A compound enzyme as an additive to a continuous anaerobic dynamic membrane bioreactor for enhanced lignocellulose removal from codigestion: Performance, membrane characteristics and microorganisms.

To explore the enzyme-enhanced strategy of a continuous anaerobic dynamic membrane reactor (AnDMBR), the anaerobic codigestion system of food waste and corn straw was first operated stably, and then the best combination of compound enzymes (laccase, endo-ß-1,4-glucanase, xylanase) was determined via a series of batch trials. The results showed that the methane yield (186.8 ± 19.9 mL/g VS) with enzyme addition was 12.2 % higher than that without enzyme addition. Furthermore, the removal rates of cellulose, hemicellulose and lignin increased by 31 %, 36 % and 78 %, respectively. In addition, dynamic membranes can form faster and more stably with enzyme addition. The addition of enzymes changed the structure of microbial communities while maintaining sufficient hydrolysis bacteria (Bacteroidetes), promoting the proliferation of Proteobacteria as a dominant strain and bringing stronger acetylation ability. In summary, the compound enzyme strengthening strategy successfully improved the methane production, dynamic membrane effect, and degradation rate of lignocellulose in AnDMBR.

Selenium Nanomaterials Enhance Sheath Blight Resistance and Nutritional Quality of Rice: Mechanisms of Action and Human Health Benefit.

In the current work, the foliar application of selenium nanomaterials (Se0 NMs) suppressed sheath blight in rice (Oryza sativa). The beneficial effects were nanoscale specific and concentration dependent. Specifically, foliar amendment of 5 mg/L Se0 NMs decreased the disease severity by 68.8% in Rhizoctonia solani-infected rice; this level of control was 1.57- and 2.20-fold greater than that of the Se ions with equivalent Se mass and a commercially available pesticide (Thifluzamide). Mechanistically, (1) the controlled release ability of Se0 NMs enabled a wider safe concentration range and greater bioavailability to Se0 NMs, and (2) transcriptomic and metabolomic analyses demonstrated that Se0 NMs simultaneously promoted the salicylic acid- and jasmonic-acid-dependent acquired disease resistance pathways, antioxidative system, and flavonoid biosynthesis. Additionally, Se0 NMs improved rice yield by 31.1%, increased the nutritional quality by 6.4-7.2%, enhanced organic Se content by 44.8%, and decreased arsenic and cadmium contents by 38.7 and 42.1%, respectively, in grains as compared with infected controls. Human simulated gastrointestinal tract model results showed that the application of Se0 NMs enhanced the bioaccessibility of Se in grains by 22.0% and decreased the bioaccessibility of As and Cd in grains by 20.3 and 13.4%, respectively. These findings demonstrate that Se0 NMs can serve as an effective and sustainable strategy to increase food quality and security.

Time-Dependent and Coating Modulation of Tomato Response upon Sulfur Nanoparticle Internalization and Assimilation: An Orthogonal Mechanistic Investigation.

Nanoenabled strategies have recently attracted attention as a sustainable platform for agricultural applications. Here, we present a mechanistic understanding of nanobiointeraction through an orthogonal investigation. Pristine (nS) and stearic acid surface-modified (cS) sulfur nanoparticles (NPs) as a multifunctional nanofertilizer were applied to tomato (Solanum lycopersicumL.) through soil. Both nS and cS increased root mass by 73% and 81% and increased shoot weight by 35% and 50%, respectively, compared to the untreated controls. Bulk sulfur (bS) and ionic sulfate (iS) had no such stimulatory effect. Notably, surface modification of S NPs had a positive impact, as cS yielded 38% and 51% greater shoot weight compared to nS at 100 and 200 mg/L, respectively. Moreover, nS and cS significantly improved leaf photosynthesis by promoting the linear electron flow, quantum yield of photosystem II, and relative chlorophyll content. The time-dependent gene expression related to two S bioassimilation and signaling pathways showed a specific role of NP surface physicochemical properties. Additionally, a time-dependent Global Test and machine learning strategy applied to understand the NP surface modification domain metabolomic profiling showed that cS increased the contents of IA, tryptophan, tomatidine, and scopoletin in plant leaves compared to the other treatments. These findings provide critical mechanistic insights into the use of nanoscale sulfur as a multifunctional soil amendment to enhance plant performance as part of nanoenabled agriculture.

Co-pyrolysis of alkali-fused fly ash and corn stover to synthesize biochar composites for remediating lead-contaminated soil.

Fly ash (FA) is mainly composed of silica, alumina, and other metal oxide components, and has a positive stabilizing effect on soil heavy metals. Biochar composites produced from FA and corn stover (CS) can improve its remediation performance. Therefore, a batch of biochar composites (alkali-fused FA-CS biochars, ABs), synthesized via co-pyrolysis of CS and alkali-fused FA (AFFA) at different temperatures of 300, 500, and 700 °C (AB300-1, AB500-1, and AB700-1) and CS to AFFA mass ratios of 10:1, 10:2, and 10:5 (AB500-1, AB500-2, and AB500-5), was used to remediate lead (Pb)-contaminated soil. Compared with pristine biochars (BCs), ABs were enriched with oxygen-containing functional groups (Si-O-Si and Si-O) and aromatic structures. The ABs prepared at lower pyrolytic temperature (≤500 °C) and lower ratio of CS to AFFA (10:1) showed higher yield and stability. The contents of Toxicity Characteristic Leaching Procedure (TCLP)-extractable Pb and DTPA-CaCl2-triethanolamine (DTPA)-extractable Pb were generally lower in the soils amended with ABs than BCs. Compared with other ABs such as AB300-1, AB500-2, AB500-5, and AB700-1, the soil amended with AB500-1 had lower contents of TCLP and DTPA-extractable Pb (24% reduction), exhibiting superior performance in stabilizing Pb in the soil. The gradual decrease of DTPA-extractable Pb content in the soil with increasing dosage of AB500-1 amendments suggests that AB500-1 facilitated the conversion of bioavailable Pb to the stable and less toxic residual fractions. Specifically, the highest percentage of residual fraction of Pb in soil amended with AB500-1 was 14%. Correlation analyses showed that the soil DTPA-extractable Pb content decreased with the increase of soil pH and cation-exchange capacity (CEC) value. ABs stabilize Pb in the soils mainly via electrostatic attraction, precipitation, cation-π interaction, cation exchange, and complexation. These findings provide insights for producing functionalized biochar composites from industrial waste like FA and biomass waste for remediating the soils polluted by heavy metals.

Inhibitory effects of black phosphorus nanosheets on tumor cell proliferation through downregulation of ADIPOQ and downstream signaling pathways.

Exposure to environmental pollutants, including nanomaterials, has a significant impact on tumor progression. The increased demand for black phosphorus nanosheets (BPNSs), driven by their exceptional properties, raises concerns about potential environmental contamination. Assessing their toxicity on tumor growth is essential. Herein, we employed a range of biological techniques, including cytotoxicity measurement, bioinformatics tools, proteomics, target gene overexpression, Western blot analysis, and apoptosis detection, to investigate the toxicity of BPNSs across A549, HepG-2, MCF-7, and Caco-2 cell lines. Our results demonstrated that BPNSs downregulated the expression of ADIPOQ and its associated downstream pathways, such as AMP-activated protein kinase (AMPK), nuclear factor erythroid 2-related factor 2 (Nrf2), and other unidentified pathways. These downregulated pathways ultimately led to mitochondria-dependent apoptosis. Notably, the specific downstream pathways involved varied depending on the type of tumors. These insightful findings not only confirm the consistent inhibitory effects of BPNSs across different tumor cells, but also elucidate the cytotoxicity mechanisms of BPNSs in different tumors, providing valuable information for their safe application and health risk assessment.

A new substrate equalization method for optimizing the influent conditions and fluid flow patterns of a multifed upflow anaerobic sludge blanket reactor with mature anammox granules.

To improve nitrogen removal efficiency (NRE) and achieve homogenous distribution of anammox sludge and substrate, a new substrate equalization theory and a cumulative overload index was proposed for multifed upflow anaerobic sludge bed (MUASB) reactors with mature anammox granules. The performance and flow patterns of MUASB reactors were investigated under various influent conditions. The results showed that the nitrogen removal performance and stability of MUASB reactors could be optimized by minimizing the cumulative load. The NRE gradually increased from 83.3 ± 2.2 %, 86.8 ± 4.2 % to 89.3 ± 4.1 % and 89.7 ± 1.6 % in feeding flow tests and feeding port tests, respectively. Furthermore, the flow patterns were compared based on residence time distribution and computational fluid dynamics, indicating that a better equilibrium distribution of microorganisms and substrates could be achieved in the MUASB reactors under the lowest cumulative load. Therefore, substrate equalization theory can be used to optimize the nitrogen removal performance of MUASB reactors with low-carbon footprints.

Comparative investigation on chemical and green synthesized titanium dioxide nanoparticles against chromium (VI) stress eliciting differential physiological, biochemical, and cellular attributes in Helianthus annuus L.

Nanotechnology is a new scientific area that promotes unique concepts to comprehend the optimal mechanics of nanoparticles (NPs) in plants under heavy metal stress. The present investigation focuses on effects of synthetic and green synthesized titanium dioxide nanoparticles (TiO2 NPs and gTiO2 NPs) against Cr(VI). Green TiO2 NPs have been produced from plant leaf extract (Ricinus communis L.). Synthesis was confirmed employing an array of optical spectroscopic and electron microscopic techniques. Chromium strongly accelerated H2O2 and MDA productions by 227 % and 266 % at highest chromium concentration (60 mg/kg of soil), respectively, and also caused DNA damage, and decline in photosynthesis. Additionally, anomalies were observed in stomatal cells with gradual increment in chromium concentrations. Conversely, foliar applications of TiO2 NPs and gTiO2 NPs considerably mitigated chromium stress. Sunflower plants treated with modest amounts of green TiO2 NPs had significantly better growth index compared to chemically synthesized ones. Principal component analysis highlighted the variations among photosynthetic attributes, oxidative stress markers, and antioxidant defense systems. Notably, gTiO2 supplementation to the Cr(VI) strained plants minimized PC3 production which is a rare report so far. Conclusively, gTiO2 NPs have been identified to be promising nano-based nutrition resource for farming applications.

Identifying the Stripping of Oxide Debris from Graphene Oxide: Evidence from Experimental Analysis and Molecular Simulation.

In this study, characteristics of oxidation debris (OD) and its stripping mechanism from graphene oxide (GO) were explored. The results demonstrated that OD contains three components, namely, protein-, fulvic acid-, and humic acid-like substances; among these, protein-like substances with lower molecular weight and higher hydrophilicity were most liable to be stripped from GO and were the primary components stripped from GO at pH < 10, whereas humic acid- and fulvic acid-like substances were stripped from GO at pH > 10. During the stripping of OD, hydrogen bonds from carboxyl and carbonyl were the first to break, followed by hydrogen bonds from epoxy. Subsequently, π-π interactions were broken, and hydrogen bond interactions induced by hydroxyl groups were the hardest to break. After the stripping of OD, the recombination of OD on GO was observed, and regions containing relatively fewer oxygen-containing functional groups were favorable binding sites for the readsorbed OD. The stripping and recombination of OD on GO resulted in an uneven GO surface, which should be considered during the development of GO-based environmental materials and the evaluation of their environmental behavior.

Novel Defluorination Pathways of Perfluoroether Compounds (GenX): α-Fe2O3 Nanoparticle Layer Retains Higher Concentrations of Effective Hydrated Electrons.

The development of efficient defluorination technology is an important issue because the kind of emerging pollutant of hexafluoropropylene oxide dimer acid (GenX) as an alternative to perfluorooctanoic acid (PFOA) has the higher environmental risks. In the UV/bisulfite system, we first developed a hydrophobic confined α-Fe2O3 nanoparticle layer rich in oxygen vacancies, which accelerated the enrichment of HSO3- and GenX on the surface and pores through electrostatic attraction and hydrophobic interaction, retaining more hydrated electrons (eaq-) and rapidly destroying GenX under UV excitation. Especially, under anaerobic and aerobic conditions, the degradation percentage of GenX obtain nearly 100%, defluorination of GenX to 88 and 57% respectively. It was amazed to find that the three parallel H/F exchange pathways triggered by the rapid reactions of eaq- and GenX, which were unique to anaerobic conditions, improved the efficiency of fluoride removal and weaken the interference of dissolved oxygen and H+. Therefore, this study provided an available material and mechanism for sustainable fluoride removal from wastewater in aerobic and anaerobic conditions.

Arbuscular Mycorrhizal Fungus Alleviates Charged Nanoplastic Stress in Host Plants via Enhanced Defense-Related Gene Expressions and Hyphal Capture.

Contamination of small-sized plastics is recognized as a factor of global change. Nanoplastics (NPs) can readily enter organisms and pose significant ecological risks. Arbuscular mycorrhizal (AM) fungi are the most ubiquitous and impactful plant symbiotic fungi, regulating essential ecological functions. Here, we first found that an AM fungus, Rhizophagus irregularis, increased lettuce shoot biomass by 25-100% when exposed to positively and negatively charged NPs vs control, although it did not increase that grown without NPs. The stress alleviation was attributed to the upregulation of gene expressions involving phytohormone signaling, cell wall metabolism, and oxidant scavenging. Using a root organ-fungus axenic growth system treated with fluorescence-labeled NPs, we subsequently revealed that the hyphae captured NPs and further delivered them to roots. NPs were observed at the hyphal cell walls, membranes, and spore walls. NPs mediated by the hyphae were localized at the root epidermis, cortex, and stele. Hyphal exudates aggregated positively charged NPs, thereby reducing their uptake due to NP aggregate formation (up to 5000 nm). This work demonstrates the critical roles of AM fungus in regulating NP behaviors and provides a potential strategy for NP risk mitigation in terrestrial ecosystems. Consequent NP-induced ecological impacts due to the affected AM fungi require further attention.

Tire plastic and road-wear particles on Yujing Expressway in the restoration area of Mu Us Sandy Land: Occurrence characteristics and ecological risk screening.

Tire plastic and road-wear particles (TPR-WP) are a current research priority as one of the main environmental sources of microplastics. We selected a unique land use type - desert restoration area, collected soil and dust samples from the Yujing Expressway and its service areas, and analyzed TPR-WP abundance, type, size and morphology by laser direct infrared (LDIR). The abundance of TPR-WP in expressway dust (14,446.87 ± 10,234.24 n/kg) was higher than that in soil (7500 ± 3253.64 n/kg). Random forest model showed that the source of TPR-WP was highly correlated with economic factors and natural climate. Overall, the proportion of small and medium-sized TPR-WP in dust was higher than soil, more than half of the TPR-WP in dust were in 20 - 50 µm range. The proportion of small particle size TPR-WP increased with the rise of elevation. The pollution load index suggested that the survey region was generally at level I risk zone, while the ecological risk index indicated that the pollution level of expressway was III and IV, and the service area was IV. In general, the study was of great significance for clarifying the distribution and risk of TPR-WP in soil and dust of expressways and service areas.

Interfacial interactions of polyethylene terephthalate microplastics and malachite green, tetracycline in aqueous environments.

Polyethylene terephthalate microplastics (PET-MPs) are one of pivotal nondegradable emerging pollutant. Here the variation of the surface physicochemical characteristics of PET-MPs with UV irradiation aging and the adsorption behaviors of PET-MPs in malachite green (MG), tetracycline (TC) solution and the effect of coexisting Cu(II) were comparatively investigated. The yellowing, weakened hydrophobicity, and increased surface negative charge, crystallinity degree and oxygen-containing functional groups were manifested specifically by the aged PET-MPs. Different from the single system, the hydrophobic interaction and metal ion bridging complexation dominated the adsorption of MG and TC, respectively, in the binary solution. While in the ternary solution, cationic ion competition of Cu(II) with MG decreased its capture, and the formation of PET-Cu(II)-TC ternary complexes promoted TC adsorption. Moreover, PET-MPs could serve as an efficient vector for MG and TC in MG/TC/Cu(II) ternary system, indicating PET-MPs tend to carry more varieties in the complex environment, that may increase the environmental risk of PET-MPs.

La2O3 Nanoparticles Can Cause Cracking of Tomato Fruit through Genetic Reconstruction.

La2O3 nanoparticles (NPs) have shown great potential in agriculture, but cracking of plant sensitive tissue could occur during application, resulting in a poor appearance, facilitating entry for insects and fungi, and increasing economic losses. Herein, exocarp cracking mechanisms of tomato (Solanum lycopersicum L.) fruit in response to La2O3 NPs were investigated. Tomato plants were exposed to La2O3 NPs (0-40 mg/L, 90 days) by a split-root system under greenhouse condition. La2O3 NPs with high concentrations (25 and 40 mg/L) increased the obvious cracking of the fruit exocarp by 20.0 and 22.7%, respectively. After exposure to 25 mg/L La2O3 NPs, decreased thickness of the cuticle and cell wall and lower wax crystallization patterns of tomato fruit exocarp were observed. Biomechanical properties (e.g., firmness and stiffness) of fruit exocarp were decreased by 34.7 and 25.9%, respectively. RNA-sequencing revealed that the thinner cuticle was caused by the downregulation of cuticle biosynthesis related genes; pectin remodeling, including the reduction in homogalacturonan (e.g., LOC101264880) and rhamnose (e.g., LOC101248505), was responsible for the thinner cell wall. Additionally, genes related to water and abscisic acid homeostasis were significantly upregulated, causing the increases of water and soluble solid content of fruit and elevated fruit inner pressure. Therefore, the thinner fruit cuticle and cell wall combined with the higher inner pressure caused fruit cracking. This study improves our understanding of nanomaterials on important agricultural crops, including the structural reconstruction of fruit exocarp contributing to NPs-induced cracking at the molecular level.

Ascertaining appropriate measuring methods to determine tire wear particle pollution on driving school grounds in China.

Tire wear particles (TWPs) are garnering increasing attention due to their potential adverse environmental impacts. However, precisely ascertaining TWPs content is challenging due to the complexity and variability of the tire components used in the environment, indicating that more reliable methods to accurately determine TWPs are necessary. In this study, driving school grounds were used as a case study to ascertain an appropriate and reliable method to determine TWPs levels based on a comprehensive comparison between different analytical results using styrene butadiene rubber (SBR), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and zinc (Zn) as analytical markers. Thermogravimetric analysis-Gas chromatography mass spectrometry (TGA-GC-MS) method reliability using SBR was verified and applied to measure TWPs levels on driving school grounds. By reliably converting SBR content to TWPs content, the average TWPs content on driving school grounds was measured at 190.13 ± 101.89 mg/g. The highest TWPs content was 281.83 ± 171.44 mg/g under the reverse stall parking driving programs, while the slope start and stop driving programs was lower at 208.36 ± 124.11 mg/g. Our findings highlight the importance of accurately determining TWPs content within specific environments while comprehensively exploring associated patterns of change to better understand the environmental risks of TWPs.

Nitrogen-Doped Carbon Dots Facilitate CRISPR/Cas for Reducing Antibiotic Resistance Genes in the Environment.

The continued acquisition and propagation of antibiotic resistance genes (ARGs) in the environment confound efforts to manage the global rise in antibiotic resistance. Here, CRISPR-Cas9/sgRNAs carried by nitrogen-doped carbon dots (NCDs) were developed to precisely target multi-"high-risk" ARGs (tet, cat, and aph(3')-Ia) commonly detected in the environment. NCDs facilitated the delivery of Cas9/sgRNAs to Escherichia coli (E. coli) without cytotoxicity, achieving sustained elimination of target ARGs. The elimination was optimized using different weight ratios of NCDs and Cas9 protein (1:1, 1:20, and 1:40), and Cas9/multi sgRNAs were designed to achieve multi-cleavage of ARGs in either a single strain or mixed populations. Importantly, NCDs successfully facilitated Cas9/multi sgRNAs for resensitization of antibiotic-resistant bacteria in soil (approaching 50%), whereas Cas9/multi sgRNAs alone were inactivated in the complex environment. This work highlights the potential of a fast and precise strategy to minimize the reservoir of antibiotic resistance in agricultural system.

Co-fermentation of titanium-flocculated-sludge with food waste towards simultaneous water purification and resource recovery.

Recovery of resources from domestic sewage and food waste has always been an international-thorny problem. Titanium-based flocculation can achieve high-efficient destabilization, quick concentration and separation of organic matter from sewage to sludge. This study proposed co-fermentation of the titanium-flocculated sludge (Ti-loaded sludge) and food waste towards resource recovery by converting organic matter to value-added volatile fatty acids (VFAs) and inorganic matter to struvite and TiO2 nanoparticles. When Ti-loaded sludge and food waste were co-fermented at a mass ratio of 3:1, the VFAs yield reached 3725.2 mg-COD/L (VFAs/SCOD 91.0%), which was more than 4 times higher than the case of the sludge alone. The 48-day semicontinuous co-fermentation demonstrated stable long-term operation, yielding VFAs at 2529.0 mg-COD/L (VFAs/SCOD 89.8%) and achieving a high CODVFAs/NNH4 of 58.9. Food waste provided sufficient organic substrate, enriching plenty of acid-producing fermentation bacteria (such as Prevotella 7 about 21.0% and Bacteroides about 9.4%). Moreover, metagenomic sequencing analysis evidenced the significant increase of the relative gene abundance corresponding to enzymes in pathways, such as extracellular hydrolysis, substrates metabolism, and VFAs biosynthesis. After fermentation, the precious element P (≥ 99.0%) and extra-added element Ti (≥99.0%) retained in fermented residues, without releasing to VFAs supernatant, which facilitated the direct re-use of VFAs as resource. Through simple and commonly used calcination and acid leaching methodologies, 80.9% of element P and 82.1% of element Ti could be successfully recovered as struvite and TiO2 nanoparticles, respectively. This research provides a strategy for the co-utilization of domestic sludge and food waste, which can realize both reduction of sludge and recovery of resources.

A multi-omics approach to unravelling the coupling mechanism of nitrogen metabolism and phenanthrene biodegradation in soil amended with biochar.

The presence of polycyclic aromatic hydrocarbons (PAHs) in soil negatively affects the environment and the degradation of these contaminants is influenced by nitrogen metabolism. However, the mechanisms underlying the interrelationships between the functional genes involved in nitrogen metabolism and phenanthrene (PHE) biodegradation, as well as the effects of biochar on these mechanisms, require further study. Therefore, this study utilised metabolomic and metagenomic analysis to investigate primary nitrogen processes, associated functional soil enzymes and functional genes, and differential soil metabolites in PHE-contaminated soil with and without biochar amendment over a 45-day incubation period. Results showed that dissimilatory nitrate reduction to ammonium (DNRA) and denitrification were the dominant nitrogen metabolism processes in PHE-contaminated soil. The addition of biochar enhanced nitrogen modules, exhibiting discernible temporal fluctuations in denitrification and DNRA proportions. Co-occurrence networks and correlation heatmap analysis revealed potential interactions among functional genes and enzymes responsible for PHE biodegradation and nitrogen metabolism. Notably, enzymes associated with denitrification and DNRA displayed significant positive correlation with enzymes involved in downstream phenanthrene degradation. Of particular interest was stronger correlation observed with the addition of biochar. However, biochar amendment inhibited the 9-phenanthrol degradation pathway, resulting in elevated levels of glutathione (GSH) in response to environmental stress. These findings provide new insights into the interactions between nitrogen metabolism and PHE biodegradation in soil and highlight the dual effects of biochar on these processes.

Antibiotics and microplastics in manure and surrounding soil of farms in the Loess Plateau: Occurrence and correlation.

The wide use of animal manure in farmland operations is a source of soil nutrients. However, the return of manure affected antibiotics and microplastics in the soil, thus the potential ecological risks cannot be overlooked. This study investigated the distribution of different antibiotics and microplastics and their correlation. It was found that multiple classes of veterinary antibiotics and microplastics could be detected simultaneously in most manure and soil. In manure, the average concentration of tetracycline antibiotics was higher than fluoroquinolones and sulfonamides. A much lower concentration of antibiotics was found in the soil samples relative to manure. The abundance of microplastics ranged from 21,333 to 88,333 n/kg in manure, and the average abundance was 50,583 ± 24,318 n/kg. The average abundance was 3056 ± 1746 n/kg in the soil. It confirmed that applying organic fertilizer to agricultural soil and the application of plastic mulch in farmlands introduced microplastics. Moreover, microplastics were found to be significantly correlated with antibiotics (r = 0.698, p < 0.001). The correlation between microplastics and antibiotics in soil was significantly weaker than that in manure. Farms could be the hotspot for the co-spread of microplastics and antibiotics. These findings highlighted the co-occurrence of antibiotics and microplastics in agricultural environments.

Microplastic fragmentation by rotifers in aquatic ecosystems contributes to global nanoplastic pollution.

The role of aquatic organisms in the biological fragmentation of microplastics and their contribution to global nanoplastic pollution are poorly understood. Here we present a biological fragmentation pathway that generates nanoplastics during the ingestion of microplastics by rotifers, a commonly found and globally distributed surface water zooplankton relevant for nutrient recycling. Both marine and freshwater rotifers could rapidly grind polystyrene, polyethylene and photo-aged microplastics, thus releasing smaller particulates during ingestion. Nanoindentation studies of the trophi of the rotifer chitinous mastax revealed a Young's modulus of 1.46 GPa, which was higher than the 0.79 GPa for polystyrene microparticles, suggesting a fragmentation mechanism through grinding the edges of microplastics. Marine and freshwater rotifers generated over 3.48 × 105 and 3.66 × 105 submicrometre particles per rotifer in a day, respectively, from photo-aged microplastics. Our data suggest the ubiquitous occurrence of microplastic fragmentation by different rotifer species in natural aquatic environments of both primary and secondary microplastics of various polymer compositions and provide previously unidentified insights into the fate of microplastics and the source of nanoplastics in global surface waters.

Suspected sources of microplastics and nanoplastics: Contamination from experimental reagents and solvents.

There is an increasing concern about the potential effects of microplastics (MPs) and nanoplastics on human health and other organisms. For the separation and detection of MPs, there are various approaches, and the distinct procedures led to different results. However, the presence of MPs in the reagents was not addressed, which could cause false and/or inaccurate results during MPs detection. In this study, the chemical reagents commonly used for the separation and detection of MPs were selected to ascertain whether these reagents introduce MPs. It was shown that a large number of MPs were detected in the reagent and solvent samples. The largest number of MPs (>1 µm) was detected in the KOH reagent, with the abundance of 3070 items/g. The order of MPs abundance in the selected reagents was: KOH > NaCl > CaCl2 > SDS > NaI > H2O2. The types of MPs were the same as the body and stopper of the reagent packaging bottles. MPs size detected in reagent bottles was primarily smaller than 10 µm. The abundance of MPs in the reagents were independent of their purity, however, there was a certain difference in MPs abundance in reagents from different manufacturers. Furthermore, the presence of nanoplastics (< 1 µm) was verified in the reagents through Py-GCMS, with the abundance (39.47-43.01 mg/kg) higher than that of MPs. The obtained results in this study raised specific requirements and cautions for MPs and nanoplastics related research in terms of quality control. Also, this work can facilitate a more accurate assessment of MPs concentrations in the environment.