Effects of different oxidants on the behaviour of microplastic hetero-aggregates.

Microplastic hetero-aggregates are stable forms of microplastics in the aqueous environment. However, when disinfecting water containing microplastic hetero-aggregates, the response of them in water to different oxidizing agents and the effect on water quality have not been reported. Our results showed that Ca(ClO)2, K2S2O8, and sodium percarbonate (SPC) treatment could lead to the disaggregation of microplastic hetero-aggregates as well as a rise in cell membrane permeability, which caused a large amount of organic matter to be released. When the amount of oxidant dosing is insufficient, the oxidant cannot completely degrade the released organic matter, resulting in DOC, DTN, DTP and other indicators being higher than before oxidation, thus causing secondary pollution of the water body. In comparison, K2FeO4 can purify the water body stably without destroying the microplastic hetero-aggregates, but it only weakly inhibits the toxic cyanobacteria Microcystis and Pseudanabaena, which may cause cyanobacterial bloom as well as algal toxin and odorant contamination in practical application. Compared with the other oxidizers, K2S2O8 provides better inhibition of toxic cyanobacteria and has better ecological safety. Therefore, when treating microplastic-containing water bodies, we should consider both water purification and ecological safety, and select appropriate oxidant types and dosages to optimize the water treatment.

Simultaneous immobilization of V and Cr availability, speciation in contaminated soil and accumulation in ryegrass by using Fe-modified pyrolysis char.

In this study, municipal waste pyrolytic char (PEWC) was prepared by pyrolysis from municipal solid waste extracted in landfills, and Fe-based modified pyrolytic char (Fe-PEWC) was prepared by modification. Focusing on the evaluation of the stabilization capacity of Fe-PEWC for vanadium (V) and chromium (Cr) in soils, the effects of PEWC addition on soil properties, bioavailability and morphological distribution of V and Cr, ryegrass growth, and V and Cr accumulation were thoroughly investigated. The results of pot experiment showed that the application of PEWC and Fe-PEWC significantly (P < 0.05) improved soil properties (such as pH, EC, total nitrogen, available phosphorus, available potassium, and organic matter). After 42 days of cultivation, Fe-PEWC has a better fixation effect on heavy metals, and the bioavailable V and Cr of 3% Fe-PEWC decreased by 14.96% and 19.48%, respectively. The exchangeable state and reducible state decreased, while the oxidizable state and residual state increased to varying degrees. The Fe-PEWC can effectively reduce the accumulation of V and Cr in ryegrass by 71.25% and 76.43%, respectively, thereby reducing their toxicity to plants. In summary, modified pyrolytic char can effectively solidify heavy metals in soil, improve soil ecology and reduce the toxicity to plants. The use of excavated waste as a raw material for the preparation of soil heavy metal curing agent has the significance of resource recycling, low price, and practical application.

Correlation analysis and predicting modeling of pyrolysis gas based on landfill excavated waste pyrolysis characteristics.

The contribution of excavated waste to waste management is multifaceted, including minimization, non-hazardous disposal, access to useable land resources, improved waste management techniques and public environmental awareness, consistent with recent circular economy initiatives. Pyrolysis can be converted into tar, pyrolysis gas and char with recyclable utilization, enriching the application of pyrolysis technology in the field of excavation waste. In this study, the pyrolysis system includes horizontal tube furnace, gas collection device and Micro GC. The excavated waste was pyrolyzed at a temperature of 500∼900 °C with a heating rate of 10 °C/min. Pyrolysis gases include H2, CO, CO2, CH4, C2H4, C2H6 and C3H8. Pyrolysis was divided into four stages, the main decomposition range is 230∼500 °C, with a weight loss rate of 68.49% and a co-pyrolysis behavior. As the temperature increases, the tar and char decreased and the gas production increased significantly, and the pyrolysis gas reached 47.02% at 900 °C. According to Pearson correlation coefficient analysis, the generation of H2 and CO is positively correlated with temperature. Therefore, the target products can be influenced by changing the parameters, when considering the practical utilization of the excavated waste pyrolysis products. On this basis, the prediction models were built by polynomial fitting method. This model can reduce the experimental exploration cycle, reduce the cost, and accurately predict the pyrolysis gas, which has practical guidance for the application of pyrolysis industry, and provides a theoretical basis for the resource recycling and energy recovery of landfill.

Functional Electrospun Nanofibrous Hybrid Materials for Colorimetric Sensors: A Review.

Electrospun nanofibrous hybrid materials have several advantageous characteristics, including easy preparation, high porosity, and a large specific surface area. Meanwhile, they can be more suitable for colorimetric detection in environmental and food areas than organic materials due to the advantages of inorganic nanomaterials, i.e., stability, low toxicity, and durability. In addition to being able to immobilize nanomaterials to avoid particle aggregation, electrospinning hybrid materials also have the advantages of high specific surface area and high porosity, which is beneficial for constructing colorimetric sensors. This review mainly summarizes the fabrication methods of electrospun nanofibrous hybrid materials and the application of electrospun nanofibrous hybrid material based colorimetric sensors. First, the preparation strategies of electrospun nanofibrous hybrid materials were discussed. Then, the applications of the obtained electrospun nanofibrous hybrid materials in the colorimetric sensors for environmental molecules in the gas and liquid phase were further investigated. Finally, this review looks forward to the development prospects and challenges of electrospun hybrid materials in practical applications of colorimetric sensors in order to support the application of colorimetric sensors in practical detection.

Coordination-Polymer-Derived Cu-CoO/C Nanocomposite Used in Fenton-like Reaction to Achieve Efficient Degradation of Organic Compounds.

In this paper, carbon-matrix-supported copper (Cu) and cobaltous oxide (CoO) nanoparticles were obtained by using coordination polymers (CPs) as a precursor. The aqueous solutions of copper methacrylate (CuMA) and cobalt methacrylate (CoMA) were preferentially prepared, which were then mixed with anhydrous ethanol to fabricate dual metal ion coordination polymers (CuMA/CoMA). After calcination under an argon atmosphere, the Cu-CoO/C nanocomposite was obtained. Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that the material has banded morphology, and the dual functional nanoparticles were highly dispersed in the carbon matrix. The prepared material was used in a heterogeneous Fenton-like reaction, with the aim of replacing traditional ferric catalysts to solve pH constraints and the mass production of ferric slime. The obtained nanocomposite showed excellent catalytic performance on the degradation of methylene blue (MB) at near-neutral conditions; the discoloration efficiency is about 98.5% within 50 min in the presence of 0.15 mmol/mL H2O2 and 0.5 mg/mL catalyst. And good reusability was verified via eight cycles. The plausible pathway for MB discoloration and the possible catalytic mechanism was also proposed.

Occurrence and transport of novel and legacy poly- and perfluoroalkyl substances in coastal rivers along the Laizhou Bay, northern China.

The pollution profiles of 25 legacy and emerging poly- and perfluoroalkyl substances (PFASs) in the estuaries along the Laizhou Bay, northern China were investigated to better understand the new structure of PFASs under international regulations and to estimate the mass loadings of PFASs in coastal rivers. About 39.87 kg/d of PFASs were discharged into the Laizhou Bay by the Xiaoqing, Mi and Zhimai Rivers. Total PFAS concentrations in the Xiaoqing River decreased notably in recent years, but were still greater than the levels in 2011. Contribution of replacement substances exhibited an increasing trend in recent years. However, the long-chain chemicals were still the larger contributors of PFASs. Perfluoromethoxypropionic acid (PFMPA) was first detected with high concentrations ranging from 165.3 to 586.3 ng/L in the Xiaoqing River. The results of this study provided baseline data for ecological risk assessment, environmental management and corresponding development of pollution treatment technology.

Responses of Chlorella vulgaris to the native bacteria in real wastewater: Improvement in wastewater treatment and lipid production.

Alga-bacterium interaction can improve wastewater treatment efficiency. To unravel the mystery of the interaction between microalgae and bacteria in wastewater, mono-cultures and co-cultures of Chlorella vulgaris and native bacteria in pretreated biochemical wastewater from landfill leachate were investigated. The results showed that the microalgae selected dominant commensal bacteria, creating a further reduction in species richness for the co-culture, which in turn aids in the dominant commensal bacteria's survival, thereby enhancing algal and bacterial metabolic activity. Strikingly, the lipid productivity of Chlorella in co-culture - namely 41.5 mg/L·d - was 1.4 times higher than in algal monoculture. Additionally, pollutant removal was enhanced in co-cultures, attributed to the bacterial community associated with pollutants' degradation. Furthermore, this study provides an important advance towards observations on the migration and transformation pathways of nutrients and metals, and bridges the gap in algal-bacterial synergistic mechanisms in real wastewater, laying the theoretical foundation for improving wastewater treatment.

One-pot preparation of supramolecularly functionalized silver nanoparticles for surface plasmon resonance based dual-modal sensing of phytotoxic polychlorinated biphenyl.

Polychlorinated biphenyls (PCBs), as a member of persistent organic pollutants (POPs), have posed a risk to humans and the environment until today. The monitoring of phytotoxic PCB which is toxic to plants, is especially important for ecological early warning and pollution management. In this work, ß-cyclodextrin modified silver nanoparticles are prepared in a one-pot method, integrating the synthesis and surface modification in one step. The nanoparticles can supramolecularly immobilize 2,4,4'-trichlorobiphenyl (PCB 28) on their surface and construct a surface plasmon resonance-based nanosensor. Surface plasmon-resonance light scattering and surface-enhanced Raman scattering sensing of PCB 28 are realized using the nanosensor. The dual-modal sensing shows excellent performance for the potential practical monitoring of phytotoxic POPs in the plant and its growing environment.

Recent advances in the unlined cast iron pipe scale characteristics, cleaning techniques and harmless disposal methods: An overview.

Drinking water discoloration and its potential health risks (e.g., heavy metals, pathogens, carcinogenic organics) have aroused wide public concerns around the world, and the characteristics and corresponding cleaning techniques of pipe scales are one of the most important research fields closely related to people's lives and health. This Overview Article summarizes the latest research achievements about the new insights into the unlined cast iron pipe corrosion scale characteristics as well as the advanced cleaning techniques applied in drinking water distribution systems. The typical pollutants such as heavy metal ions, pathogens and disinfection by-products (DBPs) in pipe scales and the main cleaning techniques including unidirectional flushing (UDF), air scouring, ice pigging and guided ultrasonic waves (GUW) are categorized and elaborated. In the final part, the current challenges and future opportunities are also further discussed from the viewpoint of evolution process of pipe scales as well as the widespread application of advanced cleaning techniques. Moreover, the possible technical route for the innocent treatment and resource utilization of pipe scale waste is also proposed. It is anticipated that this review will attract more attention toward the in-depth study of pipe scales and their cleaning techniques to enjoy cleaner and healthier drinking water for people.

Molecular dynamics study of low molecular weight gel forming salt-triggered dipeptide.

Molecular dynamics simulation method was used to study the aggregation of Na and Ca salts in different concentrations of Naphthalene-dipeptide (2NapFF) solutions. The results show that high-valence Ca2+ triggers the formation of a gel at a certain dipeptide concentration, and the low-valence Na+ system follows the aggregation law of general surfactants. The results also show that hydrophobic and electrostatic forces are the main driving forces for the formation of dipeptide aggregates, and that hydrogen bonds do not play a major role in the formation of dipeptide solution aggregates. Hydrophobic and electrostatic effects are the main driving forces for the formation of gels in dipeptide solutions triggered by Ca2+. Electrostatic attraction drives Ca2+ to form a weak coordination with four oxygen atoms on two carboxyl groups, which causes the dipeptide molecules to form a gel with a branched network structure.

Analysis of the characteristics and causations of surface deformation based on TS-InSAR: a case study of Jimo district, China.

Due to the rapid economic development and urban construction and the high exploitation rate of groundwater and geothermal resource, Jimo district existed a potential threat of surface deformation. To clarify the characteristics and causations of surface deformation, this study firstly used SBAS-InSAR (Small Baseline Subset-Interferometric Synthetic Aperture Radar) technology to analyze the surface defor-mation distribution in the whole research area. Then, three areas with different surface cover conditions were selected to analyze the causations of surface deformation. Lastly, taking central urban area as the key research area, surface deformation causations were analyzed in detail based on PS-InSAR (Persistent Scatter-Interferometric Synthetic Aperture Radar) technology. The study found that, in coastal mollisol area, farmland area, and hot spring area, the maximum subsidence velocity reached up to 46.8 mm/a, 24 mm/a, and 19.1 mm/a, respectively. The factors, including surface loading, precipitation, and the groundwater level, were the causations of surface deformation in different research areas. The trend of the surface deformation curve was consistent with that of the groundwater level curve in the central urban area, but the response time of surface deformation lagged behind the change of groundwater level by approximately 4 months.

Enhanced power generation, organics removal and water desalination in a microbial desalination cell (MDC) with flow electrodes.

This study introduced a flow electrode microbial desalination cell (FE-MDC), which used activated carbon (AC) particles and carbon nanotubes (CNTs) as the electrode to promote electron harvesting. The recovered electricity energy (0.371 KWh/m3) and columbic efficiency (66.7 %) of the FE-MDC were over 2 times higher than those of the conventional MDC without the flow electrode. Consequently, the salt and COD removal efficiencies were enhanced to 77.8 % and 91.2 %, respectively. Electrochemical analysis implied that the charge transfer resistance of the system was reduced by the flow electrode. Electron accumulation and charging-discharging experiments proved that the flow electrode could accumulate electrons and transfer the electrons to the fixed anode. Bacterial community analysis indicated that the bacterial activity was improved by the flow electrode. The content of the exoelectrogen Pseudomonas increased from 5.0 % to 14.7 %, and Hydrogenophaga improved from 1.4 % to 5.9 %. Finally, a continuous operation mode of the FE-MDC was established, and the flow electrode slurry was returned to the anodic chamber for recirculated utilization. The voltage output, COD removal, and salt removal during the operation mode reached 610 mV, 78.8 %, and 76.1 %, respectively. This study proved that the flow electrode is a promising way to promote the practical application of MDC technology.

Secondary pollution of microplastic hetero-aggregates after chlorination: Released contaminants rarely re-adsorbed by the second-formed hetero-aggregates.

In urban waters, microplastics (MPs) usually form hetero-aggregates through adsorption of organics and microbes. However, the effects of hetero-aggregates on water quality are rarely reported. In this study we found that the hetero-aggregates, which accumulated contaminants, were like a "time bomb". Chlorination was able to trigger the "time bomb" through destruction of hetero-aggregates, lysis of microbial cells and elevation of the concentration of low-molecular-mass organics. Thereupon previously adhered organics desorbed from MPs, intracellular metabolites were released from lysed cells, and re-formation of hetero-aggregates was limited. This process rapidly increased the concentration of organics but prevented the re-adsorption of organics, which leads to secondary pollution. Thus, to alleviate the risks of secondary pollution caused by hetero-aggregates, the choice of oxidant species and dose should be optimized based on the characteristics of existent hetero-aggregates when purifying urban waters containing MPs.

Insights into olation reaction-driven coagulation and adsorption: A pathway for exploiting the surface properties of biochar.

In this study, characterization of biochar for the efficient removal of cadmium was investigated. Biochar has a specific distribution of functional groups on its surface and has a natural electronegativity. Using carbonate as an olation reagent, the biochar coagulates with the olation reaction products. The maximum removal capacity reached 430.4 mg/g at pH = 4 (Langmuir Fit). Carbonate hydrolyzed on the surface of biochar, Cd2+ in solution undergoes olation with OH- and forms specially structured nanochains that are positively charged on the surface. The biochar with electronegativity on the surface coagulates with the cadmium hydroxide nanochains, and the cadmium-containing colloid formed by electrostatic attraction settles rapidly and removed. The biochar's re-flocculation performance was consistent, and the loadings could be changed to effectively remove cadmium while keeping the pH neutral at equilibrium.

The synergistic mechanism of ß-lactam antibiotic removal between ammonia-oxidizing microorganisms and heterotrophs.

Nitrifying system is an effective strategy to remove numerous antibiotics, however, the contribution of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and heterotrophs for antibiotic removal are still unclear. In this study, the mechanism of ß-lactam antibiotic (cefalexin, CFX) removal was studied in a nitrifying sludge system. Results showed that CFX was synergistically removed by AOB (Nitrosomonas, played a major role) and AOA (Candidatus_Nitrososphaera) through ammonia monooxygenase-mediated co-metabolism, and by heterotrophs (Pseudofulvimonas, Hydrogenophaga, RB41, Thauera, UTCFX1, Plasticicumulans, Phaeodactylibacter) through antibiotic resistance genes (ARGs)-encoded ß-lactamases-mediated hydrolysis. Regardless of increased archaeal and heterotrophic CFX removal with the upregulation of amoA in AOA and ARGs, the system exhibited poorer CFX removal performance at 10 mg/L, mainly due to the inhibition of AOB. This study provides new reference for the important roles of heterotrophs and ARGs, opening the possibilities for the application of ARGs in antibiotic biodegradation.

Gold nanocrystals: optical properties, fine-tuning of the shape, and biomedical applications.

Noble metal nanomaterials with special physical and chemical properties have attracted considerable attention in the past decades. In particular, Au nanocrystals (NCs), which possess high chemical inertness and unique surface plasmon resonance (SPR), have attracted extensive research interest. In this study, we review the properties and preparation of Au NCs with different morphologies as well as their important applications in biological detection. The preparation of Au NCs with different shapes by many methods such as seed-mediated growth method, seedless synthesis, polyol process, ultrasonic method, and hydrothermal treatment has already been introduced. In the seed-mediated growth method, the influence factors in determining the final shape of Au NCs are discussed. Au NCs, which show significant size-dependent color differences are proposed for preparing biological probes to detect biomacromolecules such as DNA and protein, while probe conjugate molecules serves as unique coupling agents with a target. Particularly, Au nanorods (NRs) have some unique advantages in the application of biological probes and photothermal cancer therapy compared to Au nanoparticles (NPs).

Eco-Environmental Effect Evaluation of Tamarix chinesis Forest on Coastal Saline-Alkali Land Based on RSEI Model.

Taking representative Tamarix chinensis forest in the national-level special protection zone for ocean ecology of Changyi city in Shandong province of China as the objective, this research studied how to use remote sensing technology to evaluate natural eco-environment and analyze spatiotemporal variation. In the process of constructing the index system of ecological environment effect evaluation based on RSEI (Remote Sensing Ecological Index) model, AOD (Aerosol Optical Depth), Salinity, Greenness, Wetness, Heat and Dryness, which can represent the ecological environment of the reserve, were selected as the corresponding indexes. In order to accurately obtain the value of the RSEI of the study area and to retain the information of the original indexes to the greatest extent, the SPCA (spatial principal components analysis) method was applied in this research. Finally, the RSEI was applied to evaluate the ecological and environmental effects and to analyze the spatial characteristics and spatiotemporal evolution of the study area. The results not only provide scientific evidence and technical guidance for the protection, transformation and management of the Tamarix chinensis forest in the protection zone but also push the development of the universal model of the ecological environment quality with a remote sensing evaluation index system at a regional scale.

Effects of Physicochemical Parameters on Struvite Crystallization Based on Kinetics.

The precipitation of struvite (MgNH4PO4·6H2O) is considered to be a promising method for the recovery of phosphate from wastewater. In this review, the kinetic models, which are commonly used to explain the process of struvite crystallization, are described. The mixed-suspension mixed-product removal (MSMPR) model is based on the population balance equation (the size-dependent growth model and the size-independent growth model). Thereafter, the first-order kinetic fitting model that aligned with concentration changes in the substrate is summarized. Finally, the several physical and chemical factors that affected the efficiency of struvite crystallization are determined. The supersaturation ratio, which is seen as the driving force of struvite crystallization, is the main factor that influences crystallization; however, it cannot be used in practical applications of engineering because it is indirectly associated with the following factors: pH, the molar ratio of Mg:N:P, and the interference of foreign impurities. In this study, we present conclusions that should be used to guide further research studies, and encourage the engineering practice of wastewater treatment with struvite precipitation.

A Kinetic Model for Anaerobic Digestion and Biogas Production of Plant Biomass under High Salinity.

The aim of this study is to evaluate the anaerobic digestion and biogas production of plant biomass under high salinity by adopting a theoretical and technical approach for saline plant-biomass treatment. Two completely mixed lab-scale mesophilic reactors were operated for 480 days. In one of them, NaCl was added and the sodium ion concentration was maintained at 35.8 g-Na+·L-1, and the organic loading rate was 0.58-COD·L-1·d-1-1.5 g-COD·L-1·d-1; the other added Na2SO4-NaHCO3 and kept the sodium ion concentration at 27.6 g-Na+·L-1 and the organic loading rate at 0.2 g-COD·L-1·d-1-0.8 g-COD·L-1·d-1. The conversion efficiencies of the two systems (COD to methane) were 66% and 54%, respectively. Based on the sulfate-reduction reaction and the existing anaerobic digestion model, a kinetic model comprising 12 types of soluble substrates and 16 types of anaerobic microorganisms was developed. The model was used to simulate the process performance of a continuous anaerobic bioreactor with a mixed liquor suspended solids (MLSS) concentration of 10 g·L-1-40 g·L-1. The results showed that the NaCl system could receive the influent up to a loading rate of 0.16 kg-COD/kg-MLSS·d-1 without significant degradation of the methane conversion at 66%, while the Na2SO4-NaHCO3 system could receive more than 2 kg-COD·kg-1-MLSS·d-1, where 54% of the fed chemical oxygen demand (COD) was converted into methane and another 12% was observed to be sulfide.