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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]

With the vigorous development of industrial economy, energy and environmental problems have become the most serious issues affecting people's production and life. Therefore, the demand for clean energy production, effective separation and storage is growing. Metal-organic frameworks (MOFs), as a kind of porous crystalline materials with large surface area and porosity, which is self-assembled by metal ions or clusters and organic ligands through coordination bonds. Thanks to a number of unique characteristics such as adjustable pore environment, homogeneous void structure, abundant active sites, unprecedented chemical composition tunability and functional versatility, it has been widely studied, especially for the clean energy conversion in catalysis. In this review, we focus on the research progress of clean energy in catalysis based on MOFs. Emphasis is placed on MOFs with different structures of compositions and their applications in catalytic for clean energy conversion, such as CO oxidation, CO 2 reduction and H 2 evolution. In addition, the situation of MOFs assisting environmental remediation is also briefly described. Finally, the prospects and challenges of MOFs in clean energy and the remaining issues in this field are presented. [Display omitted] • MOFs based materials for CO2 Conversion and CO oxidation are summarised. • MOFs based materials for energy related hydrogen evolution are summarised. • MOFs based materials for environment catalytic degradation are discussed. • MOFs based membranes for various separation applications are summarised. • The advantage and disadvantage of MOF membranes are discussed. [ABSTRACT FROM AUTHOR]

The taste and odor (T&O) problem represented by 2-methylisoborneol (2-MIB) and geosmin (GSM) in water is the multiple undesirable substances in the drinking water and the aquatic industry. In this study, the UV-assisted photoelectrochemical, a prospective advanced oxidation process (AOP), was evaluated for the degradation of 2-MIB and GSM. In contrast to UV photochemical and electrochemical, the degradation ratio of GSM (2-MIB) increase to 96% (95%) in 25 min. The removal ratio and rate depended on reaction time, electrolyte concentration, current density, and water quality parameters (e.g. pH, HCO 3 −, natural organic matter, and tap water). Among these parameters, a high concentration of electrolyte and acidic solutions could accelerate the rate and increase the ratio, while alkaline conditions and the impurity content had negative effects. Furthermore, the significant role of various reactive species (e.g. HO∙, Cl , ClO , etc) were highlighted by scavenging experiments. Complex free radicals exist was further verified by electron paramagnetic resonance spectroscopy (EPR) experiments. The intermediates were identified and the possible degradation pathways during the UV-assisted photoelectrochemical reactions of both compounds were proposed. Overall, the UV-assisted photoelectrochemical is beneficial to the removal of GSM and 2-MIB in water. [Display omitted] • The UV-assisted photoelectrochemical can be effective in degrading GSM and 2-MIB. • Influencing factors in degrading GSM and 2-MIB were evaluated. • The contributions of free radicals for degradation were investigated. • Possible pathways of GSM and 2-MIB degradation were proposed. [ABSTRACT FROM AUTHOR]

Strobilurin fungicides are widely used pesticides in the world. They can have toxic effects not only to target organisms, but also to nontarget organisms. To assess their ecological risk, species sensitivity distributions (SSDs) are required for the development of water quality criteria (WQC). In this paper, the acute toxicity of four methoxyacrylate fungicides were experimentally determined and evaluated at 24, 48, 72 and 96 h for the species of Rana chensinensis and Limnodrilus hoffmeisteri , respectively. Acute and chronic HC 5 (5% hazard concentration) values and WQC values were calculated from SSDs based on the toxicity values determined in this paper and compiled from literature. SSDs revealed that aquatic animals were relatively sensitive species and aquatic plants are insensitive species for the four fungicides. However, different orders of species sensitivity in the acute and chronic toxicity indicated that these four fungicides had different toxic mechanisms or mode of action (MOA) to different species. According to toxicity correlation and principal component analysis (PCA), the kresoxim-methyl toxicity was very close to trifloxystrobin as compared with others due to that they are neutral compounds with very similar physicochemical properties. Quantitative structure-activity relationship (QSAR) revealed that toxicity of strobilurin fungicides were dependent both on chemical hydrophobicity and hydrogen bond basicity. These two molecular descriptors reflect the bio-uptake process and interaction of compounds with target receptors in an organism. WQC values and interspecies correlation are valuable for assessing water quality and understanding toxic mechanisms to different species. [Display omitted] • Acute toxicity of four fungicides have been determined and evaluated at 24, 48, 72 and 96 h. • Water quality criteria of acute and chronic toxicity have been developed for four strobilurin fungicides. • Toxicity of strobilurin fungicides is related with chemical hydrophobicity and hydrogen bonding potential. • The toxicity of four fungicides is not only dependent on the species, but also on the chemical structure. • Kresoxim-methyl toxicity is significantly related to trifloxystrobin toxicity because of their similar structure. [ABSTRACT FROM AUTHOR]

Abstract Uranium phytoextraction is a promising technology, however, facing difficult that limited plant biomass due to nutrient deficiency in the contaminated sites. The aim of this study is to evaluate the potential of a symbiotic associations of a legume Sesbania rostrata , rhizobia and arbuscular mycorrhiza fungi (AMF) for reclamation of uranium contaminated soils. Results showed AMF and rhizobia had a mutual beneficial relations in the triple symbiosis, which significantly increased plant biomass and uranium accumulation in S. rostrata plant. The highest uranium removal rates was observed in plant-AMF-rhizobia treated soils, in which 50.5–73.2% had been extracted, whereas 7.2–23.3% had been extracted in plant-treated soil. Also, the S. rostrata phytochelatin synthase (PCS) genes expression were increased in AMF and rhizobia plants compared with the plants. Meantime, content of malic acid, succinic acid and citric acid were elevated in S. rostrata root exudates of AMF and rhizobia inoculated plants. The facts suggest that the mutual interactions in the triple symbiosis help to improve phytoremediation efficiency of uranium by S. rostrata. Highlights • AMF and rhizobium had a mutual beneficial relations. • The inoculation of AMF/rhizobium enhanced PCS genes expression. • AMF/rhizobium improve phytoremediation efficiency of uranium by S. rostrata. [ABSTRACT FROM AUTHOR]

Although modes of action (MOAs) play a key role in the understanding of the toxic mechanism of chemicals, the MOAs have not been investigated for antibiotics to green algae. This paper is to discriminate excess toxicity from baseline level and investigate the MOAs of 13 different antibiotics to algae by using the determined toxicity values. Comparison of the toxicities shows that the inhibitors of protein synthesis to bacteria, such as azithromycin, doxycycline, florfenicol and oxytetracycline, exhibit significantly toxic effects to algae. On the other hand, the cell wall synthesis inhibitors, such as cefotaxime and amoxicillin, show relatively low toxic effects to the algae. The concentrations determined by HPLC indicate that quinocetone and amoxicillin can be easily photodegraded or hydrolyzed during the toxic tests. The toxic effects of quinocetone and amoxicillin to the algae are attributed to not only their parent compounds, but also their metabolites. Investigation on the mode of action shows that, except rifampicin, all the tested antibiotics exhibit excess toxicity to Pseudokirchneriella subcapitata ( P. subcapitata) . These antibiotics can be identified as reactive modes of action to the algae. They act as electrophilic mechanism of action to P. subcapitata . These results are valuable for the understanding of the toxic mechanism to algae. [ABSTRACT FROM AUTHOR]

Abstract Due to its high mass transfer efficiency, microbubble ozonation has been widely used in water treatment to degrade refractory compounds. Compared to conventional bubbles (diameters larger than 1 mm), microbubbles (diameter less than 50 μm) have special interfacial characteristics that are probably advantageous in ozonation. However, the mechanisms involved are still unclear and therefore our primary aim here was to explore the interfacial effect of microbubbles during ozonation process. Phenol and nitrobenzene degradation by ozone microbubbles and conventional bubbles were carried out across a broad pH range. We found that microbubble decomposition of pollutants was markedly more efficient than conventional bubbles in terms of ozone consumption. Hydroxyl radical scavenger experiments of phenol revealed that the enhancement of microbubble might result from the increase of ozone concentration in interfacial region and a mathematical simulation further proved this synthesis by showing that ozone concentration is not homogenous throughout the reaction medium and forms a steep gradient in the liquid film of microbubbles. As for nitrobenzene, the acceleration of hydroxyl radicals was supposed to be the dominate factor which might be the consequence of high gas concentration in liquid film. These findings shed light on the mechanism of interfacial reaction in microbubble ozonation. Highlights • Microbubble decomposed pollutants more efficiently in terms of ozone consumption. • Ozone concentration forms a steep gradient in the liquid film of microbubbles. • Microbubbles could efficiently accelerate the generation of OH during ozonation. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) have been widely used for ecological remediation of micro-polluted source water. Nitrous oxide (N 2 O) from CWs has caused great concern as a greenhouse gas. However, the contribution of ammonia oxidation driven by ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) to N 2 O emission, especially at low temperature, was unknown. This study aimed to quantify the contributions of AOA and AOB to N 2 O through lab-scale subsurface CWs. The N 2 O emission flux of CW at 8 °C was 1.23 mg m−2·h−1, significantly lower than that at 25 °C (1.92 mg m−2·h−1). The contribution of ammonia oxidation to N 2 O at 8 °C (33.04%) was significantly higher than that at 25 °C (24.17%). The N 2 O production from AOA increased from 1.91 ng N·g−1 at 25 °C to 4.11 ng N·g−1 soil at 8 °C and its contribution increased from 23.38% to 30.18% (P < 0.05). Low temperature impaired functional gene groups and inhibited the activity of AOB, resulting in its declined contribution. Based on the transcriptional analysis, AOA was less affected by low temperature, thus stably contributing to N 2 O. Moreover, community diversity and relationships of AOA were enhanced at 8 °C, while AOB declined. The results confirmed the significant contribution of AOA and demonstrated molecular mechanisms (higher activity and community stability) of the increased contribution of AOA to N 2 O at low temperature. [Display omitted] • N 2 O emission from ammonia oxidation in constructed wetlands was first quantified. • AOA produced 90.2% more N 2 O at low temperature than at room temperature. • The relative contribution of AOA to N 2 O at 8 °C was 121.61% of that at 25 °C. • Low temperature impaired functional gene groups and decreased the activity of AOB. • Contributions of AOA and AOB to N 2 O could not be ignored especially at low temperature. [ABSTRACT FROM AUTHOR]

Substrate clogging is one of the major operation challenges of subsurface flow constructed wetlands (SSF-CWs). And the phosphorus (P) removal performance and stability of P accumulation of SSF-CWs would be varied with the development of substrate clogging. In this study, three horizontal SSF-CWs microcosms with different clogging degrees were conducted to explore the mechanism of P accumulation behavior influenced by substrate clogging. Increase in clogging degree resulted in hydraulic retention time (HRT) diminution and adsorption sites increase, which jointly led to reduced P removal efficiency at low clogging degree (L-CW), however, higher P removal efficiency was obtained as adsorption sites increase offset HRT diminution at high clogging degree (H-CW). Substrate adsorption was the primary removal pathway in all SSF-CW systems. It accounted for 77.86 ± 2.63% of the P input in the H-CW, significantly higher than the control (60.08 ± 4.79%). This was attributed to a higher proportion of Fe/Al–P accumulated on the substrate of H-CW, since clogging aggravated the anaerobic condition and promoted the generation of Fe ions. The increase in clogging degree also elevated the release risk of the accrued P in SSF-CWs, since Fe/Al–P was considered bioavailable and readily released under environmental disturbance. The obtained results provide new insights into the P transport and transformation in SSF-CWs and would be helpful to optimize substrate clogging management. [Display omitted] • Clogging aggravated anaerobic condition in SSF-CWs and promoted Fe remobilization. • Newly generated Fe ions precipitation with dissolved P affected P fraction. • Clogging improved P removal as adsorption sites increase offset HRT diminution. • Fe/Al–P accumulation caused by clogging elevated P release risk of SSF-CWs. [ABSTRACT FROM AUTHOR]

The toxic effect can be affected by pH in water through affecting the degree of ionization of ionizable compounds. Wrong classification of mode of action can be made from the apparent toxicities. In this paper, the toxicity data of 61 compounds to Daphnia magna determined at three pH values were used to investigate the effect of pH on the discrimination of excess toxicity. The results show that the apparent toxicities are significantly less than the baseline level. Analysis on the effect of pH on bioconcentration factor (BCF) shows that the log BCF values are significantly over-estimated for the strongly ionizable compounds, leading to the apparent toxicities greatly less than the baseline toxicities and the toxic ratios greatly less than zero. A theoretical equation between the apparent toxicities and pH has been developed basing on the critical body residue (CBR). The apparent toxicities are non-linearly related to pH, but linearly to fraction of unionized form. The determined apparent toxicities are well fitted with the toxicities predicted by the equation. The toxicities in the unionized form calculated from the equation are close to, or greater than the baseline level for almost all the strongly ionizable compounds, which are very different from the apparent toxicities. The studied ionizable compounds can be either classified as baseline, less inert or reactive compounds in D. magna toxicity. Some ionizable compounds do not exhibit excess toxicity at a certain pH, due not to their poor reactivity with target molecules, but because of the ionization in water. [ABSTRACT FROM AUTHOR]

Paraquat (PQ) pollution has become an increasing seriously threat to the ecological environment. Thus, it is vital to study novel adsorption materials capable of removing PQ. Modified carbon tubes (MCT-600) were prepared by carbonizing the seed hair fibers of Metaplexis japonica at 600 °C and further modifying with nitric acid. The MCT-600 was found to possess a regular morphology, a good graphitization degree and an abundance of carboxyl functional groups. Moreover, this materil exhibits excellent adsorption performance for paraquat (PQ), such as a fast adsorption rate (adsorption equilibrium within 20 min), large adsorption capacity (218.61 mg g−1) and good regeneration ability (reused more than 5 times). The adsorption process for PQ onto MCT-600 was found to be well matched to a Langmuir isotherm and pseudo-second-order kinetics model. Owing to its unique surface properties, green raw material source and simple preparation process, MCT-600 shows potential as an outstanding candidate for PQ removal from water. Image 1 • Low cost and widespread source carbon tubes derived from biomass are prepared. • Adsorption of material fitted with Langmuir and pseudo-second-order kinetics model. • High binding capacity and fast kinetics endow material a wide application prospect. [ABSTRACT FROM AUTHOR]

Nowadays, the visible-light-driven photocatalysis via advanced photocatalyst for PS activation have promising applications in wastewater treatment. Herein, for the first time, two novel MOFs@COFs hybrid materials (denoted as MIL-101-NH 2 @TpMA and UiO-66-NH 2 @TpMA) with nitrogen-rich building blocks were fabricated via a feasible step-by-step assembly method, and then employed as efficient photocatalytic platform coupling with sulfate radical-based advanced oxidation processes for the degradation of BPA under visible light irradiation. Detailed analyses revealed that the hybridization of MOFs and COFs could greatly boost visible light absorption, while the heterojunction formed at the interface could effectively facilitate the separation and transfer of photogenerated electron-hole pairs. More importantly, the developed solar/MOFs@COFs/PS system exhibited the excellent degradation ability toward BPA, and an incredible degradation efficiency of 99% was eventually achieved. Possible mechanism for photocatalytic degradation of BPA was also proposed. Furthermore, the prepared composites with great reusability and stability possessed a broad potential for highly effective degradation of various organic contaminants. In short, this work not only demonstrated the combination of MOFs and COFs with C 3 N 4 active unit was a feasible strategy for improving photocatalytic activities in the degradation of organic contaminants, but also provided some novel inspirations for constructing high-efficient photocatalysts with heterostructure. Image 1 • Two novel MOFs@COFs hybrid materials with C 3 N 4 active units were first synthesized. • Developed solar/MOFs@COFs/PS system exhibited great degradation ability toward BPA. • Possible mechanisms for photocatalytic degradation of BPA was proposed. • As-obtained composites possessed excellent reusability and stability. • Prepared photocatalyst had a broad potential for degradation of various contaminants. [ABSTRACT FROM AUTHOR]