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The pollution from waste plastic express packages (WPEPs), especially microplastic (MP) fragments, caused by the blowout development of the express delivery industry has attracted widespread attention. On account of the variety of additives, strong complexity, and high diversity of plastic express packages (PEPs), the multi-class classification of WPEPs is a typical large-class-number classification (LCNC). The traceability and identification of microplastic fragments from WPEPs is very challenging. An effective chemometric method for large-class-number classification would be very beneficial for the comprehensive treatment of WPEP pollution through the recycling and reuse of waste plastic express packages, including microplastic fragments and plastic debris. Rather than using the traditional one-against-one (OAO) and one-against-all (OAA) dichotomies, an exhaustive and parallel half-against-half (EPHAH) decomposition, which overcomes the defects of the OAO's classifier learning limitations and the OAA's data proportion imbalance, is proposed for feature selection. EPHAH analysis, combined with partial least squares discriminant analysis (PLS-DA) for large-class-number classification, was performed on 750 microplastic fragments of polyethylene WPEPs from 10 major courier companies using near-infrared (NIR) spectroscopy. After the removal of abnormal samples through robust principal component analysis (RPCA), the root mean square error of cross-validation (RMSECV) value for the model was reduced to 0.01, which was 21.5% lower than that including the abnormal samples. The best models of PLS-DA were obtained using SNV combined with SG-17 smoothing and 2D (SNV+SG-17+2D); the latent variables (LVs), the error rates of Monte Carlo cross-validation (ERMCCVs), and the final classification accuracies were 6.35, 0.155, and 88.67% for OAO-PLSDA; 5.37, 0.103, and 87.33% for OAA-PLSDA; and 3.12, 0.054, and 96.00% for EPHAH-PLSDA. The results showed that the EPHAH strategy can completely learn the complex LCNC decision boundaries for 10 classes, effectively break the tie problem, and greatly improve the voting resolution, thereby demonstrating significant superiority to both the OAO and OAA strategies in terms of classification accuracy. Meanwhile, PLS-DA further maximized the covariance and data interpretation abilities between the potential variables and categories of microplastic debris, thereby establishing an ideal performance identification model with a recognition rate of 96.00%. [ABSTRACT FROM AUTHOR]

Abstract Salinity can be a significant environmental stress which can govern the fate of nanoparticles in the environment as well as other factors such as pH, natural organic matter and minerals. In this research, the effects of salinity on the behavior of biogenic selenium nanoparticles (BioSeNPs) and consequences for elemental mercury (Hg0) immobilization in soil and soil solutions were investigated. It was found that homoaggregation and sedimentation of BioSeNPs were enhanced significantly with increasing salinity. Compression of the electric double layers of BioSeNPs at high ionic strengths resulted in attractive van der Waals forces dominating and leading to enhanced aggregation. Moreover, neutralization of the surface negative charge of BioSeNPs by divalent cations and the bridging of BioSeNPs via calcium binding to surface functional groups were also associated with enhanced aggregation. Such enhanced aggregation exerted inhibition of Hg0 immobilization in soil solutions/soils of varying salinity. These results indicate that salinity is an important environmental factor governing aggregation of BioSeNPs and therefore influencing the efficiency of Hg0 immobilization, and possible remediation treatments, as a consequence. Graphical abstract Unlabelled Image Highlights • Salinity is an important environmental factor governing the fate of SeNPs in soil. • Compressed EDLs, charge neutralization and Ca-bridging enhanced SeNPs aggregation. • Hg0 immobilization efficiency using SeNPs was suppressed with increased aggregation. [ABSTRACT FROM AUTHOR]

Abstract Molecular weight (MW) heterogeneity is a fundamental property of dissolved organic matter (DOM) in soil, which has been demonstrated to influence the binding behaviour between DOM and engineered nanoparticles. In the present study, DOM, extracted from black soil, was dialyzed into four fractions: above 10,000 Da, 3500–10,000 Da, 1000–3500 Da and 100–1000 Da. Homoaggregation and fluorescence quenching titration of selenium nanoparticles (SeNPs) was examined in the presence of the different DOM fractions, as well as the consequences for immobilization of elemental mercury. It was found that the intermediate MW fraction (3500–10,000 Da) rather than the high MW DOM fraction was likely to adsorb to SeNPs. Generally, low MW DOM was expected to adsorb initially due to faster diffusion and these compounds would be displaced by high MW DOM over longer time period. However, the electrostatic barrier imparted by adsorbed DOM limited such displacement, leading to preferential adsorption of the intermediate MW fraction over the high MW fraction. Adsorbed DOM fractions, especially that of intermediate MW, enhanced the stability of SeNPs which favoured immobilization of elemental mercury. These findings show that MW exerts an important impact on DOM binding with SeNPs which, in consequence, governs the fate of SeNPs and mercury bioremediation performance. Graphical abstract Unlabelled Image Highlights • Dissolved organic matter (DOM) affects Hg removal by selenium nanoparticles (SeNPs). • Intermediate molecular weight DOM preferentially adsorbed to SeNPs. • Intermediate molecular weight DOM limited its displacement by other DOM fractions. • Intermediate molecular weight DOM enhanced the stability of SeNPs and Hg removal. [ABSTRACT FROM AUTHOR]

Microbial mat extracellular polymeric substances (EPS) and their fate and transformation in natural waters are unidentified under diurnal condition. EPS from highly saline arid origins were characterised and exposed to natural sunlight conditions to identify its physico-chemical changes over 72 h. Fourier Transform Infrared Spectroscopy (FTIR) and potentiometric titration analyses confirmed the presence of −COOH and –OH functional groups in raw EPS. In addition, size exclusion chromatography (SEC) confirmed the presence of two proteins-sized molecules in the original EPS which were found to degrade upon sunlight exposure. The excitation-emission matrix (EEM) and parallel factor (EEM-PARAFAC) identified two fluorescent components: A combined humic-like and protein-like component, and an individual tyrosine-like component. FTIR in irradiated samples confirmed degradation of EPS by showing presence of the −CH 3 group at 1377 cm −1 . Two proteins-sized molecules identified in SEC were degraded, thereby causing to significant changes in the pH and redox potential (Eh). Correspondingly, three fluorescent components were identified in irradiated samples using EEM-PARAFAC modelling and found to change in their fluorescence intensities upon sunlight exposure. It is therefore suggested that photochemical processes are important for sequential transformation of EPS into various organic substances in surface waters. [ABSTRACT FROM AUTHOR]

Structural stability of aerobic granules is generally poor during long-term operation. This study precipitated seven salts inside aerobic granules using supersaturated solutions of (NH 4 ) 3 PO 4 , CaCO 3 , CaSO 4 , MgCO 3 , Mg 3 (PO 4 ) 2 , Ca 3 (PO 4 ) 2 or SiO 2 to enhance their structural stability. All precipitated granules have higher interior strength at ultrasonic field and reveal minimal loss in organic matter degradation capability at 160-d sequential batch reactor tests. The strength enhancement followed: Mg 3 (PO 4 ) 2 = CaSO 4 > SiO 2 > (NH 4 ) 3 PO 4 > MgCO 3 > CaCO 3 = Ca 3 (PO 4 ) 2 > original. Also, the intra-granular solution environment can be buffered by the precipitate MgCO 3 to make the aerobic granules capable of degradation of organic matters at pH 3. Salt precipitation is confirmed a simple and cost-effective modification method to extend the applicability of aerobic granules for wastewater treatments. [ABSTRACT FROM AUTHOR]

Microbial arsenite oxidation was observed byAcinetobactersp. XS21, this strain oxidised arsenite As(III) up to 80 mM within 48–72 h of incubation. The present strain XS21 oxidised As(III) at a very high concentration in a shorter interval of time than any of the previous reported microbes. Further, XS21 was applied to the soil to observe its ability in reducing the mobility of As(III), and we found thatAcinetobactersp. XS21 efficiently removed arsenite from soluble-exchangeable fraction and removed 70% of the arsenite as compared to control. This feature makes it a potential candidate for bioremediation. Arsenic-resistant bacteria with strong As(III)-oxidising ability may have potential to improve bioremediation of As(III)-contaminated sites. To understand their basis of resistance and transformation we found the As(III) oxidase gene using degenerate primer and amplified ∼550 bp ofaioAgene. AmplifiedaioAgene sequence exhibiting 52% identity in terms of gene and deduced protein sequence toUncultured bacterium, andAchromobactersp. arsenite oxidase of larger subunit. Arsenite oxidase, an enzyme, was also observed in this isolate, which may provide a resistance and transforming ability. This bacterium was identified asAcinetobactersp., by sequencing 16s rRNA gene sequence analysis. [ABSTRACT FROM AUTHOR]

Metal and mineral transformations are a cornerstone of geomicrobiological processes. Of central importance are the mechanisms by which microorganisms alter the speciation and mobility of metals, including their properties of mineral dissolution or mineral formation. Such processes underpin natural biogeochemical cycles for metals, and related elements such as metalloids, and metal radionuclides, as well as those elements that may be commonly associated with metal compounds and minerals, e.g., P and S. They may also determine the fate of contaminant toxic metals and radionuclides when introduced or redistributed in the environment as a result of natural or anthropogenic activities. Such contamination is an increasing problem, and microbe-based systems are increasingly viewed as potentially useful approaches for bioremediation, as well as for element biorecovery. Biomineralization is a general term for the processes by which living organisms form minerals, and this can result in metal removal from solution providing a means of detoxification as well as biorecovery. Dead biota and derived products may also provide a template for mineral deposition, the reversibility, or otherwise, of the reaction depending on physico-chemical conditions. The most common biominerals precipitated by microbes include oxides, phosphates, sulfides and oxalates, and these can have special chemical properties such as high metal sorption capacities and redox catalysis. Furthermore, some biominerals may be deposited in nanoscale dimensions, providing further significant physical, chemical and biological properties of applied significance. The purpose of this Special Issue of theGeomicrobiology JournalonBiomineralization, Bioremediation and Biorecoveryis to bring together and highlight some specific examples of metal and radionuclide biomineralization by microorganisms from the different major microbial groups such as cyanobacteria, bacteria, microalgae and fungi. A range of elements and organisms are covered together with a variety of environmental and industrial contexts where a biomineralization approach may assist bioremediation, metal biorecovery or substrate stability. [ABSTRACT FROM AUTHOR]

Heavy metal contamination of mine tailings is one of the most serious environmental challenges facing the mining industry worldwide. Conventional technologies used for the treatment of such tailing soils are expensive both in terms of operation and capital costs as well as being not so effective. In the present study, an indigenous calcifying urease producing bacterial strain was isolated from copper mine tailing soil and used for bioimmobilization of copper, lead and cadmium in contaminated mine tailing soils. Phylogenetic analysis of the 16S rRNA gene sequence identified it asBacillus firmus. The efficiency of metal bioimmobilization was based on microbially induced calcite precipitation (MICP). A five-stage sequential soil extraction procedure was carried out to obtain distribution patterns for the different metals. The mobility of the toxic metals was found to be significantly reduced in the exchangeable fraction with their concentrations markedly increasing in the carbonated fraction after bioremediation. Scanning electron microscopy showed the precipitation of calcite in association with the bacterial cells. Calcium carbonate minerals such as calcite, gwihabaite and aragonite were identified in the bioremediated tailings soils using X-ray diffraction (XRD). It is concluded that MICP holds considerable promise for the remediation of mine tailing soils by efficient immobilization of toxic metals such as copper, lead and cadmium. [ABSTRACT FROM AUTHOR]

Bioreduction of Cr(VI) to less toxic Cr(III) by chromate-reducing bacteria has offered an ecological and economical option for chromate detoxification. The present study reports isolation of chromate-resistant bacterial strain Cr8 from chromium slag, identified asPseudomonas stutzeri, based on 16S rRNA gene sequencing and their potential use in Cr(VI) reduction. The reduced product associated with bacterial cell was characterized by scanning electron microscopy–energy-dispersive x-ray spectroscopy (SEM-EDS) and x-ray diffraction (XRD) analyses. At initial concentrations of 100 and 200 mg L−1Cr(VI),P. stutzeriCr8 reduced Cr(VI) completely within 24 h, whereas it reduced almost 1000 mg L−1Cr(VI) at the end of 120 h. Further, soil column leaching experiments were performed and found that bacterial cells reduced Cr(VI) leachate at faster rate that almost disappeared at the end of 168 h. The leachate precipitates also revealed efficient chromate bioreduction. The remediation process utilizingP. stutzericould be considered as a viable alternative to reduce Cr(VI) contamination, especially emanating from the overburden dumps of chromite ores and mine drainage. [ABSTRACT FROM PUBLISHER]

Nitrate and arsenic are common pollutants in groundwater. However, we are still lacking technologies that can remove nitrate and arsenic simultaneously using a single species of microorganism. In the present study, the potential of synchronous removal of nitrate and arsenite from water by a single anaerobic nitrate-reducing Fe(II) oxidizing Citrobacter freundii strain PXL1 was assessed. The strain PXL1 could grow well in arsenite concentration of 2.85–13.65 μM and efficiently oxidize Fe(II), reduce nitrate and remove As(III) from water. Scanning electron microscopy, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy analysis showed that the strain PXL1 produced poorly crystalline Fe(III) oxides. As(III) was removed mainly by adsorption and co-precipitation of the biogenic Fe(III) oxides. The anaerobic nitrate-dependent Fe(II) oxidizing bacteria including C. freundii PXL1 are promising microbes for in situ remediation of nitrate and arsenite contaminated groundwater. [ABSTRACT FROM AUTHOR]

H 2 O 2 is an emerging biocide for bloom-forming cyanobacteria. It is important to investigate the H 2 O 2 scavenging ability of extracellular polymeric substances (EPS) of cyanobacteria because EPS with strong antioxidant activity may “waste” considerable amounts of H 2 O 2 before it kills the cells. In this study, the buffering capacity against H 2 O 2 of EPS from the bloom-forming cyanobacterium Microcystis aeruginosa was investigated. IC 50 values for the ability of EPS and vitamin C (VC) to scavenge 50% of the initial H 2 O 2 concentration were 0.097 and 0.28 mg mL −1 , respectively, indicating the higher H 2 O 2 scavenging activity of EPS than VC. Both proteins and polysaccharides are significantly decomposed by H 2 O 2 and the polysaccharides were more readily decomposed than proteins. H 2 O 2 consumed by the EPS accounted for 50% of the total amount of H 2 O 2 consumed by the cells. Cell growth and photosynthesis were reduced more for EPS-free cells than EPS coated cells when the cells were treated with 0.1 or 0.2 mg mL −1 H 2 O 2 , and the maximum photochemical efficiency Fv/Fm of EPS coated cells recovered to higher values than EPS-free cells. Concentrations of H 2 O 2 above 0.3 mg mL −1 completely inhibited photosynthesis and no recovery was observed for both EPS-free and EPS coated cells. This shows that EPS has some buffering capacity against the killing effect of H 2 O 2 on cyanobacterial cells. Such a strong H 2 O 2 scavenging ability of EPS is not favorable for killing bloom-forming cyanobacteria. The high H 2 O 2 scavenging capacity means considerable amounts of H 2 O 2 have to be used to break through the EPS barrier before H 2 O 2 exerts any killing effects on the cells. It is therefore necessary to determine the H 2 O 2 scavenging capacity of the EPS of various bloom-forming cyanobacteria so that the cost-effective amount of H 2 O 2 needed to be used for killing the cyanobacteria can be estimated. [ABSTRACT FROM AUTHOR]

Pollution with antibiotics poses a great risk to aquatic ecosystems. Although some toxic effects of antibiotics on photosystem II (PSII) have been documented, their toxicity to photosystem I (PSI) is still unclear. In this study, effects of ofloxacin on activities of both PSI and PSII of Microcystis aeruginosa (Kützing) Kützing were investigated. Exposure to 0.1 mg L − 1 ofloxacin led to increases in contents of chlorophyll a and carotenoids and photosynthetic activity of M. aeruginosa . PSI activity and its electron transport were not affected by 0.1 mg L − 1 ofloxacin. When M. aeruginosa was exposed to ≥10 mg L − 1 ofloxacin, the electron transport rates of PSI and PSII, the yield of cyclic electron flow (CEF) and the contribution of linear electron flow (LEF) to PSI decreased whereas Y(NA) (limitation of donor side of PSI) and Y(NO) (the quantum yield of non-regulated energy dissipation in PSII) significantly increased. CEF had a significant contribution to alleviating the inhibitory effect of ofloxacin on PSI of M. aeruginosa treated with low concentrations of ofloxacin. The protective role CEF for tolerance of PSI to the toxicity of ofloxacin decreased with increasing ofloxacin concentration. [ABSTRACT FROM AUTHOR]

The knowledge of the effects of Sb(V) on the physiological characteristics of cyanobacteria was still limited. In the present study, responses of photosystem I and II (PSI and PSII), cyclic electron flow (CEF), and interphotosystem electron transport of Microcystis aeruginosa to 5-100 mg/l Sb(V) were synchronously measured using the Dual-PAM-100. 5 mg/l Sb (V) significantly inhibited PSII activity, but had no significant effects on PSI activity. At higher concentrations of Sb(V), the quantum yield and electron transport of PSI were less affected compared to PSII. The ratio of Y(II)/ Y(I) significantly decreased with increasing Sb(V) concentration. It decreased from 0.7 for control to 0.4 for 100 mg/l Sb(V)-treated cells, indicating that the change of the distribution of quantum yields between two photosystems and more serious inhibition of PSII under stress of Sb(V) compared to PSI. CEF was activated associated with the inhibition of linear electron flow after exposure to Sb(V). The contribution of Y(CEF) to the quantum yield and activity of PSI increased with increasing Sb(V) concentrations. The cyclic electron transport rate made a significant contribution to electron transport rate of PSI, especially at high Sb(V) concentration (100 mg/l) and high illumination (above 555 μmol photons/m/s). The stimulation of CEF was essential for the higher tolerance of PSI than PSII to Sb(V). [ABSTRACT FROM AUTHOR]

Microbially induced carbonate precipitation (MICP) is an advanced biological treatment technology to immobilize heavy metals in form of carbonate salts. In this MICP study, ureolytic Exiguobacterium undae was employed for immobilization of cadmium in contaminated soil at low temperature (10 °C). The sequential extraction test revealed conversion of more than 90% of cadmium in the tested soil from the soluble-exchangeable fraction to carbonate-bound fraction in 14 days of treatment. The cadmium may be precipitated in a separate CdCO 3 phase or be co-precipitated in calcite crystals. Activities of urease and dehydrogenase were enhanced during MICP, which were not affected by the testing temperatures. MICP with E . undae is a biological approach that may be worth investigating further to immobilize cadmium in soils of cold regimes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Interactions between Hg(II), EPS and goethite were investigated. [•] EPS from Chroococcus sp. enhances adsorption capacity of Hg(II) on goethite. [•] EPS binds with Hg(II) to quench the EEM peaks of proteins on EPS. [•] Goethite–EPS soil is a larger Hg(II) sink than goethite alone soil. [•] Biosorption significantly affects the mobility of Hg(II) in goethite soils. [Copyright &y& Elsevier]

Highlights: [•] Microbially induced calcite precipitation to immobilize Cr(VI) from chromium slag. [•] Biocementation/bio-consolidation of Cr(VI) from chromium slag. [•] Incorporation of Cr(VI) into CaCO3 to form a strong complex. [•] Cr(VI) mobility was significantly decreased in the exchangeable fraction. [•] Cr(VI) concentrations in the leachate decreased significantly after biocementation. [Copyright &y& Elsevier]

Cd(II) adsorption of root exudates from sunflower (Helianthus annuusL.) seedling was investigated by Cd ion-selective electrode, Fourier Transform Infrared spectroscopy, and fluorescence spectroscopy. Root exudates fromHelianthus annuusL. had strong adsorption ability toward Cd(II). The adsorption process was pH-dependent and the maximum adsorption capacity, 150.8 mg g−1, was observed at pH 7.0. Root exudates hadpKa1at 4.7 for carboxyl andpKa2at 9.2 for phenolic, and amino groups. The aliphatic and aromatic (C−H) groups, amide III group, and the C (=O)−O and sulfonate groups were responsible for Cd(II) adsorption. The excitation emission matrix fluorescence spectroscopy showed protein-like substances participated in Cd adsorption and formed strong complexes, with conditional stability constants of 4.70 and 4.32, which is a little lower than that determined by potentiometric methods, 5.13. The strong Cd complexing ability of root exudates implies that root exudates may significantly affect mobility, toxicity, and phytoavailability of Cd. Cd binding of root exudates may be attributed to its interaction with the proteins, polysaccharides, and phenolic compounds in root exudates. [ABSTRACT FROM PUBLISHER]

Abstract: The denitrifying sulfide removal (DSR) process applied autotrophic and heterotrophic denitrification pathways to achieve simultaneous conversion of nitrate to N2, sulfide to elementary sulfur, and organic substances to CO2. However, autotrophic denitrifiers and heterotrophic denitrifiers have to grow at comparable rates so the long-term DSR stability can be maintained. This work assessed the autotrophic and heterotrophic denitrification activities by 16 isolates from anaerobic granules collected from a DSR-expanded granular sludge bed reactor. A group of strains with closest relatives as Pseudomonas sp. (89.9–98.3% similarity), Agrobacterium sp. (94.6% similarity) and Acinetobacter sp. (96.6% similarity) were identified with both autotrophic and heterotrophic denitrification capabilities. These facultative autotrophic denitrifiers can be applied as potential strains for lifting the limitation by balanced growth of two distinct bacterial groups in the DSR reactor. [Copyright &y& Elsevier]

In this study, effects of antimony Sb(V) on growth, pigments content, oxygen evolution, and photosystem II (PSII) activity of Microcystis aeruginosa were investigated. JIP-test, Q reoxidation kinetic test and S-state test were used in this study to study the energy distribution and electron transport in PSII. Treatment with Sb(V) at various concentrations ranging from 5 to 100 mg/l had long-term effects on growth, pigments content, and oxygen evolution of M. aeruginosa. Low concentration of Sb(V) had no significant inhibition of the biomass production and PSII activity but inhibited the pigment synthesis. Growth, pigments content, oxygen evolution, and PSII activity were seriously inhibited when treated by high concentration of Sb(V) (100 mg/l). The target sites of Sb(V) toxic effect on the PSII of M. aeruginosa were mainly on the donor side and the apparatus in the light-dependent reaction. The quantum yield for photochemistry, density of reaction centers and photosynthesis performance index decreased, whereas the dissipated energy increased. PSII activity of M. aeruginosa was promoted when exposure to 50 mg/l Sb(V) by increasing the density of active reaction centers and electron transport after Q. [ABSTRACT FROM AUTHOR]

Abstract: Contamination of aquifers or sediments by radioactive strontium (90Sr) is a significant environmental problem. In the present study, microbially induced calcite precipitation (MICP) was evaluated for its potential to remediate strontium from aquifer quartz sand. A Sr resistant urease producing Halomonas sp. was characterized for its potential role in bioremediation. The bacterial strain removed 80% of Sr from soluble–exchangeable fraction of aquifer quartz sand. X-ray diffraction detected calcite, vaterite and aragonite along with calcite–strontianite (SrCO3) solid solution in bioremediated sample with indications that Sr was incorporated into the calcite. Scanning electron micrography coupled with energy-dispersive X-ray further confirmed MICP process in remediation. The study showed that MICP sequesters soluble strontium as biominerals and could play an important role in strontium bioremediation from both ecological and greener point of view. [Copyright &y& Elsevier]

The responses of photosystem II (PSII) activity of samara and leaf of Siberian elm (Ulmus pumila L.) to chilling (5°C) and freezing (-5°C & -15°C) temperature and their recovery were investigated. There was little difference in Fv/Fm between samara and leaf. Leaf showed more efficient photosynthesis (PIABS) and electron transport (fEo & ?o) than samara. Chilling and freezing had adverse impact on PSII function in both samara and leaf. Low temperature stress decreased photochemical efficiency (Fv/Fm & PIABS) and electron transport activity (?o, fEo & ETo/RC) in both leaf and samara. PSII of samara was more tolerant to low temperature stress than leaf. Photochemical efficiency (Fv/Fm) for chilled (at 5°C) or mild frozen (at - 5°C) samara or leaf showed a recovery trend. Severe freezing stress (-15°C) led to drastic and irreversible injuries to PSII in samara and leaf. The fact that samara has photosynthetic activity and is more tolerant to low temperature than leaf is of great ecological significance for seed development, population establishment and the northern distribution limit of Siberian elm in northern hemisphere. [ABSTRACT FROM AUTHOR]

Abstract: Arsenic is a highly toxic metalloid and has posed high risk to the environment. As(III) is highly mobile in soil and leached easily into groundwater. The current remediation techniques are not sufficient to immobilize this toxic element. In the present study, an As(III) tolerant bacterium Sporosarcina ginsengisoli CR5 was isolated from As contaminated soil of Urumqi, China. We investigated the role of microbial calcite precipitated by this bacterium to remediate soil contaminated with As(III). The bacterium was able to grow at high As(III) concentration of 50mM. In order to obtain arsenic distribution pattern, five stage soil sequential extraction was carried out. Arsenic mobility was found to significantly decrease in the exchangeable fraction of soil and subsequently the arsenic concentration was markedly increased in carbonated fraction after bioremediation. Microbially induced calcite precipitation (MICP) process in bioremediation was further confirmed by ATR-FTIR and XRD analyses. XRD spectra showed presence of various biomineralization products such as calcite, gwihabaite, aragonite and vaterite in bioremediated soil samples. The results from this study have implications that MICP based bioremediation by S. ginsengisoli is a viable, environmental friendly technology for remediation of the arsenic contaminated sites. [Copyright &y& Elsevier]

Abstract: An indigenous calcifying bacterial strain CR1, identified as Kocuria flava, was isolated from soil of a mining area, Urumqi, China. An extensive copper bioremediation capacity of this isolate was studied based on microbially induced calcite precipitation (MICP). K. flava CR1 removed 97% of copper when initial Cu concentration was 1000mgL−1. The isolate produced significant amount of urease (472UmL−1), an enzyme that leads to calcite precipitation. The isolate removed 95% of copper from contaminated soil. The MICP process in bioremediation was further confirmed by FTIR and XRD analyses. FTIR analysis showed two different forms of calcium carbonate, i.e., calcite and aragonite, and the results were well supported by XRD. For the first time, the ability of K. flava has been documented in the bioremediation of polluted soil. This study showed that MICP-based bioremediation by K. flava is a viable, environmental friendly technology for cleaning-up the copper-contaminated site. [Copyright &y& Elsevier]

Abstract: Fly ash acts as a partial replacement material for both Portland cement and fine aggregate. An innovative approach of microbial calcite precipitation in fly ash-amended concrete has been investigated. This is the first report to discuss the role of microbial calcite precipitation in enhancing the durability of fly ash-amended concrete. The present study investigated the effects of Bacillus megaterium ATCC 14581 on compressive strength, water absorption and water impermeability of fly ash-amended mortar and concrete. Mortar specimens were used for compressive strength and water absorption tests, while concrete specimens were used for water impermeability tests. At the fly ash concentrations of 10%, 20% and 40% in mortars, bacterial cell enhanced mortar compressive strength by 19%, 14% and 10%, respectively, compared to control specimens. Treated mortar cubes absorbed more than three times less water than control cubes as a result of microbial calcite deposition. Microbial deposition of a layer of calcite on the surface of the concrete specimens resulted in substantial decrease of water uptake and permeability compared to control specimens without bacteria. Microbial cells also prevented ingress of water effectively in different concentrations of fly ash-amended concrete. Scanning Electron Micrography (SEM) analyses evidenced the direct involvement of bacteria in calcite precipitation. The approach of the present study gives us dual environment friendly advantages. First, use of fly ash-a recovered resource reduces depletion of natural resources and also reduces the energy-intensive manufacturing of other concrete ingredients, leading to savings in both energy usage and emissions of greenhouse gases. And second, use of bacterial cells to improve strength and durability of fly ash-amended concrete further provides greener and economic options. [Copyright &y& Elsevier]

Urease and carbonic anhydrase (CA) are key enzymes in the chemical reaction of living organisms and have been found to be associated with calcification in a number of microorganisms and invertebrates. Three bacterial strains designated as AP4, AP6, and AP9 were isolated from highly alkaline soil samples using the enrichment culture technique. On the basis of various physiological tests and 16S rRNA sequence analysis, these three bacteria were identified as Bacillus sp., B. megaterium, and B. simplex. Further, these Bacillus species have been characterized for the production of urease and CA in the process of biocalcification. One of the isolates, AP6 produced 553 U/ml of urease and 5.61 EU/ml CA. All the strains were able to produce significant amount of exopolymeric substances and biofilm. Further, efficacy of these strains was tested for calcite production ability and results were correlated with urease and CA. Isolate AP6 precipitated 2.26 mg calcite/cell dry mass (mg). Our observations strongly suggest that it is not only urease but CA also plays an important role in microbially induced calcium carbonate precipitation process. The current work demonstrates that urease and CA producing microbes can be utilized in biocalcification as a sealing agent for filling the gaps or cracks and fissures in constructed facilities and natural formations alike. [ABSTRACT FROM AUTHOR]

Abstract: High molecular weight (HMW) fractions are important components in root exudates. However, there is little available information concerning complexation of Cu(II) to the HMW fractions in root exudates. In the present study, complexation of root exudates from Salicornia europaea L. with Cu(II) was investigated using excitation emission matrix (EEM) fluorescence spectroscopy. Two protein-like fluorescence peaks were identified in the EEM spectra of root exudates. Fluorescence of both peaks was clearly quenched by Cu(II). The increase of conditional stability constant with increasing temperature indicates that the fluorescence quenching of the protein-like fluorescence by Cu(II) may be controlled by a dynamic process. The values of conditional stability constants (logK a) were in the range of 4.32–4.69, which were close to those of complexation of fulvic acid with Cu(II). This shows that the HMW fluorescent substances in root exudates from S. europaea L. were strong organic ligands for Cu(II). Our study suggests that the HMW fluorescent substances may affect chemical forms, mobility, and thus the fate of copper in wetland. [ABSTRACT FROM AUTHOR]

Abstract: Extracellular polymeric substances (EPS) are the essential components of activated sludge for removal of pollutants from wastewater. Limited information is available on the binding constants and binding mode of organic pollutants to EPS. In the present study, binding of phenanthrene (PHE) to extracellular polymeric substances (EPS) from aerobic activated sludge was investigated using fluorescence spectroscopy. Two protein-like fluorescence peaks (Ex/Em=225nm/340nm for peak A; Ex/Em=275–280nm/338nm for peak B) were identified in the three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy of the EPS. The fluorophores in EPS were clearly quenched by PHE and the quenching processes were static. The quenching constants (ln K a) were in the range of 11.27–13.82M−1 and the binding constants (log K b) in the range of 6.11–8.98M−1. The binding site number increased with increasing temperature. The corresponding thermodynamic parameters ΔG, ΔH and ΔS were calculated. The interaction of the fluorophores in EPS and PHE is spontaneous and exothermic. The binding of EPS with PHE is dominated by the hydrophobic interactions. Fluorophore A has stronger hydrophobic interaction with PHE than fluorophore B. [Copyright &y& Elsevier]

It has been demonstrated that antimony (Sb) at concentrations ranging from 1.0 to 10.0 mg L−1 inhibits O2 evolution. Deeper insight into the influence of Sb on PSII was obtained with measurements of in vivo chlorophyll fluorescence. The donor and the acceptor sides of PSII were shown to be the target of Sb. Sb treatment induces inhibition of electron transport from Q to QB/Q and accumulation of P. S2(QAQB)− charge recombination and oxidation by PQ9 molecules became more important in Q reoxidation as the electron transfer in PSII was inhibited. Sb exposure caused a steady increase in the proportion of PSIIX and PSIIβ. These changes resulted in increased fluxes of dissipated energy and decreased index of photosynthesis performance, of maximum quantum yield, and of the overall photosynthetic driving force of PSII. [ABSTRACT FROM AUTHOR]

Abstract: Binding of dicamba to soluble EPS (SEPS) and bound EPS (BEPS) from aerobic activated sludge was investigated using fluorescence spectroscopy. Two protein-like fluorescence peaks (peak A with Ex/Em=225nm/342–344nm and peak B with Ex/Em=275/340–344nm) were identified in SEPS and BEPS. Humic-like fluorescence peak C (Ex/Em=270–275nm/450–460nm) was only found in BEPS. Fluorescence of the peaks A and B for SEPS and peak A for BEPS were markedly quenched by dicamba at all temperatures whereas fluorescence of peaks B and C for BEPS was quenched only at 298K. A dynamic process dominated the fluorescence quenching of peak A of both SEPS and BEPS. Fluorescence quenching of peak B and C was governed a static process. The effective quenching constants (log Ka ) were 4.725–5.293 for protein-like fluorophores of SEPS and 4.23–5.190 for protein-like fluorophores of BEPS, respectively. Log Ka for humic-like substances was 3.85. Generally, SEPS had greater binding capacity for dicamba than BEPS, and protein-like substances bound dicamba more strongly than humic-like substances. Binding of dicamba to SEPS and BEPS was spontaneous and exothermic. Electrostatic force and hydrophobic interaction forces play a crucial role in binding of dicamba to EPS. [Copyright &y& Elsevier]

Abstract: The three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy was employed to investigate the interaction of extracellular polymeric substances (EPS) from natural biofilm with Hg(II). The EEM spectra demonstrated that EPS with molecular weight over 14kDa had two protein-like fluorescence peaks. The fluorescence intensity at both peaks was strongly dependent on the solution pH in the absence and presence of Hg(II), with the maximal fluorescence intensity at neutral pH. Fluorescence of both protein-like peaks was significantly quenched by Hg(II). The values of conditional stability constants (log K a =3.28–4.48) derived from modified Stern–Volmer equation are approximate to those for humic substances and dissolved organic matter (DOM), indicating that fluorescent components in EPS have strong binding capacity for Hg(II). Our findings suggest that EPS from biofilm is a class of important organic ligands for complexation with Hg(II) and may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the aquatic environment. [Copyright &y& Elsevier]

Abstract: Swine bone char is the combustion residues of swine bone. Cobalt adsorption to swine bone char was studied. Batch kinetics studies showed that a rapid uptake occurred during the first 5min and was followed with a very slow intraparticle diffusion process. The sorption kinetics was ideally conformed to pseudo-second equation, indicating several mechanisms involved in the adsorption process. Equilibrium sorption isotherm studies showed that the Freundlich isotherm model satisfactorily described the sorption data. The presence of co-ions had appreciable inhibiting effects on cobalt uptake by bone char because copper and zinc had higher affinity for the bone char surface than cobalt. Calcium concentration in solution and XRD analysis showed that ion exchange was involved in the removal of Co from solution over a certain initial cobalt concentration range. [Copyright &y& Elsevier]

Abstract: Effects of LH on photosynthesis of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence. O2 evolution and the photosystem II (PSII) activity were clearly inhibited by LH. Exposure to LH increased the proportion of PSIIβ and this weakened the connectivity between PSII units and hindered excitation energy-transfer between PSII units. LH decreased the density of the active photosynthetic reaction centers, inhibited electron transport, and increased the dissipated energy flux per reaction center. The inhibitory effect of LH on reoxidation process could be divided into several stages. LH first inhibited the electron transfer from to Q B by weakening the connectivity between and Q B, and PQ binding began taking part in reoxidation. At the second stage, the connectivity between and PQ pool was broken and inhibition on PQ binding occurred. At this stage, some began to be oxidized by S 2(Q A Q B)−. Finally, when the connectivity between and Q B and PQ was completely broken, all was oxidized through charge recombination. [Copyright &y& Elsevier]

Abstract: Amoxicillin is one of the widely used antibiotics of environmental concern. This study shows that amoxicillin has toxic effects on the photosynthesis of Synechocystis sp. Its inhibitory effects on photosystem II (PSII) of Synechocystis sp. were investigated by using a variety of in vivo chlorophyll fluorescence tests. The inhibitory effects of amoxicillin on PSII activity of Synechocystis sp. are concentration-dependent. Amoxicillin exposure leads to slowing down of electron transport on both donor side and acceptor side and causes accumulation of P680+. QA − reoxidation test revealed that amoxicillin hinders electron transfer from QA − to QB/QB − and more QA − is oxidized through S2(QAQB)− charge recombination. Analysis of PSII heterogeneity demonstrated that an exposure to amoxicillin increases the proportion of inactive PSII (PSIIX) centers and the proportion of PSII centers with small antenna (PSIIβ). These changes finally result in deterioration of full photosynthesis performance. [Copyright &y& Elsevier]

Abstract: Momoge wetland is an internationally important wetland not only because it is a habitat for many rare bird species but also because it is an internationally important stopover for some rare global migratory bird species. However the petroleum exploitation in wetland has brought about many environmental problems. One of the most severe problems is crude oil pollution, which has caused the dying-off Carex tato and imposes great threat on survival of rare birds. This work studied the factors that caused the dying off of Carex tato. The results showed that death of Carex tato was the result narcosis toxicity of alcohols, intermediate biodegradation products of crude oil, on the root tissue, and the fragmentization of cuticle of leaves by light components of crude oil volatized from soil surface. However, the mechanism involved was much more complex and three interactive factors including crude oil pollution of soil, long-term drought and poor permeability of soil were responsible for the dying-off of Carex tato grassland. The distribution of crude oil in soil profile was characterized with high concentrations at top silty layer and the layer below root zone and low or no crude oil at root zone layer. This distribution was relative to root system characteristics and rhizospheric biodegradation. In root zone, substantive oxygen could be transported to root zone through dense root system and well developed aerenchyma. The crude oil in root zone was easily biodegraded by aerobic rhizosphere microbes. However, some toxic intermediate products, such as some alcohols, was sealed in root zone due to poor permeability of the top soil layer and the deeper soil layer and they had lethal effects on root tissue. Above ground, low molecular components of crude oil in top soil layer was easily volatized into atmosphere during long-term drought. Some of the volatized components were adsorbed onto leaves. SEM analysis showed that these components destroyed the leaves by fragmentization of cuticle of leave. This study also shows that although wetland has natural attenuation of pollutants, natural attenuation of pollutants by natural wetland should not be overemphasized. This attenuation function may lose under some conditions such as long-term drought and poor soil texture. [Copyright &y& Elsevier]

Abstract: The binding parameters of root exudates for organic pollutants are important for understanding the mechanisms involved in phytoavailability and phytoremediation. However, quantitative information about organic pollutant binding to root exudates is lacking. Fluorescent properties and bifenthrin (insecticide) binding behavior of root exudates from maize (Zea mays L.) seedlings were investigated using excitation emission matrix fluorescence spectroscopy. The protein-like fluorophores in root exudates from (Z. mays L.) are strong complexing ligands for bifenthrin, with logK a in the range of 3.6–5.7. Two protein-like fluorescence peaks were identified in the EEM spectrum of root exudates and fluorescence of both peaks could be quenched by bifenthrin. The protein-like substances in root exudates had larger binding capacity for bifenthrin under acidic condition than under neutral and basic condition. The conditional stability constants were also higher in acidic solution than in the neutral or basic solution. Similarly, more fluorescence is accessible for bifenthrin at acidic pHs. More than one binding sites are needed in root exudates for binding one bifenthrin molecule. Enough attention should be paid to the effects of root exudates on adsorption, transport and fate of pesticides in environments. [Copyright &y& Elsevier]

Bacterial biofilms are structured cell communities embedded in a matrix of extracellular polymeric substances (EPS) and a ubiquitous growth form of bacteria in the environment. A wide range of interactions between biofilms and nanoparticles have been reported. In the present study, the influence of a mixed bacterial biofilm on retention of biogenic selenium nanoparticles (BioSeNPs) and consequences for immobilization of elemental mercury (Hg0) in a porous quartz sand system were examined. BioSeNPs were significantly retained in the presence of a biofilm through electrical double layer effects, hydrogen bonding, and hydrophobic, steric and bridging interactions. Moreover, enhanced surface roughness, pore clogging, sieving and entrapment effects mediated by the biofilm also contributed to deposition of BioSeNPs. Whereas, thiol groups associated with the biofilm is a little helpful for the capture of Hg0. It is proposed that oxidative complexation between Hg0 and thiol compounds or S containing organic matter in the biofilm may result in the formation of Hg2+-thiolate complexes and HgS during the binding of Hg0 with BioSeNPs. The formation of mercury selenide was also involved in Hg0 immobilization in the porous quartz sand system. Unlabelled Image • The coating of a microbial biofilm on quartz sand enhanced retention of BioSeNPs. • The biofilm facilitated Hg0 capture during Hg0 immobilization using BioSeNPs. • Oxidative complexation between Hg0 and thiol contributed to Hg0 removal. [ABSTRACT FROM AUTHOR]

Abstract Particulate organic matter (POM), composed of fine root fragments and other organic debris, is an important fraction of soil organic matter which can affect the fate of nanoparticles and influence their performance in nanoparticle-based remediation technologies due to aggregation. Effects of POM are not well studied compared with those of dissolved organic matter. In this research, POM was extracted from black soil by sieving, and heteroaggregation of selenium nanoparticles (SeNPs) with POM and consequences for elemental mercury (Hg0) immobilization were investigated. It was found that low concentrations of more negatively charged POM (0–60 mg L−1) inhibited homoaggregation as well as heteroaggregation with SeNPs which had a lower negative charge through electrostatic repulsion. In the presence of high concentrations of POM (80–100 mg L−1), SeNPs were more likely to attach to POM with more Hg0 remaining in the POM since a larger concentration of nanoparticles would lead to more effective collisions. However, Hg0 immobilization efficiency using SeNPs was not significantly influenced by the addition of POM. This work is helpful to further understand the nanoparticle's behaviour in the environment and consequences for toxic metal remediation. Graphical abstract Image 102269 Highlights • POM can affect the fate of SeNPs in the environment. • POM (0–60 mg L−1) inhibited its homoaggregation and heteroaggregation with SeNPs. • Hg0 immobilization efficiency by SeNPs was not inhibited in the presence of POM. [ABSTRACT FROM AUTHOR]

In natural environments, inorganic mercury (Hg2+) can be converted to the neurotoxin methylmercury (MeHg) mainly via the microbial Hg methylation process with anaerobic microorganisms. This process is a cellular reaction, and is influenced by cellular activity of Hg methylating microorganisms and by cellular Hg2+ uptake. In the present article, we review research progress of Hg bio-methylation, which includes: sites for Hg bio-methylation, Hg methylating microorganisms, mechanisms of Hg bio-methylation, and factors affecting Hg bio-methylation. Microbial Hg methylation occurs in a variety of sites such as the freshwater and marine environments as well as some unrecognized habitats. Sulfate-reducing bacteria using sulfate as their terminal electron acceptors are a group of the most extensively studied Hg methylators, followed by iron-reducing bacteria. The cellular uptake of Hg2+ before methylation may proceed via passive and/or active transport. Most Hg methylators have a pivotal gene pair encoding proteins required for methylation process. The cellular activity and bioavailable Hg2+ concentration for methylation can be determined primarily by many environmental factors i.e., temperature, redox potentials, pH value, existence of dissolved organic matter (DOM) and sulfur-containing organic compounds. A comprehensive understanding of methylation habitat, methylator, mechanism, and influencing factor is urgently required and will provide guidance for regulating net MeHg production within natural environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Selenium (Se) nanoparticles are often synthesized by anaerobes. However, anaerobic bacteria cannot be directly applied for bioremediation of contaminated top soil which is generally aerobic. In this study, a selenite-reducing bacterium, Citrobacter freundii Y9, demonstrated high selenite reducing power and produced elemental nano-selenium nanoparticles (nano-Se 0 ) under both aerobic and anaerobic conditions. The biogenic nano-Se 0 converted 45.8–57.1% and 39.1–48.6% of elemental mercury (Hg 0 ) in the contaminated soil to insoluble mercuric selenide (HgSe) under anaerobic and aerobic conditions, respectively. Addition of sodium dodecyl sulfonate enhanced Hg 0 remediation, probably owing to the release of intracellular nano-Se 0 from the bacterial cells for Hg fixation. The reaction product after remediation was identified as non-reactive HgSe that was formed by amalgamation of nano-Se 0 and Hg 0 . Biosynthesis of nano-Se 0 both aerobically and anaerobically therefore provides a versatile and cost-effective remediation approach for Hg 0 -contaminated surface and subsurface soils, where the redox potential often changes dramatically. [ABSTRACT FROM AUTHOR]

Plastic mulching has been extensively used for near 40 years in China because of the commonly recognized trade-offs between economic profit and adverse impacts. Whether the trade-offs is well kept after decades of mulching usage is poorly understood. In this study, microplastic (MP) pollution, soil physical properties, as well as the root traits and yields of cotton under plastic mulching for different years (up to 32 years) in northwest China were investigated. The results showed that average abundance of MPs in soil ranged from 28.00 to 1426.67 items kg−1 and increased with time whereas size of MPs decreased with time. With respect to soil physical properties, bulk density and penetration resistance significantly increased with mulching time while saturated hydraulic conductivity and mean weight diameter of water-stable aggregates in cotton fields decreased over time, indicating that long-term plastic mulching has irreversible adverse impact on soil function. The significantly increased soil penetration resistance and decreased hydraulic conductivity substantially restricted root growth and this finally led to remarkable reduction of seed cotton yield. It is urgent for the agricultural departments to take appropriate measures to mitigate the constantly increased negative trade-offs of plastic mulching in the arid areas. [Display omitted] • Trade-offs of plastic mulching between crop production and adverse impacts has been being broken. • Decades of plastic mulching caused significant MP pollution, soil degradation and reduced yield. • Plastic mulching worsen soil functions such as penetration resistance and hydraulic conductivity. • Deteriorated soil physical function restricted root growth and thus reduced cotton yield. [ABSTRACT FROM AUTHOR]

Acidithiobacillus ferrooxidansis a commonly used bacterial species for leaching gold ores to recover gold. The pH ofA. ferrooxidansbioleachates drastically changes from around 2.0 during bioleaching to about pH 8.0 as the cells are discharged together with the mine tailings containing high levels of Hg. It is not known how such a large pH shock would affect the properties of bacterial extracellular polymeric substances (EPS) and the transport of Hg in the mine tailings. In this study, the biochemical composition, molecular distribution, fluorescence properties and Hg(II) complexation by EPS ofA. ferrooxidanscultured at pH 2 and 8 were investigated. It was found that pH shock significantly altered the composition of EPS.A. ferrooxidansyielded more EPS under acid conditions than basic conditions. The acidic EPS contained more macromolecular proteins but less polysaccharide in comparison with the basic EPS. Phosphodiester functional groups in phospholipids and polysaccharides were found in the acidic EPS but not in the basic EPS. One tryptophan protein-like peak and one aromatic protein-like peak were identified in fluorescence spectra of the acidic EPS. Two aromatic protein-like peaks were identified from the fluorescence spectra of the basic EPS. The tryptophan protein-like substances in the acidic EPS interacted with Hg(II) and formed relatively stable complexes but with weak binding ability whereas the fluorescent aromatic protein-like substances in the acidic EPS did not bind Hg(II). However the aromatic protein-like substances in the basic EPS had a strong binding ability for Hg(II). The significant differences in composition and Hg complexation ability between EPS from acidic and basic environments indicate that a large pH shock during leaching of gold may exert a considerable impact on the behavior and fate of Hg in the mining areas. [ABSTRACT FROM AUTHOR]

• Methane and electron acceptors intersected in the groundwater table fluctuation (GTF) zone. • Anaerobic oxidation of methane (AOM) activity was notably high in the GTF zone. • Ca. Methanoperedens was highly abundant (85.4 % of Archaea) and active in the GTF zone. • Ca. Methanoperedens GTF50 oxidizes methane via the "reverse methanogenesis" pathway. Rice paddies are globally important sources of methane emissions and also active regions for methane consumption. However, the impact of fluctuating groundwater levels on methane cycling has received limited attention. In this study, we delved into the activity and microbial mechanisms underlying anaerobic oxidation of methane (AOM) in paddy fields. A comprehensive approach was employed, including 13C stable isotope assays, inhibition experiments, real-time quantitative reverse transcription PCR, metagenomic sequencing, and binning technology. Geochemical profiles revealed the abundant coexistence of both methane and electron acceptors in the groundwater table fluctuation (GTF) zone, at a depth of 40–60 cm. Notably, the GTF zone exhibited the highest rate of AOM, potentially linked to the reduction of iron oxides and nitrate. Within this zone, Candidatus Methanoperedens (belonging to the ANME-2d group) dominated the Archaea population, accounting for a remarkable 85.4 %. Furthermore, our results from inhibition experiments, RT-qPCR, and metagenome-assembled genome (MAG) analysis highlighted the active role of Ca. Methanoperedens GTF50 in the GTF zone. This microorganism could independently mediate AOM process through the intriguing "reverse methanogenesis" pathway. Considering the similarity in geochemical conditions across different paddy fields, it is likely that Ca. Methanoperedens-mediated AOM is prevalent in the GTF zones. [Display omitted] [ABSTRACT FROM AUTHOR]

Light-stabilizing additives may contribute to the overall pollution load of microplastics (MPs) and potentially enter the food chain, severely threatening aquatic life and human health. This study investigated the variation between polystyrene (PS) MPs and phthalocyanine blue (CuPC)-containing MPs before and after photoaging, as well as their effects on Microcystis aeruginosa. The presence of PS-MPs increased cell mortality, antioxidant enzyme activity, and the variation in extracellular components, while the presence of CuPC exacerbated these variations. CuPC-containing MPs caused different increasing trends in superoxide dismutase and malondialdehyde activities due to electron transfer across the membrane. Transcriptomic analysis revealed that the MPs and CuPC affected various cellular processes, with the greatest impact being on cell membranes. Compared with MPs, CuPC negatively affected ribosome and polysaccharide formation. These findings provide insights into the molecular mechanisms underlying the cellular response to MPs and their associated light-stabilizer pollution and imply the necessity for mitigating the pollution of both MPs and light-stabilizers. [Display omitted] • Systematic reports on the Light stabilizer release with Microplastics aging. • Variations caused by Mps with light stabilizer is more serious than that of Mps. • CuPC additive is prior to bring sereious effects on ribosomes and polysaccharides. [ABSTRACT FROM AUTHOR]

Silver nanowire (AgNW) networks with high transparency and conductivity are crucial to developing transparent conductive films (TCFs) for flexible optoelectronic devices. However, AgNW-based TCFs still suffer from the high contact resistance of AgNW junctions with both the in-plane and out-of-plane charge transport barrier. Herein, we report a rapid and green electrochemical redox strategy to in-situ weld AgNW networks for the enhanced conductivity and mechanical durability of TCFs with constant transparency. The welded TCFs show a marked decrease of the sheet resistance (reduced to 45.5% of initial values on average) with high transmittance of 97.02% at 550 nm (deducting the background of substrates). The electrochemical welding treatment enables the removal of the residual polyvinylpyrrolidone layer and the in-situ formation of Ag solder in the oxidation and reduction processes, respectively. Furthermore, local conductivity studies confirm the improvement of both the in-plane and the out-of-plane charge transport by conductive atomic force microscopy. This proposed electrochemical redox method provides new insights on the welding of AgNW-based TCFs with high transparency and low resistance for the development of next-generation flexible optoelectronic devices. Furthermore, such conductive films based on the interconnected AgNW networks can be acted as an ideal supporter to construct heterogeneous structures with other functional materials for wide applications in photocatalysis and electrocatalysis. [ABSTRACT FROM AUTHOR]