions

We study the influence of the addition of the Co ions on the spin-lattice relaxation rate in the (Cd,Mn)Te system. The magnetization relaxation is measured by time-resolved spectroscopy of single (Cd,Mn,Co)Te/(Cd,Mg)Te quantum wells in a magnetic field. We find that even a relatively small cobalt admixture significantly shortens the Mn relaxation time.

Single and combined effects of phenanthrene and cadmium on oxidative stress and detoxification related biomarkers in clams (Meretrix meretrix)

Biomarkers concerning antioxidant reactions and detoxification metabolics were evaluated in Meretrix meretrix exposed to cadmium (Cd, 10 μg/L) and phenanthrene (PHE, 100 μg/L) individually and in combination (10 μg/L Cd + 100 μg/L PHE) for 7 days. The accumulation of Cd and PHE measured in the digestive gland, gill, mantle, and axe foot of the clam showed significant increase in combination treatment and it was higher than the single Cd or single PHE treatment. The activities of oxidative stress-related enzymes, the expression of Cu/Zn SOD, and the content of MDA increased after Cd and PHE exposure in the digestive gland and gill at most cases. In the digestive gland, CAT gene expression was significantly induced in Cd-single group and significantly inhibited in PHE-single group and Cd-PHE mixed group at both day 3 and day 7; in the gill, CAT gene expression was significantly inhibited in all groups at day 3 and except for Cd-single group at day 7. MT expression was significantly induced in Cd-single and Cd-PHE mixed groups at day 7, while hsp70 expression was significantly inhibited in PHE-single and Cd-PHE mixed groups at day 7. The results indicated that SOD, CAT, GST, MDA, Cu/Zn SOD, CAT, MT and hsp70 were sensitive to cadmium and PHE in a water environment, and can be used as indicators of marine heavy metal pollution.

Synergistic effects of boron and cadmium on the metal enrichment and cell wall immobilization capacity of Cosmosbipinnatus

Cadmium (Cd), as a heavy metal pollutant, can seriously affect plant growth and development. Boron (B), as an indispensable nutrient element, plays an important role in plant growth and cell wall (CW) synthesis. However, the physiological effects of B and Cd on plant growth and the mechanism of Cd chelation by the CW remain unclear. Here, we investigate the effect of exogenous B on Cd accumulation in CW components of Cosmos bipinnatus roots and its mechanism of Cd mitigation. Under B deficiency and single Cd (30 μM) treatments, the growth of C. bipinnatus was significantly inhibited, but the addition of exogenous B significantly increased plant biomass, which increased the Cd content in the underground parts of C. bipinnatus by 20.18% and reduced the Cd translocation factor by 22.22%. Meanwhile, application of exogenous B affected the subcellular Cd content across various Cd forms and alleviated Cd-induced oxidative stress in C. bipinnatus. Additionally, exogenous B and Cd and their mixtures affected the functional groups of the root CW, the proportion of polysaccharide components, the Cd content of polysaccharides, and the polysaccharide uronic acid content of C. bipinnatus. However, B application increased 3-deoxy-oct-2-ulosonic acid content, pectin esterase activity, low esterified pectin content, and its Cd content by 149.52%, 55.69%, 206.38%, and 150.02%, respectively, compared to Cd treatment alone. Thus, our study showed that B mitigates the toxicity of Cd to plants, revealing the effect of B on the physiological aspects of Cd tolerance in plants.

Integrated transcriptomics, metabolomics and physiological analyses reveal differential response mechanisms of wheat to cadmium and/or salinity stress.

Many soils face dual challenges of cadmium (Cd) contamination and salinization. However, the response of crops, especially wheat, to combined Cd and salinity stress is not understood. Here, wheat was grown in a hydroponic model for 14 days under single and combined Cd and NaCl stresses. Growth parameters, tissue Cd2+ and Na+ contents, and leaf chlorophyll (Chl), O2•-, and MDA levels were determined. Comparative transcriptomic and metabolomic analyses of the leaves were performed. The results showed that combined stress had a greater inhibitory effect on Chl contents and generated more O2•- and MDA, resulting in more severe wheat growth retardation than those under Cd or NaCl stress. Stress-induced decrease in Chl levels may be attributed to the inhibition of Chl biosynthesis, activation of Chl degradation, or a decline in glutamate content. Cd addition weakened the promotional effect of NaCl on SOS1 gene expression, thereby increasing the Na+ content. Contrastingly, NaCl supplementation downregulated the Nramp and ZIP gene expressions related to Cd uptake and transport, thereby impeding Cd2+ accumulation. All stresses enhanced tryptophan content via promoting tryptophan biosynthesis. Meanwhile, Cd and NaCl stresses activated phenylpropanoid biosynthesis and purine metabolism, respectively, thereby increasing the levels of caffeic acid, fumaric acid, and uric acid. Activating the TCA cycle was important in the wheat's response to combined stress. Additionally, NaCl and combined stresses affected starch and sucrose metabolism, resulting in sucrose and trehalose accumulation. Our findings provide a comprehensive understanding of the response of wheat to the combined Cd and salinity stress.

Combined toxicity of multiwall carbon nanotubes and cadmium on rice (Oryza sativa L.) growth in soil

The comprehensive effects of nanoparticles and coexisting heavy metals on plant growth are still unclear, especially in soil medium. The single and combined effects of multiwall carbon nanotubes (MWCNTs) and cadmium (Cd) on rice (Oryza sativa L.) growth were examined in this study through a 4 months pot experiment in 2022. Rice plants were exposed to different concentrations of MWCNTs (100 and 500 mg kg−1) in the presence of 5.0 mg kg−1 Cd stress. At the tillering stage, the 500 mg kg−1 MWCNTs addition reduced plant height by 8.0% and increased soluble protein content in the leaves by 13.7%, demonstrating that a single MWCNTs had a slight negative impact on rice growth. When exposed to Cd stress, the inclusion of 500 mg kg−1 MWCNTs led to a 6.7%–9.0% decrease in bioavailable Cd level in soil, resulting in considerable reductions in Cd content in roots (23.4%–29.9%), shoots (24.5%–28.3%) and grains (28.3%–66.2%). Compared to the single Cd treatment, the O. sativa L. leaves treated with Cd and MWCNTs (500 mg kg−1) had considerably reduced levels of malondialdehyde (MDA), soluble protein, and activities of antioxidant enzymes (POD, CAT, and SOD). The findings of this study indicated that appropriate concentrations of MWCNTs application in soil could alleviate Cd-induced toxicity on rice growth.

Co-exposure to Organophosphate esters (OPEs) and Cadmium alleviated their accumulation in rice (Oryza sativa L.) by inhibiting transports' transcription

Combined contamination of Organophosphate esters (OPEs) and heavy metal has been concerning on their potential threaten to human health through food chain. In order to estimate effects of OPEs and heavy metal's combined contamination on crop, the growth of rice seedlings, pollutant accumulations and their involved in transcript regulation pathway under OPEs and Cd contamination were investigated. In results, only single OPEs pollution improved the biomass of rice, while single Cd pollution inhibited the growth of plants. Although the combined contaminations of OPEs and Cd also showed negative effect for plant growth, OPEs could alleviate the negative effect of Cd on rice. The Octanol-water partition coefficients (log Kow) of OPEs were positively correlated with root concentration factor (RCF) values in the trend line and negatively correlated with shoot concentration factor (SCRF) and translocation factor (TF). OPEs and Cd inferred with each other's accumulations in plants through reducing RCF, SCRF and TF. After addition of Cd, the expressions of OsTIL, OsLTP4, OsLTPL1, and OsMLP423 genes involved in OPEs accumulation were downregulated. Moreover, the presence of Cd also affected the binding sites and binding energy of the four proteins with OPEs. Meanwhile, the expression of OsNramp1, OsNramp5, OsHMA2, OsGS1, and OsPCS1 genes involved in Cd accumulation and toleration were also downregulated after addition of OPEs. These results suggested that OPEs and Cd directly repressed each other gene transcript involved in accumulation and toleration process.

Nano-Fe3O4: Enhancing the tolerance of Elymus nutans to Cd stress through regulating programmed cell death

Cadmium (Cd) poses a significant threat to plant growth and the environment. Nano-Fe3O4 is effective in alleviating Cd stress in plants. Elymus nutans Griseb. is an important fodder crop on the Qinghai-Tibetan Plateau (QTP). However, the potential mechanism by which nano-Fe3O4 alleviates Cd stress in E. nutans is not well understood. E. nutans were subjected to single Cd, single nano-Fe3O4, and co-treatment with nano-Fe3O4 and Cd, and the effects on morphology, Cd uptake, antioxidant enzyme activity, reactive oxygen species (ROS) levels and programmed cell death (PCD) were studied to clarify the regulatory mechanism of nano-Fe3O4. The results showed that Cd stress significantly decreased the germination percentage and biomass of E. nutans. The photosynthetic pigment content decreased significantly under Cd stress. Cd stress also caused oxidative stress and lipid peroxidation, accumulation of excessive ROS, resulting in PCD, but the effect of nano-Fe3O4 was different. Seed germination, seedling growth, and physiological processes were analyzed to elucidate the regulatory role of nano-Fe3O4 nanoparticles in promoting photosynthesis, reducing Cd accumulation, scavenging ROS, and regulating PCD, to promote seed germination and seedling growth in E. nutans. This report provides a scientific basis for improving the tolerance of Elymus to Cd stress by using nano-Fe3O4.

Responses of Physiological Traits and Soil Properties in Pinus thunbergia and Euonymus japonicus Saplings under Drought and Cadmium (Cd) Stress

Pinus thunbergii and Euonymus japonicus are two species commonly found in arid and semi-arid areas; however, their responses in terms of physiological traits and soil properties under drought and cadmium (Cd) stress are not clear. In this study, we carried out single and combined stress treatments consisting of drought and Cd on saplings of P. thunbergii and E. japonicus and investigated the responses in terms of the physiological traits and soil properties of both species. For both species, under single Cd stress, Cd was observed in both the xylem and phloem, while the root Cd2+ flow rate fluctuated at different levels of Cd stress. Under both single and combined stress, as the stress level increased, the abscisic acid (ABA) content of the leaves and roots increased significantly, while the indole-3-acetic acid (IAA) content of the leaves and roots decreased significantly. Moreover, the non-structural carbohydrate (NSC) content of the leaves, stems, and roots, as well as the leaf chlorophyll content, decreased significantly. Under drought stress, the xylem water potential and hydraulic conductivity significantly decreased, which was exacerbated by Cd stress; this led to a more significant decrease in water potential and hydraulic conductivity under the combined stresses. Meanwhile, no significant changes in the conduit lumen diameter and double-wall thickness were observed, except for the double cell wall thickness of the P. thunbergii tracheid, which increased. In addition, both the single stresses and the combined stress of drought and Cd induced significant changes in the soil properties of the two species, i.e., the ammonium nitrogen, nitrate nitrogen, and effective phosphorus of the soil increased significantly, and the increase in content was more significant under combined stress. The diversity of the soil microbial community of P. thunbergii saplings significantly increased, while no change was found in its microbial community abundance under the single stresses and combined stress; however, the diversity and abundance of the soil microbial community in E. japonicus saplings showed the opposite pattern, which indicates that the effect of Cd on soil microorganisms is more significant than the effect of drought. The activity of sucrase and catalase in P. thunbergii soil fluctuated under the single stress and combined stress when compared, and the activity of sucrase in the soil of the E. japonicus species decreased. However, its catalase activity increased significantly under the single drought and Cd stress and combined stress when compared. We found that the combined stresses exacerbated the effects of the single stress in both species. Our study provides more detailed information on the responses in terms of the physiological traits and soil properties of the two species under single and combined stress consisting of drought and Cd.

A versatile study of single and binary removals of Pb(II) and Cd(II) ions from aqueous solutions using pine cone as biosorbent

A naturally occurring biosorbent (pine cone) was utilized to remove single and binary Pb(II) and Cd(II) ions from aqueous solutions. The biosorbent has been examined using ATR-IR, SEM, XRD, and pHpzc. The impacts of process factors such as contact time, pH value, biosorbent dosage, initial concentration, and medium temperature on the biosorption of Pb(II) and Cd(II) ions were researched. Langmuir and Freundlich's isotherms were implemented to describe the equilibrium process. At the most favorable condition for each metal, the Langmuir isotherm yielded a maximum loading capacity (qmax) of 43.47 mg/g for Pb(II) and 32.89 mg/g for Cd(II). The highest biosorption was reached with a single system and then reduced in the presence of coexisting ions in the mixtures under optimal conditions. Desorption studies show that 0.5 M HNO3 is the most effective way to remove heavy metals from a biosorbent loaded with metal ions. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from temperature data indicate that the biosorption mechanism is exothermic for Pb(II) and endothermic for Cd(II), spontaneous and favorable.

Effects of cadmium and zinc interactions on the physiological biochemistry and enrichment characteristics of Iris pseudacorus

Compound pollution with cadmium (Cd) and zinc (Zn) is common in nature. The effects of compounded Cd and Zn on the growth and development of Iris pseudacorus in the environment and the plant’s potential to remediate heavy metals in the environment remain unclear. In this study, the effects of single and combined Cd and Zn stress on I. pseudacorus growth and the enrichment of heavy metals in I. pseudacorus seedlings were investigated. The results showed that under Cd (160 μM) and Zn (800 μM) stress, plant growth was significantly inhibited and photosynthetic performance was affected. Cd+Zn200 (160 μM + 200 μM) reduced the levels of malondialdehyde, hydrogen peroxide, and non-protein thiols by 31.29%, 53.20%, and 13.29%, respectively, in the aboveground tissues compared with levels in the single Cd treatment. However, Cd+Zn800 (160 μM + 800 μM) had no effect. Cd and Zn800 inhibited the absorption of mineral elements, while Zn200 had little effect on plants. Compared with that for Cd treatment alone, Cd + Zn200 and Cd+Zn800 reduced the Cd content in aboveground tissues by 54.15% and 49.92%, respectively, but had no significant effect on Cd in the root system. Zn significantly reduced the Cd content in subcellular components and limited the content and proportion of Cd extracted using water and ethanol. These results suggest that a low supply of Zn reduces Cd accumulation in aboveground tissues by promoting antioxidant substances and heavy metal chelating agents, thus protecting the photosynthetic systems. The addition of Zn also reduced the mobility and bioavailability of Cd to alleviate its toxicity in I. pseudacorus.

Migration Behaviour of the Combined Pollutants of Cadmium and 2,2′,4,4′,5,5′-Hexabrominated Diphenyl Ether (BDE-153) in Amaranthus mangostanus L. and Their Toxicity to A. mangostanus

The effects of different concentrations of cadmium and 2,2′,4,4′,5,5′-hexabrominated diphenyl ether (BDE-153) on the growth and related physiological and biochemical indexes of Amaranthus mangostanus L. (amaranth) were studied. The results showed that the presence of BDE-153 promoted the absorption of Cd by the amaranth and inhibited the migration of Cd from the roots to the shoots. At the same time, 0.1 mg/L of Cd had a synergistic effect on the migration of BDE-153, but 5 mg/L Cd inhibited the accumulation of BDE-153 in the aboveground part of the amaranth. In addition, the kinetics of the uptake of pollutants by the amaranth showed that both Cd and BDE-153 could be transported by amaranth, but Cd and BDE-153 were mainly enriched in the roots, and the presence of Cd may cause a lag in the uptake of BDE-153 in the shoots. Compared with the control group, the biomass of the amaranth affected by BDE-153 and a high concentration of Cd (5 mg/L) decreased by 30.2–49.5%, the chlorophyll content decreased by 43.0–60.3%, the Evans blue increased, and the MDA content was higher. The activities of superoxide dismutase (SOD) and catalase (CAT) also decreased with an increase in the BDE-153 concentration. This indicates that the interaction between BDE-153 and a high concentration of Cd (5 mg/L) is more toxic to amaranth than single Cd pollution. This paper provides the necessary data support for phytoremediation of heavy metal and organic compound pollution.

Competitive Adsorption of Cd(II) and Zn(II) on Biochar, Loess, and Biochar-loess Mixture

Combined heavy metal contamination in soil is a common phenomenon. Biochar amendment into the soil is considered to be an alternative for immobilization remediation of soil contaminated with heavy metals due to its adsorption and alkalization. However, much attention has been paid to the adsorption and immobilization of single heavy metals by biochar. In this paper, the competitive adsorption of Cd(II) and Zn(II) on biochar derived from cotton straw and pig manure at 500℃ (BCS500 and BPM500), loess and biochar-loess mixtures were investigated using the batch equilibrium method. The results showed that the adsorption capacities of biochars, loess, and biochar-loess mixtures to Cd(II) and Zn(II) in the mixed Cd-Zn systems increased with the increase of initial metal concentrations of Cd(II) and Zn(II). The adsorptive capacities of BCS500 and BPM500 to Cd(II) in mixed Cd-Zn system were 33% and 35% less than those in the single Cd(II)systems, while the adsorptive capacities to Zn(II) were 62% and 56% less than those in the single Zn(II) systems. The adsorptive capacities of loess to Cd(II) and Zn(II) in mixed Cd-Zn systems were 29% and 55% less than those in the single metal systems. The adsorptive capacities of loess-BCS500 (LBCS) and loess-BPM500 (LBPM) to Cd(II) in mixed Cd-Zn system were 40% and 38% less than those in the single Cd(II) systems, while the adsorptive capacities to Zn(II) were 63% and 60% less than those in the single Zn(II)systems. Moreover, the competitive adsorptive capacity of Cd(II) is greater than that of Zn(II). It can be seen that when heavy metal pollution with similar nature of multiple elements exists in soil, the amount of adsorbent should be increased to resist the possible weakened adsorption caused by competitive adsorption in order to guarantee an effective absorption treatment.

Stable Isotope Analyses Reveal Impact of Fe and Zn on Cd Uptake and Translocation by Theobroma cacao.

High concentrations of toxic cadmium (Cd) in soils are problematic as the element accumulates in food crops such as rice and cacao. A mitigation strategy to minimise Cd accumulation is to enhance the competitive uptake of plant-essential metals. Theobroma cacao seedlings were grown hydroponically with added Cd. Eight different treatments were used, which included/excluded hydroponic or foliar zinc (Zn) and/or iron (Fe) for the final growth period. Analyses of Cd concentrations and natural stable isotope compositions by multiple collector ICP-MS were conducted. Cadmium uptake and translocation decreased when Fe was removed from the hydroponic solutions, while the application of foliar Zn-EDTA may enhance Cd translocation. No significant differences in isotope fractionation during uptake were found between treatments. Data from all treatments fit a single Cd isotope fractionation model associated with sequestration (seq) of isotopically light Cd in roots and unidirectional mobilisation (mob) of isotopically heavier Cd to the leaves (ε114Cdseq-mob = -0.13‱). This result is in excellent agreement with data from an investigation of 19 genetically diverse cacao clones. The different Cd dynamics exhibited by the clones and seen in response to different Fe availability may be linked to similar physiological processes, such as the regulation of specific transporter proteins.

Transcriptome Analysis of Plant Growth-promoting Bacteria Alleviating Microplastic and Heavy Metal Combined Pollution Stress in Sorghum

Microplastics can become potential transport carriers of other environmental pollutants (such as heavy metals), so the combined pollution of microplastics and heavy metals has attracted increasing attention from researchers. To explore the mechanism of plant growth-promoting bacteria VY-1 alleviating the combined pollution stress of heavy metals and microplastics in sorghum, the effects of inoculation on biomass and accumulation of heavy metals in sorghum were analyzed using a hydroponics experiment, and the effects of inoculation on gene expression in sorghum were analyzed via transcriptomics. The results showed that the combined pollution of polyethylene (PE) and cadmium (Cd) decreased the dry weight of above-ground and underground parts by 17.04% and 10.36%, respectively, compared with that under the single Cd pollution, which showed that the combined toxicity effect of the combined pollution on plant growth was enhanced. The inoculation of plant growth-promoting bacteria VY-1 could alleviate the toxicity of Cd-PE combined pollution and increase the length of aboveground and underground parts by 33.83% and 73.21% and the dry weight by 56.64% and 33.44%, respectively. Transcriptome sequencing showed that 904 genes were up-regulated after inoculation with VY-1. Inoculation with growth-promoting bacteria VY-1 could up-regulate the expression of several genes in the auxin, abscisic acid, flavonoid synthesis, and lignin biosynthesis pathways, which promoted the response ability of sorghum under Cd-PE combined pollution stress and improved its resistance. The above results indicated that plant growth-promoting bacteria could alleviate the stress of heavy metal and microplastic combined pollution by regulating plant gene expression, which provided a reference for plant-microbial joint remediation of heavy metal and microplastic combined pollution.

ОПТИЧНА СПЕКТРОСКОПІЯ ДЕТЕКТОРНИХ ВИСОКООМНИХ МОНОКРИСТАЛІВ CdTe (111) ТА ТВЕРДИХ РОЗЧИНІВ Cd 1-x Zn x Te (х= 0,1)

Cadmium telluride is used for the manufacture of uncooled gamma radiation detectors, and solid solutions of Cd 1-x Zn x Te (x=0.1) are used for the manufacture of X-ray and gamma radiation detectors. The study of the effect of doping on the physical properties of semiconductors is relevant both for experimenters and for the theoretical substantiation of physical processes. This paper presents the results of the study of optical reflection spectra in the spectral range (0,2-1,7) . 10 -6 m and transmittance in the region of the fundamental optical transition E 0 of high-resistivity CdTe single crystals of (111) orientation with resistivity ρ = (2÷5)·10 9 Ohm∙cm doped with chlorine, as well as solid solutions of Cd 1-x Zn x Te (x = 0.1) with resistivity ρ = (5 ÷30)∙10 9 Ohm∙cm. Since the optical reflection coefficient R = f (λ) is related to the optical transmittance T = f (λ) and absorption D = f (λ) by the ratio R+T+D=1 (with the light (electromagnetic) wave scattering in the studied samples not taken into account), the absorption spectra D=1-(R+T) versus the light (electromagnetic) wavelength λ were also constructed in this work. It is determined that the energy of the fundamental optical transition E 0 of the studied materials at T = 300 K is as follows: for CdTe - 1.44 eV; and for Cd 1-х Zn х Te (x = 0.1) - 1.5 eV. The energy relaxation time of free charge carriers τ for p-CdTe (111) single crystals and Cd 1-х Zn х Te (x = 0.1) solid solutions was estimated to be 1.343-10 -14 s and 0,878·10 -14 s, respectively. The effective "optical" mobility for single crystals of p-CdTe (111) and solid solutions of Cd 1-х Zn х Te (x = 0.1) is 274 . 10 -4 ; 179,5 . 10 -4 , respectively. It has been shown that the investigated crystals are of high (detector) quality, which is crucial for the manufacture of highly sensitive and high-resolution ionising radiation sensors. The practical value of the obtained results lies in the determination of electronic and physical parameters of technically important semiconductors CdTe and Cd 1-х Zn х Te (x=0.1).

Characteristics and Mechanisms of Soil Co-Contamination Affecting the Transfer of Cadmium and Arsenic in Peanut (Arachis hypogaea L.)

Soil co-contamination with cadmium (Cd) and arsenic (As) occurs frequently and has caused increasing concern. This study aimed to explore the transfer characteristics and the chemical forms, subcellular distribution of Cd and As, as well as the synthesis of phytochelatins (PCs) and other chelates in peanut (Arachis hypogaea L.) plants grown in a Cd and As co-contaminated soil, shedding light on the mechanisms involved. Compared with the single Cd contamination, Cd–As co-contamination led to a higher accumulation of Cd in peanut plants. Conversely, compared to the single As contamination, the As content increased in peanut shoots but decreased in roots and grains under Cd–As co-contamination. Furthermore, the Cd–As interaction resulted in notable changes in peanut plants’ physiological and biochemical responses. In the roots and shoots, there was an 81.8% and 60.0% increase in water-soluble Cd. In the roots, metallothioneins (MTs) content increased by 50%, while PCs increased by 6.4% in the shoots. These changes promoted the translocation of Cd from roots to grains. The Cd–As interaction also influenced the synthesis of MTs in the roots, showing a 41.2% increase, and facilitated the transfer of As to the shoots. In peanut shoots, Cd increased the cell wall fraction of As by 34.5%, decreased the proportion of water-soluble As by 31.8%, and increased PCs content by 6.9%. These changes inhibited the migration of As from shoots to grains. Overall, Cd–As co-contamination increased Cd in peanut grains by increasing water-soluble forms and MTs in roots, while Cd–As co-contamination decreased As in peanut grains by increasing cell wall fractions and PCs in shoots. These findings provide a theoretical basis for understanding Cd–As interactions in soil–peanut systems.

Effects of Nitrogen Addition on the Growth and Physiology of Populus deltoides Seedlings under Cd and Mn Pollution

Both nitrogen (N) deposition and heavy metal pollution are important environmental concerns that threaten ecosystem stability and ecological safety. Limited research has been conducted on the effects of N deposition on the physiological processes and allocation patterns of heavy metals (HMs) in poplars, especially under combined pollution. In our study, we used Populus deltoides as a model to investigate the effects of two levels of N addition (LN, 6 g N·m−2·a−1; HN, 12 g N·m−2·a−1) on growth, activities of antioxidant enzymes, profiles of low-molecular-weight organic acids, as well as accumulation and allocation of HMs among different organs and root orders under single Cd (30 mg kg−1) or Mn pollution (168.6 mg kg−1), and their combination. The effects of N addition depended on the dosage effects of N and the types of HMs. The combined pollution did not have more negative effects on overall growth and oxidative damage in the root tips of P. deltoides compared to single Cd or Mn pollution. Both levels of N deposition, especially LN, promoted growth in P. deltoides to varying extents under all HM pollution conditions. However, N addition only mitigated oxidative damage to the fine roots under Cd-containing pollution, which may be attributed to higher levels of low-molecular-weight organic acids such as citric acid and malic acid. In contrast, HN decreased the levels of key organic acids, such as lactic acid and pantothenic acid, potentially exacerbating Mn toxicity under Mn pollution. Both levels of N addition decreased the total amount of Cd accumulated in P. deltoides under Cd pollution alone but increased the accumulation of Cd in combined pollution (especially under LN). However, under Mn-containing pollution, the addition of N increased the accumulation of Mn and its transfer to leaves, potentially aggravating Mn toxicity. Therefore, N deposition, especially under HN, may lead to more severe HM stress for plants in soils polluted by combined Cd and Mn.

Analyzing the impacts of cadmium alone and in co-existence with polypropylene microplastics on wheat growth.

Heavy metals typically coexist with microplastics (MPs) in terrestrial ecosystems. Yet, little is known about how the co-existence of heavy metals and MPs affect crops. Therefore, this study aimed to evaluate the impact of cadmium (Cd; 40 mg/L) alone and its co-existence with polypropylene (PP)-MPs (50 and 100 µm) on seed germination, root and shoot growth, seedling dry weight (DW), and antioxidant enzyme activities of wheat. The study demonstrated that the germination rate of wheat did not vary significantly across treatment groups. Yet, the inhibitory impact on wheat seed germination was strengthened under the co-existence of Cd and PP-MPs, as the effect of a single treatment on seed germination was non-significant. The germination index and mean germination time of wheat seeds were not affected by single or combined toxicity of Cd and PP-MPs. In contrast, Cd and PP-MPs showed synergistic effects on germination energy. Wheat root and shoot length were impeded by Cd alone and in combination with PP-MPs treatments. The DW of wheat seedlings showed significant change across treatment groups until the third day, but on the seventh day, marginal differences were observed. For example, on third day, the DW of the Cd treatment group increased by 6.9% compared to CK, whereas the DW of the 100 µm PP-MPs+Cd treatment group decreased by 8.4% compared to CK. The co-occurrence of Cd and PP-MPs indicated that 50 μm PP-MPs+Cd had an antagonistic impact on wheat seedling growth, whereas 100 μm PP-MPs+Cd had a synergistic impact due to the larger size of PP-MPs. The antioxidant enzyme system of wheat seeds and seedlings increased under single Cd pollution, while the activities of superoxide dismutase, catalase, and peroxidase were decreased under combined pollution. Our study found that Cd adversely affects wheat germination and growth, while the co-existence of Cd and PP-MPs have antagonistic and synergistic effects depending on the size of the PP-MPs.

Metal uptake and translocation by Chinese brake fern (Pteris vittata) and diversity of rhizosphere microbial communities under single and combined arsenic and cadmium stress.

Chinese brake fern (Pteris vittata) can increase tolerance to arsenic (As) and cadmium (Cd) toxicity by regulating rhizosphere microbial diversity. However, effects of combined As-Cd stress on microbial diversity and plant uptake and transport remain poorly understood. Therefore, effects of different concentrations of As and Cd on Pteris vittata (P. vittata) metal uptake and translocation and rhizosphere microbial diversity were examined in a pot experiment. The results indicated that As primarily accumulated aboveground in P. vittata (bioconcentration factor (BCF) ≤ 51.3; translocation factor (TF) ≈ 4), whereas Cd primarily accumulated belowground (BCF ≤ 39.1; TF < 1). Under single As, single Cd, and As-Cd combined stress, the most dominant bacteria and fungi were Burkholderia-Caballeronia-P (6.62-27.92%) and Boeremia (4.61-30.42%), Massilia (8.07-11.51%) and Trichoderma (4.47-22.20%), and Bradyrhizobium (2.24-10.38%) and Boeremia (3.16-45.69%), respectively, and their abundance ratios had a significant impact on the efficiency of P. vittata for As and Cd accumulation. However, with increasing As and Cd concentrations, abundances of plant pathogenic bacteria such as Fusarium and Chaetomium (the highest abundances were 18.08% and 23.72%, respectively) increased, indicating that As and Cd concentrations reduced P. vittata resistance to pathogens. At high soil concentrations of As-Cd, although plant As and Cd contents increased and microbial diversity was highest, enrichment efficiency and transportability of As and Cd decreased substantially. Therefore, pollution intensity should be considered when evaluating P. vittata suitability for phytoremediation of combined As-Cd contaminated soils.