Doped Cu0 and sulfidation induced transition from R-O• to •OH in peracetic acid activation by sulfidated nano zero-valent iron-copper.

Peracetic acid (PAA) has emerged as a new effective oxidant for various contaminants degradation through advanced oxidation process (AOP). In this study, sulfidated nano zero-valent iron-copper (S-nZVIC) with low Cu doping and sulfidation was synthesized for PAA activation, resulting in more efficient degradation of sulfamethoxazole (SMX, 20 µM) and other contaminants using a low dose of catalyst (0.05 g/L) and oxidant (100 µM). The characterization results suggested that S-nZVIC presented a more uniform size and distribution with fewer metal oxides, as the agglomeration and oxidation were inhibited. More significantly, doped Cu0 and sulfidation significantly enhanced the generation and contribution of •OH but decreased that of R-O• in S-nZVIC/PAA/SMX system compared with that of nZVIC and S-nZVI, accounting for the relatively high degradation efficiency of 97.7% in S-nZVIC/PAA/SMX system compared with 85.7% and 78.9% in nZVIC/PAA/SMX and S-nZVI/PAA/SMX system, respectively. The mechanisms underlying these changes were that (i) doped Cu° could promote the regeneration of Fe(Ⅱ) for strengthened PAA activation through mediating Fe(Ⅱ)/Fe(Ⅲ) cycle by Cu(Ⅰ)/Cu(Ⅱ) cycle; (ii) S species might consume part of R-O•, resulting in a decreased contribution of R-O• in SMX degradation; (iii) sulfidation increased the electrical conductivity, thus facilitating the electron transfer from S-nZVIC to PAA. Consequently, the dominant reactive oxygen species transited from R-O• to •OH to degrade SMX more efficiently. The degradation pathways, intermediate products and toxicity were further analyzed through density functional theory (DFT) calculations, liquid chromatography-mass spectrometry (LC-MS) and T.E.S.T software analysis, which proved the environmental friendliness of this process. In addition, S-nZVIC exhibited high stability, recyclability and degradation efficiency over a wide pH range (3.0∼9.0). This work provides a new insight into the rational design and modification of nano zero-valent metals for efficient wastewater treatment through adjusting the dominant reactive oxygen species (ROS) into the more active free radicals.

Simultaneous elimination of antibiotic-resistant bacteria and antibiotic resistance genes by different Fe-N co-doped biochars activating peroxymonosulfate: The key role of pyridine-N and Fe-N sites.

The coexistence of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in the environment poses a potential threat to public health. In our study, we have developed a novel advanced oxidation process for simultaneously removing ARGs and ARB by two types of iron and nitrogen-doped biochar derived from rice straw (FeN-RBC) and sludge (FeN-SBC). All viable ARB (approximately 108 CFU mL-1) was inactivated in the FeN-RBC/ peroxymonosulfate (PMS) system within 40 min and did not regrow after 48 h even in real water samples. Flow cytometry identified 96.7 % of dead cells in the FeN-RBC/PMS system, which verified the complete inactivation of ARB. Thorough disinfection of ARB was associated with the disruption of cell membranes and intracellular enzymes related to the antioxidant system. Whereas live bacteria (approximately 200 CFU mL-1) remained after FeN-SBC/PMS treatment. Intracellular and extracellular ARGs (tetA and tetB) were efficiently degraded in the FeN-RBC/PMS system. The production of active species, primarily •OH, SO4•- and Fe (IV), as well as electron transfer, were essential to the effective disinfection of FeN-RBC/PMS. In comparison with FeN-SBC, the better catalytic performance of FeN-RBC was mainly ascribed to its higher amount of pyridine-N and Fe0, and more reactive active sites (such as CO group and Fe-N sites). Density functional theory calculations indicated the greater adsorption energy and Bader charge, more stable Fe-O bond, more easily broken OO bond in FeN-RBC/PMS, which demonstrated the stronger electron transfer capacity between FeN-RBC and PMS. To encapsulate, our study provided an efficient and dependable method for the simultaneous elimination of ARGs and ARB in water.

Transport and retention of ciprofloxacin with presence of multi-walled carbon nanotubes in the saturated porous media: impacts of ionic strength and cation types.

The environmental fate and risks of ciprofloxacin (CIP) in the subsurface have raised intensive concerns. Herein, the transport behaviors of CIP in both saturated quartz sand and sand/multi-walled carbon nanotubes (MWCNTs) mixtures under different solution ionic strength of the solution and coexisting cation types were investigated. Batch adsorption experiments highlighted growing adsorptive capacity for CIP with the increasing content of MWCNTs in the MWCNTs-quartz sand mixtures (from 0.5% to 1.5%, w/w). Breakthrough curves (BTCs) of CIP in the MWCNTs-quartz sand mixtures were well fitted by the two-site chemical nonequilibrium model (R2 > 0.833). The estimated retardation factors for CIP increased from 9.68 to 282 with growing content of MWCNTs in the sand column, suggesting the presence of MWCNTs significantly inhibited the transport of CIP in saturated porous media. Moreover, the values of retardation factors are negatively correlated with the ionic strength and higher ionic strength could facilitate the transport of CIP in the saturated porous media. Compared with monovalent cations (Na+), the presence of divalent cations (Ca2+) significantly facilitated the transport of CIP in the columns due to the complexation between CIP and Ca2+ as well as deposition of MWCNTs aggregates on the sand surface. Results regarding CIP retention in columns indicated that MWCNTs could enhance the accumulation of CIP in the layers close to the influent of sand columns, while they could hinder upward transport of CIP to the effluent. This study improves our understanding for transport behaviors and environmental risk assessments of CIP in the saturated porous media with MWCNTs.

Molecular insights into linkages among free-floating macrophyte-derived organic matter, the fate of antibiotic residues, and antibiotic resistance genes.

Macrophyte rhizospheric dissolved organic matter (ROM) served as widespread abiotic components in aquatic ecosystems, and its effects on antibiotic residues and antibiotic resistance genes (ARGs) could not be ignored. However, specific influencing mechanisms for ROM on the fate of antibiotic residues and expression of ARGs still remained unclear. Herein, laboratory hydroponic experiments for water lettuce (Pistia stratiotes) were carried out to explore mutual interactions among ROM, sulfamethoxazole (SMX), bacterial community, and ARGs expression. Results showed ROM directly affect SMX concentrations through the binding process, while CO and N-H groups were main binding sites for ROM. Dynamic changes of ROM molecular composition diversified the DOM pool due to microbe-mediated oxidoreduction, with enrichment of heteroatoms (N, S, P) and decreased aromaticity. Microbial community analysis showed SMX pressure significantly stimulated the succession of bacterial structure in both bulk water and rhizospheric biofilms. Furthermore, network analysis further confirmed ROM bio-labile compositions as energy sources and electron shuttles directly influenced microbial structure, thereby facilitating proliferation of antibiotic resistant bacteria (Methylotenera, Sphingobium, Az spirillum) and ARGs (sul1, sul2, intl1). This investigation will provide scientific supports for the control of antibiotic residues and corresponding ARGs in aquatic ecosystems.

Microplastics/nanoplastics in porous media: Key factors controlling their transport and retention behaviors.

Till now, microplastics/nano-plastics(M/NPs) have received a lot of attention as emerging contaminant. As a typical but complex porous medium, soil is not only a large reservoir of M/NPs but also a gateway for M/NPs to enter groundwater. Therefore, the review of the factors controlling the transport behavior of M/NPs in porous media can provide important guidance for the risk assessment of M/NPs in soil and groundwater. In this study, the key factors controlling the transport behavior of M/NPs in porous media are systematically divided into three groups: (1) nature of M/NPs affecting M/NPs transport in porous media, (2) nature of flow affecting M/NPs transport in porous media, (3) nature of porous media affecting M/NPs transport. In each group, the specific control factors for M/NPs transport in porous media are discussed in detail. In addition to the above factors, some substances (colloids or pollutants) present in natural porous media (such as soil or sediments) will co-transport with M/NPs and affect its mobility. According to the different properties of co-transported substances, the mechanism of promoting or inhibiting the migration behavior of M/NPs in porous media was discussed. Finally, the limitations and future research directions of M/NPs transport in porous media are pointed out. This review can provide a useful reference for predicting the transport of M/NPs in natural porous media.

Antibiotic resistance in soil-plant systems: A review of the source, dissemination, influence factors, and potential exposure risks.

As an emerging environmental contaminant, the widespread of antibiotic resistance has caused a series of environmental issues and human health concerns. A load of antibiotic residues induced by agricultural practices have exerted selective pressure to bacterial communities in the soil-plant system, which facilitated the occurrence and dissemination of antibiotic resistance genes (ARGs) through horizontal gene transfer. As a result, the enrichment of ARGs within crops at harvest under the influence of food ingestion could lead to critical concerns of public health. In this review, the prevalence and dissemination of antibiotic resistance in the soil-plant system are highlighted. Moreover, different underlying mechanisms and detection methods for ARGs transfer between the soil environment and plant compartments are summarized and discussed. On the other hand, a wide range of influencing factors for the transfer and distribution of antibiotic resistance within the soil-plant system are also presented and discussed. In response to exposure of antibiotic residues and resistomes, corresponding hazard identification assessments have been summarized, which could provide beneficial guides of the toxicological tolerance for the general population. Finally, further research priorities for detection and management ARGs spread are also suggested.

Effect of Phanerochaete chrysosporium inoculation on manganese passivation and microbial community succession during electrical manganese residue composting.

Electrolytic manganese residue poses potentially threats to the environment and therefore needs eco-friendly treatment. Composting has been reported to effectively passivate heavy metals and alleviate their ecotoxicity. Observation of the Mn concentration during composting indicated that the mobility of Mn was significantly reduced, with the easily extraction fraction (acid extractable and easily reduction fraction) of Mn in the control pile (pile 1 without Phanerochaete chrysosporium inoculation) and treat pile (pile 2 with Phanerochaete chrysosporium inoculation) decreasing by 17% and 29%, respectively. The inoculation of Phanerochaete chrysosporium prompted the passivation of manganese, prolonged the thermophilic period, and enriched the microbial community structure, which was attributed to the rapid growth and reproduction of thermophilic bacteria. Moreover, Phanerochaete chrysosporium inoculation promoted the effect of pH on the stabilization of Mn, but the opposite contribution of organic matter. This study would provide a new perspective for remediating EMR contaminated soil via composting.

Nitrogen-doped nanocarbon derived from candle soot for persulfate activation on sulfamethoxazole removal: Performance and mechanism.

Recently, carbon materials have attracted much attention in activating persulfate (PS) for the removal of organic pollutants. Seeking a greener, lower-cost, and higher-performance carbon material has become an important aspect of research. In this study, candle soot was innovatively used as a nanocarbon material, and its performance for PS activation was improved by simple ammonium ferric citrate modification. The optimal catalytic performance was achieved using 0.15 g/L modified candle soot (AS) and only 0.1 mM PS, with sulfamethoxazole (SMX) removal efficiency up to 95.5% within 120 min. Quenching tests, together with electron paramagnetic resonance measurements, showed that O2- and 1O2 were the main reactive species for SMX degradation. Meanwhile, electron transfer pathway was also occurred. Various characterization results showed that graphitic N and carbonyl group were the main active sites for PS activation. Moreover, AS/PS system exhibited high catalytic activity and stability for SMX degradation over a wide initial pH range (3∼9), or even in the presence of Cl-, H2PO4- and NO3-. This work not only taps the potential of candle soot as an environmental functional material, but also showcases the roadmap for the discovery, design, and resource utilization of other waste carbon materials in wastewater treatment.

Microplastics removal and characteristics of a typical multi-combination and multi-stage constructed wetlands wastewater treatment plant in Changsha, China.

Wastewater treatment plants (WWTPs) are an important source of microplastics (MPs) entering the aquatic environment. As environmental awareness increases, WWTPs are gradually using constructed wetlands (CWs) in the depth treatment stage. There were few studies related to MPs removal efficiency of CWs, especially in multi-stage and multi-combinations CWs. Therefore, we studied MPs characteristics and removal in a typical CWs WWTP in Changsha, comparing the MPs removal efficiencies of different processes in a WWTP, focusing on the MPs abundance variation in different stages CWs. Result showed that the MPs removal efficiency of Phase Ⅰ was 87.72% and that of Phase II was 80.65%. Approximate estimates showed that the daily discharge of MPs reached 7.20 * 108 items. The MPs removal efficiency of vertical flow CWs was 25.71%. The MPs removal efficiencies of secondary and tertiary horizontal subsurface flow CWs (HSSFCWs) were 32.00% and 21.43%. The MPs removal efficiencies of secondary and tertiary surface flow CWs were 23.53% and 12.50%. The MPs removal efficiencies of three bio-ponds were -23.08%, -12.90%, and -27.27%. Combined system of bio-pond + CWs reduced the MPs removal efficiency. The most dominant shape of MPs in wastewater was fibers. The most common MPs were polyethylene and polystyrene. The primary treatment in the Changsha WWTP had the highest MPs removal efficiency. Results of this investigation showed the multi-combination and multi-stage CWs WWTP can remove most of MPs in influent, which greatly reduced the amount of MPs discharged into the aquatic environment through WWTP and provided data for analyzing the distribution of MPs in the aquatic environment.

Recent advances on the transport of microplastics/nanoplastics in abiotic and biotic compartments.

Plastics enter the environment and break up into microplastics (MPs) and even nanoplastics (NPs) by biotic and abiotic weathering. These small particles are widely distributed in the environmental media and extremely mobile and reactive, easily suspending in the air, infiltrating into the soil, and interacting with biota. Current research on MPs/NPs is either in the abiotic or biotic compartments, with little attention paid to the fact that the biosphere as a whole. To better understand the complex and continuous movement of plastics from biological to planetary scales, this review firstly discusses the transport processes and drivers of microplastics in the macroscopic compartment. We then summarize insightfully the uptake pathways of MPs/NPs by different species in the ecological compartment and analyze the internalization mechanisms of NPs in the organism. Finally, we highlight the bioaccumulation potential, biomagnification effects and trophic transfer of MPs/NPs in the food chain. This work is expected to provide a meaningful theoretical body of knowledge for understanding the biogeochemical cycles of plastics.

Uniform polypyrrole electrodeposition triggered by phytic acid-guided interface engineering for high energy density flexible supercapacitor.

Unevenly distributed polypyrrole (PPy) films/coatings with extensive "dead volumes" via electrodeposition have emerged as a main challenge for high energy density flexible supercapacitor. In this work, we have fabricated a phytic acid-guided graphite carbon felt/polypyrrole (GF@PA@PPy) 3D porous composite with less "dead volumes" via electrodeposition. After the activation of phytic acid (PA), the quantity and content of defects and oxygen-containing groups on the surface of carbon felt (GF) have increased. First, these functional groups improve the hydrophilicity of the surface of GF, resulting in the preferential uniform distribution of pyrrole monomer (Py). While significantly, the synergistic effects between the defects and oxygen-containing groups boost the attraction of pyrrole ring, and thus promotes the formation of perfect PPy films with less "dead volume" on GF. Finally, the supercapacitor assembled from the GF@PA@PPy-40 displays a high areal energy density of 0.0732 mWh cm-2, exceeding the previously reported PPy-based electrodes values. The deeper understanding of the role for the defects and oxygen-containing groups in the synthesis of PPy/carbon materials offers a new strategy to construct advanced PPy-based supercapacitors.

Research progress of microplastics in soil-plant system: Ecological effects and potential risks.

The effect of microplastics on soil ecosystem is a hot topic in recent years. It is increasingly recognized that soil is also an important sink for microplastics in addition to the aquatic environment. This review aims to discuss the direct and indirect effects of microplastics on the soil-plant system, focusing on the effects of microplastics on soil aggregates and soil nutrient cycling as well as the combined effects of microplastics and other pollutants on soil-plant systems. Microplastics have been shown to affect the rooting ability of plants by altering soil bulk density and water-holding capacity, as well as reducing photosynthetic rate by directly interfering with the balance of plant chlorophyll a/chlorophyll b ratios. In addition, microplastics affect the stability of aggregates by interfering with abiotic factors (e.g., sesquioxide and exchangeable cations) or biotic factors (e.g., soil organic matter and organism activities in the soil). Moreover, microplastics may affect soil nutrient cycling by altering the dominant bacteria phyla in the soil or genes and enzymes associated with the carbon, nitrogen, and phosphorus cycle. When microplastics and other pollutants have combined effects on plants, microplastics attached onto the root surface physically hamper the contact of the pollutants with the roots but are more likely to exacerbate the damage of pollutants to plants. Different types, sizes and concentrations of microplastics have different effects on the soil-plant system. Microplastics with similar shape and size to soil particles have less significant effects, while microfibers, small-sized microplastics and biodegradable plastic particles have more significant effects. Finally, this review also provides an outlook for future research.

Microplastics removal and characteristics of constructed wetlands WWTPs in rural area of Changsha, China: A different situation from urban WWTPs.

Wastewater treatment plants (WWTPs) are important pathways that discharged microplastics into the natural environment, but few relevant research has been conducted in rural areas, especially with horizontal subsurface flow constructed wetlands (HSSFCWs). This study systematically investigates the removal efficiency and characteristics of microplastics in two rural WWTPs with HSSFCW in Changsha city of China and compared the microplastic pollution data of urban and rural WWTPs, to provide some advice for improving the microplastics removal efficiencies in rural WWTPs. 3 L wastewater were collected at each sampling point. Then microplastics in wastewater were extracted by density separation. The size, shape, color, and type of microplastics were analyzed and identified using the integrated microscope and FTIR. The whole experiment was carried out about a month. The results showed that the microplastics removal efficiency of rural WWTP1 was 72.38%, and that of rural WWTP2 was 68.10%, which were lower than that of most urban WWTPs. The microplastics removal efficiency of constructed wetlands in rural WWTP1 was 26.59%, and that in rural WWTP2 was 10.61%. Based on the daily discharge volume and the abundance of microplastics in the effluent of WWTPs, approximately 1.45 ∗ 107 items and 1.73 ∗ 107 items of microplastics were released each day from two rural WWTPs, separately. Fiber was the primary microplastic in both influent and effluent. The polyethylene (PE) and polystyrene (PS) were the main ingredients. The primary source of microplastics in rural WWTPs was inferred as domestic sewage. Microplastics removal efficiencies of rural WWTPs can be improved by regular maintenance, reducing the grid spacing, increasing the hydraulic stay time of biochemical pool, and increasing plant density, changing plant species, or adjusting the size and fill order of matrix in HSSFCWs, which can effectively help to prevent secondary pollution of microplastics from rural WWTPs.

Microplastics retention by reeds in freshwater environment.

Microplastic pollution has recently gained increasing attention. The accumulation of microplastics in plants has been confirmed in the marine environment. However, the extent of the microplastic retention in freshwater plants is still unknown. In this study, sediment and plant samples from six reed farms in the wetland of East Dongting Lake were collected and analyzed. The abundance of microplastics in the sediment of reed farms varied from 125.7 to 1219.5 items/kg dry weight (dw), with an average of 511.2 ± 295.0 items/kg. Moreover, different levels of microplastic abundance were found in reeds from 0 to 14 items/individual. The abundance of microplastics in sediment samples was moderate compared to that worldwide and higher than that in other regions of Dongting Lake. The microplastic pollution level was significantly higher in the reed vegetation belt than that in other sampling positions. On the basis of the distribution and characteristics of the collected microplastics, lake water and fishery are suggested as important sources of microplastics. Furthermore, the factors influencing microplastic retention in the reeds are discussed. This study, as the first direct evidence demonstrating that freshwater reeds tend to accumulate microplastics, constitutes valuable reference for future research.

Phytoremediation of poly- and perfluoroalkyl substances: A review on aquatic plants, influencing factors, and phytotoxicity.

Poly- and perfluoroalkyl substances (PFASs) are a group of emerging organic contaminants which are persistent to normal physicochemical treatments. The widespread use of PFASs has caused significant environmental issues. The bioaccumulation and distribution of PFASs within plant compartments have revealed great potentials for phytoremediation. In this review, the roles of aquatic plants in the process of PFASs remediation were highlighted. Moreover, there were different underlying mechanisms of PFASs uptake between terrestrial and aquatic plants. On the other hand, a wide range of influencing factors for bioaccumulation and translocation of PFASs within plant compartments are also presented and discussed. In response to exposure of PFASs, corresponding phytotoxic effects has affected the growth and metabolism of plants, which could provide beneficial guides of the phytotoxic tolerance for plant species selection in applications of phytoremediation. Finally, the discussion about whether phytoremediation is a viable option for PFASs removal and further research priorities are suggested.

Boron nitride quantum dots decorated MIL-100(Fe) for boosting the photo-generated charge separation in photocatalytic refractory antibiotics removal.

Metal organic frameworks (MOFs) have great potential for photocatalysis, but only possess moderate activity due to their slow charge transfer and low solar energy conversion. Herein, heterostructures photocatalysts constructed by boron nitride quantum dots (BNQDs) and MIL-100(Fe) (MNB) were successfully fabricated for overcoming these shortcomings. It was indicated that the composites possessed large surface area, mesoporous structure, and enhanced visible light absorption. The MNB photocatalysts exhibited excellent photocatalytic activity for tetracycline hydrochloride (TC-HCl) degradation under visible light irradiation. Compared with MIL-100(Fe), the photodegradation rate of TC-HCl by MNB-1 was 0.02383 min-1, which was 5.3 times higher than that of pure MIL-100(Fe). The close contact of MIL-100(Fe) with BNQDs and the synergistic effect between them were the main reasons for the improved photodegradation performance. This study reveals that a rational combination of MIL-100(Fe) and BNQDs can improve photocatalytic activity to enhance molecular oxygen activation. Therefore, it is reasonable to believe that quantum dots/MOFs photocatalysts have great potential in environmental remediation.