The combined effect of oxidative stress and TRPV1 on temperature-induced asthma: Evidence in a mouse model.

Temperature is one of the possible activators for asthma. As global warming continues, the health hazard of high temperatures is increasing. It is unclear, nevertheless, how high temperatures affect asthma. The research aims to examine how asthma is affected by high temperatures and underlying molecular mechanisms. The BALB/c mice were adopted in a model of asthma. The mice were exposed at 24 °C, 38 °C and 40 °C for 4h on weekdays from day 1 to day 30. After the experiment, the lung function was measured in vivo, and then serum protein, pulmonary inflammation and immunohistochemistry assay was assessed in vitro. As the temperature increased from 24 °C to 40 °C, there was a significant increase in serum protein, while there is no discernible difference in serum protein of OVA-sIgE and OVA-sIgG between the OVA (38 °C) group and OVA (24 °C) group. The immunohistochemistry assay showed a change in the pro-inflammatory cytokines. The histopathological analysis exhibited the change of airway structure after high-temperature exposure, especially for exposure at 40 °C. The results of signals protein showed a remarkable rise of TRPV1 for OVA+40 °C. Our results revealed that high temperatures may make asthmatic airway dysfunction severe, and the higher the temperature, the more serious asthma. The oxidative stress and TRPV1 receptor can be a potential drug target for asthma. It will provide a new tool for precision medicine in asthma.

Effect and mechanism of microplastics exposure against microalgae: Photosynthesis and oxidative stress.

The occurrence of microplastics (MPs) within aquatic ecosystems attracts a major environmental concern. It was demonstrated MPs could cause various ecotoxicological effects on microalgae. However, existing data on the effects of MPs on microalgae showed great variability among studies. Here, we performed a meta-analysis of the latest studies on the effects of MPs on photosynthesis and oxidative stress in microalgae. A total of 835 biological endpoints were investigated from 55 studies extracted, and 37 % of them were significantly affected by MPs. In this study, the impact of MPs against microalgae was concentration-dependent and size-dependent, and microalgae were more susceptible to MPs stress in freshwater than marine. Additionally, we summarized the biological functions of microalgae that are primarily affected by MPs. Under MPs exposure, the content of chlorophyll a (Chl-a) was reduced and electron transfer in the photosynthetic system was hindered, causing electron accumulation and oxidative stress damage, which may also affect biological processes such as energy production, carbon fixation, lipid metabolism, and nucleic acid metabolism. Finally, our findings provide important insights into the effects of MPs stress on photosynthesis and oxidative stress in microalga and enhance the current understanding of the potential risk of MPs pollution on aquatic organisms.

Unraveling the role of multi-walled carbon nanotubes in a corn-soil system: Plant growth, oxidative stress and heavy metal(loid)s behavior.

In the age of nanotechnological advancement, carbon nanotubes (CNTs) are drawing global attention. However, few studies have been published on the crop growth responses to CNTs in heavy metal(loid)s contaminated environments. A pot experiment was conducted to assess the effect of multi-walled carbon nanotubes (MWCNTs) on plant development, oxidative stress, and heavy metal(loid)s behavior in a corn-soil system. Corn (Zea mays L.) seedlings were cultivated in soil containing Cadmium (Cd) and Arsenic (As) that had been primed with 0, 100, 500, and 1000 mg kg-1 MWCNTs. The application of 100 and 500 mg kg-1 MWCNTs improved shoot length by 6.45% and 9.21% after 45 days, respectively. Total plant dry biomass increased by 14.71% when treated with 500 mg kg-1 MWCNTs but decreased by 9.26% when exposed to 1000 mg kg-1 MWCNTs. MWCNTs treatment did not affect Cd accumulation in plants. On the other hand, the bio-concentration factor of As was inversely associated with plant growth (p < 0.05), which was declined in MWCNTs treatments. Oxidative stress was aggravated when plants were exposed to MWCNTs, thus activating the antioxidant enzymes system in the corn. In contrast, TCLP-extractable Cd and As in soil significantly decreased than in the control. Additionally, the soil nutrients were changed under MWCNTs treatments. Our findings also revealed that a particular concentration of MWCNTs can mitigate the toxicity of Cd and As in corn seedlings. Therefore, these results suggest the prospective application of CNTs in agricultural production, ensuring environmental and soil sustainability.

Pleiotropic melatonin-mediated responses on growth and cadmium phytoextraction of Brassica napus: A bioecological trial for enhancing phytoremediation of soil cadmium.

Melatonin (MT) has recently gained significant scientific interest, though its mechanism of action in enhancing plant vigor, cadmium (Cd) tolerance, and Cd phytoremediation processes are poorly understood. Therefore, here we investigated the beneficial role of MT in improving growth and Cd remediation potential of rapeseed (Brassica napus). Plants, with or without MT (200 µM L-1), were subjected to Cd stress (30 mg kg1). Without MT, higher Cd accumulation (up to 99%) negatively affected plant growth and developmental feature as well as altered expression of several key genes (DEGs) involved in different molecular pathways of B. napus. As compared to only Cd-stressed counterparts, MT-treated plants exhibited better physiological performance as indicated by improved leaf photosynthetic and gaseous exchange processes (3-48%) followed by plant growth (up to 50%), fresh plant biomass (up to 45%), dry plant biomass (up to 32%), and growth tolerance indices (up to 50%) under Cd exposure. MT application enhanced Cd tolerance and phytoremediation capacity of B. napus by augmenting (1) Cd accumulation in plant tissues and its translocation to above-ground parts (by up to 45.0%), (2) Cd distribution in the leaf cell wall (by up to 42%), and (3) Cd detoxification by elevating phytochelatins (by up to 8%) and metallothioneins (by upto 14%) biosynthesis, in comparison to Cd-treated plants. MT played a protective role in stabilizing hydrogen peroxide and malondialdehyde levels in the tissue of the Cd-treated plants by enhancing the content of osmolytes (proline and total soluble protein) and activities of antioxidant enzymes (SOD, CAT, APX and GR). Transcriptomic analysis revealed that MT regulated 1809 differentially expressed genes (828 up and 981 down) together with 297 commonly expressed DEGs (CK vs Cd and Cd vs CdMT groups) involved in plant-pathogen interaction pathway, protein processing in the endoplasmic reticulum pathway, mitogen-activated protein kinase signaling pathway, and plant hormone signal transduction pathway which ultimately promoted plant growth and Cd remediation potential in the Cd-stressed plants. These results provide insights into the unexplored pleiotropic beneficial action of MT in enhancing in the growth and Cd phytoextraction potential of B. napus, paving the way for developing Cd-tolerant oilseed crops with higher remediation capacity as a bioecological trial for enhancing phytoremediation of hazardous toxic metals in the environment.

Insights into growth-promoting effect of nanomaterials: Using transcriptomics and metabolomics to reveal the molecular mechanisms of MWCNTs in enhancing hyperaccumulator under heavy metal(loid)s stress.

Carbon nanotubes present potential applications in soil remediation, particularly in phytoremediation. Yet, how multi-walled carbon nanotubes (MWCNTs) induced hyperaccumulator growth at molecular level remains unclear. Here, physio-biochemical, transcriptomic, and metabolomic analyses were performed to determine the effect of MWCNTs on Solanum nigrum L. (S. nigrum) growth under cadmium and arsenic stresses. 500 mg/kg MWCNTs application significantly promoted S. nigrum growth, especially for root tissues. Specially, MWCNTs application yields 1.38-fold, 1.56-fold, and 1.37-fold enhancement in the shoot length, root length, and fresh biomass, respectively. Furthermore, MWCNTs significantly strengthened P and Fe absorption in roots, as well as the activities of antioxidative enzymes. Importantly, the transcriptomic analysis indicated that S. nigrum gene expression was sensitive to MWCNTs, and MWCNTs upregulated advantageous biological processes under heavy metal(loid)s stress. Besides, MWCNTs reprogramed metabolism that related to defense system, leading to accumulation of 4-hydroxyphenylpyruvic acid (amino acid), 4-hydroxycinnamic acid (xenobiotic), and (S)-abscisic acid (lipid). In addition, key common pathways of differentially expressed metabolites and genes, including "tyrosine metabolism" and "isoquinoline alkaloid biosynthesis" were selected via integrating transcriptome and metabolome analyses. Combined omics technologies, our findings provide molecular mechanisms of MWCNTs in promoting S. nigrum growth, and highlight potential application of MWCNTs in soil remediation.

Two plant growth-promoting bacterial Bacillus strains possess different mechanisms in affecting cadmium uptake and detoxification of Solanum nigrum L.

Microorganisms affect cadmium (Cd) extraction by hyperaccumulators to varying degrees, but the potential mechanism has not been completely studied. Here, two plant growth-promoting bacteria (PGPB, Bacillus paranthracis NT1 and Bacillus megaterium NCT-2) were assessed for their influence on Cd uptake by Solanum nigrum L. and their influence mechanisms. The results showed that both two strains could regulate phytohormones secretion, alleviate oxidative stress and promote S. nigrum growth when exposed to Cd (dry weight was significantly increased by 21.51% (strain NCT-2) and 21.23% (strain NT1) compared with the control, respectively). Additionally, strain NCT-2 significantly elevated the translocation factor (TF) and bioconcentration factor (BCF), and thus significantly facilitated total Cd uptake by 41.80% of S. nigrum, whereas strain NT1 significantly reduced the BCF and TF, resulting in insignificant effect on total Cd uptake of S. nigrum compared with the control. Results of qPCR illustrated that the two strains influenced the detoxification of Cd in S. nigrum by affecting the expression of antioxidant enzyme genes and gene PDR2. Moreover, the differential expression of heavy metal transport genes IRT1 and HMA may lead to the difference of Cd accumulation in S. nigrum. Principal component analysis and Pearson correlation coefficient analysis further verified the positive roles of salicylic acid and indole-3-acetic acid on Cd detoxification of S. nigrum, and the positive correlation relationship between transportation of Cd from underground to shoot, plant biomass and Cd uptake. Altogether, our results demonstrated that these two PGPB have great potential in helping plants detoxify Cd and could provide insights into the mechanism of PGPB-assisted phytoremediation of Cd-contaminated soil.

A sustainable approach for bioremediation of secondary salinized soils: Studying remediation efficiency and soil nitrate transformation by bioaugmentation.

Nitrate is the main nitrogen source for plant growth, but it can also pollute the environment. A major cause of soil secondary salinization is the rising level of nitrates in the soil, which poses a threat to the sustainability and fertility of global greenhouse soils. Herein, Bacillus megaterium NCT-2 was used as a microbial agent to remove nitrate by bioaugmentation, and the remediation efficiency of secondary salinized soil in different degrees was evaluated. The findings showed that the highest nitrate removal rate of 62.76% was in a medium degree of secondary salinized soil. Moreover, the results of 16S rRNA high-throughput sequencing and quantitative real-time PCR (qPCR) demonstrated that NCT-2 agent reduced the microbial diversity, increased the microbial community stability, and changed the composition and function of the microbial community were changed by NCT-2 agent in all districts soil. Further analysis demonstrated that the NCT-2 bacterial agent significantly increased the key enzyme genes of the assimilation pathway (nitrite reductase gene NasD, 87-404 times, and glutamine reduction enzyme gene GlnA, 13-52 times) and dissimilatory reduction to ammonium (DNRA) (nitrate reductase gene NarG, 14-56 times) in different degrees of secondary salinized soils. This proved that NCT-2 agent could promote the nitrate assimilation and the dissimilation and reduction to ammonium in secondary salinized soil. Thus, the current findings suggested that the NCT-2 agent has a significant potential for reducing excessive nitrate levels in secondary salinized soil. The remediation efficiency was related to the microbial community composition and the degree of secondary salinization. This study could provide a theoretical basis for the remediation of secondary salinized soil in the future.

Comparative cytology combined with transcriptomic and metabolomic analyses of Solanum nigrum L. in response to Cd toxicity.

Cadmium (Cd) triggers molecular alterations in plants, perturbs metabolites and damages plant growth. Therefore, understanding the molecular mechanism underlying the Cd tolerance in plants is necessary for assessing the persistent environmental impact of Cd. In this study, Solanum nigrum was selected as the test plant to investigate changes in biomass, Cd translocation, cell ultrastructure, metabolites and genes under hydroponic conditions. The results showed that the plant biomass was significantly decreased under Cd stress, and the plant has a stronger Cd transport capability. Transmission electron microscopy revealed that increased Cd concentration gradually damaged the plant organs (roots, stems and leaves) cell ultrastructure, as evidenced by swollen chloroplasts and deformed cell walls. Additionally, metabolomics analyses revealed that Cd stress mainly affected seven metabolism pathways, including 19 differentially expressed metabolites (DEMs). Moreover, 3908 common differentially expressed genes (DEGs, 1049 upregulated and 2859 downregulated) were identified via RNA-seq among five Cd treatments. Meanwhile, conjoint analysis found several DEGs and DEMs, including laccase, peroxidase, D-fructose, and cellobiose etc., are associated with cell wall biosynthesis, implying the cell wall biosynthesis pathway plays a critical role in Cd detoxification. Our comprehensive investigation using multiple approaches provides a molecular-scale perspective on plant response to Cd stress.

When nanoparticle and microbes meet: The effect of multi-walled carbon nanotubes on microbial community and nutrient cycling in hyperaccumulator system.

Carbon nanotubes can potentially stimulate phytoremediation of heavy metal contaminated soil by promoting plant biomass and root growth. Yet, the regulating mechanism of carbon nanotubes on the rhizosphere microenvironment and their potential ecological risks remain poorly characterized. The purpose of this study was to systematically evaluate the effects of multi-walled carbon nanotubes (MCNT) on the diversity and structure of rhizosphere soil bacterial and fungal communities, as well as soil enzyme activities and nutrients, in Solanum nigrum L. (S. nigrum)-soil system. Here, S. nigrum were cultivated in heavy metal(loid)s contaminated soils applied with MCNT (100, 500, and 1000 mg kg-1 by concentration, none MCNT addition as control) for 60 days. Our results demonstrated more significant urease, sucrase, and acid phosphatase activities in MCNT than in control soils, which benefit to promoting plant growth. Also, there were significant reductions in available nitrogen and available potassium contents with the treatment of MCNT, while the organic carbon and available phosphorus were not affected by MCNT application. Notably, the alpha diversity of bacterial and fungal communities in the MCNT treatments did not significantly vary relative to control. However, the soil microbial taxonomic compositions were changed under the application of MCNT. Compared to the control, MCNT application increased the relative abundances of the Micrococcaceae family, Solirubrobacteraceae family, and Conexibacter genus, which were positively correlated with plant growth. In addition, the non-metric multidimensional scaling (NMDS) analysis revealed that the community structure of bacterial and fungal communities did not significantly change among all the treatments, and bacterial community structure was significantly correlated with soil organic carbon. At the same time, sucrase activity had the highest relation to fungal community structure. This study highlighted soil microbes have strong resistance and adaptation ability to carbon nanotubes with existence of plants, and revealed linkage between the rhizosphere microenvironment and plant growth, which well improved our understanding of carbon nanotubes in heavy metal phytoremediation.

Targeting Cd coping mechanisms for stress tolerance in Brassica napus under spiked-substrate system: from physiology to remediation perspective.

Cadmium (Cd) is a prevalent, non-essential, carcinogenic, and hazardous heavy metal that reduces plant productivity and capacity of arable land area around the globe. In the present substrate-based pot study, seedlings of Brassica napus 180015 were grown equidistantly in the spiked-substrate medium for 60 days under increasing concentrations of Cd (0, 10, 20, 30, 40, 50 mg kg-1). Following harvest, the morpho-physio-biochemical, antioxidative, and Cd-induced tolerance responses were evaluated in B. napus under an increasing Cd stress regime. Additionally, these parameters were also investigated to select the plant's threshold tolerance limit for Cd under the spiked-substrate system. B. napus showed dynamic behavior regarding morpho-physio-biochemical attributes, including agronomic features, biomass, photosynthetic pigments, relative water content under increased Cd toxicity. Cd stress-induced hydrogen peroxide (H2O2) production with high MDA contents and passive EL, followed by the orchestration of both enzymatic (SOD, POD, APX, CAT, and GR) and non-enzymatic antioxidants (flavonoids, TPC, TPA, proline, and total soluble protein) up to a certain limit. In addition, Cd-induced stress upregulated transcriptional levels of antioxidative enzyme SOD, POD, APX, GR, and MT encoded genes in B. napus. The increasing trend of Cd accumulation in different tissues at the highest Cd concentration was as follows: root > leaf > stem. In spiked substrate system, B. napus demonstrated improved metal extractability performance and a high potential for phyto-management of low to moderate Cd contamination, implying that this study could be used for integrative breeding programs and decontaminating heavy metals in real contaminated scenarios.Novelty statementThis study provides an insight into Cd-coping mechanisms of oilseed rape involved in alleviating toxicity and simultaneous phyto-management of increasing Cd concentration under spiked substrate system. The current study is the first scientific evidence of using a Cd-spiked soilless substrate medium. The present study will further strengthen our understanding of Cd-instigated positive responses in B. napus. Furthermore, it will provide a useful basis for integrative breeding programs and decontaminating heavy metals in real contaminated scenarios.

Small structures with big impact: Multi-walled carbon nanotubes enhanced remediation efficiency in hyperaccumulator Solanum nigrum L. under cadmium and arsenic stress.

With the fast development of nanotechnology, nanomaterials are being increasingly applied for the remediation of contaminated soils. However, few researches have been reported on the complex interactions of carbon nanotubes with heavy metal (loid)s in phytoremediation. Here, we conduct a pot experiment to investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the plant growth and behavior of heavy metal (loid)s in hyperaccumulator-soil system. Cd hyperaccumulator Solanum nigrum L. (S. nigrum) were cultivated in Cadmium (Cd) and Arsenic (As) contaminated soils amended with MWCNTs at 100, 500, and 1000 mg kg-1 for 60 days, respectively. The application of MWCNTs increased the shoot length and plant dry biomass by 5.56%∼25.13% and 5.23%∼27.97%. Whereas, root and leaf growth were inhibited in 1000 mg kg-1 MWCNTs treatments. Meanwhile, MWCNTs at 500 mg kg-1 significantly enhanced the accumulation of heavy metal (loid)s in S. nigrum（18.29% for Cd and 32.47% for As）and alleviated co-contamination induced toxicity, by motivating plant growth, stimulating antioxidant enzymatic activities, and increasing micronutrient content (p < 0.05). The bio-concentration factor of As was decreased (15.31-28.08%) under MWCNTs application, which plays an important role in the alleviation of phytotoxicity. Besides, bioavailable Cd and As were reduced in rhizosphere soils, and the most significant reduction (16.29% for Cd and 8.19% for As) were shown in 500 mg kg-1 MWCNTs treatment. These findings demonstrate that suitable concentration of MWCNTs can enhance remediation efficiency. Our study gives a strong evidence to promote the phytoremediation for co-contaminated soils by using nanomaterials.

Streptomyces griseorubens JSD-1 promotes rice straw composting efficiency in industrial-scale fermenter: Evaluation of change in physicochemical properties and microbial community.

The influence of Streptomyces griseorubens JSD-1 on microbial community succession during rice straw composting in an industrial-scale fermenter was assessed by high-throughput sequencing technology. Compared to uninoculated control, JSD-1 inoculation effectively raised composting temperature and improved other maturation indices. JSD-1 inoculation increased the relative abundance of Actinobacteria in thermophilic phase and Firmicutes in cooling and maturation phases. At the genus level, JSD-1 inoculation increased the abundance of organic matter degrading bacteria (Virgibacillus) and lignocellulose degrading fungi (Chaetomium and Melanocarpus); while it decreased the abundance of pathogenic fungi (Geosmithia and Acremonium). Moreover, JSD-1 changed microbes that differed significantly and altered the key connecting nodes of microbial community. Organic matter and temperature were the most significant indices that had mutual influences on bacterial and fungal communities, respectively. This study demonstrated that JSD-1 was an effective inoculant on rice straw fast composting in the industrial-scale fermenter.

Influence of Cd toxicity on subcellular distribution, chemical forms, and physiological responses of cell wall components towards short-term Cd stress in Solanum nigrum.

Solanum nigrum is a well-documented cadmium (Cd) hyperaccumulator; however, its Cd-induced tolerance capability and detoxification mechanism remain elusive. Hence, a short-term hydroponic experiment was performed in a multiplane glasshouse to determine the influence of Cd toxicity on subcellular distribution, chemical forms, and the physiological responses of cell wall towards Cd stress in a 4-week-old plant. The experiment was conducted following completely randomized design (CRD) with five treatments (n = 4 replicates). The results showed that Cd stress showed dose-dependent response towards growth inhibition. The subcellular distribution of Cd in S. nigrum was in the order of cell wall > soluble fractions > organelles, and Cd was predominantly extracted by 1 M NaCl (29.87~43.66%). The Cd contents in different plant tissues and cell wall components including pectin, hemicellulose 1 (HC1), hemicellulose 2 (HC2), and cellulose were increased with the increase in Cd concentrations; however, the percentage of Cd concentration decreased in pectin and cellulose. Results of the polysaccharide components such as uronic acid, total sugar contents, and pectin methylesterase (PME) activity showed Cd-induced dose-dependent increase relative to exposure Cd stress. The pectin methylesterase (PME) activity was significantly (p < 0.05) enhanced by 125.78% at 75 µM Cd in root, 105.78% and 73.63% at 100 µM Cd in stem and leaf, respectively. In addition, the esterification, amidation, and pectinase treatment of cell wall and Fourier transform infrared spectroscopy (FTIR) assay exhibited many functional groups that were involved in cell wall retention Cd, especially on carboxyl and hydroxyl groups of cell wall components that indicated that the -OH and -COOH groups of S. nigrum cell wall play a crucial role in Cd fixation. In summary, results of the current study will add a novel insight to understand mobilization/immobilization as well as detoxification mechanism of cadmium in S. nigrum.

Two plant growth promoting bacterial Bacillus strains possess different mechanisms in adsorption and resistance to cadmium.

Microorganisms are promising biosorbents for decontaminating cadmium-polluted soil or water systems, but the underlying remediation mechanisms are still unclear. In this study, the cadmium biosorption mechanisms and capabilities of plant growth-promoting microorganisms (Bacillus megaterium NCT-2 and Bacillus paranthracis NT1) were investigated. Batch biosorption experiments showed that the optimal biosorption conditions for B. megaterium NCT-2 and B. paranthracis NT1 were pH 6.0, a biomass dosage of 1.0 g L-1, and an initial Cd2+ concentration of 10 mg L-1, and pH 8.0, a biomass dosage of 1.0 g L-1, and an initial Cd2+ concentration of 10 mg L-1, respectively. The biosorption processes of both biosorbents were well described by the pseudo-second order kinetic model, which indicated that the biosorption of Cd2+ was mainly chemisorption. The intracellular accumulation portion of adsorbed Cd2+ in B. megaterium NCT-2 was much higher than in B. paranthracis NT1 (43.11% and 3.25%, respectively), which resulted in the lower cadmium tolerance (14 mg L-1 and 280 mg L-1, respectively) and higher cadmium removal efficiency (46.79% and 20.45%, respectively) of B. megaterium NCT-2 compared to B. paranthracis NT1. SEM-EDS and FTIR analysis suggested the probable interactions of Cd2+ with the biosorbent surface ligands, such as -OH, -NH, -SO3, CO and -COOH during surface adsorption. Results of qRT-PCR illustrated that the difference in cadmium resistant mechanism and adsorption performance between B. megaterium NCT-2 and B. paranthracis NT1 may be regulated by the genes cadA, zitB, khtT, and bshA and cadA, trkA, czcD, and bshA, respectively. Our results revealed that these two biosorbents have the potential for further use in the development of cadmium remediation technologies and could provide insight into the mechanisms of cadmium biosorption.

Pennisetum giganteum: An emerging salt accumulating/tolerant non-conventional crop for sustainable saline agriculture and simultaneous phytoremediation.

Soil salinity is a global threat to the environmental sustainability, in particular to the developing countries due to their limited resources for soil reclamation. In a greenhouse pot experiment, Pennisetum giganteum, was investigated for its tolerance to salt stress and simultaneous phytoremediation capability. 4 weeks post-germination, NaCl (10, 50, 150, 250, 350, 450 and 550 mM) and tap water (control) was applied after every 2 consecutive days for two weeks in a completely randomized design and their effects were established in the growth and physico-chemical aspects of these plants. Our results indicated that P. giganteum withstood high salt stress (with 550 mM NaCl tolerance threshold level). Interestingly, the plants grown under saline conditions had higher biomass yield when compared to the control. Furthermore, the antioxidant activity and proline content of plants under saline conditions were significantly (p < 0.05) higher than those of control plants, indicating their adaptability to high salt stress. Biochemical analysis such as chlorophyll contents, total soluble sugar, total phenol and protein contents revealed considerable differences between plants grown under higher NaCl stress compared to the control conditions. Additionally, significantly different ionic flux along with high K+/Na+ ratio was observed in plants grown under a range of saline conditions. The results obtained are therefore of value to indicate P. giganteum an eco-friendly alternate source for the phytoremediation of saline soils and may be used as base for future research on this plant. Effective strategies need to be adopted with this plant to reclaim saline-degraded as well as marginal soils.

Optimization of NPK fertilization combined with phytoremediation of cadmium contaminated soil by orthogonal experiment.

In the current experiment, influence of NPK composition on the Cd contaminated soil-plant (Solanum nigrum L.) system as well as the phytoremediation efficiency were comprehensively studied. The composition of NPK was optimized for a sustainable phytoremediation and simultaneous agronomic technique in Cd-contaminated soil by orthogonal (L14) experiment, aimed to achieve plant productivity and maximum phytoremediation potential enhancement. Results showed that different treatments of NPK composition enhanced soil properties including saccharase, urease, catalase and acid phosphatase activities as compared to the control treatment, however, soil pH was slightly decreased by 3.64%~6.67% with different composition of NPK treatments. Plant biomass and Cd concentration in the aboveground part (stem and leaves) of S. nigrum were significantly (P < 0.05) enhanced by 14.19%~48.97% and 38.50%~127.15% as compared to control plants with the addition of NPK fertilizers having different composition. Meanwhile, with the application of NPK fertilizer root/shoot Cd ratio and translocation factor (TF) was significantly decreased, however, bioconcentration factor (BCF) was increased as compared to control. Additionally, different composition of NPK fertilizers significantly increased photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids) and soluble protein in comparison to control. The activities of antioxidant enzymes in S. nigrum including ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and glutathione reductase (GR) were increased, while malonaldehyde (MDA) and proline contents were decreased. Principal component analysis (PCA) showed that N3P2K2 treatment had the highest comprehensive score amongst other studied treatments of NPK composition, owing to its optimal composition for the investigated soil-S. nigrum system. Moreover, it was found that optimal composition (N3P2K2) of fertilizer resulted in increase of the plant resistance to Cd and the efficiency of phytoextraction. Therefore, it is suggested to all the small-holder famers and scientific community that precise composition of NPK fertilizer should be utilized according to soil properties, environmental conditions and plant requirements under Cd-stress condition in order to achieve maximum biomass, Cd uptake efficiency as well phytoremediation potential in moderately Cd contaminated soil.

[Passivation of Simulated Pb-and Cd-Contaminated Soil by Applying Combined Treatment of Phosphate, Humic Acid, and Fly Ash].

In this study, three kinds of amendments including superphosphate, humic acid, and fly ash and their complex combination were adopted to passivate the artificially simulated Pb-and Cd-containing soils. The passivation efficiency evaluation was performed via the CaCl2 and triethylenetriaminepentaacetic acid (DTPA) extraction method as well as a BCR morphological classification experiment. The microstructures and structures of the soil were explored further via X-ray diffraction (XRD) and scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-EDS) to elaborate the passivation mechanism. The results demonstrated that all passivation processes, excluding single humic acid addition, could reduce the CaCl2 and DTPA extraction contents of Pb and Cd in soils, where the optimal efficiency could be achieved by the sequential addition of superphosphate and humic acid, followed by fly ash. There was a weakly positive correlation between soil pH and CaCl2/DTPA extraction content of Pb, a negative correlation between soil pH and CaCl2/DTPA extraction content of Cd, and a significantly negative correlation between available phosphorous content and CaCl2/DTPA extraction contents of Pb and Cd, suggesting the crucial role of available phosphorous contents to control the activities of Pb and Cd. In the presence of phosphate, humic acid, and fly ash, the Pb and Cd could convert from active weak acid extraction to low-activity residual speciation, resulting in effectively reducing Pb and Cd transferability. Throughout the XRD and SEM-EDS analyses, it was found that ion exchange was the predominant mechanism in heavy metal passivation by single superphosphate, wherein the heavy metals were transformed into an insoluble Ca-containing phosphate mixture. The dissolving/precipitation or surface adsorption could be concluded as the main mechanism in the combination of the three passivation agents that converted heavy metals to lead phosphate precipitate[(Pb3(PO4)2] or mixed heavy metal mineral[PbFe3(SO4)(PO4)(OH)6], so as to obtain superior heavy metal passivation achievement.

[Mixture Leaching Remediation Technology of Arsenic Contaminated Soil].

Soil contamination of arsenic pollution has become a severely environmental issue, while soil leaching is an efficient method for remediation of arsenic-contaminated soil. In this study, batch tests were primarily conducted to select optimal mixture leaching combination. Firstly, five conventional reagents were selected and combined with each other. Secondly, the fractions were analyzed before and after the tests. Finally, to explore the feasibility of mixed leaching, three soils with different arsenic pollution levels were used to compare the leaching effect. Comparing with one-step washing, the two-step sequential washing with different reagents increased the arsenic removal efficiency. These results showed that the mixture of 4 h 0.5 mol · L⁻¹ NaOH + 4 h 0.1 mol · L⁻¹ EDTA was found to be practicable, which could enhance the removal rate of arsenic from 66.67% to 91.83%, and the concentration of arsenic in soil was decreased from 186 mg · kg⁻¹ to 15.2 mg · kg⁻¹. Furthermore, the results indicated that the distribution of fractions of arsenic in soil changed apparently after mixture leaching. Leaching process could significantly reduce the available contents of arsenic in soil. Moreover, the mixture of 0.5 mol · L⁻¹ NaOH + 0.1 mol L⁻¹ EDTA could well decrease the arsenic concentration in aluminum-type soils, while the mixture of 0.5 mol · L⁻¹ OX + 0.5 mol · L⁻¹ NaOH could well decrease the arsenic concentration in iron-type soils.

[Preparation of Visible-light-induced g-C3N4/Bi2S3 Photocatalysts for the Efficient Degradation of Methyl Orange].

Visible light responsive heterojunctions of graphitic carbon nitride (g-C3N4) and Bi2S3 were successfully designed and constructed by a simple solvothermal process. The as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectroscopy (DRS). Under visible light irradiation, the as-prepared g-C3N4/Bi2S3 photocatalysts exhibited highly enhanced photochemical efficiency in the degradation of methyl orange (MO) compared with pure g-C3N4 and Bi2S3. On the basis of the calculated energy bands, the excellent enhancement was attributed to the efficient separation of photoinduced electron-hole pairs. In addition, a detailed degradation pathway of MO degradation by g-C3N4/Bi2S3 composites was proposed to further elucidate the inner photodegradation mechanism. This research may provide a cost-effective and easy-scaling up approach to develop visible-light-driven photocatalysts, which could be applied in wastewater treatment.

Response of rhizosphere microbial community structure and diversity to heavy metal co-pollution in arable soil.

Due to the emerging environmental issues related to heavy metals, concern about the soil quality of farming lands near manufacturing district is increasing. Investigating the function of soil microorganisms exposed to long-term heavy metal contamination is meaningful and important for agricultural soil utilization. This article studied the potential influence of several heavy metals on microbial biomass, activity, abundance, and community composition in arable soil near industrial estate in Zhuzhou, Hunan province, China. The results showed that soil organic contents (SOC) were significantly positive correlated with heavy metals, whereas dehydrogenase activity (DHA) was greatly depressed by the heavy metal stress. Negative correlation was found between heavy metals and basal soil respiration (BSR), and no correlation was found between heavy metals and microbial biomass content (MBC). The quantitative PCR (QPCR) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis could suggest that heavy metal pollution has significantly decreased abundance of bacteria and fungi and also changed their community structure. The results could contribute to evaluate heavy metal pollution level in soil. By combining different environmental parameters, it would promote the better understanding of heavy metal effect on the size, structure, and activity of microbial community in arable soil.