A Wetting and Capture Strategy Overcoming Electrostatic Repulsion for Electroreduction of Nitrate to Ammonia from Low-Concentration Sewage.

Ammonia production by electrocatalytic nitrate reduction reaction (NO3 RR) in water streams is anticipated as a zero-carbon route. Limited by dilute nitrate in natural sewage and the electrostatic repulsion between NO3 - and cathode, NO3 RR can hardly be achieved energy-efficiently. The hydrophilic Cu@CuCoO2 nano-island dispersed on support can enrich NO3 - and produce a sensitive current response, followed by electrosynthesis of ammonia through atomic hydrogen (*H) is reported. The accumulated NO3 - can be partially converted to NO2 - without external electric field input, confirming that the Cu@CuCoO2 nano-island can strongly bind NO3 - and then trigger the reduction via dynamic evolution between Cu-Co redox sites. Through the identification of intermediates and theoretical computation. it is found that the N-side hydrogenation of *NO is the optimal reaction step, and the formation of N─N dimer may be prevented. An NH3 product selectivity of 93.5%, a nitrate conversion of 96.1%, and an energy consumption of 0.079 kWh gNH3 -1 is obtained in 48.9 mg-N L-1 naturally nitrate-polluted streams, which outperforms many works using such dilute nitrate influent. Conclusively, the electrocatalytic system provides a platform to guarantee the self-sufficiency of dispersed ammonia production in agricultural regions.

Rapid detection of chemical oxygen demand, pH value, total nitrogen, total phosphorus, and ammonia nitrogen in biogas slurry by near infrared spectroscopy.

Effective treatment of sewage requires accurate measurement of important water quality parameters, such as chemical oxygen demand (COD), pH value, total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH3-N). Traditional detection techniques can result in secondary contamination and are time- and labor-intensive. Near infrared spectroscopy was used in this study to create a model of these parameters of pig manure anaerobic fermentation sewage. The models' viability for quickly estimating the aforementioned water quality characteristics was reviewed, and the models' performance in predicting the results of several samples (biogas slurry, supernatant, and biogas residue) was contrasted. By analyzing the near infrared spectrograms with a spectral range of 4000 cm-1 and 12 500 cm-1 and using second derivative (SD), Savitzky-Golay smoothing (SG) and standard normal variable (SNV) to preprocess the spectra, partial least squares (PLS) was selected to establish the prediction model. The results showed that the effect of the NIR model constructed from the supernatant was better than that of biogas slurry and biogas residue. The determination coefficients for COD, pH value, NH3-N and TN were 0.69, 0.87, 0.81, and 0.94, respectively. This study could provide reference for on-line monitoring of wastewater in the future.

Electrochemical reduction of wastewater by non-noble metal cathodes: From terminal purification to upcycling recovery.

A shift beyond conventional environmental remediation to a sustainable pollutant upgrading conversion is extremely desirable due to the rising demand for resources and widespread chemical contamination. Electrochemical reduction processes (ERPs) have drawn considerable attention in recent years in the fields of oxyanion reduction, metal recovery, detoxification and high-value conversion of halogenated organics and benzenes. ERPs also have the potential to address the inherent limitations of conventional chemical reduction technologies in terms of hydrogen and noble metal requirements. Fundamentally, mechanisms of ERPs can be categorized into three main pathways: direct electron transfer, atomic hydrogen mediation, and electrode redox pairs. Furthermore, this review consolidates state-of-the-art non-noble metal cathodes and their performance comparable to noble metals (e.g., Pd, Pt) in electrochemical reduction of inorganic/organic pollutants. To overview the research trends of ERPs, we innovatively sort out the relationship between the electrochemical reduction rate, the charge of the pollutant, and the number of electron transfers based on the statistical analysis. And we propose potential countermeasures of pulsed electrocatalysis and flow mode enhancement for the bottlenecks in electron injection and mass transfer for electronegative pollutant reduction. We conclude by discussing the gaps in the scientific and engineering level of ERPs, and envisage that ERPs can be a low-carbon pathway for industrial wastewater detoxification and valorization.

Long-term mulching of biodegradable plastic film decreased fungal necromass C with potential consequences for soil C storage.

The use of biodegradable plastic film mulching as a replacement for polyethylene plastic film has gained recognition due to its reduced environmental pollution. However, its impact on soil environment is not yet fully understood. Here, we compared the effects of different plastic film mulching on the accumulation of microbial necromass carbon (C) and its contribution to soil total C in 2020 and 2021. Results showed that biodegradable plastic film mulching decreased the accumulation of fungal necromass C compared to no plastic film mulching and polyethylene film mulching. However, the bacterial necromass C and soil total C were not affected by the plastic film mulching. Biodegradable plastic film mulching decreased the soil dissolved organic carbon content after maize harvest. Random forest models suggested that soil dissolved organic C, soil pH and the ratio of soil dissolved organic C to microbial biomass C were important factors in regulating the accumulation of fungal necromass C. The abundance of the fungal genus Mortierella was also found to have a significant positive contribution to the accumulation of fungal necromass C. These findings suggest that biodegradable plastic film mulching may decrease the accumulation of fungal necromass C by changing substrate availability, soil pH, and fungal community composition, with potential implications for soil C storage.

The potential risks posed by micro-nanoplastics to the safety of disinfected drinking water.

Micro-nanoplastics (M-NPs) have become an emerging critical issue in the environment because they migrate easily, can bioaccumulate with toxic effects, and are difficult to degrade. Unfortunately, the current technologies for removing or degrading M-NPs in drinking water are insufficient to eliminate them completely, and residual M-NPs in drinking water may pose a threat to human health by impairing human immunity and metabolism. In addition to their intrinsic toxic effects, M-NPs may be even more harmful after drinking water disinfection than before disinfection. Herein, this paper comprehensively summarizes the negative impacts of several commonly used disinfection processes (ozone, chlorine, and UV) on M-NPs. Moreover, the potential leaching of dissolved organics from M-NPs and the production of disinfection byproducts during the disinfection process are discussed in detail. Moreover, due to the diversity and complexity of M-NPs, their adverse effects may exceed those of conventional organics (e.g., antibiotics, pharmaceuticals, and algae) after the disinfection process. Finally, we propose enhanced conventional drinking water treatment processes (e.g., enhanced coagulation, air flotation, advanced adsorbents, and membrane technologies), detection of residual M-NPs, and biotoxicological assessment as promising and ecofriendly candidates to efficiently remove M-NPs and avoid the release of secondary hazards.

Advances in iron-based electrocatalysts for nitrate reduction.

Excessive nitrate has been a critical issue in the water environment, originating from the burning of fossil fuels, inefficient use of nitrogen fertilizers, and discharge of domestic and industrial wastewater. Among the effective treatments for nitrate reduction, electrocatalysis has become an advanced technique because it uses electrons as green reducing agents and can achieve high selectivity through cathode potential control. The effectiveness of electrocatalytic nitrate reduction (NO3RR) mainly lies in the electrocatalyst. Iron-based catalysts have the advantages of high activity and low cost, which are well-used in the field of electrocatalytic nitrates. A comprehensive overview of the electrocatalytic mechanism and the iron-based materials for NO3RR are given in terms of monometallic iron-based materials as well as bimetallic and oxide iron-based materials. A detailed introduction to NO3RR on zero valent iron, single-atom iron catalysts, and Cu/Fe-based bimetallic electrocatalysts are provided, as they are essential for the improvement of NO3RR performance. Finally, the advantages of iron-based materials for NO3RR and the problems in current applications are summarized, and the development prospects of efficient iron-based catalysts are proposed.

Disentangling the impact of straw incorporation on soil microbial communities: Enhanced network complexity and ecological stochasticity.

Straw incorporation is typically employed to enhance the nutrient content of soil and promote crop growth in intensive agricultural systems. Despite studies regarding the effects of straw incorporation on soil microbial communities, the underlying mechanisms of its effect on community co-occurrence interactions and assembly processes remain poorly understood. Herein, soil samples with or without straw incorporation were collected across a latitudinal gradient from north to central China. We found that straw incorporation considerably altered the structure of soil microbial community. The relative abundance of bacterial Latescibacterota and fungal Mortierellomycota were higher in straw-amended soils owing to their ability to decompose straw residues. The co-occurrence network in straw-amended soil exhibited greater complexity, including more network connectivity and keystone species, and higher average degrees and clustering coefficients compared with the control sample network. The network robustness and vulnerability indices suggested that straw incorporation increased the microbial network stability. Normalized stochastic ratios demonstrated that the stochastic process was the dominant mechanisms shaping the assembly of microbial communities in straw-amended soils. Concurrently, null model analysis revealed that straw increased the contribution of dispersal limitation to the assembly of bacterial and fungal communities. The migration rate of the microbial community, obtained from Sloan neutral community model, was relatively low in straw-amended soil at all the sample sites, potentially indicating the great importance of dispersal limitation. These findings would enhance our understanding of the ecological patterns and interactions of soil microbial communities in response to straw incorporation.

Enhanced removal of heavy metals by α-FeOOH incorporated carboxylated cellulose nanocrystal: synergistic effect and removal mechanism.

Simultaneous and highly efficient removal of heavy metal cations and oxyanions is significant for both water and soil remediation, but it remains a major challenge due to the complexity. In this work, a novel hybrid of α-FeOOH incorporated carboxylated cellulose nanocrystal (Fe/CNC) is synthesized via a hydrothermal process, which shows improved α-FeOOH dispersion and heavy metal removal capacity. In single adsorbate system, maximum adsorption capacities toward Pb(II), Cd(II), and As(V) by Fe/CNC reach 126.06, 53.07, and 15.80 mg g-1, respectively, and the Fe leaching is much lower than that of α-FeOOH. In binary and ternary adsorption systems, simultaneous removal of Pb(II), Cd(II), and As(V) is proved, and the competition and synergy coexist among heavy metals. FTIR and XPS spectra have revealed the synergistic removal mechanism: Pb(II) and Cd(II) are mainly removed by surface complexation with oxygen-containing functional groups on C-CNC and α-FeOOH, and precipitation on the surface of α-FeOOH, while ligand exchange with Fe-OH is responsible for As(V) removal. The soil incubation experiments show that exchangeable and carbonate-bound Pb, Cd, and As are transformed into more stable forms in contaminated soil containing Fe/CNC composites. This work provides a novel composite material for remediation of heavy metal-contaminated environments.

Recent Advances in Carbon-Based Materials for Adsorptive and Photocatalytic Antibiotic Removal.

Antibiotics have been a primary environmental concern due to their widespread dispersion, harmful bioaccumulation, and resistance to mineralization. Unfortunately, typical processes in wastewater treatment plants are insufficient for complete antibiotic removal, and their derivatives in effluent can pose a threat to human health and aquatic communities. Adsorption and photocatalysis are proven to be the most commonly used and promising tertiary treatment methods. Carbon-based materials, especially those based on graphene, carbon nanotube, biochar, and hierarchical porous carbon, have attracted much attention in antibiotic removal as green adsorbents and photocatalysts because of their availability, unique pore structures, and superior physicochemical properties. This review provides an overview of the characteristics of the four most commonly used carbonaceous materials and their applications in antibiotic removal via adsorption and photodegradation, and the preparation of carbonaceous materials and remediation properties regarding target contaminants are clarified. Meanwhile, the fundamental adsorption and photodegradation mechanisms and influencing factors are summarized. Finally, existing problems and future research needs are put forward. This work is expected to inspire subsequent research in carbon-based adsorbent and photocatalyst design, particularly for antibiotics removal.

Electrocatalytic Hydrogenation Boosts Reduction of Nitrate to Ammonia over Single-Atom Cu with Cu(I)-N3C1 Sites.

The conversion of nitrate to ammonia can serve two important functions: mitigating nitrate pollution and offering a low energy intensity pathway for ammonia synthesis. Conventional ammonia synthesis from electrocatalytic nitrate reduction reactions (NO3RR) is often impeded by incomplete nitrate conversion, sluggish kinetics, and the competition of hydrogen evolution reactions. Herein, atomic Cu sites anchored on micro-/mesoporous nitrogen-doped carbon (Cu MNC) with fine-tuned hydrophilicity, micro-/mesoporous channels, and abundant Cu(I) sites were synthesized for selective nitrate reduction to ammonia, achieving ambient temperature and pressure hydrogenation of nitrate. Laboratory experiments demonstrated that the catalyst has an ammonia yield rate per active site of 5466 mmol gCu-1 h-1 and transformed 94.8% nitrate in wastewater containing 100 mg-N L-1 to near drinking water standard (MCL of 5 mg-N L-1) at -0.64 V vs RHE. Extended X-ray absorption fine structure (EXAFS) and theoretical calculations showed that the coordination environment of Cu(I) sites (Cu(I)-N3C1) localizes the charge around the central Cu atoms and adsorbs *NO3 and *H onto neighboring Cu and C sites with balanced adsorption energy. The Cu(I)-N3C1 moieties reduce the activation energy of rate-limiting steps (*HNO3 → *NO2, *NH2 → *NH3) compared with conventional Cu(II)-N4 and lead to a thermodynamically favorable process to NH3. The as-prepared electrocatalytic cell can run continuously for 84 h (14 cycles) and produce 21.7 mgNH3 with only 5.64 × 10-3 kWh energy consumption, suitable for decentralized nitrate removal and ammonia synthesis from nitrate-containing wastewater.

Transcriptome alterations in zebrafish gill after exposure to different sizes of microplastics.

Most studies on microplastics (MPs) focused on gut, liver, and brain, and MPs toxicity was size-dependent, but less has been reported on gill. Here, zebrafish were exposed to three sizes of MPs (45-53 µm, 90-106 µm, and 250-300 µm). Next, comparative transcriptome analysis and determination of physiological indices were performed in zebrafish gills to elucidate the size-associated toxicity of MPs to fish gills. Compared with the control, 60, 344, and 802 differentially expressed genes (DEGs) were identified after exposure to 45-53 µm, 90-106 µm, and 250-300 µm MPs for 5 days, respectively. More DEGs in treatment with bigger MPs suggested that bigger MPs might induce more changes in zebrafish gills than smaller ones. These DEGs were significantly enriched in the FoxO signaling, cellular senescence, circadian rhythm and p53 signaling pathways. Besides, 90-106 µm and 250-300 µm MPs treatments inhibited the cell cycle and prevented the apoptosis. The GSH content significantly increased after MPs exposure, suggesting the induction of oxidative stress. AChE and Na+/K+-ATPase activities were significantly lowered in all MPs treatments than in the control, suggesting the inhibition of neurotransmission and ion regulation. These changes might negatively influence the normal functioning of gills, such as osmoregulation, ion regulation, and respiration.

Effect of Long-Term Biodegradable Film Mulch on Soil Physicochemical and Microbial Properties.

Biodegradable mulches have become the focus of attention, as pollution caused by leftover plastic mulch material becomes increasingly severe. However, the impact of biodegradable mulches to the soil needs to be further investigated. An experiment was conducted to evaluate the impact of no-mulch, biodegradable film mulch (BM) and polyethylene film mulch (PM) on the soil's physical, chemical and biological properties after six years (2013-2019) of mulching in garlic growing season in a garlic-maize rotation. Results showed that the soil bulk density of the 10-20 cm soil layer under BM decreased by 12.09-17.17% compared with that under PM. The soil total nitrogen content increased significantly by 14.75-28.37%, and the soil available phosphorus and potassium content increased by 64.20% and 108.82%, respectively. In addition, BM increased the soil's microbial, soil urease, and soil catalase activities compared with those for PM. To sum up, BM can reduce soil bulk density, and long-term use of BM does not cause a decrease in soil nutrient content and microbial activity. On the contrary, it can improve soil quality. This study helps accumulate data for the environmental safety evaluation of BM and provides theoretical and technical support for the large-scale promotion of biodegradable mulches.

Multi-component removal of Pb(II), Cd(II), and As(V) over core-shell structured nanoscale zero-valent iron@mesoporous hydrated silica.

The application of nanomaterials for the removal of heavy metals has received a great deal of attention because of their high efficiencies in the environment. But it is difficult to remove multiple heavy metals simultaneously with high efficiency and stability. Herein, the core-shell structured nanoscale zero-valent iron (nZVI) encapsulated with mesoporous hydrated silica (nZVI@mSiO2) were prepared for efficient removal of heavy metals including Pb(II), Cd(II), and metalloid As(V). The material prepared uniformly with a high surface area (147.7 m2 g-1) has a nZVI core with the particle size of 20-60 nm and a modified dendritic mesoporous shell of 19 nm. 0.15 g L-1 of the optimal material exhibited an extraordinary performance on removing Cd(II) and the maximum adsorption capacity for Pb(II), Cd(II), and As(V) reached 372.2 mg g-1, 105.2 mg g-1, and 115.2 mg g-1 with a pH value at 5.0, respectively. The dissolved iron during the reaction showed that the mesoporous silica (mSiO2) played an important role in enhancing the stability of nZVI. In addition, the competitive relationship between the coexistence of two heavy metals was discussed and it was found that the removal efficiency of the material for both was improved when Cd(II) and As(V) were removed synergistically.

Effects of biodegradable film mulching on bacterial diversity in soils.

The spread of biodegradable plastic films (BDFs) not only increases grain yield but also reduces environmental pollution from plastic film to a large extent. Soil microbes are considered to be involved in biodegradation processes. However, the study of microbe diversity in soil mulched with biodegradable plastic film remains limited. Here, we compared the diversity of microbes between soils with biodegradable film and nonbiodegradable film (NBDF) mulch. The results showed that BDFs affected total C, P and NH4+-N, especially organism C content, as well as microbe species richness (ACE; Chao1) and diversity (Simpson index; Shannon index). In terms of dominant phyla and genera, BDFs and NBDF can influence the abundance of disparate species. Furthermore, BDFs could also contribute to improving the richness of the important functional bacterial groups in soil, e.g., Pedomicrobium and Comamonas, both of which are involved in the degradation of plastic residues in soil. Finally, we found that BDFs improved the transformation of nitrogen by significantly increasing the abundances of Nitrobacter and Nitrospira. Our results highlight the impact of BDF mulch on the abundance of functional bacteria in the soil.

Enhanced degradation of micropollutants over iron-based electro-Fenton catalyst: Cobalt as an electron modulator in mesochannels and mechanism insight.

Heterogeneous electro-Fenton (hetero-EF) process is an emerging alternative for effective oxidation of recalcitrant micropollutants, but it is hampered by limited hydroxyl radical (•OH) generation and low stability on the iron-based cathodes. Herein, we demonstrate an enhanced hetero-EF performance via modulation of iron electronic structure in an ordered mesoporous carbon (OMC). By tuning the cobalt incorporation, the highly-dispersed iron-cobalt (FeCo) nanoalloys in mesochannels (Fe0.5Co0.5@OMC) show a 3-fold increase in •OH yield compared with Fe@OMC, achieving degradation efficiency with 92% of sulfamethazine (SMT) and 99% of rhodamine B (RhB), and the corresponding total organic carbon (TOC) removal with 66% of SMT and 85% of RhB within 2 h in neutral pH, respectively. Experimental results and density functional theory (DFT) calculations demonstrate that iron incorporated with cobalt reduces energy barrier for facile generation of H2O2 and •OH from O2 through direct electron transfer, along with decreased overpotential. Meanwhile, cobalt doping promotes H2O2 decomposition by accelerated Fe(II)/Fe(III) cycle and Co(II)/Co(III) redox. Furthermore, spatially confined and half-embedded structure endows the nanocatalyst (8 nm) excellent durability within a wide pH value range and good stability in cycle tests. A plausible reaction mechanism and degradation pathway for SMT are proposed. Moreover, the superiority of Fe0.5Co0.5@OMC cathode is maintained in simulated wastewater, suggesting an enormous potential in practical wastewater treatment.

The time-dependent variations of zebrafish intestine and gill after polyethylene microplastics exposure.

Microplastics (MPs) are common environmental contaminants that present a growing health concern due to their increasing presence in aquatic and human systems. However, the mechanisms behind MP effects on organisms are unclear. In this study, zebrafish (Danio rerio) were used as an in vivo model to investigate the potential risks and molecular mechanisms of the toxic effects of polyethylene MPs (45-53 µm). In the zebrafish intestine, 6, 5, and 186 genes showed differential expression after MP treatment for 1, 5, and 10 days, respectively. In the gills, 318, 92, and 484 genes showed differential expression after MP treatment for 1, 5, and 10 days, respectively. In both the intestine and the gills, Gene Ontology (GO) annotation showed that the main enriched terms were biological regulation, cellular process, metabolic process, cellular anatomical entity, and binding. KEGG enrichment analysis on DEGs revealed that the dominant pathways were carbohydrate metabolism and lipid metabolism, which were strongly influenced by MPs in the intestine. The dominant pathways in the gills were immune and lipid metabolism. The respiratory rate of gills, the activity of SOD and GSH in the intestine significantly increased after exposure to MPs compared with the control (p < 0.05), while the activity of SOD did not change in the gills. GSH activity was only significantly increased after MP exposure for 5 days. Also, the MDA content was not changed in the intestine but was significantly decreased in the gills after MP exposure. The activity of AChE significantly decreased only after MPs exposure for 5 days. Overall, these results indicated that MPs pollution significantly induced oxidative stress and neurotoxicity, increased respiratory rate, disturbed energy metabolism and stimulated immune function in fish, displaying an environmental risk of MPs to aquatic ecosystems.

Ultrasound-assisted electrodeposition synthesis of nZVI-Pd/AC toward reductive degradation of methylene blue.

A novel composite (nZVI/Pd-AC) was prepared by loading nanoscale zero-valent iron (nZVI) and Pd on activated carbon (AC) electrode under electrodeposition with ultrasound, which was used to reductive degradation of methylene blue (MB). The loading contents of Fe and Pd in composite materials were 15.84% and 2.06%, respectively. XPS results further confirmed that the as-prepared material contained Fe0 and Pd0. Without external conditions, MB could be degraded in the presence of nZVI/Pd-AC and reached equilibrium within 180 min. To investigate the reusability, the re-electrodeposition strategy was effective to refresh the active sites of nZVI/Pd-AC, and the removal efficiency only reduced by 4.51% in five circles indicating the good reusability of nZVI/Pd-AC composites. GC-MS was used to identify possible degradation pathways of MB; the results showed that the degradation products were mainly N, N-dimethylaniline and 2-amino-5-dimethylamino-benzenesulfonic acid. And the S-C, C-N bonds are the sites easier to be attacked.

Algal density affects the influences of polyethylene microplastics on the freshwater rotifer Brachionus calyciflorus.

Most previous researches focused on the toxicity of polystyrene microplastics (MPs) to marine organisms, but less on polyethylene MPs and freshwater zooplanktons. The present study aims to elucidate the toxicity of polyethylene (PE) MPs (diameter = 10-22 µm) to the typical freshwater rotifer Brachionus calyciflorus. Firstly, fluorescent microscope observation showed that rotifers could ingest PE MPs and accumulate them in their digestive tracts. Life-table experiments revealed that exposure to 0.5 × 103, 2.5 × 103, and 1.25 × 104 particles/mL PE MPs significantly reduced net reproductive rate and intrinsic rate of pollution increase of rotifers under algal densities (Scenedesmus obliquus) of 0.1 × 106, and 0.5 × 106 cells/mL, but no significant effects were observed under 2.5 × 106 cells/mL algal density. These results showed that PE MPs suppressed the reproduction of rotifer and this negative effect could be alleviated by increasing food supply. The swimming linear speed of rotifers significantly decreased with increasing MP concentrations. The activities of superoxide dismutase and Na+-K+-ATPase significantly decreased in treatments with high concentration of PE MPs under 0.1 × 106 cells/mL algal density, but did not change significantly in MP treatments under 0.5 × 106 and 2.5 × 106 cells/mL, compared to the control. Glutathione peroxidase activity significantly increased in treatments with 1.25 × 104 particles/mL and 2.5 × 103 particles/mL under 0.1 × 106 and 0.5 × 106 cells/mL algal density, respectively, but did not change significantly in all MP treatments under 2.5 × 106 cells/mL. Exposure to PE MPs might lower the gathering capacity of algae, induce oxidative stress, trigger cell membrane damages and disturb energy metabolism in rotifers, which can explain the PE MPs toxicity to rotifer reproduction.

Efficiency and mechanisms of simultaneous removal of Microcystis aeruginosa and microcystins by electrochemical technology using activated carbon fiber/nickel foam as cathode material.

The significant removal efficiency of microcystis aeruginosa was presented using Pt/Ti anode and activated carbon fiber/nickel foam (ACF/Ni) cathode by addition of Fe2+ slightly in a wide range of initial pH (3-9). Results showed that about 93% of the Microcystis aeruginosa cells were removed within 15 min for Pt/Ti-ACF/Ni-Fe2+ system. Dosage of Fe2+, current density, and initial pH had remarkable effects on the removal efficiency of microcystis aeruginosa. The mechanism of algae removal in the Pt/Ti-ACF/Ni-Fe2+ electrochemical system was revealed by the comparison between Pt/Ti-ACF/Ni-Fe2+ process and classical Fenton process, the analysis on Microcystis aeruginosa and ACF/Ni by SEM, the specific surface area and pore size analysis of ACF, and the determination of UV254, OD620 and microcystin-LR (MC-LR). Results showed that the main mechanism of this system was the electro-Fenton process, which was accompanied by electro-adsorption, electro-floatation, and electro-coagulation process. And the cooperation mechanism on the electrochemical removal system was further speculated. With the breakdown of algal cells during the electrolysis, the MC-LR and other substances released from the cells were effectively degraded. Besides, the new cathode exhibited favorable and stable reusability. This study built up a high-efficiency algae removal system, which broke through the limits of narrow working pH range and large consumption of exogenous chemicals in electro-Fenton process.

Morphological differentiation of Brachionus calyciflorus caused by predation and coal ash pollution.

Different rotifer stains exhibited remarkably morphological differences which could not be eliminated under laboratory conditions. In the present study, we hypothesized that predation pressure and pollution might be two forces driving morphological differentiation of rotifer. To test this hypothesis, rotifers (Brachionus calyciflorus) belonging to two sibling species were collected from three special lakes (with coal ash pollution, high predation pressure or neither) and cultured for more than three months to investigate their potential differentiation in morphology. Twelve morphological parameters were measured and compared among three lakes at four food density (Scenedesmus obliquus). The results showed that most of the tested morphological parameters changed in response to food level and differed among three habitats. Rotifers from the habitat with high predation pressure evolved stable long posterior lateral spine and relatively small body size. Rotifers collected from the polluted habitat was of smaller body size, compared with those from ordinary habitat. Bigger eggs were laid by rotifers from polluted area or lake with high predation pressure, enabling newborns more resistant to pollution or predation, and thus ensuring the survival rate of newborns. Finally, we concluded that both predation and pollution could affect the morphological differentiation and evolution of rotifers.